This release fixes a number of minor issues with v6.338.0, as well as a
major regression of the frame mixing code.
Fixes and performance enhancements:
- fix H.274 grain database PRNG
- fix compilation on FreeBSD
- fix unnatural peak detection flicker on mostly black samples
- fix plplay 'Use detected luminance' checkbox
- fix unnecessary recompilation when changing antiring strength
- properly disable anti-ringing for non-negative filters
- fix double-callback on sliced texture uploads
- dispatch callback slightly sooner in pointer texture upload fallback
- slightly improve saturation when tone mapping by large factors
- various improvements to the benchmark
- fix regression when frame mixing low FPS sources
- update various misleading comments