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

Christina Brien christina.brien at polygonindustrial.com
Sun Apr 2 23:33:35 EEST 2017


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.


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