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Public AAC Listening Test @ ~96 Kbps [July 2011]. 277

Posted by timothy
from the listening-for-artifacts dept.
The folks at the Hydrogen Audio Forums have for years been benefiting the world with their patience, technical skills, and hyper-focus on sound quality, by comparing the real-world sound of various codecs and bit-rates for audio encoding. Under the scope for the latest public listening test (slated to run until July 27) are the following AAC encoders: Nero 1.5.4; Apple QuickTime 7.6.9 true VBR; Apple QuickTime 7.6.9 constrained VBR; Fraunhofer (Winamp 5.62); Coding Technologies (Winamp 5.61); and ffmpeg's AAC (low anchor).
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Public AAC Listening Test @ ~96 Kbps [July 2011].

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  • FLAC (Score:3, Interesting)

    by ThePhilips (752041) on Sunday July 24, 2011 @07:19PM (#36865968) Homepage Journal

    I'm staying mostly with FLACs. Works for me. The difference between AAC/MP3 and FLAC (and CD player *) my hi-fi allows to hear quite clearly.

    (*) Source for AAC/MP3/FLAC is the Squeezebox Touch (via DacMagic) and when compared to the CD player, the difference of sound quality is noticeable. Not out right bad (that would be Squeezebox w/o DacMagic), in fact quite OK, but still far from the proper hi-fi CD player.

  • Re:What? (Score:4, Interesting)

    by Skarecrow77 (1714214) on Sunday July 24, 2011 @08:47PM (#36866606)

    I too had this same question awhile back. Why doesn't HA test commonly used codecs at, say, 192kbps or 256kbps?

    The answer? the tests fail because nobody can tell the difference. they make for very boring results.

    they run the test at 96kbps because they get usable results. people over a wide range of sound systems and hearing conditions can provide usable responses.

    What would you do with that data? hard to say. you can't really extrapolate that, say, if codec A is better than codec B at 96kbps, the same will hold true at 192kbps. In fact, I've seen the direct opposite of that in past HA tests, where various codecs trade the lead depending on bitrate.

    So "who is 96kbps for?" I don't know. but "why test 96kbps?" that's easy.

  • by evilviper (135110) on Sunday July 24, 2011 @10:47PM (#36867146) Journal

    If you can reliably tell the difference in proper blind testing, you are likely have better hearing/perception than 99.9999 % of the population.

    This is not true.

    Frequency-domain codecs have known artifacts that CANNOT be eliminated. Pre-echo is probably the best-known example. A sample with heavy percussion or other complex impulses (like audience applause) will stand out like a sore thumb... Audience applause is one of the standards dating back to the 70s when human audio perception / lossy audio compression research was first beginning. Now applause and percussion samples are often omitted entirely from codec testing, because those paying for the studies just want some amazing, if fake, numbers for their brochures... these are the amazing 3X compression improvements you hear advertised. (See DVB+ marketing nonsense).

    Modern audio codecs don't even try to sound indistinguishable from the original. The very earliest codecs developed (by AT&T, Philips, etc.) fit that need so very well that there's very little room for improvement in that area. Instead they focus on sounding good (not perfect) in low-bitrate encoding, and the old codecs (like MPEG-1 Layer 2) simply continue to be used by broadcasters, and anyone in-the-know. Ever wonder why there's no "AC-4" codec in development?

    To suit modern codecs that don't try to sound like the original, testing methodologies were changed entirely, and you'll rarely hear a mention of this fact, even when marketing folks go and foolishly compare results from recent and 30-year-old tests using the different methodologies. Look-up some terms like MUSHRA and Perceptual Entropy.

  • Re:FLAC (Score:3, Interesting)

    by Velimir (1680794) on Monday July 25, 2011 @12:38AM (#36867656) Homepage
    I heard the difference between an iTunes-encoded 320kbps MP3 and FLAC in 2/7 samples I used. This is through ABXing and using statistics. Granted, these samples were chosen as good examples that show differences between lossy and lossless. I wrote up a series of blog posts on it here: http://www.vel.co.nz/vel.co.nz/Blog/Entries/2009/8/21_ABX_of_Lossless_versus_MP3_-_Part_3_-_Results_and_Discussion.html [vel.co.nz]

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