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Comment by FullyFunctional | Hacker News Reader

That’s great. I’d love to see how they fare on this glitter which seems to destroy all compressors: https://m.youtube.com/watch?feature=youtu.be&v=MG_Lyg74UlU&t...

(I saw a similar problem with a famous monarch butterfly footage that I don’t have time to chase down)

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The HBO intro’s white noise background is pretty bad too. Quite blocky and degraded.

Wow, that really was awful. Does this sort of thing require kind of like a specific optimisation to fix, or is there a general technique that would fix this and other stuff?

Codecs with better understanding of what a complex scene looks like (and allocates more bitrate accordingly) will do better, and codecs that are better are blurring away details instead of blocking will do better as well.

Keep in mind this is on Youtube and uploaded by some shitty clip site, so it's a very biased example. In this case there are four lossy encode steps involved: master -> bluray -> clipsite's master -> Youtube encode. Youtube in particular has absolutely horrific, just inexcusably bad bitrate even at the highest quality they'll give you. I'd have to see what the original Bluray looks like in this case to see if there's really a problem worth worrying about here.

Actually I first saw it on a plane and wondered how we have gotten to this stage where obviously garbled video is ok to give to paying customers. Yes, more bits will solve this, bit it’s still a great example that breaks encoding assumptions.

there isn't necessarily a fix. all compression algorithms expand the size of the data on most inputs in order to make certain inputs with sufficiently regular patterns a lot smaller. it just so happens that most of the images/video/audio/text/etc people are interested in is fairly regular. with a lossy compression algorithm that is required to hit a certain compression ratio to keep the bitrate under some threshold, the only way to be able to guarantee that it is hit on uncompressible input is to introduce regularity/remove randomness, and in the case of video the easiest and least visually distorting way to do so is to pixelate it. this particular video is basically random noise which is incompressible by definition, which is why the result is so bad. if it was 1080p going in and the output size is required to be reduced by 16x, reducing the resolution to 480x270 is about as good you can do.

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