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Bitrate Questions

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I have a couple of questions about bitrate.

  1. ARE THERE BLU-RAYS DONE AT 16MBPS?
    If H.264 can re-encode 8mbps DVD down to 2.5mbps with no noticeable drop in quality, couldn’t you get Blu-Ray quality video at 16mbps? Are there any movies on BluRay that have done this?
  2. WHAT ARE 4K BITRATES LIKE?
    What’s the average bitrate of a 4k Blu-Ray? I’ve heard it’s usually around 42mbps, which makes sense calculating it up from the 33.5mbps of many regular Blu-Rays. (factor​ing in the quadrupled resolution, 12-bit color space, and efficiency of h265.), but taking my 16mbps theory into account, could 4k be done at 26mbps? or is that just blasphemy?
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If you’re saying a 8 mbps MPEG2 stream can lose little quality as 2.5 mbps h264, that doesn’t mean that 8 mbps h264 can compress to 2.5 mbps and look the same. The same goes for the idea of 35 mbps h264 going down to 16.

If you just mean extrapolating from 2.5 to 16, the standards of downloaders/homebrew types of things are different from commercial standards. Yes, you’ll definitely see people here release things at bitrates such as 16, as downloaders don’t always want enormous files. But it’s not perfect, and customers would rightly complain if they got a disc with a bitrate like that. That said, legal streaming bitrates can certainly often be lower.