Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
Music Media

AAC Put To The Test 353

Posted by timothy from the musical-ambitions dept.
technology is sexy writes "Following the increasing popularity of AAC in online music stores and the growing amount of implementations in software and hardware, the format is now being put to the test. How well does Apple's implementation fare against Ahead Nero, Sorenson or the Open Source FAAC at the popular bitrate of 128kbps? Find out for yourself and help by submitting the results. You can find instructions on how to participate here. The best AAC codec gets to face MP3, MP3Pro, Vorbis, MusePack and WMA in the next test. Previous test results at 64kbps can be found here."
This discussion has been archived. No new comments can be posted.

AAC Put To The Test More

AAC Put To The Test

Comments Filter:

  • i prefer just to steal the music (Score:5, Funny)

    by Anonymous Coward on Monday June 09, 2003 @07:48PM (#6157105)
    this makes the format rather irrelevant.

  • crap in, crap out (Score:5, Interesting)

    by larry bagina ( 561269 ) on Monday June 09, 2003 @07:53PM (#6157137) Journal
    just remember, every codec depends on the quality of what it is encoding. I haven't heard any AAC encoded music myself (i use uncompressed wav or 256khz mp3 myself), but Apple allegedly uses the master recordings to encode their files.

    Most mp3s or oggs you find out there are from someone's CD-Rom drive, who knows how the disc looked, or how much jitter there was. I have heard stories of people downloading songs to find a skip or two in the middle, or been an amalgam of two different files accidently spliced together.

    I'd hazard a guess that most people that encode with ogg-vorbis do a better ripping and encoding job, though.

    • Re:crap in, crap out (Score:5, Funny)

      by jpt.d ( 444929 ) <abfall AT rogers DOT com> on Monday June 09, 2003 @08:01PM (#6157192)
      256khz mp3? That is amazing, I only ever use 44khz

    • Re:crap in, crap out (Score:5, Insightful)

      by Guppy06 ( 410832 ) on Monday June 09, 2003 @08:58PM (#6157522)
      "I'd hazard a guess that most people that encode with ogg-vorbis do a better ripping and encoding job, though."

      Only because right now you'd have to know a thing or two about the intricacies of digital music to have ever heard the phrase "ogg vorbis." If a big on-line music player were to standardize on this format instead of MP3 and it too becomes the common man's format, you can be sure the quality of ogg files will go down just as well.
    • I have heard stories of people downloading songs to find a skip or two in the middle

      You can probably thank iTunes for that- I had numerous problems with encoding my CDs. Songs has skips, and more commonly, ended early- often by more than 15-20 seconds. It was extremely irritating.

      Curiously, I never had such problems with Xing's AudioCatalyst, an awesome encoder for the Mac(it was, and I think still is, the only encoder for the Mac that can do live encoding from line-in). AudioCatalyst was also exceed

      • Re:Thank iTunes for the skips etc. (Score:5, Informative)

        by cide1 ( 126814 ) * on Monday June 09, 2003 @09:34PM (#6157763) Homepage
        I disagree on the 160 vs 256 kbps statement. I listen to mostly rock and punk, so I took a Thursday song, which is kindof in the middle of the two genres, and encoded it at 32, 48, 56, 64, 96, 112, 128, 160, 192, 256 and 320 kbps. I wanted to encode my whole CD selection (350 cds) at a bitrate that I couldn't hear the differance, and a bitrate that I could stream at decently. For streaming, 56 was the magic number. Any less and it sounded like crap, any more, and my DSL line couldn't host 2 streams at once. For music, 192 was good, but I could still hear the mp3 compression. I find that bass tends to get distorted in mp3s, and once I went to 256 this seemed to go away. I did all these tests with an audigy2 under windows XP, using Lame with q=9. Playback was through the Infinity HTS-20 Speaker System.

      • 160 Kbps MP3 NOT very good! (Score:5, Insightful)

        by benwaggoner ( 513209 ) <ben.waggoner@micr o s o ft.com> on Monday June 09, 2003 @09:56PM (#6157888) Homepage
        Over 160? Maybe you've been to too many Megadeth concerts or something, but 160 Kbps is quite audibly lossy in my experience. Now, I'm fussy about encoding artifacts, but 160 is the lowest I'll use for listening to on headphones on an airplane. It has to be at least 192 for me to not find artifacts distracting while listening on a good stereo (Paradigm Active/20 reference monitors attached to my video editing rig, in my case, self-powered with all XLR signal routing from the jukebox machine. I grant this is overkill for the casual listener).

        Personally, I encode my library at 320 Kbps Normal Stereo without any filtering. This is overkill for listening, but that's enough data that I can recompress to another, more portable format like AAC on an iPod without windup up with a audible multigeneration artifacts.

        All things being equal, I'd use FLAC, but I really really like the iTunes interface, and 320 MP3 is the best format it has historically supported. It now does 320 AAC, and I'm toying with switching to that (although I haven't yet, since the files won't be quite as widely interoperable).
        • Yep!! I encoded my entire CD collection at 192 bits, and I don't waste my time listening to anything less, if I can help it. I find it maddening that most people still encode at 128 bits and think it sounds "good enough". It only sounds ok on cheap speakers, or perhaps even moderate priced speakers + some audio processing enabled to "enhance" the sound.

          Whenever I listen to 128-bit MP3s through my set of studio monitors, they sound "thin". Even in my car (I have a Rio MP3 car player), with Diamond Audio
      • an awesome encoder for the Mac(it was, and I think still is, the only encoder for the Mac that can do live encoding from line-in).

        Nope. SoundJam (which was ironically the basis for iTunes) could do that as well.
    • I can understand uncorrectable errors cropping up, but how does jitter affect the CD rip? When ripping, jitter itself doesn't matter jack unless you are actually loosing or shuffing bits.

    • Re:crap in, crap out (Score:3, Interesting)

      by 73939133 ( 676561 )
      I haven't heard any AAC encoded music myself (i use uncompressed wav or 256khz mp3 myself), but Apple allegedly uses the master recordings to encode their files.

      Unless you are psychic, you won't be able to tell the difference between an MP3 ripped from a "master recording" (whatever that may be) and an MP3 ripped from a CD. And unless you are an alien, a dog, or an infant, you are lucky to hear anything meaninful above 16khz, which means that 44khz sampling is plenty.

      Most mp3s or oggs you find out ther

    • Re:crap in, crap out (Score:3, Interesting)

      by evilviper ( 135110 )

      I have heard stories of people downloading songs to find a skip or two in the middle, or been an amalgam of two different files accidently spliced together.

      These artifacts are almost always the result of early P2P networks, that would download a missing piece of a file from anything that had the same name... Of course you can find these now, because even with the improvements, people often keep their old files.

      I will admit that some pops were the results of bad audio rippers, but that was in the infancy

  • An honest question - who cares? (Score:3, Interesting)

    by LeoDV ( 653216 ) on Monday June 09, 2003 @07:55PM (#6157145) Journal
    This might get modded Troll, but it's an honest question. Whenever I rip a CD, I encode it into mathematically loseless MP3s, and with the cheapness of disk space these days, I can't stop being amazed at how many people don't do the same. If the quality can be compressed into something loseless from the original digital medium (the CD), then who cares if AAC sounds better than OGG sounds better than WMA sounds better than MP3 at 64 kb/s?

    Please enlighten me, I'm actually, honestly, curious.
    • CDs = expensive. mp3s = free!
      Disk space = cheap. Bandwith = expensive.

      There you have it.
    • Same here. I bought 2 250 GB hard drives, and just encode to FLAC. 91 albums (so far) = 26.3 GB. Back up to DVD. Basically, movies today are to music a few years ago: still need to compress em.

      I expect by late 2005 I'll have a couple of terabytes and just rip movies unocompressed too.
      • Um, have you ever done raw video work?

        At 190MB per second of 1920x1080 24fps (1080p HDTV standard) 16-bit YUV 4:2:2 video, even if you have a TB (~1024 GB), saving just the LoTR-FoTR (178 minutes) would require ~1.9 TB. And that's JUST the video...audio not included. Now granted, perhaps you didn't mean uncompressed at mastering quality, but 1080p is an eventuality and appears to be THE emerging mastering standard for film.

        You'd need several terabytes to store more than a few movies at production quali

    • Re:An honest question - who cares? (Score:5, Informative)

      by markv242 ( 622209 ) on Monday June 09, 2003 @08:05PM (#6157229)
      "...I encode it into mathematically loseless [sic] MP3s..."

      Not possible. MP3 by its very nature is a lossy encoding scheme, hence there will always be artifacts when you pass the audio through the encoder. You may not be able to hear the quality change (even after passing the files over and over and over through the encoder) but you will be generating noise.

      As far as your original question, it all comes down to file portability. It takes people a bit longer to send a 65 meg wav to their friends, compared to a 6.5 meg mp3.

    • Well it matters because some people are buying shitty 128k aac file from Apple (a LOT aparantly, they have sold almost 4 million tracks already). I too rip to high quality mp3 (~220kbps VBR mp3's from LAME which passed tripple blind with wav and ogg) but I guess it's usefull to know what quality you can expect from this service since Apple will be coming out with iTunes for windows later this year and bringing their online service to the masses.
      • It looks like they're working with 16-bit source, not the 24-bit source that most of the iTunes AAC files are ripped from. So this test, while certainly very interesting, won't be useful to determine the iTunes music store quality.
        • The quality loss in dithering 24->16 is much less than the quality loss in doing a lossy encode to 128kbps AAC, by at least an order of magnitude.
          • Oh, it certainly won't be a night and day difference. But it is a factor. When doing a FFT or any transfer into frequency domain, rounding errors are always a significant factor when delivering with the same precision as the source. I imagine this would matter more for content with a high dynamic range like classical, and less for typical pop/rock content.

            This is of course an emperical question. A good test would be to take a 24-bit source file, and encode it to AAC-LC in QuickTime in Better and then Best
      • It doesn't sound like you use a Mac or the iTunes Music Store, so why do you say the AACs from Apple are shitty?

        There are at least three distinct things to keep in mind:
        MP3s encoded from your music using LAME at 220kbps VBR is one quality
        AACs encoded with Quicktime 6.3 is one quality
        AACs encoded from masters, ala iTunes Music Store, are another quality

        You, in one sentence, mix all three quality levels as if they are currently comparable.

        The music from the iTunes music store is encoded from a higher quality source, and can arguably be of higher quality than even your 220kbps mp3s. It's hard to make any educated guess because I don't know anyone who's done a comparison between AAC files ripped from masters vs MP3s ripped from CD.

        The music you get from iTunes itself is based on Quicktime 6.3, and that *is* being compared and characterized in this test; this will probably illustrate the level of quality iTunes for Windows will have, and is more directly comparable to your 220kbps mp3s, but only *after* the test is performed.

        it's fine to believe that your mp3s are better, but there is no proof yet.
        • Sorry but with the exception of really horrible examples like the xing encoder most lossy encoders sound fairly comparable at an equivilant bitdepth, and to my ears everything sounds shitty at 128kbps SBR. It doesn't matter how good the master is if you are throwing away that much accoustic information, you will lose low and high end fidelity and you will most likely get compression artifacts (some encoders do a good job of avoiding the artifacts even at fairly low bitrates). Also I HAVE heard a couple exam
          • You've actually listenened to AAC files and think they're shitty :)

            Most of the population (at least 90% I bet) haven't had access to a Mac, the iTunes Music Store, or Apple encoded AACs, and thus the complaints of most folk are... probably purely speculative.

            Myself, I find AAC by iTunes is >> MP3 by iTunes, and AAC by Apple is ~> than AAC by iTunes and MP3 by iTunes.

            It is worthy to note that I'm not using LAME, so my basis for quality is already lower than yours.
          • And before MP3 you would have said that anything encoded at less that 220Kbit sounded shitty. Before CDs you might have said that anything encoded digitally at all sounded shitty.

            Technology advances. Computing power advances. In the future there may be codecs that are capable of maintaining all the fidelity of an analog master tape at 30kbit. You can dismiss that out of hand if you like, but who knows.

            Hopefully in the near future storage and bandwidth capacities will grow to allow us to store and move unc
      • What is "triple blind?"

        A blind test is where the test subjects don't know what specifically they are sampling. The researcher prepares the samples and knows what is going on.

        Double-blind is where neither the researcher nor the test subjects know specifically what is being tested. The samples are prepared by a dis-interested third party and given to the researcher and test subjects without any identification. This eliminates researcher induced errors/data fudging.

        There are no other parties to such tests,
        • I'm not sure what the original post meant, but from my days working in the psych labs, "triple blind" is a colloquial term for when the two parties are not aware of the test or the true nature of the test.

          For example, I am the researcher, and you are the subject. I am giving you the Pepsi challenge. I do not know which container has Pepsi, and which one was Coke. I administer the test. However, Xavier, the research director has been slowly increasing the temperature in the room to observe if this affects

    • Re:An honest question - who cares? (Score:5, Informative)

      by Monkelectric ( 546685 ) <slashdot AT monkelectric DOT com> on Monday June 09, 2003 @08:14PM (#6157279)
      You are grossly misinformed. MP3 and most other audio compression formats perform FFT's and throw away coefficents of the FFT that are least noticeable (thats a gross simplification).

      There *are* lossless codecs like FLAC and SHN, but they generally achieve between 10 - 30% compression.

      • DCT, actually, and the rouding and quantiziation of coefficents is lossy, yes, but nothing compared to the havoc wreaked by the psycho-acoustic modelling.

        Perhaps that's what you meant by throwing away. Losses are incurred in many places. The whole DCT and quantitize phase is very similar to jpegs', BTW.
      • There *are* lossless codecs like FLAC and SHN, but they generally achieve between 10 - 30% compression.

        Actually, the compression ratio [firstpr.com.au] for SHN is much better. As much as 74% compression can be achieved on techno and pop. I would call 55% typical for live shows from etree.org [etree.org].

        FLAC has similiar compression rates. FLAC's strengths lie in its ability to compress 24bit audio and built-in checksums.

    • I care. (Score:5, Interesting)

      by crapulent ( 598941 ) on Monday June 09, 2003 @08:53PM (#6157490)
      I care because I have not fallen for the "golden ears" fallacy. To me, 192kbps ABR lame-encoded sounds exactly like the original. I don't have super expensive speakers attached to the computer, nor do I have a fancy sound card (Creative Live 5.1.) Storing music losslessly is a waste of space to me. Sometimes I like to share music files and it's a heck of a lot easier and others are a heck of a lot more interested in trading compressed music compared to lossless files. And I can put a heck of a lot more of them on a CDR. And should I wish to listem to them in my MP3 player with limited memory, I'm sure as hell not going to use a lossless format.

      If YOU want to use up your hard drive space, internet bandwidth, and blank media with huge lossless encoded files, feel free. But don't get all smug and proclaim to not have any idea why anyone would not want to waste their resources.

      Oh, and I'm not going to touch that "mathematically lossless" crap, others have covered that already.

      • Re:I care. (Score:3, Interesting)

        by Admiral Burrito ( 11807 )

        I care because I have not fallen for the "golden ears" fallacy. To me, 192kbps ABR lame-encoded sounds exactly like the original. I don't have super expensive speakers attached to the computer, nor do I have a fancy sound card (Creative Live 5.1.) Storing music losslessly is a waste of space to me.

        The only problem is, if MP3 or AAC or whatever lossy format fall out of fashion (due to patent or whatever), you could end up with a bunch of files you can't play on the latest gadgets and software. Then yo

    • First of all, there is no such thing as a mathematically lossless MP3. I assume this was just a typo on your part though...

      The reason I use MP3 (with --alt-preset standard) over something lossless like FLAC is because they work on my nomad jukebox, sound identical to the source 99% of the time, and are on average 1/4 the size of the FLACs.

      Also, AAC is going to be used for things like digital radio, internet radio, streaming etc. You just can't do that with lossless due to bandwidth restrictions.

      Honestly

  • aahh... AAC sux, anyway... (Score:5, Funny)

    by Corporate Drone ( 316880 ) on Monday June 09, 2003 @07:55PM (#6157146)
    ... especially if they allow Miami, BC, and Syracuse in...

  • DVDA (Score:5, Funny)

    by Graspee_Leemoor ( 302316 ) on Monday June 09, 2003 @07:55PM (#6157148) Homepage Journal
    I prefer DVDA.

    What hyphen?

    graspee

  • I happen to own a Panasonic SV-AV30 (4-in-1), and music management app that comes with it has to options to save in MP3 or MPEG2-AAC. Lately, I have been transcoding the audio from mp3s and cd to 96kbps AAC and the results are surprisingly good. I play it in my car and have not really noticed a much of a difference.

    Obviously, the tracks which were bad to begin with will be bad as AACs.

    BTW, I have been playing/making music for 14 years and have a pretty good ear when it comes to tone and timbre. Hi-hats on
  • I note that in the 64 Kbps test, they used the AAC-LC encoder from QuickTime 6.0. This was a pretty darn lousy one, lacking any ability to specify a sample rate at a given data rate, and had poor quality. The current version of QuickTime 6.3 (for Windows and MacOS X), has a much improved, more flexible AAC-LC encoder, so if they did that test today AAC would likely rank higher.

    If using the Apple encoder, encode in "Better" mode with 16-bit source, and in "Best" mode with source that's more than 16-bits per sample (and hence isn't a CD rip). Support for mastering from 24-bit when running in "Best" is one of the reasons why the AAC-LC files as part of iTunes sound so good.
    • Also, I didn't mean that to be a criticism of the original test. 6.0 was the current version of QuickTime when they did the test, so it looks like a fair test for the state of the technologies at the time.

  • Pfffft... (Score:5, Funny)

    by Squirrel of Doom ( 677325 ) on Monday June 09, 2003 @08:06PM (#6157233)
    In the Billy and the Boingers' "U Stink But I Luv U" encoding test, the OOP-AAC compression scheme won by a wide margin.
    • Oh dear God, I haven't laughed that hard in a while now. I think I still have an original audiosheet that I have no way to play. If anyone actually has a rip of this, please send to jhodge@biglizard.net. Don't worry about copyright, I already own two originals. Joe

  • Sigh. Not a way to get good results (Score:2, Interesting)

    by Anonymous Coward
    Please note that the survey's host makes no claims that what he's doing is in any way scientific. Keep that in mind. The reasons why the results are to be taken with a grain of salt:

    1. There is no guarantee of clean data - the users are expected to generate their own files. MIstakes happen.
    2. The type of user who participates in this (and more likely in the OGG vs AAC coming debate) may have some predisposed bias. There is no way to weed out any placebo effects.
    3. There is no way to weed out folks who ha

    • Re:Sigh. When will people RTFA and get a clue? (Score:5, Informative)

      by Anonymous Coward on Monday June 09, 2003 @08:40PM (#6157416)
      First, read this:

      http://www.ff123.net/abchr/abchr.html

      This describes the program and testing methodology used here, which, btw, is based on widely accepted perceptual testing conventions. And yes, by the scientific community. These are the same techniques used by the scientists that do the research and development on these formats. Please note the references at the bottom of the page.

      1. Wrong, the MP4 files are already encoded and created for the user, stored in the .zip files.
      2. Wrong, the Hidden Reference (ABC/*HR*, please read the page at the first link), ensures that if the user honestly cannot tell the difference but thinks that one exists (placebo), and rates the original lower than one of the encoded versions, that their results are discarded.
      3. This is where the statistics come in. With enough listeners, the "noise" gets weeded out of relevant results. Most past tests using this methodology have been shown to provide highly relevant and fairly uniform results when all the data is factored together.

      An open call to the masses is the only way to measure the perception of the masses, and if the test is performed properly (which it is in this case), then it *is* scientific.

      Next time, please read up a little more on what is happening before jumping to all sorts of incorrect conclusions.
    • The other respondent answered your other questions sufficiently (ABC/HR is very well-established testing methodology, and your other claims are just flat-out counterfactual).

      As for asking people to submit their opinions, that is exactly what scientific perceptual testing does (and other scientific fields as well). All sorts of studies are run this way: a call for volunteers to take some test. Sometimes they pay you $20 to participate in some psychology experiment for an hour, sometimes they pay you $100

  • Heise did a public test about them one years ago (Score:5, Informative)

    by Psychic Burrito ( 611532 ) on Monday June 09, 2003 @08:36PM (#6157395)
    Read more about the test here [heise.de] (german link).

    With 6000 participants, the double-blind public test results were:

    1. Ogg
    2. WMA
    3. RealAudio
    4. Mp3Pro
    5. MP3
    6. AAC (Sic!)
    Of course, this was crazy, with AAC even behind MP3, but these really were the results...

    • Re:Heise did a public test about them one years ag (Score:5, Informative)

      by mindriot ( 96208 ) on Monday June 09, 2003 @09:14PM (#6157654)

      The complete results can be found in issue 19/2002 of Heise's offline magazine C't. Along with the online public test, some 'experts' (such as some music producers, hobby listeners, a singer, and a young student and choir singer) were consulted.

      In the online public test, the 64 kBit/s comparison yielded

      1. Ogg
      2. MP3Pro
      3. WMA (WMA9 Beta)
      4. AAC
      5. RealAudio
      6. MP3

      The parent's results were the ones for 128 kBit/s. The eight experts compared the codecs on 160 kBit/s as well, with much more varying results (not much of a surprise). But on average, the results were

      1. Ogg
      2. AAC
      3. WMA
      4. Real
      5. MP3
      6. MP3Pro (sic)

      As I said, those were an average, with the individual results of the eight experts strongly deviating. Ogg was placed once 1st, once 2nd, twice 3rd and 4th, and once 5th and 7th. (One had actually placed the plain wave reference 5th...)

  • Why not show spectrum analasys of different songs encoded into the given formats too?

    Perhaps I'm just an audio freak, but I would find that a lot more interesting than just ratings [ff123.net].

  • Some more 64 and 128 Kbit/s AAC listening results (Score:5, Informative)

    by florin ( 2243 ) on Monday June 09, 2003 @08:46PM (#6157450)
    As was previously mentioned [slashdot.org] on Slashdot, a highly regarded German magazine called C'T dedicated an article to a similar comparison of various audio compression codecs last year.

    They created fourteen different .WAV recordings containing 3 short excerpts from various CD music tracks (pop, classical and jazz) that had previously been encoded by 6 popular codecs, each at both 64 Kbit/s and 128 Kbit/s (or as close as possible for VBR-only encoders). For verification of the results, 2 of the recordings came directly from CD and had not gone through any encoding process. Because the .WAV files were all the same size, there was no way for the listener to know which encoder had been used on a particular file. Participants were asked to rank their preferences among these files. The encoders included MP3, MP3PRO, Ogg Vorbis, WMA, RealAudio and AAC.

    Over 6000 people downloaded those tracks and submitted their preferences. Unfortunately, the results of that test were only published in print and I haven't been able to find an online version of it. A few noteworthy results are below however.

    The percentages indicate how many people put a particular codec at a particular ranking:
    MP3 64 KBit/s
    1st place: 1 %
    2: 1%
    3: 1%
    4: 1%
    5: 2%
    6: 4%
    7th place: 90%

    As might be expected for the oldest codec, almost everyone agreed that the file that had been run through MP3 at 64 Kbit was the worst sounding of all. At 128 KBit however, listeners were clearly divided on whether MP3 sounded worse or better than others:

    MP3 128 Kbit/s
    1: 11%
    2: 14%
    3: 15%
    4: 15%
    5: 16%
    6: 16%
    7: 14%

    Now the AAC results. At 64 Kbit, it was ranked a slightly below average performer:
    AAC 64 KBit/s
    1: 7%
    2: 12%
    3: 17%
    4: 26%
    5: 22%
    6: 14%
    7: 2%

    What's interesting is that at 128 Kbit/s, more people ranked AAC the worst sounding encoder than any other codec in the test including MP3!
    AAC 128 KBit/s
    1: 11%
    2: 11%
    3: 13%
    4: 12%
    5: 14%
    6: 14%
    7: 26%

    Not surprisingly, the files that had been read directly from CD without any encoding steps done in between got the best rankings of all. Ogg Vorbis did very well indeed and came in second overall.

  • Sounds Better != High Fidelity (Score:5, Insightful)

    by Josuah ( 26407 ) on Monday June 09, 2003 @08:47PM (#6157454) Homepage
    This experiment is really designed to test which codec overall sounds better to the average user, for an arbitrary and inconsistent range of hardware setups, acoustic environments, and listening preferences (e.g. do I pay more attention to the primary beat or to the background harmony). I wouldn't place any value on this test other than to choose which codec I might choose if I wanted to please the ignorant consumer (a valid market, of course!). It does nothing to address how accurately a codec reproduces the artist's original sound.

    I'll put a lot more stock in the Report on the MPEG-2 AAC Stereo Verification Tests [uni-hannover.de] put together by David Meares (BBC), Kaoru Watanabe (NHK), Eric Scheirer (MIT Media Labs) for the ISO. And the other MPEG Audio Public Documents [uni-hannover.de].

  • How can this possibly be accurate? (Score:3, Insightful)

    by NeoOokami ( 528323 ) <(neowolf) (at) (gmail.com)> on Monday June 09, 2003 @08:48PM (#6157462) Homepage
    You're basically asking for a lot of people to submit their opinions. This will show you what the people who participated in it prefer, but it doesn't really reveal much in they way of actual sound quality. Everyone has their own opinions already about which audio codec is supperior. The only way you could rule out the placebo affect is to give the test blind, so that they have no clue which file is which. Even then since the results are being turned in on good faith, you have to accept that some people may simply lie about the results based on their own biases. You'd need an objectional third party to administer a test like this, and even then almost no one would agree on a third party in the end. If someone's favorite format lost they'd just bitch about the test being rigged. The only un arguable test would to actully compare the integrity of the audio to the original via an olliscope or some other device. Audio's not my area of expertise so I could be wrong there. It seems to me it's best to just not worry about it and use what you're happy with. Seeing a test like this wouldn't change my mind really. "Person A liked Audio B encoded with mp3 the best!" It just doesn't seem to hold that much sway over me.

    • Re:How can this possibly be accurate? (Score:4, Informative)

      by Anonymous Coward on Monday June 09, 2003 @09:05PM (#6157569)
      It's rather obvious that you haven't bothered to read anything about the test, the program used, etc.

      The test *is* blind, and it is based on widely accepted perceptual testing techniques. It uses hidden references (references to the original vs the encoded sample, on a per sample basis in which the user is not aware of which is which, thus if they rate the original as being worse than the encoded version, their result is discarded) as a control. The program devised has been developed by someone who has taken the time to do the proper research, read the appropriate papers and other sources, discuss the idea with developers of many different audio codecs (LAME, Vorbis, PsyTEL AAC, etc). The technique here works, and has been used many times before. It's not simply some amateurish scheme that someone who knew nothing about the appropriate sciences dreamed up simply because he wanted to find out if "Person A liked Audio B".
      • While the first post was way off-base, there are two massive problems with this testing method: first, there is no standardized reproduction equipment. If you wanted to test only the codec, the test would need to be performed with everyone listening on the same (reference-quality) equipment. Secondly, because the test uses a nonrandom sample of people rather than professional listeners, the test measures how good people think the music sounds, rather than which codec actually reproduces the original recordi

  • Re-encoding (Score:3, Interesting)

    by cmason ( 53054 ) on Monday June 09, 2003 @09:15PM (#6157665) Homepage
    For what should be fairly obvious reasons, I'd rather see a comparison of encoders re-encoding AAC to MP3. I tried this several weeks ago [slashdot.org] using AudioHijack [rogueamoeba.com] and the iTunes MP3 encoder, and the results were less than stellar.

    I imagine that an encoder could be optimized for re-encoding. I wonder if anyone is working on this. I'd like to write a program which would automatically do this conversion in my music library, but currently I can't stand the loss of quality.

    • Re:Re-encoding (Score:3, Informative)

      by cmason ( 53054 )
      So a quick google search yielded iLoveMP3 [netgate.net] which is able to re-encode encrypted AAC to MP3 using LAME. If it doesn't sound good using LAME, it probably won't sound good using anything else.

      I'll post results when the encoding finishes.

    • Re:Re-encoding (Score:3, Informative)

      by afidel ( 530433 )
      Transcoding is never recommended as there are fundamental differences in the way that different encoders (even different implementations of the same format) will decide on what data is unneeded and so you will get more and more data thrown away in each step. There is no panacea in this regard so the only solutions are to reencode everything or rip to a lossless format in first place. More and more people I know are doing the latter so that they can encode to whatever codec happens to be popular this year.

      • Re:Re-encoding (Score:3, Interesting)

        by cmason ( 53054 )
        This is obviously true. However, the reason I want to do this is to play iTunes Music Store purchased music on non-Apple hardware. I have no source material to rip from other than the AAC track I download.

        I think LAME actually does a pretty good job [cmason.com] of re-encoding AAC to MP3. At least, I can't tell the difference (unlike when using iTunes to re-encode, where I most definitely could). This is good enough for me.

        -c

  • Ogg (Score:4, Funny)

    by Anonymous Coward on Monday June 09, 2003 @09:34PM (#6157770)
    Well, I'm not using AAC until it supports Ogg.

  • Apple vs. punk rock ethic (Score:5, Funny)

    by switcha ( 551514 ) on Monday June 09, 2003 @09:48PM (#6157848)
    for a company who sold one of their first computers for $666 dollars, I'd imagine some of the bands are very disappointed in them using such a good codec.

    I mean, damn them! Nirvana didn't pay $606.17 to record Bleach so that some Corporate Asswipe could make a high fidelty copy of it!

    The Ramones would be very peeved to find all the work they put into keeping most songs to three, dingy, distorted chords, ripped to a high fidelty format.

  • Law & Order (Score:4, Funny)

    by xihr ( 556141 ) on Monday June 09, 2003 @10:06PM (#6157938) Homepage
    The African American Congress? Okay, okay, I'll be the first to admit I watch too much Law & Order.

  • My own test (Score:3, Informative)

    by withinavoid ( 553723 ) on Monday June 09, 2003 @10:15PM (#6157996)
    I did my own test [slashdot.org] of this a while back (AAC,MP3,OGG only). I didn't do 128K CBR but instead did 160K VBR.

    My results were:
    1. AAC
    2. OGG Vorbis
    3. MP3

    • Re:My own test (Score:4, Funny)

      by evilviper ( 135110 ) on Tuesday June 10, 2003 @07:42AM (#6159775) Journal
      Since you said it, it must be true...

      I did my own test a while back. My results were:

      1. Phonograph
      2. DVD
      3. Reel-to-reel
      4. CD
      5. SACD

      Yes, I'm joking, but mod me up too... I post at +2, and have a good list of fans (unlike the parent), so I must be right...

Slashdot Top Deals

There are two ways to write error-free programs; only the third one works.

Close