Posted by
Hemos
on from the learn-more-about-it dept.
bullitB writes "For fans of the world wide patent conspiracy's latest audio format, the latest double blind AAC encoder comparison test results are in. If nothing else, this suggests much of the complaints regarding the iTunes Music Store's lossyness might be unfounded."
173 comments
Discussion
by
doofusclam
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· Score: 5, Informative
You can discuss this test with the author and others at http://www.hydrogenaudio.org
Glad to see development on AAC's sound quality...especially on the free side with the vast improvement of the previously terrible quality of FAAC.
More 'useful' (although it would stir the pot a bit more) would be a comparison with the latest MP3 encoders. To stay within the AAC bubble in comparisons won't encourage people to convert (or to stay away).
I thought FAAC was a non-lossy compression format? In that case I surprised that it rated so badly. In fact thinking about it, maybe they should have played the orginal CD as a control and indicated how that rated.
Is anybody else in this subthread plagued by associations with the sound of a duck squawking "AFLAC!"?
-- Shop as usual. And avoid panic buying.
Re:iTMS music does NOT sound lossy
by
doofusclam
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· Score: 3, Informative
Absolute rubbish.
Maybe you don't understand the nature of the tests?
FWIW, with the Norah Jones track 'Creepin In' (not used in this test) I can not only ABX every codec bar musepack, I can also spot the aac and mp3 variants because of the way they degrade.
Being a medical student, I assume you understand basic psychoacoustic principles?
Lossy is lossy
by
Anonymous Coward
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· Score: 5, Interesting
When will people realise that half the trouble with a lossy format is transcoding? Sure, AAC may sound high-quality when it's in its original format, but when you transcode it to MP3 for your MP3 player, the quality turns to shit. This is inevitably the case when dealing with lossy formats, and why I'd rather buy CDs and rip them to FLAC.
Why would you go from AAC to MP3? Of course that's going to degrade the quality.
Oh, don't have an iPod to play your AACs? Do you have a CD player? Because you can burn them.
(Anybody burned them and then ripped them to mp3 from the CD? I can imagine that would be less lossy than straight transcoding.)
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
(Anybody burned them and then ripped them to mp3 from the CD? I can imagine that would be less lossy than straight transcoding.)
Huh? It's exactly the same deal. When you burn an AAC file to a CD, you don't get all the information back that you threw away when encoding to AAC. It doesn't get you anything more than straight transcoding. There's no magical property of an audio CD that raises the quality of a file.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
AAC may sound high-quality when it's in its original format, but when you transcode it to MP3 for your MP3 player, the quality turns to shit.
Don't convert it to MP3. Play it as it was meant to be, as AAC.
Nobody expects vinyl to sound as good when it's recorded to tape, so play it as vinyl. It'll sound good.
Don't expect AAC to sound as good when recorded as MP3, so play it as AAC. It'll sound good.
Why would burning AAC's to CD and then ripping to MP3 be any less lossy than straight transcoding?
Considering that all transcoding does is render the AAC data into a waveform and then translate the waveform into MP3, what difference would storing the waveform on some intermediate medium make?
Re:Lossy is lossy
by
gl4ss
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· Score: 4, Insightful
*(Anybody burned them and then ripped them to mp3 from the CD? I can imagine that would be less lossy than straight transcoding.)*
if every device was perfect it would be bitwise identical. and what in the world led you to believe otherwise? if you ran it through analog form in some point you might get 'smoother' sound or something but that's just it and self deceit.
that being said, if you buy music for an mp3 player, buy it in mp3. or rip it yourself from a cd, or just get high enough bitrate it doesn't matter for your golden ears if you code it from one format to another.
better yet buy from some independends that are willing to provide both formats. or fuck, just encode good old amiga mods.
-- world was created 5 seconds before this post as it is.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 2, Insightful
You completely missed my point. My MP3 player wasn't obsolete when I bought it. And an AAC player won't be obsolete if I buy it today. But all formats are obsoleted eventually. What happens when I'm stuck with a load of AAC files, and FormatX is the popular one? I have the choice of hunting down a player that still supports AAC, or transcoding and getting a load of artifacts, or throwing away my music.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 1, Interesting
Everybody says this, but have you actually tried it? If you're using it on an MP3 player, you're probably not playing it on your audiophile-quality (heh) stereo in a well designed listening room. You're probably either in the car or out and about, listening on cheap headphones. You won't be able to tell the difference under such conditions, especially if you encode at the highest VBR quality.
Think of it this way: AAC takes out some stuff you can't hear anyway. MP3 takes out some other stuff you can't hear. If both are done at sufficient quality, what are you left with? You still have all the stuff you could hear from the original! Of course this assumes the listening environment is not the best, as above. You probably will hear it in a pristine environment on great equipment, but then you wouldn't do any of this in that case anyway!
There are many mp3 players that are not iPods;D
As well as many reasons for choosing another player (ogg vorbis support?). Too bad I don't have time to research on this matter...
and sorry my english
-- \m/
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
That approach is unmaintainable. Now, I need to keep track of two sets of files, the ones that sound decent on my home system, and the ones that work with my portable.
Re:Lossy is lossy
by
FlipmodePlaya
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· Score: 3, Interesting
Pricing the way it is, I didn't even consider an iPod when looking for a HDD based player. I decided on the Neuros (www.neurosaudio.com), and bought one Friday. I'll post a quick list of its advantages as compared to the 20GB iPod:
-Half the price, at $200 -Ogg support -Open source firmware and software, including good Linux support. -Removable HDD 'back packs', you can buy additional 20GB storage for a reasonable ~$100 -Built in FM radio reciever and broadcaster (very cool) -Hardware MP3 enocding, you can record audio from the radio or its line-in port -Longer lasting battery -etc.
The first three are huge for me, and probably a lot of Slashdot. The only major disadvantages are that it is USB 1 (upgradeable in the near future), and that it is larger (not a big deal to us large-pocketted punk whipper snappers!)...
If I had enough money for an iPod, I'd spend it on an iRiver iHP-140, Rio Karma, or maybe even a Nomad Zen Xtra 40GB player.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
Well, dumbass, if you only have an mp3 player, why the fuck are you collecting AAC files?
Re:Lossy is lossy
by
Snowspinner
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· Score: 3, Insightful
Yeah, I looked at many of those players.
Then I bought an iPod, because it was actually well designed - it had an interface that actually lends itself to playing music. I want an mp3 player that I can change the song on while driving - that is, one that's fast to use, and is forgiving of being put down halfway through a menu and picked up again five minutes later because the traffic got bad.
And, frankly, though I could carry an mp3 player larger than an iPod around, if I don't have to, I'm just as happy not to. I mean, yeah, a larger thing would fit in my pocket, but I'd just as soon also put in my gloves, hat, scarf, phone, pen, GBA, candy bar, and whatever the hell else I'm carrying on a given day.
Well, OK, but in the context of the question, the person has already chosen one that doesn't have AAC support. Considering that, to the best of my knowledge, none of the major music stores actually distribute in anything other than mp3 and AAC, and that, frankly, there's not a lot of file trading going on in Ogg format, Ogg support is really more of a geek pride feature than a functional one.
I respect that you prefer Apple's insterface, it is well designed. I'm not willing to say it's better than those of the other players I've used, but it is nice. Still, is that worth $200 and features to you?
In the second paragraph it seems like you're suggesting that a GBA and all of that other stuff occupies the amount of space you save with an iPod... We're talking a few cubic inches here. All those things must require a few cubic feet.
In terms of the features offered, sure it is - I don't listen to the radio, I have little in Ogg format (And what I have, I've converted to mp3), and I don't need more than 20 GB of mp3s at a time.
As for size, it certainly helps. The stuff listed isn't that big, in the end. Could I fit a slightly larger mp3 player - sure. But I'd have a bitch of a time operating it. The few inches saved lets me reach in and tap a button.
To say nothing of the summer, when I'm not wearing a jacket. At that point, an mp3 player that fits in my breast pocket looks pretty damn good.
I don't think you get it. I'm saying the quality is also relevent when converting to other formats, and when buying music, I absolutely demand non-lossy formats, as lossy formats are inherently low-quality when transcoding.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
Okay, my trollometer is bleeping like mad now. I give a rationale for not using AAC, and you call me a dumbass for using AAC? I absolutely refuse to believe that anybody who can string a sentence together can be capable of such stupidity. Thread's over, go home, troll.
I find a tape adapter and the passenger seat works just fine.
Somehow I don't think that's a viable solution in a discussion about audio quality.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
WMA. Though that abomination can barely be called an audio format.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
All of those formats are lossy. Redbook audio is lossy. You can't convert from analog to digital without lossiness.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
All of those formats are lossy.
"Lossy" is a specific term to describe a property of a compression format - namely whether it can fully represent the information given to it uncompressed.
None of the formats I mention are lossy.
Re:Lossy is lossy
by
Snowspinner
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· Score: 3, Insightful
Somehow, I don't think that car speakers and highway noise are a viable solution for audio quality too.
I mean, you're driving. If you're being safe, your sound quality is going to be hampered by the fact that your stereo isn't louder than the sounds your car and the road are making.
Well, I can still hear a noticeable difference between a CD nnmy CD player and a tape adapter. Not mentionning that: a. you're screwing up your tape drive. I destroyed 2 of mine with tape adapters. Not that I'm ever going to use them for anything else than tape adapter but still... b. There is a wire and a "floating device" to handle while driving. c. You have to buy a charger for your iPod which I guess is very expensive if you plan on letting it in the car.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
Just say it won't make any difference you stupid cock. No need to write it like some kind of nerd challenge. Get a fucking clue.
Re:Lossy is lossy
by
Anonymous Coward
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· Score: 0
Isn't it great to be an audio nazi?
Re:iTMS music does NOT sound lossy
by
doofusclam
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· Score: 0, Troll
I shout 'Troll'.
Any chance of you expanding on your theories? I'd especially like to know how being a 'medical student' has any bearing on whether you're talking rubbish or otherwise.
Re:AAC is an aberration that should go away
by
doofusclam
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· Score: 1
I have to admit i'm surprised that aac was considered worse than mp3 at these bitrates.
I'm sticking to musepack. I've got 23000+ tunes (1700 albums-ish) on my home server, but can only casually find ~4-5 tunes which seem degraded from the original. Hardware support would be nice, though.
Re:iTMS music does NOT sound lossy
by
misterpies
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· Score: 5, Informative
I can tell you're a medical student and not a doctor, because most doctors are much more realistic about the limits of their knowledge. "Scientific" limits on the capabilities of biological systems are often wrong because of some overlooked or unknown factor.
A famous example of this is that for many years scientists could not work out how bees could fly. Their wings were too small, muscles too weak and bodies too heavy. It turned out that bees were able to use previously unknown aerodynamic effects to generate more lift than our previous "knowledge" allowed. Another example is that many birds of prey have visual acuity better than the laws of optics, applied to their eyes, would seem to permit. It turned out that the visual signal processing in their brains is so advanced that birds can actually 'see' features that are below the resolution limit of their eyes.
Similarly, we shouldn't be too dogmatic about what humans can and cannot hear. MP3s (and presumably AACs) compress music by suppressing parts you "can't" hear, not because they're outside your range of hearing but because the brain, assuming those parts should be there, fills in for them even when they're absent.
But it may be that you can't hear something consciously but still tell that it's not there. For example, there was a news story a week or so back showing that people could somehow tell when a picture had changed by the removal of an item in it, even though consciously they could not explain what the difference was - it just 'felt different'.
So, if someone claims to be able to tell the difference between 1 128Kb AAC and a CD, test that claim in a double-blind experiment. Only when he fails the test can you say he was imagining things.
-- The author of this post asserts his moral rights.
I'm not a doctor, but I play one on television
by
AtariAmarok
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· Score: 4, Informative
It's either that, or "Damn it, Jim, I'm a doctor, not an audiophile!"
It is clear you have no idea what you are talking about. Just because you can't tell the difference does not mean others can.
The people who are "able to tell" just happen to have more sensitive hearing. I'm probably not one of them, but I have known several, including someone who cannot listen to CD's because there is a whine on all of them associated with the digital nature (this same guy does not like going into Radio Shack because of the noise made by their security system.)
Just because you are not a sensitive-eared audiophile does not mean everyone has the same cloth-ears as you do.
-- Don't blame Durga. I voted for Centauri.
Re:I'm not a doctor, but I play one on television
by
boobsea
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· Score: 0, Flamebait
Uhh, there is no such thing as a whine of a digital nature. You're spewing complete crap.
Any whine is a result of really crappy audio amplification or something that was RECORDED onto the CD.
I am an EE so shut the fuck up with your elitist prick know-it-allism.
Re:I'm not a doctor, but I play one on television
by
Golias
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· Score: 5, Informative
The parent to this post was modded down for being rude to the grandparent, I suppose... but the point was correct. "The Digital Sound," as we used to call it back in the 80s, turned out to be the result of poor D/A conversion, poor error correction, and amplification hardware that was tweaked to compensate the shortcomings of LPs. Like I mentioned on another audio-related thread last week, a $300 Rotel CD player connected to a modern high-end stereo will sound as good or better when compared to a $3000 air-suspended, laser-guided turntable. (Especially after the LP has been played a few dozen times.)
--
Information wants to be anthropomorphized.
Re:I'm not a doctor, but I play one on television
by
AtariAmarok
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· Score: 1
a $300 Rotel CD player connected to a modern high-end stereo will sound as good or better when compared to a $3000 air-suspended, laser-guided turntable.
It will sound as good to me, but not to my super-sensitive-eared friend, whose hearing is bothered by the low digital "resolution" of CD audio, and it causes unpleasant effects for him. I've never noticed the problem myself, just as I never noticed the Radio Shack security system sound that he heard.
-- Don't blame Durga. I voted for Centauri.
Re:I'm not a doctor, but I play one on television
by
Golias
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· Score: 5, Insightful
I used to think the same way as your friend, because in the 80s and early 90s there did not seem to be any chance that digital sources could sound as good as my favorite LPs.
Then I heard what good CD players can sound like, and realized that the harshness of CD audio had nothing to do with resolution, and everything to do with component makers cutting corners. Your friend might make the same discovery, if he goes to a good listening room with an open mind.
--
Information wants to be anthropomorphized.
Re:I'm not a doctor, but I play one on television
by
fingerfarm
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· Score: 4, Interesting
The people who are "able to tell" just happen to have more sensitive hearing. I'm probably not one of them, but I have known several, including someone who cannot listen to CD's because there is a whine on all of them associated with the digital nature (this same guy does not like going into Radio Shack because of the noise made by their security system.)
I'm getting sick of hearing about how Jimmy the cat boy can't listen to CDs, so the rest of the Budweiser crowd has to bow down to his codec choices.
These people are either freaks who feel the need to expound their superiority at any given chance, or audiophiles who feel they're somehow making a difference by making us waste storage space.
At some point you have to choose whether you're listening to the music or the technology used to reproduce it.
Re:I'm not a doctor, but I play one on television
by
NeverNow
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· Score: 0, Offtopic
"I'm not a doctor, but I play one on television"
What's this, a quote from Joey of Friends?
Re:I'm not a doctor, but I play one on television
by
Anonymous Coward
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· Score: 0
Oh yeah, mod this as very interesting. I'm sick of hearing how Mod the owl boy can't understand what is relevent to a discussion and what is a post solely about someone who is "sick of..."/. Lamers...
Re:I'm not a doctor, but I play one on television
by
Fwonkas
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· Score: 1
...including someone who cannot listen to CD's because there is a whine on all of them...
Ok, I don't hear that, but a muted television drives me nuts. Most have a high pitch squeal. Apparently, not everyone can hear it. I don't consider myself an audiophile by any stretch. I'm pretty sure my hearing is moderately damaged from too many close encounters with loud bands in small bars. But a muted tv really irritates me. Even when it's not muted, I can hear it, though it's not so bad.
Anyone else know what I'm talking about? I've met 1 or 2 people who can hear it too.
-- COMPUTER! Whatever happened to Blueberry Muffin?
Re:iTMS music does NOT sound lossy
by
thatguywhoiam
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· Score: 4, Funny
FWIW, with the Norah Jones track 'Creepin In' (not used in this test) I can not only ABX every codec bar musepack, I can also spot the aac and mp3 variants because of the way they degrade.
Did you calibrate the flux capacitor?
-- If Jesus wants me it knows where to find me.
Re:iTMS music does NOT sound lossy
by
NatasRevol
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· Score: 0, Offtopic
You think you, can but you just can't Nemo!
-- There are two types of people in the world: Those who crave closure
Re:AAC is an aberration that should go away
by
DiscoOnTheSide
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· Score: 4, Informative
AAC is a standard format. Perhaps you've heard of the people that made it... Dolby? Ring a bell? Just about anything doing with excelence in audio comes from them. I can see four things in my shoebox of a dormroom that has their logo on it.
I also find that most of the people that are so violently against DRM (in any form) are the people who would be analy raped by the RIAA/MPAA if they raided your house. I find that the DRM used in the iTunes store is fair, and more or less barely noticeable. Don't have a player that can play AAC? Buy one or shut the fuck up. You bought a player that doesn't do what you want it to, thats no one's fault but your own. Thats like buying DVDs then bitching because your VCR won't play them.
Grow up.
-- Viva La Revolucion! Buy a Mac!
Audiophile opinion
by
Amiga+Lover
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· Score: 3, Interesting
I used to work for an auto electronics installer, and the most discerning fuckers would pay out the nose for single directional cable which sounded JUST that bit better.
I used to get my jollies installing the cable the wrong way round on one side. Not one of the audionerds noticed by listening.
Want to know how much flowery crap they can go on with? Take a look here. You only have to read the descriptions of a few of those turntables to realise these guys are as wacked out as alien abductees and the guy on the street corner who tells you every morning he has the FBI after him.
Re:Audiophile opinion
by
doofusclam
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· Score: 4, Insightful
Ha! The audiophiles are nutters, it's true.
But this is different. Bear in mind 'CD quality' ('Red Book' audio) has been established as a base line for the last 10 years or so. Lossy compression degrades this quality by variable amounts depending on what codec is used, what the source material is and at what bitrate it is compressed. The reason for so much development on these codecs isn't to find an audio nirvana, but to minimize the loss from the source material.
Re:Audiophile opinion
by
Amiga+Lover
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· Score: 5, Insightful
Oh there's definitely a difference in pure analogue vs cd quality vs lossy compression codecs. Just taking a compression ratio down to 96kbit will make most listeners wince when their favourite tracks are played
I think that's part of it for many people. We might not hear parts of the music just like we may not "see" parts of a video clip on the first run round, but after 3 years listening to Louis Armstrong direct from CD, hearing him on 128kbit MP3 can be harsh. Humans learn and learn well, and the repitition of that playing guarantees we'll hear things that we're not meant to! or rather, things that we don't need to in order to identify a particular artist and recording. But we don't just listen to something to identify it, we listen to enjoy. That's different.
Most of the time 128kbit is fine for me. 192kbit for the things I'm familiar with.
Re:Audiophile opinion
by
qengho
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· Score: 2, Funny
read the descriptions of a few of those turntables to realise these guys are as wacked out as alien abductees
As soon as you find someone who starts talking to you about directional audio cables, you must do two things: discount anything else they have ever said to you, and laugh in their faces. While it may seem, to the uninformed, that music 'flows' from the CD / record player out to the speakers, we must always remember that speakers are AC. Alternating current is required to make the speaker cones move in and out.
The real problem is that with all that back and forth motion, the electrons can get very very tired. I recommend that everyone with directional cables should only play their scratchy old LPs for a few minutes each day, lest the electrons in their very expensive cables succumb to extreme fatigue. Come to think of it, the Golden Ear crowd better buy replacements for all their cables once a month -- just in case!
--
Mike van Lammeren It will challenge your head, your brain, and your mind.
Re:Audiophile opinion
by
Golias
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· Score: 4, Interesting
Actually, frequent listening will make your brain better at filling in the data which isn't there. For example: watching DVDs use to bother the heck out of me whenever diffuse lighting created that "layered" effect. Now I hardly ever notice it unless it's ultra-obvious (as with 2001 or some film noir movies), or I'm actively watching for it. My mind usually just interprets it as light fading to darkness now.
The better you know a subject, the more clearly you can "see" it through a dirty window.
P.S. Most of Louis Armstrong's best stuff was recorded on very harsh-sounding "clay 78s." No matter what format you play his Hot Fives and Hot Sevens singles on, it's going to sound like mush. This is another example: People who listen to a lot of live jazz have no trouble listening through all the ticks, pops, scratches, microphone clipping, bad accoustics, etc. and in their "mind's ear" can hear just how brilliant and beautiful Armstrong's recordings are. Those who don't can barely make out a fuzzy-sounding trumpet in an echo-filled hall, and wonder what all the fuss is about.
--
Information wants to be anthropomorphized.
Re:Audiophile opinion
by
SnowDog74
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· Score: 3, Interesting
There is a certain engineering logic behind why the cables are designed that way... unidirectional grounding forces does remove line noise... but the levels of line noise in an already massively-shielded cable are so miniscule that the typical audience for these expensive cables (rich people with bad ears), can't tell the difference anyway.
I have over 24 channels of audio cabling running around my studio and I do find unidirectional grounding makes a difference... but then I'm actually recording music.
Re:Audiophile opinion
by
node+3
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· Score: 2, Informative
The claim of CD quality isn't for MP3 at 128kb/s, it's for AAC at 128kb/s. It's interesting that you said that 192kb/s is what you prefer, since that's the MP3 bit rate that 128kb/s AAC is said to equal.
The ribbons are surrounded by what Ramsey refers to as an "air-core dielectric," alleviating what many feel is a significant source of sound degradation.
Feel is the key word there, of course.
Man, I wish I could find the kind of people who'd cough up $1500 for an audio cable..
-jcr
-- The only title of honor that a tyrant can grant is "Enemy of the State."
I too doubt there's anything audibly different with directional cables, but I wouldn't discount the possibility. The point that the current is AC (so electrons move in both directions) is irrelevant. The electrons are just carriers of the signal, and nobody can deny that the SIGNAL moves in one direction - from amp to speaker. (If you doubt it, consider the net energy flux: the amp powers the speaker, so energy is being carried down the wire.) It's like a sound wave: the individual carriers of the wave move both ways, but the wave itself moves forward.
Now clearly there are components that transmit an electrical SIGNAL better in one direction than another (a diode is an extreme example). Given that, it's not impossible that a cable could be engineered to transmit a signal better in one direction than another. For example, IIRC AC signals get reflected at discontinuities in impedance (resistance), which tends to occur when one component (a cable) meets another (a speaker or amp terminal). Gradual changes in impedance will rather tend to attenuate/accentuate a signal. So maybe by a careful arrangement of the impedance structure, they can come up with a cable that minimises reflection of the forward carrying signal while absorbing any back-reflection that might interfere with the signal.
-- The author of this post asserts his moral rights.
Yeah, that dude's gone off the deep end. For the record, it's a $1500 power cable.
The lifelike timing and pace the Clairvoyant brings to music will startle some listeners. This AC cord dramatically improves the immediacy of a transient's inception, allowing for an incredible expanse of harmonic information and musical envelopment to follow. With the Clairvoyant handling AC, music leapt out of the speakers and created a see-through window into the recording that held me rapt throughout the review period. This AC cord takes music from zero to sixty, quiet to loud, and hard to soft faster than any power product I've encountered.
Not all audiophiles are that whacked out. I'm one of those guys that can tell if your speaker wires are out of phase, and I've had a hell of a hard time going to the movies lately because of the blotchy "domino" copy protection.
Then again, I've spent a bit of time as a musician and an effects artist and I've trained my eyes and ears to pick up on that sort of thing. Sometimes you can ignore annoyances fairly well (speakers out of phase as an example), sometimes you just can't stop paying attention to 'em (blotchy copy protection -- once you've seen it once, you see em every 120 frames or so for the rest of the film).
Unfortunately...
by
lotsofno
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· Score: 5, Informative
Winamp 5.02's encoder (which got a lot of help from hydrogenaudio's own Menno, a FAAD AAC-decoder developer/Ahead MPEG4 developer) wasn't included in the listening test because of a bug they found before testing.
Too bad, too. I would've loved to have seen how it compared.
As a physicist, I'd just like to draw everyone's attention to the error bars on these charts. For the majority of the tests, it's possible to draw a horizontal line through the 95% confidence intervals of nearly all the points.
Hence, the conclusions declaring clear winners/losers in these cases are invalid. If 99% confidence intervals were used (which gives a better statistical test), I feel that no clear winners or losers would be drawn.
Be careful with these sort of studies - even though the author has used confidence intervals, he has failed to use them to infer the proper conclusions.
That said, it's awfully nice to see error bars on this sort of website. Simple data points give such a false sense of precision, I find...
Re:Error bars
by
patman600
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· Score: 5, Informative
As a high school senior in a Statistics AP class currently studying confidence intervals and hypothesis testing, I think you are missing something. At the beginning, he clearly states your point: "One codec can be said to rated better than another codec with 95% confidence if the bottom of its line segment is at or above the top of the competing codec's line segment." The author gives which one is in first place, but announces at the beginning the requirements for a clear winner. And the author seems to me to be requiring at least half an interval of difference to even say that, much of the time he says they are tied.
Good point. You also have to very be careful about doing multiple comparisons like this without some form of correction (such as Bonferroni)--otherwise your 95% confidence interval gets progressively weaker for each test you add since the probability that you made a Type I error *somewhere* becomes very high very quickly.
>The author gives which one is in first place, but announces at >the beginning the requirements for a clear winner.
The more comparisons we do, the greater the chance that we made an error in one of our comparisons (you can model this with a binomial distribution fairly trivially). Here, in each graph, there are 10 possible comparisons. The odds of us having a false positive in one of those graphs is around 40.1%. Across multiple studies, like this one, you can imagine the odds that one of our comparisons, somewhere, is off.
The "error bars methodology" only gets you so far. There are a lot of potentially good methodologies here, but this isn't one of them. There is a reason that ANOVA is used with comparisons among multiple groups.
Disclaimer: I haven't read whether he used a correction or even his general statistical methodology. He may of and I just don't know about it--this is all from a cursory analysis.
ANOVA is used in the analysis. But in separating the means, no pval correction is used. The method for separating the means is a protected Fisher LSD.
So yes, you can perform a more conservative analysis (for example, a resampling method) that assumes neither a normal distribution and also corrects the pval for multiple comparisons. But hey, we're not talking about bringing a drug to market here. This is a listening test, for Christ's sake!
The statistics aren't the weakest link in interpreting the results of the test.
>ANOVA is used in the analysis. But in separating the means, no >pval correction is used. The method for separating the means >is a protected Fisher LSD.
Fisher LSD is better than I thought, but you are still going about it the wrong way. The only way the Fisher LSD is protected is if you do the ANOVA first and it shows a significant difference between the groups, then you do the post hoc tests accordingly. Just doing the LSD without doing the ANOVA first to determine a significant difference between your groups doesn't accomplish much.
The Fisher LSD is also generally not recommended for exactly the situation you have here--close values, with one or two outstanding groups. There are a lot of tests that are much better (not even getting into nonparametric tests).
Incidentally, the odds of you making at least one Type I error, using your current method (posthoc tests before the ANOVA), is 99.8%
>. But hey, we're not talking about bringing a drug to market >here. This is a listening test, for Christ's sake!
My problem is that you are adding apparent legitimacy to the study without appreciably strengthening the analysis.
This is in many ways functionally similar to the problem of pseudoreplication--you are claiming a stronger analysis than you actually have.
>The statistics aren't the weakest link in interpreting the results >of the test....and you should address these in your analysis.
Fisher LSD is better than I thought, but you are still going about it the wrong way. The only way the Fisher LSD is protected is if you do the ANOVA first and it shows a significant difference between the groups, then you do the post hoc tests accordingly.
That is exactly what is happening here. A blocked ANOVA (each listener is a block) is used to determine if there is a significant difference anywhere. Fisher LSD is used if the ANOVA is significant (this is what it means to be protected).
As I mentioned in another message, if people really want to nitpick, they should take the raw data and run it through my bootstrap resampling program, which does not assume a normal distribution and corrects for multiple comparisons.
However, you can't get the nice graphs that Roberto showed (tabular pvalues are the best you can get), and the difference in the conclusions will be something that is more conservative than the Fisher LSD. But again, who cares? So there is a bigger chance that you'll get a type I error. Get over it. It's not a black and white thing, where if you do it one way the results are totally wrong, like you're making it out to be. Are the conclusions reasonable? Yes. Are they significant to 95% confidence? Maybe if you use ANOVA/Fisher LSD. Maybe not (90% confidence?) if you use another, more conservative method. It's not the end of the world.
BTW, Blocked ANOVA with Fisher LSD is what the book, "Sensory Evaluation Techniques," by Meilgaard, Civille, and Carr recommends for subjective tests like these.
Also BTW, there really isn't one or two results which are strikingly different from the others. There was no low anchor included in this test, which would have produced such a result.
as a PhD student in perception the confidence intervals should be at 95%. this is standard in psychology for more reasons than i will ever have time to write here.
http://ione.psy.uconn.edu/~cespaweb/
I think you have an excellent point, and said it well. Unlike certain EE trolls further up the thread line.
-- Don't blame Durga. I voted for Centauri.
Re:You may have a point
by
BorgCopyeditor
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· Score: 5, Informative
They may be pricks (or trolls), but they have some good points. If you can get past the annoying exterior, you might find some good information on these issues by googling for "audiophile" in rec.audio.pro, a group populated primarily by very good recording engineers. These are guys (mostly) who got where they are through both excellent (and aesthetically attuned) hearing and scientific knowledge of how audio works at every point in the signal chain. To watch them dismiss, with unimpeachable arguments and long experience, the claims of "sensitive" audiophiles can be instructive. I speak as one who has been schooled.
-- Shop as usual. And avoid panic buying.
AAC is not a standard format
by
Anonymous Coward
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· Score: 0
"AAC is a standard format. Perhaps you've heard of the people that made it... Dolby?"
The original DivX is a standard. Perhaps you've heard of the people that made it: Circuit City?
The "78" record album is a standard too, I guess, but it is not THE standard.
"I find that the DRM used in the iTunes store is fair, and more or less barely noticeable"
It's far from fair, since it requires the kludgey solution of burning to CD and then ripping to an actual usable format in order to make use of your OWN files on your OWN machines.
"Don't have a player that can play AAC? Buy one or shut the fuck up."
No, I'd rather buy one that uses a standard format.
"You bought a player that doesn't do what you want it to, thats no one's fault but your own. "
My non-AAC player does what I want it to, thanks. There is no need for DRM (or DRD: digital rights denial).
"Thats like buying DVDs then bitching because your VCR won't play them"
No, it is like having a DVD player and a VCR player, and then bitching when someone comes out with an unnecessary non-standard format (imagine Sony Gamma-Max) that no-one needs. Use the standard formats.
Re:AAC is not a standard format
by
reiggin
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· Score: 1
CircuitCity's DIVX and the DivX codec are two completely different things. Move along, nothing to see here, folks.
Re:AAC is not a standard format
by
EricWright
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· Score: 3, Insightful
I somewhat understand your angst, but the following is a bit ridiculous:
"I find that the DRM used in the iTunes store is fair, and more or less barely noticeable"
It's far from fair, since it requires the kludgey solution of burning to CD and then ripping to an actual usable format in order to make use of your OWN files on your OWN machines.
If you got a track from iTMS, you MUST have downloaded it with iTunes. Thus, you have a solution for using the original file on your machine (Windows and Mac). Don't complain about the lack of Linux support. It's apple's baby and they can do what they want with it.
I'm not saying you have to like AAC, or support its right to exist, but if you knowingly buy an iTMS track, caveat emptor.
Also, I'd like to know what rights Fairplay has denied you? The right to share music with all your friends? Copyright law already forbids that. Fairplay only enforces it. Your example of AAC to CD to MP3/WMA/etc. claims that you have lost the right to directly convert AAC to another format. I hardly find that overly restrictive, considering the alternatives (only one machine, only one portable music player, limited times burning the track, etc.)
Re:AAC is not a standard format
by
BorgCopyeditor
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· Score: 1
It seems that for you, "DRM" and "fair" could never be in the same sentence without a "not" thrown in there somewhere. No surprise, then, that you're not persuaded.
-- Shop as usual. And avoid panic buying.
Re:AAC is not a standard format
by
switcha
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· Score: 1
It's far from fair, since it requires the kludgey solution of burning to CD and then ripping to an actual usable format in order to make use of your OWN files on your OWN machines.
What the hell is a "usable format"? I use my mine how I like them just fine. Download and listen from laptop or iPod.
Ohhhh, you meant "usable" in the sense of your own opinion. Nice 'standard' compliance there, chief.
-- You know what?... A little club soda *did* get that out!
Re:AAC is not a standard format
by
Anonymous Coward
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· Score: 1, Insightful
Linux support for Apple DRM: http://www.videolan.org
Why do people act like VLC does not exist in discussions about Apple DRM?
Have Apple zealots been told by God Jobs to not talk about it so the RIAA doesn't find out?
Fair Use and DRM are mutually exclusive.
Re:AAC is not a standard format
by
Anonymous Coward
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· Score: 0
it IS a standard format, as it's a derivative of MPEG-4. So you don't like some aspects of it and that doenst make it "standard"? You're an asshole. And why would you want to strip the DRM from the iTunes store? Perhaps because you're a whiney little music pirate who feels that all music is OWED to you for free cause you've got a ph47 p1p3?
I'm no angel myself, but I'm not going to fight against DRM like it's the work of satan himself. It's a business strategy needed to make money because of greedy self-important fucks like yourself. Get around it, or I don't know... PAY FOR IT. God.
Or are you just mad cause you have to take your sister to prom this year?
Of course
by
Anonymous Coward
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· Score: 0
"CircuitCity's DIVX and the DivX codec are two completely different things"
Of course. That is why I called it Circuit City's original DIVX (to show that I was not referring to the codec).
Re:iTMS music does NOT sound lossy
by
mhoward736
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· Score: 5, Insightful
Bollocks! BUT...
If I listen to an MP3 or AAC file on my computer with its sound card and speakers (SB Audigy, Boston Accoustics) I can tell the difference between the same (160kbs) MP3 file and a (128k) AAC - the AAC sounds better. I can't tell the difference between the AAC and a WAV file however.
If I move up to my ($$$$) home stereo then I can easily tell the difference between the compressed and non-compressed versions of the same song. AAC still sounds better to me than MP3 however.
The difference here is money and environment, my office is a noisy place with all the computers etc running. My listening room is quiet and I spent a lot of time setting the stereo up so that its at its best.
I have not looked at OOG or any of the other formats so I can't comment on the relative merits of them.
Re:iTMS music does NOT sound lossy
by
iblink
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· Score: 3, Interesting
On a moderate audiophile system (under $10K) there is a clear difference difference between an AAC encoded file downloaded from itunes (and then burned onto a CD with itunes) and an original CD. I spent the money to download songs I already owned in order to make a comparison. I do not have great sensitivity any more -- I'm 41 -- but there was no mistaking the lack of "fullness" in the AAC, particularly at the high end, with instruments such as a violin. True, my test was not double-blinded, but the difference was obvious.
That said, I continue to purchase music on itunes. I simply avoid purchasing music that is more sensitive to the encoding.
Perspective
by
UnknowingFool
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· Score: 5, Insightful
Not to quash anybody's personal opinion of AAC, there are a few things that we should note.
1) Most people can't tell the difference between formats that are similiar in performance.
2) Some people actually can tell the difference.
3) Some people are just posers who can't tell the difference but say they can.
4) Lastly, most people don't really care as long as it is convenient to use either format.
-- Well, there's spam egg sausage and spam, that's not got much spam in it.
Re:Perspective
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Anonymous Coward
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· Score: 0
And I'd like to say authoritatively that most slashdotters fall into category 3!
Re:Perspective
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Anonymous Coward
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· Score: 0
Wow, so much for stating the obvious AND getting mod points.
AAC vs. AAC not the issue
by
carbona
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· Score: 4, Interesting
Most of the complaints I've heard registered about the iTunes Music Store 128 Kbps format isn't that it sounds like crap compared to other AAC implementations. The major complaint is that it not only falls far behind Apple's claim that it sounds indistinguishable from the original lossless CD, but it also fails to sound even as good as MP3 with a decent encoder like LAME using --alt-preset standard or OGG at medium quality.
I understand Apple trying to keep filesizes to a minumum, but in these days of 3.0 Mbps DSL links to people's apartments and storage prices at absolutely mind-boggling low price points, their logic is becoming less and less understandable with each passing month.
AAC actually sounds like a well-developed and efficient lossy format but let's up the bitrate a bit especially when the price of a physical CD with all the artwork and liner notes along with lossless tracks and the ability to rip them to a lossy format for portable use is only a few dollars more, and in some cases the same price, than an album on the iTMS.
Re:AAC vs. AAC not the issue
by
Anonymous Coward
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· Score: 0
> understand Apple trying to keep filesizes to a minumum..
i think iTMS uses 128 kbps to discourage conversions to MP3 (then to P2P, in RIAA's mind), not to keep the file sizes small.
this was something Apple had to tell the exec's at RIAA: "look, even if they get MP3s from our music, it will sound crappy."
Re:AAC vs. AAC not the issue
by
dylansm
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· Score: 1
I want to second this thought. I won't buy songs off iTunes for this reason: the sound quality really stinks. This, combined with the DRM and lack of support on portable players, means that I still buy CD's so I can rip at a reasonable bitrate.
Re:AAC vs. AAC not the issue
by
jo_ham
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· Score: 2, Interesting
Storage space is not the issue - it's bandwidth on the server end. It might only be a small increase in file size for the consumer, but Apple's bills soon add up with that extra size.
I know they use Akami, land of the infinite bandwidth, but that doesn't mean it's free.
Re:AAC vs. AAC not the issue
by
Anonymous Coward
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· Score: 1, Insightful
They allow people to preview 30 seconds of a song. Figuring an average song is 3 minutes, I'd say most of their bandwidth is squandered by previews.
Hehe, Akamai, land of infinite bandwidth =D
Sounds good to me
by
kherr
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· Score: 4, Informative
I had all of my CDs ripped to 192kbps MP3. When iTunes came out with AAC, I did a bunch of rip testing. I ripped from Donald Fagen's The Nightfly in a bunch of formats and bitrates. I found, for my personal preference, that 128kbps AAC was at least as good as 192kbps MP3, if not better. So I reripped all of my CDs to 128kbps AAC and got more songs onto my 5GB iPod. Now I'm on to ripping all of my old vinyl to AIFF, eventually to end up as AAC. Huzzah!
Re:Sounds good to me
by
MikeXpop
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· Score: 4, Interesting
I found,
for my personal preference, that 128kbps AAC was at least as good as 192kbps MP3, if not better.
This statement irks me to no end. Your wording is better than most others though as you used for your preference.
The thing to remember is that MP3 and AAC are different encodings. Comparing AAC to MP3 (to OGG to WMA...) is not like comparing MP3 algorithms. AAC will throw out different sounds that MP3 will keep, and vice versa. For example, a symbol crash sounds a lot better on an MP3 than it does on a similarly encoded AAC (I use LAME MP3s and iTunes AACs, they might sound different on others). However, vocals are clearer on AAC than MP3. I find overall AAC is superior to MP3, and that's what I have my songs as. However, saying a 192 AAC == 128 MP3 is a bit faulty. Both have their strengths and both have their weaknesses.
-- Etiquette is etiquette. He kills his mother but he can't wear grey trousers.
Re:Sounds good to me
by
hondo77
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· Score: 2, Interesting
. So I reripped all of my CDs to 128kbps AAC and got more songs onto my 5GB iPod.
Sounds like what I did. Then I played my iPod through my home stereo. Yikes! Now I'm re-ripping to 256 MP3. Like you said, though, it's personal preference and what you're using the files for and everybody's different.
-- I live ze unknown. I love ze unknown. I am ze unknown.
Re:Sounds good to me
by
Anonymous Coward
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· Score: 1, Insightful
>Sounds like what I did. Then I played my iPod through my home stereo. Yikes! Now I'm re-ripping to 256 MP3. Like you said, though, it's personal preference and what you're using the files for and everybody's different.
So you jumped from 192kbps MP3 to 128kbps AAC then back to 256kbps MP3... Did you at least try AAC at higher bitrates?
So you jumped from 192kbps MP3 to 128kbps AAC then back to 256kbps MP3... Did you at least try AAC at higher bitrates?
Sad but true. I didn't do any listening tests outside of headphones the first few times (I know--dumb). After I heard 128 AAC through the home stereo I spent a good chunk of a Saturday comparing formats. AAC beats MP3 at the cheap headphone (or ear clips, in my case) level. However, I was surprised that MP3 beat AAC at the home stereo level. While 256 MP3 VBR isn't as good as uncompressed it's pretty close (all ripped with iTunes). I couldn't hear much difference between 256 and 320 MP3 but I could hear a difference between the higher rate MP3 and AAC (always comparing to uncompressed). Like I said, I was surprised but that's what my ears told me.
-- I live ze unknown. I love ze unknown. I am ze unknown.
Re:Sounds good to me
by
Anonymous Coward
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· Score: 0
Dude, he didn't say they were mathematically equal. Take a valium.
Thread over.
Re:Sounds good to me
by
Anonymous Coward
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· Score: 0
No no no, that's what your EYES told you.
Re:Sounds good to me
by
Anonymous Coward
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· Score: 0
mod DOWN
Re:Sounds good to me
by
Anonymous Coward
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· Score: 0
For example, a symbol crash sounds a lot better on an MP3
Yikes! now why are you using 256kbps mp3s when VBR mp3s using the latest version of LAME and --preset standard average around 190kbps and sound better? And don't say compatibility - damn near everything will play them just fine.
Why this response got a 4 score and Interesting is beyond me. This is MAJOR TROLL. The original message says "for my personal preference". The original poster is talking about how he hears the difference, NOT the technical difference in encoding a waveform. WHO CARES about how the music is encoded if the listener finds one version better to LISTEN TO than another.
I read responses like this all the time and it is all a MAJOR PILE.... No one cares how an audio stream is encoded. All they care about is how the decoding sounds in the end.
Anyone that argues one algorithm over another, GET A LIFE!!!!!!
Do you ask a car mechanic...
by
SnowDog74
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· Score: 5, Insightful
For the chemical formula for internal combustion? No.
Likewise, I wouldn't go to the local audiophile shop to ask them about audio engineering-related issues.
After being accosted by about ten salespeople in ten minutes at a local audio store that sells everything from Sony ES, to Krell, Wadia, Sunfire and the like... I caught a sales rep in a bold-faced lie.
I was looking for a receiver without many bells and whistles, and he tried steering me towards Denon.
When I asked why Denon is "better", he replied, "Because they focus solely on making audio components unlike Sony."
I chuckled and asked him to explain to me the funadamental difference between the sample & hold buffers on a Sony DAC vs. a Denon DAC... Naturally, he had no clue what I was talking about.
The "double-blind" survey is somewhat misleading... but that being said, it's clearly not measuring which format is superlative... it's only measuring people's perceptions. And people were pretty much even on those various formats.
The study in question just shows that people cannot consistently tell the difference between AAC formats.
Now, I've read articles in audiophile magazines that insisted that SACD (Super Audio CD) was brilliant in comparison to CD. And every one of those articles was a load of crap.
Fundamentally, even the most "discriminating" audiophiles cannot tell the difference between 16-bit, 44.1kHz PCM (Pulse Code Modulation - e.g. AIFF, WAV, in the computer world) and the 1-bit, 2.7GHz DSD bitstream of SACD... nevermind the minute differences betweeen various AAC-enabled codecs.
Hell, I would challenge anyone to be able to tell the difference between 16-bit PCM and MPEG-4 AAC.
The AES (Audio Engineering Society) has stated that MPEG-4 AAC is perceptibly indistinguishable from uncompressed 16-bit, dual channel PCM (e.g. CD-DA spec audio).and I would wager any experienced audio engineer's pair of ears (my own included) against any consumer "audiophile" any day of the week.
My advice to the idle rich? Don't buy the $45,000 pair of speakers... instead buy yourself better hearing and some common sense.
My personal preference? MPEG-4 AAC. As a content creator intensely familiar with a variety of media standards including AES, NTSC, ISO, ITU-R/CCIR, etc. I believe MPEG-4 w/AAC (not Quicktime MPEG-4, mind you, but straight MPEG-4) is the superlative format for compressed audiovisual media.
However, for critical listening, only uncompressed audio is the way to go. The general rule of thumb is that higher bitrates are preferable over higher sampling frequencies. Frequency response roll-off is what you want to avoid. But in order to support the higher bitrates, you need a D/A Converter (DAC, Digital-to-Analog Converter) with an effective sample-hold buffer that can crunch the necessary data to make an accurate conversion of the digital source.
That being said, I'm going to begin digitally remastering my own compositions soon... and go straight from the 24-bit master to a 24-bit multichannel DVD-Audio format. Why? Even an audiophile deafened by the sound of their money burning a hole in their wallet can actually tell the difference between my 24-bit master recordings and the dithered 16-bit CD audio.
Re:Do you ask a car mechanic...
by
SnowDog74
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· Score: 1
Typo... replace "2.7GHz" with "2.7MHz".
Re:Do you ask a car mechanic...
by
dmdimon
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· Score: 1
Nice to read this here;)
But... about AES statement: What hearing conditions and sound material do they use for their tests?
And seems like you possibly know: what is the MAX dynamic range of compressed (AAC, MP3, whatever) sound? WTF, not only that, but I can't find ANY (s/n, distortions, intermodulations, etc) parameters of this conversion. I really can't found that, trying hard. And I have no interest/time(to recall) in calculating by myself, so, if you have something on this, please, share info/link.
Re:Do you ask a car mechanic...
by
GlassHeart
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· Score: 2, Insightful
The "double-blind" survey is somewhat misleading... but that being said, it's clearly not measuring which format is superlative... it's only measuring people's perceptions.
And here I was thinking that the whole point of lossy audio compression was about throwing away information that people could not hear.:)
The format that throws away the least audible information (as determined, in fact, by "measuring people's perceptions"), other things (encoder complexity, file size, etc) being equal, is the winner.
for critical listening, only uncompressed audio is the way to go.
Somehow I don't think 99-cent files that can be downloaded in seconds was meant for "critical listening". I'm not saying you're wrong, just that you may want to evaluate a product or technology against its stated goals, not against your personal goals. Apple has stated that it basically breaks even at 99 cents per song, so what would it mean for their business model if you increase their bandwidth expenses tenfold?
Re:Do you ask a car mechanic...
by
valkraider
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· Score: 3, Insightful
All the "formats" sound the same when played through my fairing speakers on my motorcycle - at 75mph...
However, when I am in my car playing them off my iPod->TapeDeckConvertor, well - all the formats still sound the same.
At home on my expensive stereo, I can easily tell the difference between CD and AAC. The AAC is the one playing off my iPod, and the CD is stored in a corrigated box in the basement...
Re:Do you ask a car mechanic...
by
Anonymous Coward
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· Score: 0
Nyquist theorem states that the maximum dynamic range is, theoretically, one half the sampling frequency.
This is how they arrived at 44100Hz as the optimum frequency for reproducing sounds within the human hearing range, because the peak of our hearing range is somewhere around 22050Hz. I can't remember the exact formulae off the top of my head for calculating SNR, 1/f, etc. but the key problem is frequency response roll-off.
What happens as you approach 22050Hz? Well, think about it... at 44100Hz sampling frequency, the number of times a 22050Hz signal will be sampled is twice per peak-trough cycle... once at the very peak, once at the very trough... any lower a sampling frequency, and it would miss the trough of a 22050Hz signal.
ideally, you'd want a system that didn't operate on algebraic principles, but instead operated like a calculus formula.... and this is where perceptual coding could take us.
In algebra, much like PCM sampling, a wave is represented by plotting multiple points along the wave... However, that creates aliasing or jagged steps in between each plot point, if you really think about it. Calculus, on the other hand, can determine complex vectors without plotting every damned point along the way.
The problem is... the algorithms required to be stored by an audio playback system to accurately reproduce such complex vectors from limited sampling requires massive amounts of data storage that were absolutely infeasible for even the highest-quality playback systems... until now.
Let's look at the representation here...
16 bits x 2 channels x 44.1kHz = 1411kbps
Now, let's remember... there's a huge difference in the logic behind pulse code modulated audio and a codec like AAC.
Because AAC is a Dolby-licensed technology, I have no idea how specifically their algorithm compresses and decompresses information.
What matters is two things:
1. How much of the imperceptible frequencies that are discarded will affect lower-order harmonics that are heard...
2. How the decompressions schema itself works.
Codecs do two things... they discard some data, and then they compress other data. The remaining data that is compressed is done something like this...
If the same sequence of code, e.g. "XYZ", were to appear, let's say, five times, in a file... the compression schema would, conceivably, tell the decoder "I have five instances of string 'XYZ' at these A, B, C, D and E positions in the file...."
That is how lossless compression works... it doesn't actually eliminate data... it tells the decompressor how many redundant sets of data they are, identifies them once, tells the decompressor how many times they appear and the codec knows where to put them because it understands the order and manner in which data is truncated by the compressor that is part and parcel of the same codec.
But AAC does two things... it reduces data chunks in the same manner as lossless compression after it's eliminated data that is considered to be immaterial to human perception. It borrows heavily on AC-2 and AC-3 for this technology.
For more information on Dolby Laboratories, AC-2, AC-3 and AAC, visit Dolby Laboratories.
I also recommend reading Principles of Digital Audio by Ken Pohlmann. It has everything you ever wanted to know about the mathematics behind digital audio.
Re:Do you ask a car mechanic...
by
dmdimon
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· Score: 1
You get me a bit wrong. To be clean - I got MD in institute of radioelectronics some time ago. So, I do know basic digitizing principles not so bad. I asked in first place not about frequency range, but about dynamic range. Mean 20lg(loudest/quietest). Mean 20lg(2^16) speaking of 16 bit PCM (forgetting of quiet signal form) And I was at Sony (Atrac), Dolby(AC, AAC), Sorensen, etc. NOBODY of them tells nothing EXACTLY about dynamic range, SNR, intermodulations. Going to learn actual audio compression algorythms, you'd see that there have to be noticeable intermodulations and dynamic range compression. As I have no such a big interest now in this field, I have no interest to reconstruct/calculate or measure this. And yes, I can do this, but for some one-two types of simple enough input signals, which is of no interest.
For example, 5 to 7 years ago I was shocked by Sony's MD recorder dynamic range (measured) near 68 dB. Got what I mean?
By the way, remember that "104 dB on iPod" thread? NOBODY answered, where that 104 dB come from. Nowhere on Apple can't you get that digit. No digits about sound quality at all. So on Sony, Dolby, AES too.
So, again - is there some data on that to read? Some statistical/calculated/speculated even?
Re:Do you ask a car mechanic...
by
Anonymous Coward
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· Score: 0
And this is insightful how?
His only point is in the last paragraph.
How do these findings compare with mp3, wmf, etc?
by
Blinkslowly
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· Score: 2
I would like to see a graph or two comparing AAC, MP3, WMF, and OGG.
Wow!
by
Anonymous Coward
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· Score: 0
All that knowledge and you still can't buy yourself a paragraph or ten....
Re:iTMS music does NOT sound lossy
by
dmdimon
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· Score: 3, Informative
Being a medical student who has a particular interest in this stuff, you have to know that due to compression method AAC, MP3, ATRAC, etc generates artifacts during compression. I mean due to "harmonising". Furthermore, there exists some "dynamic range compression" So I have to tell that:
a) if you are listening in APPROPRIATE conditions and on APPROPRIATE sound system (mean amplifyer&speakers&QUET room) you easily can distinguish compressed from flat by dynamic range. Possibly you can't tell what's difference is, but you CAN hear it. b) it's not so hard to generate a soundwave that will compress very bad (you easily can point difference) at any bitrate.
Example: get audiotest CD, compress it, listen to what you get.
Which 78s sound best, RCA or Columbia?
by
dpbsmith
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· Score: 1, Informative
I have to admit to being puzzled as to why people spend so much time and energy trying to determine the relative merits of lossy formats.
I find the music I've downloaded from iTMS perfectly acceptable; ditto the music I hear on my car's factory-equipment FM receiver. That doesn't mean I can't tell the difference between them and better sound.
Actually, I've been transferring my LP's to CD... and recently I've been converting the CD's to.mp3 format with iTunes. The first recording I compressed, using some middle-of-the-road "high-quality" setting, happened to be a recording I liked because of the warmth of the violins. Remember, this is an old LP... digitized on a $250 consumer-grade CD recorder. To my utter astonishment, I could instantly tell the difference. After some experimentation, I upped everything to the max, encoded at 256k bits/second... and could still tell the difference.
On the other hand, with popular music (e.g. the Beatles) and some classical recordings, I couldn't.
The point is, if I can hear the difference between a CD and an.mp3 at 256k bits per second, that tells me that the difference in quality is NOT in some rarefied, golden-ears, territory. It's like the difference between a CD and FM radio.
So, why even bother to agonize over minute differences in an imperfect format when a) upping the bit rate does far more to improve quality than fussing over which format is best; b) the mileage varies so much depending on program material; c) they're obviously inferior to CD sound to begin with?
Isn't it a little like arguing over which electrically-recorded 1950s 78's sound better... RCA or Columbia?
Re:Which 78s sound best, RCA or Columbia?
by
moosesocks
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· Score: 1
Actually, you bring up an interesting issue.
Many people will use vinyl simply for the reason that it does sound better than a CD. While the sound from a vinyl may not be as accurate as a CD, most people will find that they rather enjoy the distortion caused by the vinyl when compared.
News flash, folks. Many people perfer vinyl to CD... if you have a good record, expensive player, you'll notice that vinyl does sound a lot better as long as those two conditions are met. Of course, the beauty of a CD is that it sounds virtually the same no matter what. It would have been an intersting comparision to compare the CD you made to the 'real' CD sold by the record company. They probably sound quite different, and you may find yourself perferring the one you made.
My guess is that you preserved about 75% of the vinyl 'artifacts' when you initially digitized the LP. When you ripped it to MP3, you lost most of those artifacts. Remember, MP3 is a lossy format, and tries to eliminate 'unnecessary sound', and may have deemed the vinyl hisses, pops, etc. as unnecessary, and dropped them in the encoding. In the process, some 'good' sound is lost too. Once again, it would be a really neat idea to go get the 'real' CD, rip that to MP3, and compare. I find that MP3 has better luck encoding things that are already digital.
Lastly, you may even be experiencing trouble ripping the CD. Some of the more flaky rippers don't do a great job ripping CD-Rs, and degrade sound quality as a result. Using a good ripper like Paranoia will give you excellent quality at the expense of being painfully slow. If in dobut, rip to a WAV, and see how that compares.
-- --
If you try to fail and succeed, which have you done? - Uli's moose
Re:Which 78s sound best, RCA or Columbia?
by
metamatic
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· Score: 1
You can get a bigger sound quality improvement by switching from iTunes to LAME for your MP3s. Unfortunately, iTunes has a very poor MP3 encoder.
-- GCHQ Quantum Insert installed. If only our tongues were made of glass, how much more careful we would be when we speak
Re:Which 78s sound best, RCA or Columbia?
by
ratsnapple+tea
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· Score: 1
As to your point (c), they're not necessarily inferior to CD. Remember CD audio is itself a downsampled version of the original master. So if you have access to the master DAT, you could theoretically make an AAC or even an MP3 with a signal closer to the original than the CD, even at a much lower bitrate. (Apple rips most of their iTunes tracks from the original master.)
That's the theory, anyway. In the real world I doubt the AACs in question are actually more faithful to the master than the CD versions. Do I care? Nah, I can't tell the difference. YMMV.
yours
Re:Which 78s sound best, RCA or Columbia?
by
JebusIsLord
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· Score: 1
Lossy codecs don't discard "unnecessary" sounds, they discard inaudible sounds. If you can hear a scratch or 'pop' in the original, then it's going to be in the lossy version as well. This is in theory of course. In practice, even the best perceptual codec throws away some things that the human ear will miss.
-- Jeremy
Re:iTMS music does NOT sound lossy
by
Anonymous Coward
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· Score: 0
Dammit, slashdot! I selected -1, Troll for moderation, but it came back as +1, Underrated! Ack. Posting to try to undo that. This should be Score:1!
I'm assuming slashdot will screw up again and post with my real name, rather than anonymously. Yay.
Don't use ANOVA here
by
fscmj
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· Score: 4, Insightful
In this analysis he presents the results of an ANOVA (Analysis of Variance). This reminds me of the saying: "If your only tool is a hammer, every problem looks like a nail". The tool the author is using is ANOVA and so he is trying to force the data into that form. Hovever, the assumptions of any ANOVA is that the data is independent, normally distributed, and has constant variance. The response ranges from 1.0 to 5.0. I haven't taken the test myself and do not know if users were allowed to select non-integer values or not but even if they were we can see from the graphs he does present that most of the responses were near the upper bound of 5.0. This type of response is clearly not normally distributed. ANOVA is faily resistant to departures from normality but one would need to fully explore the degree of the departure before placing any weight to the confidence intervals presented. My gut feeling here is that it is highly skewed and will present confidence intervals smaller than what they should be (data is forced to be artifically close due to the upper bound and having so many people report values close to that upper bound). The data can probably be viewed as independent but it must be recognized that this is an assumption. Constant variance departures may be a problem as higher responses are less variable than middle responses (due to the upper bound again). It would probably be much better to use a non-parametric test alternative to ANOVA such as a Kruskal-Wallis.
Scope of inference: This is not a random sample from any population and as such cannot be interpreted to represent anything more than the perceptions of the respondants themselves.
-chris
Re:Don't use ANOVA here
by
ff123
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· Score: 2, Insightful
The intervals in the rating scale are 0.1 steps, which is close enough for argument's sake.
And ANOVA is a robust method as you've commented, so it's probably reasonable to assume normality. In any case, the raw data is available for any stats weenies to play with, and there are a couple of more conservative methods besides the Fisher LSD readily available to try, if anyone has an uncontrollable urge.
where you can run a non-parametric analysis of the raw data using a web form if you like. Or download the program to correct the pvals for multiple comparisons using Tukey's Honestly Significant Difference instead of the Fisher LSD (either paramteric or non-parametric).
And if you want to really geek out, you can do a bootstap resampling method with different methods of correcting the pvals for multiple comparisons:
But let's not lose the forest for the trees here. The blocked ANOVA/Protected Fisher LSD used for the test provides a reasonable (if not the most conservative) summary of the results.
A couple of more important weaknesses of the test are (and they're related):
1. Only 12 samples were used. Although this is probably close to the practical limit, more samples always provides a more comprehensive picture. The results are suggestive, but not definitive.
2. The selection of the samples makes a difference. If you listen mainly to classical for example, this test may not be representative for you.
the comments
by
eclectic4
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· Score: 2, Interesting
"Easy Listening
Results: iTunes wins, with Nero closely behind it, more or less tied. Faac is tied with Nero, and Compaact! and Real are tied just below Faac."
"House (Electronic/Techno)
Results: iTunes and Nero tied at first place, Real and Compaact!tied with Nero, and Faac tied to Real and Compaact!."
They were like that. Did we really need a play by play? Did he think we wouldn't be able to "decipher" these "complex" graphs?
...
--
"The greatest obstacle to discovery is not ignorance - it is the illusion of knowledge." - Daniel Boorstin
They were like that. Did we really need a play by play? Did he think we wouldn't be able to "decipher" these "complex" graphs?
Blind people listen to music, and would probably be very interested in his results (many of them having more acute hearing than we sighted folk). However, they would be unable to decipher or even perceive the graphs. I'm not sure how well their screen readers would deal with "faac" or "compaact!" though.
--
Hey kids, there's only 5 days left 'til Yak Shaving Day!
"The greatest obstacle to discovery is not ignorance - it is the illusion of knowledge." - Daniel Boorstin
Its all about the file size
by
acomj
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· Score: 3, Insightful
People agonize because they want the best quality / size ratio. for example if aac encodes at 128 Kbps as well as mp3 at 192 Kbps you can fit more tunes on you harddrive in the same space and be happy. This isn't critical on computers with they're large hard drives, but for portables] players it matters. People also don't want to rip all there CDs multiple times.
In someways your right, people should pick a bit rate/format that works for them and not worry about it. but this is slashdot..
Re:obligatory Ogg Vorbis reply...
by
RegalBegal
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· Score: 0
The Mod today obviously is one of five that is pissed the iPod doesn't support Ogg.
I was just surprised not to see someone outline the 'benefits' of Ogg before my comment. I guess good humor isn't appreciated..hehehe.
--
"It'll destroy you if you try to make it mean anything to anyone but yourself." - Henry Rollins
Re:iTMS music does NOT sound lossy
by
Anonymous Coward
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· Score: 0
Does anyone else see a similarity to wine snobs in this review? Here are some of my favorite highlights.
The lifelike timing and pace the Clairvoyant brings to music will startle some listeners. This AC cord dramatically improves the immediacy of a transient's inception, allowing for an incredible expanse of harmonic information and musical envelopment to follow. With the Clairvoyant handling AC, music leapt out of the speakers and created a see-through window into the recording that held me rapt throughout the review period. [...] The Clairvoyant's ability to recapture the subtle dynamic shades of each musician's instrument highlighted the nearly telepathic interplay among this amazing trio on the track "Whisper Not." [...] The Clairvoyant's signature is engaging, energetic, and bristling with light and microdynamic life. If you're looking to add color to music, fix an existing sound problem or you prefer dark and lovely tones, this AC cord may not be for you.
Oh, the pretentiousness! "This [power cable] has an award-winning oaken taste, with a hint of cinnamon and cherry to it. Clearly the well-aged vines, the robustness of the soil, and the gentle rainfall of the region bring a certain quiet zest to this year's vintage."
Thanks for sharing that review. What a bunch of nutjobs!
-- If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
Re:iTMS music does NOT sound lossy
by
switcha
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· Score: 2, Funny
I have not looked at OOG or any of the other formats so I can't comment on the relative merits of them.
You, sir, are most certainly not aware of where you are posting that statement. On/., there is little to no precident for needing knowledge of any technology to authoritatively comment on it's merits.
-- You know what?... A little club soda *did* get that out!
Re:iTMS music does NOT sound lossy
by
Anonymous Coward
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· Score: 0
On a moderate audiophile system (under $10K) there is a clear difference difference between
an AAC encoded file downloaded from itunes (and then burned onto a CD with itunes) and an original CD.
I'd say the answer's "yes, he effing said that didn't he", wouldn't you?
Re:AAC is an aberration that should go away
by
Anonymous Coward
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· Score: 0
you hit the nail on the head there. MP3 allow me to 'borrow' other peoples ripped music as well. I don't give a rats what the quality is like, I just want the free music.
It's pretty apparent to me when the tracks I've encoded as AIFF come up on my playlist as opposed to my AAC ones (until there's flac AIFF is fine cuz disk space is cheap). The big tell is that the top end gets a lot more clear and articulate. I'm pretty sure that AAC has a tendency to cut off some of the higher harmonics and notes. It cuts from all ranges but these are the easiest for me to notice. That and the lack of richness in super-low lows.
Look at Roberto's previous listening tests
by
waaka!
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· Score: 3, Informative
You might find the graphs for a previous listening test interesting if you want to see how AAC stacks up against other codecs.
A warning to potential HA posters
by
waaka!
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· Score: 4, Informative
For good reasons, the posters on Hydrogenaudio don't take kindly to people making unfounded assertions about which codecs are better, so if you're going to argue with them, think twice and ABX first. You will be, after all, arguing with many audio developers, e.g. people who make contributions to LAME, people who've tuned the Vorbis encoder, and a surprising number of people who work for Ahead (makers of Nero, of course).
Just a minor detail to mention here. Dolby licenses two different versions of their AAC codes. iTunes, when encoding for end users, uses the Dolby Consumer codec (affordably licensed by Apple in Quicktime 6). The Itunes Music Store uses the Dolby Professional codec (which would not be affordable to license in iTunes).
Thus, AACs coming out of the iTunes Music Store have a higher quality at the same compression rate than the same songs you rip and convert on your own copy of iTunes.
-- "It is our blasphemy which has made us great, and will sustain us, and which the gods secretly admire in us." - Zelazny
Re:Minor Detail
by
bullitB
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· Score: 2, Interesting
This is unfortunately not really true. Just to quote your source,
What is the difference between a "professional" encoder or decoder product, and a "consumer" encoder or decoder product?
A professional product is purchased for commercial (i.e., revenue generating) purposes. A consumer product is purchased or made available for non-revenue generating purposes. Examples of professional products include broadcast encoders, and high-end audio or audio/video workstation applications. Professional products are typically used in a production environment or within the context of a backend distribution system. Examples of typical consumer products include jukebox products for creating a personal digital music library, portable digital music players, DVD/CD players, or television receivers.
Notice how they don't mention anything about the actual quality of the encoder? In fact, that's because there's no difference. The Pro/Consumer differentiation is a ploy they use to make commercial users pay more (perhaps because because they have the money to do so). You might notice that Microsoft does with with Student/Home versions of Office which cost 75% less than the business versions of the same code.
Re:Minor Detail
by
Anonymous Coward
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· Score: 0
While you are almost certainly right, it is still likely that some iTMS-purchased songs will sound better than the same song ripped at home, since some of the iTMS songs are encoded from studio master tapes, often using equipment better than what was used to press the CDs in the first place (particularly for older releases).
Also, the iTunes software doesn't do "secure" ripping, so it is possible for home-ripped files to have some errors, especially if the CD is less than pristine.
Objectively comparing formats
by
Experiment+626
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· Score: 2, Insightful
These kinds of tests comparing codecs always seem to be something involving playing two versions of the song and asking someone which in their opinion sounded better. Isn't there a more quantitative way to measure the effect of the lossy compression? For instance:
Start with the digitized CD recording
Make a copy of it
Compress the copy with the codec to be analyzed
Do a lossless uncompression of the MP3 or whatever it is back to CD-resolution
At each sample point (44k per second) on the resulting track, compare the 16-bit sample value of the compressed-and-back version to the control version.
Sum the absolute value of the differences across all sample points.
In other words, whichever codec introduces the least error into the track in a closed loop encode and decode test did the best job of faithfully reproducing the original signal. No subjective human testing required. You might have to tweak it a bit (say, sum the squares of the error or something) but would an approach like this work to settle the codec debates, or is there a fundamental flaw in this technique?
Re:Objectively comparing formats
by
Anonymous Coward
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· Score: 0
Are you kidding me?
The whole point of lossy audio compression is that it creates a signal that looks totally different at the sample-by-sample level, but sounds the same, subjectively, to humans.
If you send a sine wave with a 90 degree phase through an AAC codec, you might get out a sine wave with a 45 degree phase or a 234 degree phase, which will have almost no correspondence pixel-wise to the original signal, but will sound exactly the same to a human.
You have to use subjective tests, unless you can create a perfect artificial model of the human aural perceptual system.
Re:Objectively comparing formats
by
topham
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· Score: 1
Unfortunately useless with lossy audio codecs. The moment a frequency, or range is dropped the wave form is significantly different than when it started, even if that frequency (say 22Khz) can't be heard in the music.
You could do a fourier analysis and get the frequencies / phase, but how do you visually compare these when they could be significantly different but sound virtually identical. (and which one is more pleasing and less distracting)
I'm waiting for audiophiles to start comparing and critiquing loss-less audio codecs based on sound quality.
I agree with you 100%, most audiophiles are deluding themselves. But why do they do it? In fact, why do people constantly claim that x, y or z sounds better to them than a, b or c (usually a, b and c being some vanilla variety of something, be it equipment, encoding formats or what-have-you). It's ego, I reckon. They want to be able to claim that, even though the differences are small, THEIR ears are better than the average Joe's. They just want something to hold on to and be superior about. That's all. They just want one, tiny little element of their otherwise unremarkable lives to stand out from the crowd. Even if by doing so they often prove that their brains are generally inferior.
"I find overall AAC is superior to MP3, and that's what I have my songs as."
Thats exactly what the previous poster is saying.
"However, saying a 192 AAC == 128 MP3 is a bit faulty."
No! no! no! thats not what the poster said, you've just made that up. This is what the poster said, and you should know, because you quoted it:
"I found, for my personal preference, that 128kbps AAC was at least as good as 192kbps MP3, if not better."
Moderators, do your job and mod this foolish reply down.
--
"My cat's breath smells like cat food." - The Tao of Ralph Wiggum.
Re:Read the post!
by
Anonymous Coward
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· Score: 0
That was totally not the point of his arguement. It was a typo, and has no bearing on anything he said. His comment was that certain things with each codec sound better, MP3s -> Symbol Clash, AAC -> Vocals. His point was that you can't simply go off comparing AAC to MP3 in the same way that this article did, because this article is comparing encoding schemes of different AAC codecs. He then also listed his preference -> AAC, but the point of his post was not to disagree with the guy's preference above, but to just comment.
Get a clue.
Re:iTMS music does NOT sound lossy
by
stux
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· Score: 2, Interesting
Slightly metalic, with a hint of a whistle and definately less bright
--
---
Live Long & Prosper \\//_
CYA STUX =`B^) 'da Captain,
Jedi & Last *-fytr
Whoa there! Look at the error bars...
by
Jon+Abbott
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· Score: 2, Informative
I have looked at these sorts of test results before, and used to take them as the truth. That was before I started taking a Design of Experiments grad class, and have some evidence to the contrary. For what it's worth, I'm the top performer in the class right now.
The issue I have is with the error bars. These are the vertical lines above and below the mean of each encoder. Like the beginning of the report says, "One codec can be said to rated better than another codec with 95% confidence if the bottom of its line segment is at or above the top of the competing codec's line segment." This is very much true for these sorts of statistical tests -- if the error bars overlap, that indicates that the means of the two groups are statistically identical. One could always adjust their confidence interval to a lower percentage, but 95% is quite often the standard.
Note how many of the plots in this test have overlapping error bars. In the first plot, for example, all of the encoders tested have overlapping error bars. The results drawn from this plot should be that no encoder was measurably different than any other encoder -- not that iTunes won, like the results say. (Note: I own a Powerbook G4, and am typing this post on it right now, and I love Apple. I just don't like bad statistics, that's all)
The results given in many of the plots are based strictly on the means of the samples, and not the error bars, which are actually more important in this case. Do not trust them. Interpreting the plots with the logic stated at the beginning of the article is the only statistically sound method (that I know of). I hope this sheds some more light on these tests...
Re:iTMS music does NOT sound lossy
by
enormouspenis
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· Score: 0
Speak for yourself. I am also a medical student. Before I entered medical school I played and recorded professionally. I was taught in medical school the "limits" of human hearing. I was also taught that there is no absolute. My personal experience is that many professionals (and likely others) can hear lower and higher than what is generally accepted. I KNOW I can and I have worked with many others who can. It is just silly (and sometimes dangerous) to make sweeping statements about anatomy/physiology; i. e., "The Long Thoracic nerve is always exactly right here" or the ever popular, "It is impossible for this patient to feel pain with this much (drug) on board". The issue of frequency response also neglects the effects of harmonics. All those forces add up whether heard or not and affect the overall audible sound. Play with a high pass and low pass filter with a good system and you will "hear" the effect of missing frequencies even if you can't "hear" them.
-- "I didn't spend six years in Evil Medical School to be called 'Mr.Evil,' thank you very much!"
All this fussing over miniscule differences in quality is plain stupid. I'm yet to hear a stereo system that could make me think that the performers were actually in the room with me - or even come close (at least for reproductions of acoustic material - electronically generated sounds can of course be reproduced convincingly). This is like arguing over which of two different lumps of shit is actually the better gourmet meal.
-- Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
Slashdot Mirror
You can discuss this test with the author and others at http://www.hydrogenaudio.org
Glad to see development on AAC's sound quality...especially on the free side with the vast improvement of the previously terrible quality of FAAC. More 'useful' (although it would stir the pot a bit more) would be a comparison with the latest MP3 encoders. To stay within the AAC bubble in comparisons won't encourage people to convert (or to stay away).
I am Jack's witty signature line
Absolute rubbish.
Maybe you don't understand the nature of the tests?
FWIW, with the Norah Jones track 'Creepin In' (not used in this test) I can not only ABX every codec bar musepack, I can also spot the aac and mp3 variants because of the way they degrade.
Being a medical student, I assume you understand basic psychoacoustic principles?
When will people realise that half the trouble with a lossy format is transcoding? Sure, AAC may sound high-quality when it's in its original format, but when you transcode it to MP3 for your MP3 player, the quality turns to shit. This is inevitably the case when dealing with lossy formats, and why I'd rather buy CDs and rip them to FLAC.
I shout 'Troll'.
Any chance of you expanding on your theories? I'd especially like to know how being a 'medical student' has any bearing on whether you're talking rubbish or otherwise.
I have to admit i'm surprised that aac was considered worse than mp3 at these bitrates.
I'm sticking to musepack. I've got 23000+ tunes (1700 albums-ish) on my home server, but can only casually find ~4-5 tunes which seem degraded from the original. Hardware support would be nice, though.
I can tell you're a medical student and not a doctor, because most doctors are much more realistic about the limits of their knowledge. "Scientific" limits on the capabilities of biological systems are often wrong because of some overlooked or unknown factor.
A famous example of this is that for many years scientists could not work out how bees could fly. Their wings were too small, muscles too weak and bodies too heavy. It turned out that bees were able to use previously unknown aerodynamic effects to generate more lift than our previous "knowledge" allowed. Another example is that many birds of prey have visual acuity better than the laws of optics, applied to their eyes, would seem to permit. It turned out that the visual signal processing in their brains is so advanced that birds can actually 'see' features that are below the resolution limit of their eyes.
Similarly, we shouldn't be too dogmatic about what humans can and cannot hear. MP3s (and presumably AACs) compress music by suppressing parts you "can't" hear, not because they're outside your range of hearing but because the brain, assuming those parts should be there, fills in for them even when they're absent.
But it may be that you can't hear something consciously but still tell that it's not there.
For example, there was a news story a week or so back showing that people could somehow tell when a picture had changed by the removal of an item in it, even though consciously they could not explain what the difference was - it just 'felt different'.
So, if someone claims to be able to tell the difference between 1 128Kb AAC and a CD, test that claim in a double-blind experiment. Only when he fails the test can you say he was imagining things.
The author of this post asserts his moral rights.
It's either that, or "Damn it, Jim, I'm a doctor, not an audiophile!"
It is clear you have no idea what you are talking about. Just because you can't tell the difference does not mean others can.
The people who are "able to tell" just happen to have more sensitive hearing. I'm probably not one of them, but I have known several, including someone who cannot listen to CD's because there is a whine on all of them associated with the digital nature (this same guy does not like going into Radio Shack because of the noise made by their security system.)
Just because you are not a sensitive-eared audiophile does not mean everyone has the same cloth-ears as you do.
Don't blame Durga. I voted for Centauri.
Did you calibrate the flux capacitor?
If Jesus wants me it knows where to find me.
You think you, can but you just can't Nemo!
There are two types of people in the world: Those who crave closure
AAC is a standard format. Perhaps you've heard of the people that made it... Dolby? Ring a bell? Just about anything doing with excelence in audio comes from them. I can see four things in my shoebox of a dormroom that has their logo on it. I also find that most of the people that are so violently against DRM (in any form) are the people who would be analy raped by the RIAA/MPAA if they raided your house. I find that the DRM used in the iTunes store is fair, and more or less barely noticeable. Don't have a player that can play AAC? Buy one or shut the fuck up. You bought a player that doesn't do what you want it to, thats no one's fault but your own. Thats like buying DVDs then bitching because your VCR won't play them. Grow up.
Viva La Revolucion! Buy a Mac!
I used to work for an auto electronics installer, and the most discerning fuckers would pay out the nose for single directional cable which sounded JUST that bit better.
I used to get my jollies installing the cable the wrong way round on one side. Not one of the audionerds noticed by listening.
Want to know how much flowery crap they can go on with? Take a look here. You only have to read the descriptions of a few of those turntables to realise these guys are as wacked out as alien abductees and the guy on the street corner who tells you every morning he has the FBI after him.
Winamp 5.02's encoder (which got a lot of help from hydrogenaudio's own Menno, a FAAD AAC-decoder developer/Ahead MPEG4 developer) wasn't included in the listening test because of a bug they found before testing.
Too bad, too. I would've loved to have seen how it compared.
As a physicist, I'd just like to draw everyone's attention to the error bars on these charts. For the majority of the tests, it's possible to draw a horizontal line through the 95% confidence intervals of nearly all the points.
Hence, the conclusions declaring clear winners/losers in these cases are invalid. If 99% confidence intervals were used (which gives a better statistical test), I feel that no clear winners or losers would be drawn.
Be careful with these sort of studies - even though the author has used confidence intervals, he has failed to use them to infer the proper conclusions.
That said, it's awfully nice to see error bars on this sort of website. Simple data points give such a false sense of precision, I find...
I think you have an excellent point, and said it well. Unlike certain EE trolls further up the thread line.
Don't blame Durga. I voted for Centauri.
"AAC is a standard format. Perhaps you've heard of the people that made it... Dolby?"
The original DivX is a standard. Perhaps you've heard of the people that made it: Circuit City?
The "78" record album is a standard too, I guess, but it is not THE standard.
"I find that the DRM used in the iTunes store is fair, and more or less barely noticeable"
It's far from fair, since it requires the kludgey solution of burning to CD and then ripping to an actual usable format in order to make use of your OWN files on your OWN machines.
"Don't have a player that can play AAC? Buy one or shut the fuck up."
No, I'd rather buy one that uses a standard format.
"You bought a player that doesn't do what you want it to, thats no one's fault but your own. "
My non-AAC player does what I want it to, thanks. There is no need for DRM (or DRD: digital rights denial).
"Thats like buying DVDs then bitching because your VCR won't play them"
No, it is like having a DVD player and a VCR player, and then bitching when someone comes out with an unnecessary non-standard format (imagine Sony Gamma-Max) that no-one needs. Use the standard formats.
"CircuitCity's DIVX and the DivX codec are two completely different things"
Of course. That is why I called it Circuit City's original DIVX (to show that I was not referring to the codec).
Bollocks! BUT...
If I listen to an MP3 or AAC file on my computer with its sound card and speakers (SB Audigy, Boston Accoustics) I can tell the difference between the same (160kbs) MP3 file and a (128k) AAC - the AAC sounds better. I can't tell the difference between the AAC and a WAV file however.
If I move up to my ($$$$) home stereo then I can easily tell the difference between the compressed and non-compressed versions of the same song. AAC still sounds better to me than MP3 however.
The difference here is money and environment, my office is a noisy place with all the computers etc running. My listening room is quiet and I spent a lot of time setting the stereo up so that its at its best.
I have not looked at OOG or any of the other formats so I can't comment on the relative merits of them.
On a moderate audiophile system (under $10K) there is a clear difference difference between an AAC encoded file downloaded from itunes (and then burned onto a CD with itunes) and an original CD. I spent the money to download songs I already owned in order to make a comparison. I do not have great sensitivity any more -- I'm 41 -- but there was no mistaking the lack of "fullness" in the AAC, particularly at the high end, with instruments such as a violin. True, my test was not double-blinded, but the difference was obvious. That said, I continue to purchase music on itunes. I simply avoid purchasing music that is more sensitive to the encoding.
1) Most people can't tell the difference between formats that are similiar in performance.
2) Some people actually can tell the difference.
3) Some people are just posers who can't tell the difference but say they can.
4) Lastly, most people don't really care as long as it is convenient to use either format.
Well, there's spam egg sausage and spam, that's not got much spam in it.
Most of the complaints I've heard registered about the iTunes Music Store 128 Kbps format isn't that it sounds like crap compared to other AAC implementations. The major complaint is that it not only falls far behind Apple's claim that it sounds indistinguishable from the original lossless CD, but it also fails to sound even as good as MP3 with a decent encoder like LAME using --alt-preset standard or OGG at medium quality.
I understand Apple trying to keep filesizes to a minumum, but in these days of 3.0 Mbps DSL links to people's apartments and storage prices at absolutely mind-boggling low price points, their logic is becoming less and less understandable with each passing month.
AAC actually sounds like a well-developed and efficient lossy format but let's up the bitrate a bit especially when the price of a physical CD with all the artwork and liner notes along with lossless tracks and the ability to rip them to a lossy format for portable use is only a few dollars more, and in some cases the same price, than an album on the iTMS.
I had all of my CDs ripped to 192kbps MP3. When iTunes came out with AAC, I did a bunch of rip testing. I ripped from Donald Fagen's The Nightfly in a bunch of formats and bitrates. I found, for my personal preference, that 128kbps AAC was at least as good as 192kbps MP3, if not better. So I reripped all of my CDs to 128kbps AAC and got more songs onto my 5GB iPod. Now I'm on to ripping all of my old vinyl to AIFF, eventually to end up as AAC. Huzzah!
For the chemical formula for internal combustion? No. Likewise, I wouldn't go to the local audiophile shop to ask them about audio engineering-related issues. After being accosted by about ten salespeople in ten minutes at a local audio store that sells everything from Sony ES, to Krell, Wadia, Sunfire and the like... I caught a sales rep in a bold-faced lie. I was looking for a receiver without many bells and whistles, and he tried steering me towards Denon. When I asked why Denon is "better", he replied, "Because they focus solely on making audio components unlike Sony." I chuckled and asked him to explain to me the funadamental difference between the sample & hold buffers on a Sony DAC vs. a Denon DAC... Naturally, he had no clue what I was talking about. The "double-blind" survey is somewhat misleading... but that being said, it's clearly not measuring which format is superlative... it's only measuring people's perceptions. And people were pretty much even on those various formats. The study in question just shows that people cannot consistently tell the difference between AAC formats. Now, I've read articles in audiophile magazines that insisted that SACD (Super Audio CD) was brilliant in comparison to CD. And every one of those articles was a load of crap. Fundamentally, even the most "discriminating" audiophiles cannot tell the difference between 16-bit, 44.1kHz PCM (Pulse Code Modulation - e.g. AIFF, WAV, in the computer world) and the 1-bit, 2.7GHz DSD bitstream of SACD... nevermind the minute differences betweeen various AAC-enabled codecs. Hell, I would challenge anyone to be able to tell the difference between 16-bit PCM and MPEG-4 AAC. The AES (Audio Engineering Society) has stated that MPEG-4 AAC is perceptibly indistinguishable from uncompressed 16-bit, dual channel PCM (e.g. CD-DA spec audio).and I would wager any experienced audio engineer's pair of ears (my own included) against any consumer "audiophile" any day of the week. My advice to the idle rich? Don't buy the $45,000 pair of speakers... instead buy yourself better hearing and some common sense. My personal preference? MPEG-4 AAC. As a content creator intensely familiar with a variety of media standards including AES, NTSC, ISO, ITU-R/CCIR, etc. I believe MPEG-4 w/AAC (not Quicktime MPEG-4, mind you, but straight MPEG-4) is the superlative format for compressed audiovisual media. However, for critical listening, only uncompressed audio is the way to go. The general rule of thumb is that higher bitrates are preferable over higher sampling frequencies. Frequency response roll-off is what you want to avoid. But in order to support the higher bitrates, you need a D/A Converter (DAC, Digital-to-Analog Converter) with an effective sample-hold buffer that can crunch the necessary data to make an accurate conversion of the digital source. That being said, I'm going to begin digitally remastering my own compositions soon... and go straight from the 24-bit master to a 24-bit multichannel DVD-Audio format. Why? Even an audiophile deafened by the sound of their money burning a hole in their wallet can actually tell the difference between my 24-bit master recordings and the dithered 16-bit CD audio.
I would like to see a graph or two comparing AAC, MP3, WMF, and OGG.
All that knowledge and you still can't buy yourself a paragraph or ten....
Being a medical student who has a particular interest in this stuff, you have to know that due to compression method AAC, MP3, ATRAC, etc generates artifacts during compression.
I mean due to "harmonising".
Furthermore, there exists some "dynamic range compression"
So I have to tell that:
a) if you are listening in APPROPRIATE conditions and on APPROPRIATE sound system (mean amplifyer&speakers&QUET room) you easily can distinguish compressed from flat by dynamic range. Possibly you can't tell what's difference is, but you CAN hear it.
b) it's not so hard to generate a soundwave that will compress very bad (you easily can point difference) at any bitrate.
Example: get audiotest CD, compress it, listen to what you get.
I have to admit to being puzzled as to why people spend so much time and energy trying to determine the relative merits of lossy formats.
.mp3 format with iTunes. The first recording I compressed, using some middle-of-the-road "high-quality" setting, happened to be a recording I liked because of the warmth of the violins. Remember, this is an old LP... digitized on a $250 consumer-grade CD recorder. To my utter astonishment, I could instantly tell the difference. After some experimentation, I upped everything to the max, encoded at 256k bits/second... and could still tell the difference.
.mp3 at 256k bits per second, that tells me that the difference in quality is NOT in some rarefied, golden-ears, territory. It's like the difference between a CD and FM radio.
I find the music I've downloaded from iTMS perfectly acceptable; ditto the music I hear on my car's factory-equipment FM receiver. That doesn't mean I can't tell the difference between them and better sound.
Actually, I've been transferring my LP's to CD... and recently I've been converting the CD's to
On the other hand, with popular music (e.g. the Beatles) and some classical recordings, I couldn't.
The point is, if I can hear the difference between a CD and an
So, why even bother to agonize over minute differences in an imperfect format when a) upping the bit rate does far more to improve quality than fussing over which format is best; b) the mileage varies so much depending on program material; c) they're obviously inferior to CD sound to begin with?
Isn't it a little like arguing over which electrically-recorded 1950s 78's sound better... RCA or Columbia?
"How to Do Nothing," kids activities, back in print!
I'm assuming slashdot will screw up again and post with my real name, rather than anonymously. Yay.
In this analysis he presents the results of an ANOVA (Analysis of Variance). This reminds me of the saying: "If your only tool is a hammer, every problem looks like a nail". The tool the author is using is ANOVA and so he is trying to force the data into that form. Hovever, the assumptions of any ANOVA is that the data is independent, normally distributed, and has constant variance. The response ranges from 1.0 to 5.0. I haven't taken the test myself and do not know if users were allowed to select non-integer values or not but even if they were we can see from the graphs he does present that most of the responses were near the upper bound of 5.0. This type of response is clearly not normally distributed. ANOVA is faily resistant to departures from normality but one would need to fully explore the degree of the departure before placing any weight to the confidence intervals presented. My gut feeling here is that it is highly skewed and will present confidence intervals smaller than what they should be (data is forced to be artifically close due to the upper bound and having so many people report values close to that upper bound). The data can probably be viewed as independent but it must be recognized that this is an assumption. Constant variance departures may be a problem as higher responses are less variable than middle responses (due to the upper bound again). It would probably be much better to use a non-parametric test alternative to ANOVA such as a Kruskal-Wallis. Scope of inference: This is not a random sample from any population and as such cannot be interpreted to represent anything more than the perceptions of the respondants themselves. -chris
"Easy Listening
Results: iTunes wins, with Nero closely behind it, more or less tied. Faac is tied with Nero, and Compaact! and Real are tied just below Faac."
"House (Electronic/Techno)
Results: iTunes and Nero tied at first place, Real and Compaact!tied with Nero, and Faac tied to Real and Compaact!."
They were like that. Did we really need a play by play? Did he think we wouldn't be able to "decipher" these "complex" graphs?
...
"The greatest obstacle to discovery is not ignorance - it is the illusion of knowledge." - Daniel Boorstin
People agonize because they want the best quality / size ratio. for example if aac encodes at 128 Kbps as well as mp3 at 192 Kbps you can fit more tunes on you harddrive in the same space and be happy. This isn't critical on computers with they're large hard drives, but for portables] players it matters. People also don't want to rip all there CDs multiple times.
In someways your right, people should pick a bit rate/format that works for them and not worry about it. but this is slashdot..
The Mod today obviously is one of five that is pissed the iPod doesn't support Ogg. I was just surprised not to see someone outline the 'benefits' of Ogg before my comment. I guess good humor isn't appreciated..hehehe.
"It'll destroy you if you try to make it mean anything to anyone but yourself." - Henry Rollins
You were playing an AAC file on your CD player?
Thanks for sharing that review. What a bunch of nutjobs!
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
" The odds of us having a false positive in one of those graphs is around 40.1%. "
That should read "The odds of having a false positive among the tests on any one of those graphs is around 40.1%"
Integrate Keynote and LaTeX
You, sir, are most certainly not aware of where you are posting that statement. On /., there is little to no precident for needing knowledge of any technology to authoritatively comment on it's merits.
You know what?
you hit the nail on the head there. MP3 allow me to 'borrow' other peoples ripped music as well. I don't give a rats what the quality is like, I just want the free music.
It's pretty apparent to me when the tracks I've encoded as AIFF come up on my playlist as opposed to my AAC ones (until there's flac AIFF is fine cuz disk space is cheap). The big tell is that the top end gets a lot more clear and articulate. I'm pretty sure that AAC has a tendency to cut off some of the higher harmonics and notes. It cuts from all ranges but these are the easiest for me to notice. That and the lack of richness in super-low lows.
Photos.
You might find the graphs for a previous listening test interesting if you want to see how AAC stacks up against other codecs.
For good reasons, the posters on Hydrogenaudio don't take kindly to people making unfounded assertions about which codecs are better, so if you're going to argue with them, think twice and ABX first. You will be, after all, arguing with many audio developers, e.g. people who make contributions to LAME, people who've tuned the Vorbis encoder, and a surprising number of people who work for Ahead (makers of Nero, of course).
Just a minor detail to mention here. Dolby licenses two different versions of their AAC codes. iTunes, when encoding for end users, uses the Dolby Consumer codec (affordably licensed by Apple in Quicktime 6). The Itunes Music Store uses the Dolby Professional codec (which would not be affordable to license in iTunes). Thus, AACs coming out of the iTunes Music Store have a higher quality at the same compression rate than the same songs you rip and convert on your own copy of iTunes.
"It is our blasphemy which has made us great, and will sustain us, and which the gods secretly admire in us." - Zelazny
These kinds of tests comparing codecs always seem to be something involving playing two versions of the song and asking someone which in their opinion sounded better. Isn't there a more quantitative way to measure the effect of the lossy compression? For instance:
In other words, whichever codec introduces the least error into the track in a closed loop encode and decode test did the best job of faithfully reproducing the original signal. No subjective human testing required. You might have to tweak it a bit (say, sum the squares of the error or something) but would an approach like this work to settle the codec debates, or is there a fundamental flaw in this technique?
I agree with you 100%, most audiophiles are deluding themselves. But why do they do it? In fact, why do people constantly claim that x, y or z sounds better to them than a, b or c (usually a, b and c being some vanilla variety of something, be it equipment, encoding formats or what-have-you). It's ego, I reckon. They want to be able to claim that, even though the differences are small, THEIR ears are better than the average Joe's. They just want something to hold on to and be superior about. That's all. They just want one, tiny little element of their otherwise unremarkable lives to stand out from the crowd. Even if by doing so they often prove that their brains are generally inferior.
"I find overall AAC is superior to MP3, and that's what I have my songs as."
Thats exactly what the previous poster is saying.
"However, saying a 192 AAC == 128 MP3 is a bit faulty."
No! no! no! thats not what the poster said, you've just made that up. This is what the poster said, and you should know, because you quoted it:
"I found, for my personal preference, that 128kbps AAC was at least as good as 192kbps MP3, if not better."
Moderators, do your job and mod this foolish reply down.
"My cat's breath smells like cat food." - The Tao of Ralph Wiggum.
Slightly metalic, with a hint of a whistle and definately less bright
---
Live Long & Prosper \\//_
CYA STUX =`B^) 'da Captain,
Jedi & Last *-fytr
I have looked at these sorts of test results before, and used to take them as the truth. That was before I started taking a Design of Experiments grad class, and have some evidence to the contrary. For what it's worth, I'm the top performer in the class right now.
The issue I have is with the error bars. These are the vertical lines above and below the mean of each encoder. Like the beginning of the report says, "One codec can be said to rated better than another codec with 95% confidence if the bottom of its line segment is at or above the top of the competing codec's line segment." This is very much true for these sorts of statistical tests -- if the error bars overlap, that indicates that the means of the two groups are statistically identical. One could always adjust their confidence interval to a lower percentage, but 95% is quite often the standard.
Note how many of the plots in this test have overlapping error bars. In the first plot, for example, all of the encoders tested have overlapping error bars. The results drawn from this plot should be that no encoder was measurably different than any other encoder -- not that iTunes won, like the results say. (Note: I own a Powerbook G4, and am typing this post on it right now, and I love Apple. I just don't like bad statistics, that's all)
The results given in many of the plots are based strictly on the means of the samples, and not the error bars, which are actually more important in this case. Do not trust them. Interpreting the plots with the logic stated at the beginning of the article is the only statistically sound method (that I know of). I hope this sheds some more light on these tests...
Slashdot's first reaction to VMware
This only means that you don't have a good enough stereo!
Treehugger? Treehugger... Treehugger!
Speak for yourself. I am also a medical student. Before I entered medical school I played and recorded professionally. I was taught in medical school the "limits" of human hearing. I was also taught that there is no absolute. My personal experience is that many professionals (and likely others) can hear lower and higher than what is generally accepted. I KNOW I can and I have worked with many others who can. It is just silly (and sometimes dangerous) to make sweeping statements about anatomy/physiology; i. e., "The Long Thoracic nerve is always exactly right here" or the ever popular, "It is impossible for this patient to feel pain with this much (drug) on board". The issue of frequency response also neglects the effects of harmonics. All those forces add up whether heard or not and affect the overall audible sound. Play with a high pass and low pass filter with a good system and you will "hear" the effect of missing frequencies even if you can't "hear" them.
"I didn't spend six years in Evil Medical School to be called 'Mr.Evil,' thank you very much!"
All this fussing over miniscule differences in quality is plain stupid. I'm yet to hear a stereo system that could make me think that the performers were actually in the room with me - or even come close (at least for reproductions of acoustic material - electronically generated sounds can of course be reproduced convincingly). This is like arguing over which of two different lumps of shit is actually the better gourmet meal.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.