[FFmpeg-user] FFmpeg accuracy issues.

Michael Bradshaw mbradshaw at sorensonmedia.com
Wed Aug 15 20:57:58 CEST 2012

On Wed, Aug 15, 2012 at 12:46 PM, Roger Pack <rogerdpack2 at gmail.com> wrote:
>> Actually just doing a test like this (converting mp3 to mp3 over and over again):
>> $ ffmpeg -i yo.mp3 -vn -acodec libmp3lame yo2.mp3
>> yields durations like:
>> yo.mp3 (start): 50.25 seconds
>> yo2.mp3 : 00:00:53.28
>> yo3.mp3 : 00:00:53.30
>> yo4.mp3 : 00:00:53.32
>> Something doesn't seem quite right here, the same audio file appears
>> to be getting longer and longer...
> Ok no response so filing a trac.

Actually, wait a bit on that. MP3s suffer from added encoder/decoder
delays. LAME FAQ talks about it here:

So re-encoding an MP3 just keeps accumulating delays, so it's slowly
getting longer. But three seconds (the first transcode) is a very
large jump... the other ones are more consistent with LAME's delays.


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