[Libav-user] does mp2 (MPEG audio layer 2) -format contain timecodes?
sgutten at ms2-gmbh.de
Mon Mar 5 15:29:43 EET 2018
Thanks again for the clarification!
>> And about „wrong mailing list“, any recommendations for the correct one?
> No questions should ever be sent there, but if you have a question
> concerning the ffmpeg command line tool (your email indicated
> this), then ffmpeg-user is the right mailing list.
Well, not really. In my original email I was (somewhat reluctantly, because maybe I wouldn’t even be capable)
offering to work on the source code and try improving that issue, that’s why I thought it might be relevant to ffmpeg-devel.
But indeed it had a question-part, but that question was more about the mp2-format, not so much about ffmpeg usage
(already assuming that with different ffmpeg-usage I cannot do anything about it),
and that’s why I eventually posted it here, on libav-user.
However, it seems that in the meantime I found a workaround that removes my need to look into the source code…
Instead of using the original command which has 4 seconds of delay:
ffmpeg -ss 4:0:0 -i bigfile.mp2 test.mp3
I’m now using the following combination of dd (on Linux, in order to cut a portion of a file) and ffmpeg without noticable delay:
dd ibs=1152 skip=600000 count=200 if=bigfile.mp2 | ffmpeg -i pipe:0 test.mp3
In my example file, my frames have a constant frame size of 1152 bytes with a duration of 24ms. So I skip 600000 blocks of 24ms which correspond to 4 hours.
This command starts transcoding without any noticable delay!
I actually think that this kind of information could be interesting for ffmpeg-devel. Or should I file something on bug-tracker?
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