[Libav-user] Motion vector extraction

Vadim Kantorov vadimkantorov at gmail.com
Mon Apr 30 15:52:55 CEST 2012

Hi all,

I'm using libavformat / libavcodec to extract motion vectors from files
encoded by different codecs (MPEG-2, H.264,...).

Do I understand correctly that if motion vectors exist for macro-block or
can be predicted, they are available in the motion_val field?

What happens when a macro-block contains several links to other blocks (the
case of a B-frame; ability for weighted mixtures in H.264)? Is any kind of
motion vector (say, to past reference frames for B-type blocks) inserted in
the motion_val at all for such blocks?

If I'm misunderstanding something, please correct me. I've just started to
dig in the topic.

Vadim Kantorov
+33 (603) 292-769
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