[Libav-user] Possible values of AVMotionVector source field

lukas lukas.bommes at gmx.de
Fri Nov 29 04:02:27 EET 2019

Dear libav users,

I am working on a visual tracker that uses motion vectors extracted from
H.264 and MPEG4 encoded videos. So far, I only observed values +1 and -1
for the "source" field of AVMotionVector struct:

Now, I am wondering whether the source value can have an absolute value
larger than 1. The documentation is a bit ambiguous as it contains the
note: 'XXX: set exact relative ref frame reference instead of a +/- 1
"direction"'. Looks like a Todo to me which would imply that currently
only values +1/-1 are used.

Any ideas on how I can force the encoder to produce some vectors with
absolute source values larger than 1? I want to test my algorithm to
ensure it won't brake once it encounters different source values.

Thanks a lot!

Kind regards,

Lukas Bommes

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