Audio Compression Primer

Hack Jandy writes "For those of you with a little extra time this afternoon, check out Sudhian's primer to all things concerning audio compression. The article details everything from DRM to CRC matrixes (with a healthy dosage of Ogg)."

Comments

Is FLAC worth it?

[Megaweapon]

"FLAC is the Linux users lossless audio codec of choice"

Unless your doing some form of audio editing or "production" recording, is lossless really worth the extra size compared to a 192kbps Ogg or MP3? I usually have more problems with static from the stupid 3.5mm jack than a lossy format.

Re:Is FLAC worth it?

[pete-classic]

The nice thing about FLAC is you don't have to commit to a lossy codec or particular encoding settings. I can re-encode from the same rip every time a new lossy codec comes out, or if I decide I want more music at lower quality on my portable player, or whatever.

-Peter

Re:Is FLAC worth it?

[Jherek Carnelian]

Unless your doing some form of audio editing or "production" recording, is lossless really worth the extra size compared to a 192kbps Ogg or MP3?

300GB hard disk = $150.
Average flac compressed CD =~ 250MB
That equals 1200 albums stored on $150 of hardware, or 13 cents per CD and it is only getting cheaper.

The question should really be - for long term storage, is it really worth not going lossless? Remember, you can always convert from flac to your favorite lossy format at whatever bitrate you want, but you can never convert from lossy back to lossless.

Re:Is FLAC worth it?

[Edward Faulkner]

I keep my entire CD collection on disk as FLAC, and then transcode to the lossy format(s) most useful to me at the time (currently Vorbis to play in my Rio Karma). If I ever need a new format I can go back to the FLAC and reencode without transcoding from another lossy format.

That's exactly why I switched to FLAC as well. When you choose a lossy codec, you're locking yourself in to it. With FLAC, I can reencode to anything else with minimal effort and no transcoding loss.

My flac albums are an average of 5 times larger than ogg vorbis (quality 6). Not that bad, and disk keeps getting cheaper.

Virtually dismisses lossy compression

[Sanity]

This article doesn't seem to talk much about ogg at all, unless I am missing something, in fact, it virtually dismisses all lossy algorithms in favour of lossless algorithms which achieve only 50% compression (instead of 90% compression with lossy).

Each to their own, but I am more than satisfied with oggs or mp3s encoded at a reasonable bitrate - I think the popularity of hardware such as iPods suggest that most other people are too.

Re:Virtually dismisses lossy compression

[Anonymous Coward]

The iPod plays Apple Lossless. In fact, the recent huge up-surge in iPod popularity (4.5 million sold over this year's holiday season) follows after the release of Apple Lossless. So you just might be wrong about people's preferences, Sanity.

Re:128K should be enough for everyone

[aceh0]

FM Radio is far from CD quality hence there isnt really a need to use very high bitrate MP3s or whatever

Re:Developers?

[Anonymous Coward]

More ranting.

And what the fuck is this? The sampling rate of the sound has absolutely nothing to do with "rounding errors". There is rounding only within the sample itself, as it is quantized to an x-bit value.

This guy should take a math class.

Waste of time . . .

[barryman_5000]

Not very informative for slashdot ppl. I think we should have had an article more about code or something. I think most slashdotters understand codecs and the differences in lossless and lossy compressions. Waste of 15 minutes.

Re:Waste of time . . .

[Anonymous Coward]

No they don't. Most people still think lossless is all about quality, and the only reason to go with lossless is because you think you're an "audiophile". That couldn't be further from the truth.

Lossless is useful because it's the only proper way to archive digital music. With a proper lossless archive, you can convert to any lossy format for use in a portable music player (which I do often). You're not locked in like you would be with a lossy collection. You could re-create your entire cd collection, bit-for-bit, if you had to. You have your archive forever, and you'll never have to touch your cd collection again. That is the difference between lossless and lossy audio compression.

I still hear MDCT distortions

[ikewillis]

I've stopped liking Modified Discrete Cosine Transform-based codecs like Vorbis, MP3(+), etc. even though they (i.e. aoTuV Vorbis) consistently win in low bitrate listening tests among random listeners. Why? Well, unfortunately, I've been listening to audio encoded with this transform for so long that I can't help but hear the distortions they create, namely pre-echo (which is often described as a 'muddiness' or an 'underwater' sound) and distorted treble detail (often described as 'twinkling')

Call me crazy, but I insist that there are certain 'killer' tracks where I can hear this distortion even at higher bitrates in advanced MDCT codecs like Vorbis, namely Led Zeppelin / Rock and Roll whose drumline consists of a ridiculous number of cymbal crashes in rapid succession.

The way I see it, the future is lossless. With hard drives burgeoning to over 500GB and Fiber-to-the-Home becoming a reality within the near future, why bother saving a little extra space at the cost of degraded quality, which, the more you listen to audio compressed with a certain transform, the more likely you are to hear distortions? I think in the future we'll see a greater trend towards lossless audio compression with codes like FLAC and its ilk.

128/192 kbps is enough for everyone...

[katharsis83]

I second that.

On repeated double-blind tests on very expensive equipment, even audiophiles are unable to distinguish between CD quality and LAME encoded 192 kbps MP3 files. Those who say they are able to aren't using double-blind tests or have super-human mutant ears. If you go check over at Hydrogen-Audio (where audiophiles and people who care far too much about LAME settings hang out), most of the forum posts indicate that anything above 192 kbps is transparent even to their equipment, which is pretty above average.

On regular equipment, PC World did a small test a while ago on standard equipment: http://www.pcworld.com/reviews/article/0,aid,64123 ,pg,1,00.asp.
Their results found that ~192 kbps is pretty much transparent as well.

mp3-tech.org also has a listening test availible. On their run, they found 192 CBR kbps to be nearly transparent (*feels* different, but don't know why), and 256 kbps CBR to be completely transparent (can't tell compressed from source CD).

"The listening equipment is the following :

* Teac VRDS 25 CD reader
* MIT T2 cables
* Yamaha AX 1050 amplifier
* Denon PMA 960 amplifier (for frequencies 50Hz)
* Celestion speakers"

This test was also done a while ago on an older mp3 compression program( c. 1998), so current LAME encoding probably allows for complete transparency at 192kbps or so.

Hey! Me too!

[Just Some Guy]

I do the exact same thing, except that I keep my entire CD collection on CD. If I ever need a new format, I can go back to the CD and reencode without transcoding from another lossy format.

I've got about 350GB of lossless audio goodness in a set of nice oak bookshelves built into my wall. Considering that the time it takes to get up, get a CD, rip it, and encode it is not much longer than it takes to locate a FLACed album on my fileserver and encode it - that is, the encoding stage is several times longer than the "get up and rip the first track before starting to encode" phase - I think I'll stick with my current system.