[libav-api] Packaging Raw H264/AAC frames into FLV/RTMP Stream

Evgeny Yakimov john.yakimov at gmail.com
Mon Oct 3 15:16:34 CEST 2011

Hello Lu

I am using the same h264 raw frames (in this case from x264) both in my app
and the ones that avconv reads from using the command:
avconv -i /mnt/videos/raw.h264 -vcodec copy -f flv test.flv

I have just created two flv files, one from my own code, and the other from
the command above, which both use the same raw frames.

I then wrote a quick program to read and dump the frames from the flv files
so that I can compare them:

It seems that the first frame is much bigger, and every key frame is also at
least 2 bytes bigger, every non key frame although the same size has been
modified in byte 3 and 4. So it seems that avconv modifies these frames
before writing them into the flv container.

I have uploaded the entire program that I use to create my flv here (argv[1]
points to a source file of raw 422 frames which are converted to 420 prior
to being sent to x264)
(please ignore the audio for the time being)

Any Idea on how avformat modifies these frames?

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