Comment by the8472
10 years ago
> Chroma Subsampling.
Sadly, this is what makes video encoders designed for photographic content unsuitable for transferring text or computer graphics. Fine edges, especially red-black contrasts start to color-bleed due to subsampling.
While a 4:4:4 profile exists a lot of codecs either don't implement it or the software using them does not expose that option. This is especially bad when used for screencasting.
Another issue is banding, since h.264's main and high profiles only use 8bit precision, including for internal processing, and the rounding errors accumulate, resulting in banding artifacts in shallow gradients. High10 profile solves this, but again, support is lacking.
This is also the bane of powerpoint presentations. Many TVs only support 4:2:0, so red on black text quickly becomes an smudgey mess.
It's easy to make a 4:2:0 upscaler that doesn't color bleed. Everyone just uses nearest-neighbor, which sucks, and then blames the other guy.
How would you make a 4:2:0 upscaler that doesn't color bleed?
50% solution: bicubic or bilinear. 90% solution: EEDI3. (kinda slow) 99% solution: use the full resolution Y plane for edge-direction.
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