VDub2 Canopus HQX 16-bit negotiation issue - Page 6

poisondeathray · 11th April 2021, 16:49

Quote:

Originally Posted by kolak

Side note- ProRes444 modes do pass those reserved bits (in official Apple encoder).

Good to know;. But you would expect it to store 0-1023 for 10bit and 0-4095 for 12bit variants because the 4444 variants need to store the alpha channel. You can't have clipping in an alpha channel, or it would be completely useless

kolak · 11th April 2021, 18:11

Well, alpha is a separate "stream" inside ProRes444. It's just losslessly compressed bits, more like a data than video.
444 is always encoded as 12bit. Alpha can be processed as 8 or 16bit.

poisondeathray · 11th April 2021, 22:34

kolak did you use resolve to encode Pr444 or something else ? Did you use that test pattern ? Can you upload the Pr444 output ?

ffmpeg pr444 variant encode results in 4-4091 in 12bit, with the expected gaps at 12bit

If you down convert to 10bit, you get 1-1023, but smooth, basically perfect except for the missing zero value. PSNR y:90.300512

And if you feed native 12bit src, the ffmpeg pr4444 variant is still 4-4091 (and with gaps at 12bpc , not smooth)

kolak · Yesterday, 18:13

It was done in Resolve on Mac.

ffmpeg ProRes444 encoder is 'broken'- 10bit only. They fixed only decoder.

11th April 2021, 22:34	#103 \| Link
poisondeathray Registered User Join Date: Sep 2007 Posts: 4,551	kolak did you use resolve to encode Pr444 or something else ? Did you use that test pattern ? Can you upload the Pr444 output ? ffmpeg pr444 variant encode results in 4-4091 in 12bit, with the expected gaps at 12bit If you down convert to 10bit, you get 1-1023, but smooth, basically perfect except for the missing zero value. PSNR y:90.300512 And if you feed native 12bit src, the ffmpeg pr4444 variant is still 4-4091 (and with gaps at 12bpc , not smooth) Last edited by poisondeathray; 11th April 2021 at 22:55.

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11th April 2021, 18:11	#102 \| Link
kolak Registered User Join Date: Nov 2004 Location: Poland Posts: 2,530	Well, alpha is a separate "stream" inside ProRes444. It's just losslessly compressed bits, more like a data than video. 444 is always encoded as 12bit. Alpha can be processed as 8 or 16bit.