[FFmpeg-user] ac3 to mp3 converting bug

Ingo Brückl ib at wupperonline.de
Tue Jul 3 12:42:47 CEST 2012

Nicolas George wrote on Tue, 3 Jul 2012 09:49:41 +0200:

> Le quintidi 15 messidor, an CCXX, Ingo Brückl a écrit :
>> I use to convert ac3 (dolby) audio files using ffmpeg linked with a static
>> version of lame to mp3 which was working fine so far. Since recently this
>> doesn't work any longer. The mp3 output file seems ok, but does contain
>> nothing but 0x55 blocks and thus is mute. A conversion from an other format
>> (like wav) to mp3 works fine, so it can't be lame.

>> $ ffmpeg -i Broadway-5.1-48khz-448kbit.ac3 -acodec libmp3lame -ab 128k -ac 2 test.mp3 2> log1

> I can see no problem with that exact command line and a fresh build. The
> output MP3 starts with 3+ seconds of silence, but so does the input AC3
> file.

> Can you be more precise about your test protocol and build environment?

Sure. What information would you need?

As stated in my other posting, I've bisected it down to commit
fc49f22c3b735db5aaac5f98e40b7124a2be13b8 and could confirm now that it
actually created the bug. After checking out to it and reverting the change
to ffmpeg.c everything is fine again. Unfortunately, this patch is big and
I'm not familiar with ffmpeg so I can't find the issue by myself, but I can
assist in whatever is needed to track down the problem.


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