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A lot of these "rules" with color use some broad generalizations. When you work with video compression a lot, you start training yourself to see color different

A lot of these "rules" with color use some broad generalizations. When you work with video compression a lot, you start training yourself to see color differently and the illusions begin to fall apart. For me: I really don't enjoy looking at 4:2:0 or 4:1:1 chroma subsampling (4:2:2 usually doesn't cause problems) 4:2:0 sort of works for live scenes which don't typically have sharp chroma boundaries but when you see solid red/blue graphics superimposed over a scene, the blocky bleed of color across the scene is like knives in my eyes.

coldpie 11y ago
I'm interested in this. When you said, "When you work with video compression a lot," what did you mean? Working with video compression at an algorithm level, or applying different compressions to the same video and comparing the results, or something else?
- gilgoomesh 11y ago
  The middle one ("applying different compressions to the same video and comparing the results"). I write streaming video servers. An aspect of the job is continuously optimizing parameters and codecs to satisfy PSNR and perceptual video quality test cases across a large library of test files. It's not a fun aspect of the job.
theandrewbailey 11y ago
> but when you see solid red/blue graphics superimposed over a scene, the blocky bleed of color across the scene is like knives in my eyes. I still wonder why that happens to red, mostly because it looks like someone's bleeding everywhere. I don't seem to notice it for green or blue. At first I thought it was the downsampling, but it has to be something else (a combination, maybe?), since JPEG seems to handle downsampled red comparatively better when highly compressed. Right now, I just think it's a flaw in H.264, it's encoders and/or decoders.
- gilgoomesh 11y ago
  Bleed definitely happens with blue too but since solid blue chrominance is less common in graphics (graphics tend to use brighter sky/azure/royal blue) whereas solid red is quite common. But bleed won't happen with green because green is basically the luminance channel in YCbCr/YUV. This means that green runs at full sample resolution compared to red and blue which run at 50% to 25% resolution (depending on subsampling).

coldpie 11y ago

I'm interested in this. When you said, "When you work with video compression a lot," what did you mean? Working with video compression at an algorithm level, or applying different compressions to the same video and comparing the results, or something else?

gilgoomesh 11y ago
The middle one ("applying different compressions to the same video and comparing the results"). I write streaming video servers. An aspect of the job is continuously optimizing parameters and codecs to satisfy PSNR and perceptual video quality test cases across a large library of test files. It's not a fun aspect of the job.

theandrewbailey 11y ago

> but when you see solid red/blue graphics superimposed over a scene, the blocky bleed of color across the scene is like knives in my eyes. I still wonder why that happens to red, mostly because it looks like someone's bleeding everywhere. I don't seem to notice it for green or blue. At first I thought it was the downsampling, but it has to be something else (a combination, maybe?), since JPEG seems to handle downsampled red comparatively better when highly compressed. Right now, I just think it's a flaw in H.264, it's encoders and/or decoders.

gilgoomesh 11y ago
Bleed definitely happens with blue too but since solid blue chrominance is less common in graphics (graphics tend to use brighter sky/azure/royal blue) whereas solid red is quite common. But bleed won't happen with green because green is basically the luminance channel in YCbCr/YUV. This means that green runs at full sample resolution compared to red and blue which run at 50% to 25% resolution (depending on subsampling).