[vorbis] mp3-wav-cd-audio "acoustically equivalent" to wav-cd-audio ?

[Marshall Eubanks]

>A friend of mine made the following comment in a discussion I had with
>him that on a website we adminster we should offer
>
>a) WAV or maybe shorten files
>b) Ogg as a decent reference lossy encoded version
>
>He's been trying to convince me that we should offer MP3 (in lieu of
>WAV) and possibly Ogg.
>
>The audio files are primarily vocals
>
>I am not a physics guy but his statements don't intuitively feel right. 
>Maybe he has a misunderstanding which can be clarified
>
>Regards, Yusuf
>----------------------------------------------------------------------
>regarding WAV, we used to store the masters on the disk, but moved them
>offline due to space concerns. If a user downloads the MP3 and creates a WAV

>from it, that is going to be precisely equivalent on the audio CD in
>quality. I have tested it myself in MATLAB using spectral and phase analysis

>(I am a physics guy, after all).

IMHO, as a professional physicist, he has no clue.

MP3 is a lossy encoding. That means you lose something.
At a low bit rate, you tend to lose a lot.
Just try doing this at 32 kbps stereo and you _will_
notice the acoustic nonequivalence.

Regards
Marshall Eubanks

>
>recite WAV -> MP3 -> WAV -> CD Audio is *acoustically equivalent* to recite

>WAV -> CD audio.
>
>to confirm, Perform this experiment at home (I have done so)
>
>1. recite to WAV. save as A.wav
>2. encode A.mp3 from A.wav
>3. create B.wav from A.mp3.
>4. ask someone to burn A.wav and B.wav to an audio CD (double blind -
>neither you, nor they, shoudl know which is which).
>5. listen to the CD in a standard player. You will hear zero differrence in

>sound quality.
>
>I am NOT saying,  not to make WAV available. But I am pointing out that the

>vast majority of repackagers only want to create CDs. And that they will not

>be able to improve upon the sound quality , though it is quite possible they

>may degrade it, during their own post-processing stages. We can safely
>assume that most repackagers will choose to go the easy route, and we can
>easily have a note saying "true WAV masters for many audio files are
>available for more advanced processing. Please contact Webmaster etc etc".

>
>as an aside - there are already several excellent freeware tools which allow

>you to create playlists of MP3 files and burn them straight to audio CD,
>doing the WAV interpolation for you directly. No such tools yet exist for
>OGG of course, but they too will come in a year or so (the ones I have seen

>for OGG are still quite unstable - if it doesnt come from vorbis.com, I dont

>trust it).
>
>----------------------------------------------------------------------
>
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>

Marshall Eubanks

tme at 21rst-century.com

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