Blender used to do video frame YUV->RGB conversion and image vertical
flip in the same step, but that was removed in 2ed73fc97e in order
to fix problems with video widths that aren't multiple of SIMD width
(e.g. 32). However many common video resolutions (e.g. 1920x1080) are
compatible with that, so try to reintroduce that.
Playing back 1080p resolution video in VSE, the ffmpeg_postprocess
step (deinterlace, YUV->RGB, vertical flip) on Windows / Ryzen 5950X
goes from 2.41ms down to 1.18ms
Playing back 1080p resolution video in VSE, the ffmpeg_postprocess
step (deinterlace, YUV->RGB, vertical flip) on Windows / Ryzen 5950X
goes from 3.05ms down to 2.41ms
Aras Pranckevicius