[FFmpeg-devel] [PATCH] Add example transcoding.c

Andrey Utkin andrey.krieger.utkin at gmail.com
Tue Feb 18 12:23:29 CET 2014

2014-02-18 11:02 GMT+02:00 Nicolas George <george at nsup.org>:
> Le decadi 30 pluviôse, an CCXXII, Andrey Utkin a écrit :
>> Besides comments, _testing_ is appreciated.
>> I have tested it under valgrind with file with mpeg4 video and mp2 audio,
>> generated with:
>> ffmpeg  -f lavfi -i testsrc  -f lavfi -i aevalsrc=0 -map 0 -map 1 -vcodec mpeg4 -acodec mp2 -f mpegts ~/testmp4_long.ts -y
>> With this file it works without leaks, except for
>> ==20556== 40 bytes in 1 blocks are still reachable in loss record 1 of 1
>> ==20556==    at 0x4C2A018: memalign (vg_replace_malloc.c:727)
>> ==20556==    by 0x4C2A0A7: posix_memalign (vg_replace_malloc.c:876)
>> ==20556==    by 0xCE7A29: av_malloc (mem.c:94)
>> ==20556==    by 0xA294F9: default_lockmgr_cb (utils.c:78)
>> ==20556==    by 0xA3007B: ff_lock_avcodec (utils.c:3292)
>> ==20556==    by 0xA30288: avcodec_open2 (utils.c:1190)
>> ==20556==    by 0x5C59B1: avformat_find_stream_info (utils.c:2989)
>> ==20556==    by 0x465533: main (transcoding.c:62)
>> anybody knows is this curable?
> What would need to be cured?

Non-empty valgrind report. This wasn't here before.

>> Haven't tried with subtitles yet.
>> This example doesn't work with h264 reencoding, because i libx264 refuses
>> to work because of "broken settings". I gave up investigating what is
>> wrong with that. Apparently this has something to do with
>> avcodec_copy_context() (which i used to init encoders' avctxs, too),
>> because libx264 behaves well if you manually setup all AVCodecContext
>> fields from scratch.
> Then you probably should not be using avcodec_copy_context() at all.

I haven't used it in my apps before in this case, but i would like to
use it at last here for brevity, because internally it really does
what is needed - it copies all properties. And it feels wrong to
rewrite similar procedure in each project. It just copies something
what is usually not set, and this confuses libx264.

Andrey Utkin

More information about the ffmpeg-devel mailing list