[Libav-user] Speex encoding difference only in the very last encoded frame

Nicolas George nicolas.george at normalesup.org
Tue Aug 20 12:18:54 CEST 2013

Le duodi 2 fructidor, an CCXXI, Joe Flowers a écrit :
> When I encode the same audio file with a program I am writing that uses
> libavcodec I get a 26,372 byte Speex encoded file - FileB. BUT, 9 bytes in
> the middle of the last 38 bytes of encoded data are different between the 2
> encoded files (FileA and FileB). All of the other bytes are exactly the
> same between the two encoded files.

I would suggest to add a dump of each frame before encoding, in both your
program and ffmpeg (or just in libavcodec). I suspect something in the
padding / very end of the last frame may be different.

> What makes this weirder to me is that if I decode my Speex encoded file
> (FileB) with the other part of my program that uses libavcodec I get the
> EXACT same decoded file contents and length as I do if I decode the
> FFMPEG-encoded file (FileA) with FFMPEG.

That would be consistent with what I suspect: the difference you see would
manifest on the next decoded frame if there was one.


  Nicolas George
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