[FFmpeg-devel] H.261 chroma motion vector rounding.

Clément Bœsch u at pkh.me
Sun Apr 2 20:46:28 EEST 2017

On Sun, Apr 02, 2017 at 10:17:05AM +0100, Christina Brien wrote:
> Hi
> Having written a clean-room implementation of H.261 and comparing it to the output of FFMPEG, I have found that FFMPEG is not spec-compliant with regard to negative chroma motion vectors. The spec states that chroma motion vectors are the luma motion vectors divided by two, and rounded *towards zero*. FFMPEG currently rounds towards negative infinity.
> This patch makes FFMPEG compliant, but breaks the regression tests.
> Christina

I can't comment on the correctness of the patch, but wouldn't
ROUNDED_DIV() macro be more appropriate?

Also, the Changelog is not supposed to include these kind of changes.


Clément B.
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