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Old 24th January 2023, 14:36   #741  |  Link
FranceBB
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Quote:
Originally Posted by birdie View Post
I've not noticed any perceivable compression artifacts, the bitrate is outright insane, for the file that I downloaded, it's 1 332 878 kb/s, which surely looks like compression, if there is any, is minimal.

4K Bluray has around 75Mbps bitrate - files from the observatory are ~ 18 times denser.
Yeah, they're called mezzanine files. It's what professional broadcast studios use internally.
For instance, you might have Grass Valley playout ports that play such a file and then output a signal via SDI. Such a signal is then received by an hardware encoder which encodes it as either MPEG-2 for SD channels, H.264 for HD/FULL HD channels and H.265 for UHD channels at consumer tier bitrates, generally around 2.5 Mbit/s for MPEG-2, 12 Mbit/s for H.264 FHD and 25 Mbit/s for H.265 UHD.
Internally, though, it's really not uncommon to see those kind of mezzanine files used and stored/archived.
Keep in mind that what users see is not what studios archive.
As I said, AVID systems use DNxHR, which is quite similar and can reach similar bitrates.
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Old 24th January 2023, 21:02   #742  |  Link
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Originally Posted by birdie View Post
The codec used is hqx (CHQX / 0x58514843), yuv422p16le(10 bpc) - no idea what it is, but it must be uncompressed.
Uncompressed 3840x2160 10 bpc @ 25 fps is 6220800 kbps (10 x 3 x 3840 x 2160 x 25). 1332878 kb/s is 4.67 times smaller. A very light compression ratio for video, but still compressed.
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Old 25th January 2023, 21:11   #743  |  Link
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Uncompressed 3840x2160 10 bpc @ 25 fps is 6220800 kbps (10 x 3 x 3840 x 2160 x 25). 1332878 kb/s is 4.67 times smaller. A very light compression ratio for video, but still compressed.
Yeah, lossless compressed HEVC is only 2-3x larger. We have a ton of peer-reviewed data about mezzanine codecs not impacting final video quality visibly after dozens of generations of reencodes.
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