Doom9's Forum - View Single Post - madVR - high quality video renderer (GPU assisted)

Asmodian · 19th January 2020, 01:49

Yes, subsampling chroma requires having the chroma separate from the luma.

RGB has these concepts mixed together, changing R (or G/B) changes both the chroma and the luma values. The chroma is Cb and Cr (color information) while the luma is Y (black and white information). Subsampling the chroma is simply resizing the Cb and Cr channels to 960x1080 (422) or 960x540 (420) for nominally 1920x1080 video.

YCbCr is an odd concept, originally developed to make color TV signals backwards compatible with black and white TVs (well it is the digital version of YUV, the analog version of this concept). You could make red and blue half the resolution of green for a similar (but much worse) kind of subsampling but no hardware actually supports such a terrible quality option. Doing the matrix math to first convert to YCbCr is definitely worth it if you want to subsample.

19th January 2020, 01:49	#58403 \| Link
Asmodian Registered User Join Date: Feb 2002 Location: San Jose, California Posts: 4,407	Yes, subsampling chroma requires having the chroma separate from the luma. RGB has these concepts mixed together, changing R (or G/B) changes both the chroma and the luma values. The chroma is Cb and Cr (color information) while the luma is Y (black and white information). Subsampling the chroma is simply resizing the Cb and Cr channels to 960x1080 (422) or 960x540 (420) for nominally 1920x1080 video. YCbCr is an odd concept, originally developed to make color TV signals backwards compatible with black and white TVs (well it is the digital version of YUV, the analog version of this concept). You could make red and blue half the resolution of green for a similar (but much worse) kind of subsampling but no hardware actually supports such a terrible quality option. Doing the matrix math to first convert to YCbCr is definitely worth it if you want to subsample. __________________ madVR options explained Last edited by Asmodian; 19th January 2020 at 01:58.