The best target audio format may be "the best" by certain criteria:
- sound quality,
- device/software compatibility,
- file size.
Lossless formats
To achieve maximal sound quality lossless formats are recommended.
These formats support PCM (*.wav, *.flac, *.aiff, .alac,...) and DSD (.dsf, *.dff, *.iso [sacd iso]) audio stuff.
Lossless formats store audio stuff without altering.
File size compression
To reduce file size, compressed formats are used.
Compressed formats are:
- lossless: *.flac, *.ape, *.m4a(ALAC), MLP,... lossy: *.mp3,
- lossy: *.m4a(AAC), *.ogg, ...
Lossy formats
Lossy formats lose part of audio information, but have significant file size reducing.
As rule, very popular mp3 have high sound quality at high bitrates 256...320 kbps.
AAC format developers, promise better sound quality of AAC than mp3. But, I suppose, it should be checked individually for each of your audio systems.
AAC supports multichannel configuration. Though it is not so important for mobile devices, that have stereo outputs (headphones) rather.
As rule, mp3 and AAC formats have no metadata support issues.
Audiophile formats
For audiophile applications FLAC and ALAC may be recommended.
If you have DSD capable audio device, DSF file may be better choise, because it supports metadata (text and artworks).
Some of digital audio players support *.iso [sacd iso] images. However these files can contains 2 versions of single album: stereo and multichannel. It consume additional hard disk space. And it may be important for stereo mobile audio device with limited hard disk space.
The issue may be solved via extracting stereo tracks to DSF or FLAC.
Also multichannel music files may be downmixed to stereo.
Read details about audio formats and look at sound quality researching links here.
Excellent answer. In answer to your question regarding the trade off between quality and disk space, I always find that 128kbps - 320kbps mp3's offer a good balance of sound (for my portable mp3 player) and space for storage on my hdd. I have a lot of music and find 128kbps mp3's an acceptable size. The styles of music I listen to really don't improve all that much with higher bit-rates IMO. Then again there could be something wrong with my hearing, or my music :) – hardlywired – 2012-05-09T08:11:41.177
1Voted you up, but I still want to point out that different codecs for the same format (e.g. LAME vs. FrH vs. tooLAME, etc.) as well as different versions of the same codec can produce very different results. Likewise, different codecs can produce optimal results at different bitrates, and the actual compression settings you choose for each codec can also make a huge impact, as with the type of audio you're compressing. Furthermore, these perceptual tests are somewhat subjective, and different people may prefer different codecs. – Lèse majesté – 2012-05-09T08:17:38.423
1@Lèsemajesté You're correct pointing that out, thank you! Perceptual tests are subjective, but they're averaged over a number of participants, so if you're an average listener, the results might apply to you. I agree that if you're really passionate about music, you should think more carefully about which encoder to use. It's up to the OP to try different implementations. – slhck – 2012-05-09T08:24:03.523
1Also, this comparison seems to have left out Ogg/Vorbis, which a lot of people prefer for both its quality and open source status. Though the two most popular PMPs don't support it--which brings up another point. You should also consider what formats are most suited to your playback methods. At the end of the day, the difference between AAC/Vorbis/MP3 are likely to matter less than what your car MP3 player or PMP supports. – Lèse majesté – 2012-05-09T08:24:39.123
@Lèsemajesté Yeah. Same goes for video. I'm pretty sure the free / open source codecs will never see the same popularity as the MPEG/ITU standardized ones. – slhck – 2012-05-09T08:26:57.640
1
@slhck: Yea, unless you're an audiophile, then results from perceptual tests from a large sample population are probably a decent (and convenient) indicator of which codecs currently provide the best quality. But if you're really anal about this sorta thing, here are some other public perceptual tests: Hydrogen Audio June 2011 and SoundExperts.org. There used to be a site where you can perform the test yourself online, but I can't find it ATM.
– Lèse majesté – 2012-05-09T08:32:53.840@hardlywired Don't complain too much about not being able to hear a significant difference between 128k mp3 and higher quality encodings. It'll save you a small fortune in audio gear vs audiophiles chasing speakers better than their ears. – Dan is Fiddling by Firelight – 2012-05-09T12:37:14.510