Tell ffmpeg swscale to do accurate YUV->RGB conversion, instead of
slightly faster but not really accurate one. Fixes banding and some
color shifts in video files, particularly in dark regions.
The accurate conversion is a bit slower though, on 4K resolution video,
time taken to convert video frame from YUV to RGB:
- x64 (Ryzen 5950X): 2.3ms -> 3.7ms
- arm64 (M1 Max): 0.6ms -> 2.9ms
My take is that paying 1-2ms per 4K video playback is acceptable
since the result is obviously "more correct" and matches what VLC/ffplay
produces.
From what I can tell, "accurate conversion" turns off some dedicated
assembly code paths within ffmpeg. Maybe someday ffmpeg would get
accurate and assembly-optimized routines for that.
With more accurate decoding, we can now lower the expected render
test threshold again, since x64 & arm64 decoding is much closer now.
Comparison screenshots in the PR.
Pull Request: https://projects.blender.org/blender/blender/pulls/130383
bbbe08d0b0