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Old 26th September 2022, 09:42   #1  |  Link
spoRv
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AV1: MOD2 or MOD8 - which is better?

I'd like to convert some DCP 2K trailers; as they are 2048x858 and 1998x1080, hence MOD2, I'd like to know if, padding video with black borders until I obtain MOD8 (2048x864 and 2000x1080), AV1 will encode better or if it's the same.

AFAIR there were problems with MOD2 AVC and HEVC encoding with some hardware players; it's still the case with AV1?
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Old 26th September 2022, 21:17   #2  |  Link
benwaggoner
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Quote:
Originally Posted by spoRv View Post
I'd like to convert some DCP 2K trailers; as they are 2048x858 and 1998x1080, hence MOD2, I'd like to know if, padding video with black borders until I obtain MOD8 (2048x864 and 2000x1080), AV1 will encode better or if it's the same.

AFAIR there were problems with MOD2 AVC and HEVC encoding with some hardware players; it's still the case with AV1?
Mod compatibility issues are almost entirely due to decoder/video rendering problems, not encoding problems. In general, I'm 100% confident in Mod8, and secure with Mod4 as long as I can test across older players. The good news about using AV1 is that there isn't old AV1 hardware, so in theory everything should work, and any issues could be addressed with a firmware fix.
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Old 5th October 2022, 17:07   #3  |  Link
spoRv
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Originally Posted by benwaggoner View Post
Mod compatibility issues are almost entirely due to decoder/video rendering problems, not encoding problems.
My fault... I wrote encoding when I meant decoding...

I try to use MOD8 at least - and MOD16 whenever possible.

Back to DCP resolution: I'm aware that 1998x1080 is perfectly 1.85:1, but isn't it "better" (easier? faster? better quality?), for resizers, to have for example 2000x1080 that, when multiplied x0.96 is 1920x1036.8 instead of 1998x1080 that should use x0.96096096... to get 1920x1037.8378368... ?
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Old 6th October 2022, 11:12   #4  |  Link
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JFYI, BlueRay h264 rip to MKV of 1920x1080 shows in DGIndexNV log window as being 1920x1088 internally.
(shows internal and external dimensions, Might depend upon encoder).
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Old 6th October 2022, 18:50   #5  |  Link
spoRv
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I was aware of the 1920x1088 "thing" - I guess it was to maintain MOD16; I remember that some HDTV recording were indeed 1920x1088, and IIRC few were 1280x1088!
Indeed MOD16 was used for SD resolution on DVD, VCD, SVCD, DVB: 720x576, 704x576, 720x480, 704x480, 544x576, 544x480, 480x480, 352x288, 352x240
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Old 7th October 2022, 10:09   #6  |  Link
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Internally h264 is always mod16, and more modern codecs even use bigger blocks and av1 can use up to 128x128 superblocks resulting in a theoretical maximum of mod128, but in reality the encoder is likely going to use smaller blocks at the borders. All of these are technical details and irrelevant to the user, as the video is properly cropped automatically by the decoder to ignore the excess needed solely for encoding.
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