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  1. #1
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    Stereophile Article: MP3 vs AAC vs FLAC vs CD

    Article from Stereophile about the age old argument, with lots of graphs included.

    http://www.stereophile.com/features/308mp3cd/

  2. #2
    Senior Member opaqueice's Avatar
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    Quote Originally Posted by Nikhil View Post
    Article from Stereophile about the age old argument, with lots of graphs included.

    http://www.stereophile.com/features/308mp3cd/
    While the graphs are kind of interesting, they'd be much more so if he'd actually explain a bit more about why they look like that. It's not like it's a mystery.

    Then there are posturings like this:

    Quote Originally Posted by John Atkinson
    Given the bigger bit budget at 320kbps, the AAC codec produces a result that may well be indistinguishable from CD for some listeners some of the time with some music.
    So he's claiming that by looking at a graph of this particular test-tone he can tell whether or not these effects are audible on music. And yet he didn't bother to do a listening test - in the time it took him to prepare that article, he could have performed a whole series. That would have been interesting, because what most people really want to know is which format to use and at what level of compression. This kind of vague cursory analysis and unsubstantiated statements isn't useful.

    Frankly, I very much doubt he would have been able to hear the differences between 320 MP3 or AAC and CD (at least not without lots of practice and choosing the test track very carefully), and after all the whining Stereophile has been doing recently that wouldn't look very good.

  3. #3
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    Quote Originally Posted by opaqueice View Post
    While the graphs are kind of interesting, they'd be much more so if he'd actually explain a bit more about why they look like that. It's not like it's a mystery.
    Indeed

    Frankly, I very much doubt he would have been able to hear the differences between 320 MP3 or AAC and CD (at least not without lots of practice and choosing the test track very carefully),
    That's something I have been wanting to ask for a while. Just to be on the safe side (future proof and archival value), and since storage is becoming cheaper by the day, I have been using FLAC for quite a few years now. I can certainly spot the limitations of 128 kbps mp3s and very early in this game, I was very unhappy even with 256kbps encoded mp3s. But in the several years since I bothered to test, the encoding has obviously got a lot better. Are there any particular tracks that can showcase the limitations of todays best mp3 encodings (ie, 320 kbps or high VBR mp3s?)

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    Senior Member adamslim's Avatar
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    Quote Originally Posted by opaqueice View Post
    So he's claiming that by looking at a graph of this particular test-tone he can tell whether or not these effects are audible on music. And yet he didn't bother to do a listening test - in the time it took him to prepare that article, he could have performed a whole series. That would have been interesting, because what most people really want to know is which format to use and at what level of compression. This kind of vague cursory analysis and unsubstantiated statements isn't useful.

    Frankly, I very much doubt he would have been able to hear the differences between 320 MP3 or AAC and CD (at least not without lots of practice and choosing the test track very carefully), and after all the whining Stereophile has been doing recently that wouldn't look very good.
    Yes, a typical JA article. This is the man who won't listen to a SET amp as he considers it a tone control, IIRC.

    It would be so easy for them to do a detailed blind test using a high resolution system; they could even highlight any changes in the results generated by the listeners getting familiar with the MP3/AAC artefacts. That would have been interesting! The vague 'ooh look at those charts' tone of the article is at best pointless, at worst misleading.

    Moral: don't expect investigative reporting in the hifi press!
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  5. #5
    Senior Member opaqueice's Avatar
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    Quote Originally Posted by Nikhil View Post
    That's something I have been wanting to ask for a while. Just to be on the safe side (future proof and archival value), and since storage is becoming cheaper by the day, I have been using FLAC for quite a few years now. I can certainly spot the limitations of 128 kbps mp3s and very early in this game, I was very unhappy even with 256kbps encoded mp3s. But in the several years since I bothered to test, the encoding has obviously got a lot better. Are there any particular tracks that can showcase the limitations of todays best mp3 encodings (ie, 320 kbps or high VBR mp3s?)
    I too use FLAC, and for the same reasons haven't paid that much attention to lossy formats. However my impression is that the MP3 codec has improved considerably in recent years. One obvious thing is to use VBR (variable bit rate) rather than CBR. AFAIK VBR is always superior, and yet most MP3s don't use it.

    As for 320, my understanding is that if you know the weak points of the particular MP3 encoder you're using you can find of construct a track that will reveal them pretty easily. I've never seen a positive ABX result for 320 MP3, but I wouldn't be surprised if they exist.

    Actually I'd say a good bet is a strongly asymmetric test tone. You can hear absolute polarity inversion with that pretty easily, and I think all these lossy algorithms completely destroy phase coherency, so that should manifest itself as a subtle change in the pitch of asymmetric tones. Never tried it though.

    The best place I know of to ask questions like that is the hydrogenaudio forums - I think some of the designers of these codecs hang out there.

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    Quote Originally Posted by opaqueice View Post
    Then there are posturings like this:
    Quote:
    Originally Posted by John Atkinson
    Given the bigger bit budget at 320kbps, the AAC codec produces a result that may well be indistinguishable from CD for some listeners some of the time with some music. [/quote]

    Quote Originally Posted by opaqueice View Post
    i]That[/i] would have been interesting, because what most people really want to know is which format to use and at what level of compression. This kind of vague cursory analysis and unsubstantiated statements isn't useful.
    Geez, isn't that what he said?

    Quote Originally Posted by opaqueice View Post
    Frankly, I very much doubt he would have been able to hear the differences between 320 MP3 or AAC and CD (at least not without lots of practice and choosing the test track very carefully), and after all the whining Stereophile has been doing recently that wouldn't look very good.
    Who's posturing now?

    Quote Originally Posted by opaqueice View Post
    I too use FLAC, and for the same reasons haven't paid that much attention to lossy formats. "HOWEVER MY IMPRESSION" is that the MP3 codec has improved considerably in recent years. One obvious thing is to use VBR (variable bit rate) rather than CBR. "AFAIK" VBR is always superior, and yet most MP3s don't use it.

    As for 320, "MY UNDERSTANDING" is that "IF" you know the weak points of the particular MP3 encoder you're using you can find of construct a track that will reveal them pretty easily. I've never seen a positive ABX result for 320 MP3, but I wouldn't be surprised "IF" they exist.

    Actually I'd say "A GOOD BET" is a strongly asymmetric test tone. You can hear absolute polarity inversion with that pretty easily, and "I THINK" all these lossy algorithms completely destroy phase coherency, so that "SHOULD" manifest itself as a subtle change in the pitch of asymmetric tones. "NEVER TRIED IT THOUGH".
    Thanks for the chuckles.

    RG

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    Senior Member ralphpnj's Avatar
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    Actually that particular Stereophile article is a direct result of a recent thread on the Stereophile forum. (http://forum.stereophile.com/forum/s...fpart=all&vc=1)
    Note: I'm "jazzfan" on the Stereophile forum)

    If you take the time to read/scan through the thread you'll see that JA takes all these things very seriously and does respond to forum posts. As for the lack of comparison testing I can only guess that since JA and Stereophile take the position that files made with lossy compression are do not offer true high end sound quality, then why bother to run all those tests. And while I completely agree that in this day and age of cheap storage there is no reason to use a lossy codec, it would still be nice to know which lossy codec to use in the event that one has a need for it (think iPod).
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  8. #8
    Senior Member opaqueice's Avatar
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    Quote Originally Posted by RGibran View Post
    Thanks for the chuckles.
    Glad to oblige.

    Quote Originally Posted by ralphpnj View Post
    As for the lack of comparison testing I can only guess that since JA and Stereophile take the position that files made with lossy compression are do not offer true high end sound quality, then why bother to run all those tests.
    But then why bother with the graphs, or the article at all, for that matter?

    And while I completely agree that in this day and age of cheap storage there is no reason to use a lossy codec, it would still be nice to know which lossy codec to use in the event that one has a need for it (think iPod).
    Yeah, it would be nice. And this is one case where subjective assessments are all you need. No one doubts that 128 kbps MP3 is easily distinguishable from redbook, so the question becomes which codec and settings are the least objectionable.

    But the issue is fast become irrelevant in any case - the latest HD-based ipods have 160GB of memory, and the flash-based ones are getting up there fast. I suppose the next debate will be over the necessity of hi-res formats.

  9. #9
    Senior Member pfarrell's Avatar
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    Stereophile Article: MP3 vs AAC vsFLAC vs CD

    opaqueice wrote:
    >> And while I completely agree that in this day and age of cheap storage
    >> there is no reason to use a lossy codec, it would still be nice to know
    >> which lossy codec to use in the event that one has a need for it (think
    >> iPod).

    >
    > But the issue is fast become irrelevant in any case - the latest
    > HD-based ipods have 160GB of memory, and the flash-based ones are
    > getting up there fast. I suppose the next debate will be over the
    > necessity of hi-res formats.


    The question was moderately interesting when folks used "56KB" modems to
    download stuff. But its really moot now.

    In any environment that you will do serious listening to the music, you
    don't need to compress the hell out of it. So don't. If you are riding a
    New York subway, or in any car short of a Rolls Royce or big Mercedes,
    it doesn't matter.

    Store your files long term in something like FLAC, transcode them to
    suit your PMP to something like 386KB VBR, and be done. Further
    optimization is silly.

    All IMHO, but this is audiophiles....


  10. #10
    Senior Member ralphpnj's Avatar
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    Could someone please explain just where all the voodoo science is in the following statement (taken from the article in question):

    As a CD plays, the two channels of audio data (not including overhead) are pulled off the disc at a rate of just over 1400 kilobits per second. A typical MP3 plays at less than a tenth that rate, at 128kbps. To achieve that massive reduction in data, the MP3 coder splits the continuous musical waveform into discrete time chunks and, using Transform analysis, examines the spectral content of each chunk. Assumptions are made by the codec's designers, on the basis of psychoacoustic theory, about what information can be safely discarded. Quiet sounds with a similar spectrum to loud sounds in the same time window are discarded, as are quiet sounds that are immediately followed or preceded by loud sounds. And, as I wrote in the February 2008 "As We See It," because the music must be broken into chunks for the codec to do its work, transient information can get smeared across chunk boundaries.
    Seems to all be based on good sound reasoning and hard scientific facts not voodoo or magic. The only issue is whether or not one believes that these changes to the musical waveform are audible and if they are indeed audible then under what conditions will they be audible. After that is only a matter of determining whether or not those conditions where the changes to the waveform are audible are important to one's normal listening situation.
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