Re: [linux-audio-dev] decoding mp3 files

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Subject: Re: [linux-audio-dev] decoding mp3 files
From: Mark Rages (markrages_AT_mlug.missouri.edu)
Date: Sat Jun 08 2002 - 08:12:43 EEST

On Fri, Jun 07, 2002 at 08:30:23PM +0200, Kristian Peters wrote:
> Martin Wolters <martinw_AT_atc.creative.com> wrote:
> > I expect about 1200 - 1230 added zeros at the beginning. The number of
> > added zeroes in the end can vary. There is a finite number of
> > possibilities from the mp3 algorithm (like for the beginning), plus a
> > number of zero padding samples that is depend on the size of the
> > original wav-file. (In order to fill up frames).
>
> Oh.. Not only zeros are added at the beginning. I calculated that 9024 bytes are added by mpg123. (It's not easy to determine that cause the output differs.. But I hope the number is correct.)
>
> 9024 / (channels) / sizeof(bits) == 1128.
>
> (I used a 16bit stereo wav.)
>
> I'll test other decoders. Hopefully that one will not vary.
>
> Thanks, *Kristian
>
> :... [snd.science] ...:
> :: _o)
> :: http://www.korseby.net /\\
> :: http://gsmp.sf.net _\_V
> :.........................:

When I was doing some codec analysis, I found it necessary to find the
maximum of the cross-correlation of the source and destination files and
zero-pad the files to align them. A little more work to setup your test,
but it fixes that kind of problem automatically.

Regards,
Mark
mark.rages.net

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