Reference
What is chroma subsampling?
Chroma subsampling reduces colour-detail resolution while preserving full or higher luma detail. It is one reason video can be compressed efficiently without simply lowering the picture resolution.
4:2:0 vs 4:2:2 vs 4:4:4
| Notation | Colour sampling | Common use |
|---|---|---|
| 4:2:0 | Chroma reduced horizontally and vertically | Streaming, Blu-ray/UHD delivery, consumer cameras |
| 4:2:2 | Chroma reduced horizontally, retained more strongly vertically | Broadcast/acquisition/post-production |
| 4:4:4 | No chroma subsampling | High-end production, graphics, specialist mastering |
Chroma subsampling is not colour bit depth
4:2:0 / 4:2:2 / 4:4:4 describe spatial colour sampling. 8-bit / 10-bit / 12-bit describe numerical precision per component. A video can therefore be 10-bit 4:2:0 or 10-bit 4:4:4.
The codec profile matters
H.264, HEVC and AV1 all have profiles that allow different combinations of bit depth and chroma. Knowing only the codec name is not enough to know whether a file is 8-bit or 10-bit, or 4:2:0 versus 4:4:4.
See H.264 profiles, HEVC profiles and AV1 profiles.