Bitrate Peeling with Ogg Vorbis

Yort writes "Thought this might be interesting to some audiophile /.ers - there's been some discussion on the Ogg Vorbis lists, summarized in the most recent Ogg Traffic, about "bitrate peeling". In short, it's where you can simply "peel off" the high resolution data from the ends of an audio stream packet to come up with a smaller, lower quality stream. Brings up a number of geek-cool opportunities."

Comments

Re:Wow

[unterderbrucke]

"That may be true if it were peeling off the copyright instead of the bitrate."

I don't think you read the article, so I'll summarize it again in a more informative way:

There is a technology called "Bitrate peeling" that the Ogg Vorbis team is considering adding into the codec which would allow an audio stream's bit rate to be dynamically raised and lowered based on connection speed availability.

This would help net radio *immensely* because the cable modem users don't have to use the same 60 kbps stream as the 28.8k modem users, and the 28.8k modem users don't have to use the same 192kbps stream as the cable modem users. Also, it would decrease the cost of operation for the net radio stations that run multiple servers in order to meet the connection needs of different users.

good idea, but...

[ameoba]

Bitrate peeling is a briliant idea, and would be a major win for Vorbis if they ever actually provide an implementation of it. It's something that the format supposedly supports, but right now it's still just a hypothetical application.

Let me know when they've got something working THEN I'll be impressed

Audiophiles?

[Pinball Wizard]

So who out there is an audiophile and listens to compressed streams of music?

Lately I've been finding all I can download off P2P programs like Direct Connect and Furthurnet. Its mostly live shows, and they are all in .shn format, which is a lossless compression format that restores to the original .wav file.

These communities shun both compressed files like .mp3 and trading anything that has been released commercially. What you do get is great recordings of live music from bands like U2, DMB, Grateful Dead, etc., all ethically traded and in their full audio glory.

The audiophiles I know pretty much don't listen to mp3, ever.

Re:Audiophiles?

[pthisis]

Shorten (.shn) is not a free program (libre--it is gratis). It also doesn't compress as well as some of the other lossless codecs and as far as I know there aren't any hardware devices that support it.

I use FLAC to compress my music, which is free and lossless. It outperforms shorten on average (smaller compressed files), and is also supported by some hardware playback devices (Rio, Phatbox, some Kenwood stuff) unlike Shorten.

I play back through a Hoontech card with digital output and use an offboard MSB Link DAC III (the computer is acoustically isolated from the listening room) which feeds into a Creek 5350 integrated amp driving Vandersteen 2ce Signature loudspeakers.

I also use lossy compression for my car mp3 player--the stereo there isn't audiophile quality anyway.

Sumner

Re:Audiophiles?

[NineNine]

play back through a Hoontech card with digital output and use an offboard MSB Link DAC III (the computer is acoustically isolated from the listening room) which feeds into a Creek 5350 integrated amp driving Vandersteen 2ce Signature loudspeakers.


And we should care about this, why?

Re:Audiophiles?

[Monkelectric]

I am a certified audiophile... High bit rate mp3 are very difficult to tell from the original... however most mp3s are made by amateurs with bad encoders that are *crap*.

Before encoding my cd collection I spent a month playing with different encoders and settings to find what might satisfy my ears. I eventually settled on lame with the "new vbr method" and the highest quality settings and I've been very happy with the results. If something better comes along, I'll get my CDs out from under my bed and re-encode :) The only time I've been able to tell one of my mp3s from the CD is on albums I am intimately familiar with, i.e. the Steely Dan Box set. I have easily heard it 500 times, and every once in awhile you notice the timbre of a cymbal is just a little bit different then you remembered it.

However, something no one ever thinks about is your mp3 *player* and sound card. An internal sound card is worthless for listening to music (I use a M-Audio Delta1010 which is part of my studio setup). Also the mp3 player makes a *huge* difference. It will probably come as no surprise that Winamp is shit. I like CoolPlayer which is based on libmad -- a 24 bit integer only mp3 decoder. The extra bits are important because they reduce quantization errors during decoding, there is a noticeable difference in clarity between coolplayer and winamp. Also, standalone MP3 players tend to have better mp3 decoding because they (usually) use a DSP to decode the and DSP programmers are well aware of accuracy issues.

My point is, mp3 is tolerable for casual listening even to an audiophile *IF* it's done correctly. The problem of course is that the computer is about the *worst* place to be listening to music because its at such a disadvantage (poor quality signals, noisy electronics, bad DACs, shitty speakers).

However, your need for a higher quality signal is directly proportional to the cost of your stereo. If you have a small portable stereo, the radio is about the best quality you can reproduce anyways. The quality of mp3's is superior to what the average computer can reproduce. But If you have a 30,000$ stereo as some obsessive audiophiles do, its pretty silly to listen to mp3s on it (but you're gobbling up dvd-audio discs as fast as they are made anyways).

Re:Audiophiles?

[NickSD]

First of all, for the best quality out of the LAME MP3 encoder, you shouldn't be using those CBR modes (160, 192, etc). Use either --alt-preset standard or --alt-preset extreme for best quality. Those presets are better in many ways than the CBR modes you mentioned.

Secondly, I understand that it is hard (and sometimes impossible) to hear the differences between a properly-encoded MP3 and the original, but that does not mean it will be true for all cases. Music varies greatly, and while you may not be able to hear a difference on certain songs, there may be others where it is quite apparent. I don't think anyone can debate (anymore) that a properly-encoded MP3 using --alt-preset standard with LAME is easy to pick out. Most of the time, to most people, it will be transparent. However, arguing that people should use MP3 over lossless is a whole different ballgame.

One nice thing about lossless is that you always have the choice of converting it back to the original WAV and using that as source data for further processing. Once you've converted something to MP3 (or any lossy format) you can't go back. There are applications for lossy and applications for lossless, but I think comparing the filesizes and claiming MP3 is the way to go isn't really appropriate. Just IMHO, of course. I am speaking from the point of view that your intent is to archive your audio or something similar.

Re:Audiophiles?

[tswinzig]

Just keep in mind also that MP3 is the same type of compression than DTS & AC3 (Dolby Digital) and I've never heard someone complain about those (especially DTS).

Yes I've heard Dolby Digital compression is similar to MP3 compression. However, DTS uses very little compression, which is why it sounds better and takes up more space on your DVD disc. Check out the DTS FAQ.

Re:portables

[NickSD]

>personally, i'm converting over from 256kbps mp3 to > 128kbps vbr ogg and i'm saving TONS of space and > not really sacrificing any quality... Although OGG Vorbis is superior to MP3, transcoding from MP3 to OGG will generally lead to a noticable loss in quality. Transcoding in general is bad, but transcoding down to a lower bitrate and between two transform codecs (as is the case) isn't really a great idea... but to each their own. With hard drives so cheap these days I'd just leave the MP3s as is. Especially considering most MP3s out on the P2P networks are encoded using outdated/flawed encoders such as Blade or Xing and are bad enough as is!

Re:Peeling!

[Jucius Maximus]

"Please donate [vorbis.com] to Xiph.org, and then go listen [diff-eng.net] to some tunes. Enjoy!"

I really would like to donate, but not through PayPal. Could you please offer some other method of payment like the Amazon Honour System or Element5?

Some basic Math...

[Lemmeoutada Collecti]

Looking at your example of storing the variable bit rates as seperate files as an example, let's do some theoretical math:

Original High Quality file: 10mb
3/4 Quality file: 7.5mb
Half quality file: 5mb
Quarter quality file: 2.5mb
Total for all variations without peeling: 25mb

Or, store the High Quality 10mb original only and dynamically peel. Savings, 15mb (1.5 times more files)
No need te reencode a new file for each device (and some of us have many!)

Just FYI

Re:Handy? Nah, Perfect!

[Anonymous Coward]

wrong. it takes cpu to convert to an mp3, and you have to have the original cd to not get artifacts. it takes no intensive cpu to shave bits (just ignore a part of the stream) and yhou do not have to have the original CD.

Re:Handy? Nah, Perfect!

[rseuhs]

this is not an ogg specific killer app... substitue ogg_to_bitrate(); with mp3_to_bitrate(); and your killer app will work for the 'competition'

No, mp3 would have to be reencoded, which would make the quality much worse and would take a lot of time.

When I want to put music into my player, I want it now, I don't want to wait 1-2 hours.

Re:Alternative use..

[Jahf]

Holographic? No. Progressive (similar to progressive JPEG)? Yes.

DTS has similar system

[nedron]

The home theatre version of DTS uses a similar mechanism, allowing DTS to continue to add discreet channels and additional features while remaining compatible with older DTS decoders. Basically, the decoder ignores any information in the stream header that it doesn't understand.

That's how DTS was able to add a discrete surround channel (DTS ES) without causing problems with older receivers. Dolby can't change their header without breaking backward compatibility, which is why their extra surround channel (DD EX) is matrix encoded.