[Libav-user] how to translate avcodec to vfw?

Anton Shekhovtsov shekh.anton at gmail.com
Sun Aug 28 16:36:03 EEST 2016

I am trying to encode with ffv1 codec and write avi file (not using
avformat, by intent).
Since vfw codec can only return single block of data per frame I am trying
to pass AVPacket data and this actually works with small frame size.
However with bigger frames the produced avi file is invalid (ffplay shows
all kinds or errors about missing header data).

Looks like the problem is related to AVCodecContext::extradata.
The description says "encoding: Set by libavcodec". But then what? Does it
get into muxing somewhere? I could`n find anything relevant in examples,
ffmpeg.c, avienc.c, mux.c

So can somebody explain the workflow of extradata or more specifically how
to write it to avi file?

Or maybe there is something else involved in "avcodec to vfw" problem?
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