[Libav-user] There is no picture in the output file while encoding with libx264 as codec.

Brian Chi beyond702 at gmail.com
Tue Dec 25 10:08:10 CET 2012


I want to realize an application that firstly decode a multi-media
file(such as test.mp4 file, video codec id is H264), get a video stream and
an audio stream, then make some different in the audio stream, at last
encode the video stream(use libx264) and audio stream into a result
file(result.mp4). To promote the efficiency, i omitted the decode and
encode of video stream, i get the video packet via function
"av_read_frame", then output it directly into the result file via function
"av_write_frame". But there is no picture in the output file, and the size
of output file is fairly small.

I tracked the ffmpeg code and found that in the function
"av_write_frame->mov_write_packet->ff_mov_write_packet", it will call
function "ff_avc_parse_nal_units" to obtain the size of nal unit, but the
return value is very small(such as 208 bytes).

I can't find where the problem is. Does anybody know that? I'm very
appreciate it.

Best Regards,
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