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Why is everybody talking about recoding? Can't they just keep the current videos as they are and encode new things in a different codec? As far as I know all th
by FooBarWidget 17y ago
Why is everybody talking about recoding? Can't they just keep the current videos as they are and encode new things in a different codec? As far as I know all the old H263 videos on Youtube have never been recoded. And why would they? Recoding H263 to H264 would just degrade quality.
- nailer 17y agoI understand what you're saying, and I'd love to be educated if you know more about the topic, but aren't they both perceptual encoders? Ie, wouldn't the parts of each frame they're identifying as unimportant be quite similar? (I'm quite certain I'm wrong on this point, but I'm interested in learning why)
- sp332 17y agoEach encode removes information from the video. No matter how nice the encoders are, the video quality will degrade every time.
- nailer 17y agoI understand the sentence, but what I'm trying to understand is why the information removed is (significantly) different - since they're both perceptual codecs, there should be a large overlap in what is removed from the output. Eg, take a frame which has a solid chunk of blue. Codec 1 removes some of data to make things more consistent and then compresses it. Codec 2 looks at the output of codec 1, sees the consistently large blue area, doesn't see any info worth removing, and compresses it.
- FooBarWidget 17y agoI don't know all the maths behind it, but try saving a JPG, close it, open it, save it again, repeat a few times. You'll see quality degrade every time you close it. My guess is that the lossy compressors try their best to preserve the previous compression artifacts, but in doing so they introduce more compression artifacts.
- sp332 17y agoGoogle stores the original uploaded videos, just for purposes of re-encoding later.