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

Joe Flowers joe.flowers at nofreewill.com
Tue Aug 20 00:20:04 CEST 2013

Hello Everyone,

When I encode a 222,000 byte, s16le RAW audio file with FFMPEG I get a
26,372 byte Speex encoded file - FileA.

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.

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.

Is this a known anomaly on the last 38 byte frame of encoded Speex data or
have I been staring at this screen for too long today???


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