[Sparktank]

Originally Posted by feisty2

the precise and more correct way to convert from HD to SD, SD to HD likewise
0. expand to PC range
1. resample to 444
2. convert to gamma compressed RGB with matrix "709"
3. convert to linear RGB with "709" transfer
4. convert to CIE XYZ with "709" primaries
5. convert to CIE Lab
6. scale to SD
7. convert back to CIE XYZ
8. convert to linear RGB with "601 NTSC" or "601 PAL" primaries
9. apply "709" transfer
10. apply "601" matrix
11. resample to 422/420 or keep it as 444
12. shrink to TV Range

Interesting.
This almost looks like the dither_resize16 process.
Dither_convert_yuv_to_rgb(...)
Dither_y_gamma_to_linear
Dither_resize16
Dither_y_linear_to_gamma
Dither_convert_rgb_to_yuv(...)

Except, I dont apply 444 and PC range first (and TV range last, then 420/422). (and also don't do that CIE XYZ & CIE LAB thingy)
I've always been curious about that, though.
For DVD processing.