noggin wrote: 04 Jan 2020, 17:57
Worst case - it's just HDR10 flagged just enough to trigger a DV logo?
Better case - it's HDR10 + useful DV RPUs that trigger DV and improve tone mapping on DV displays?
I'm going to guess it does nothing with a Full Extension Layer to take it to 12 bit from 10...
According to the statement here from wesk05 about DVDFab single layer, a Plex Forum member (TobyX) and I discussed a lot about the topic. We have come to the conclusion that words do not help much but we have to check it ourselves. I read a lot of Dolby documents to understand how DV works...
First of all - wesk05 is right that the monkey does not create a single layer according to Dolby's specifications. A single layer must already have the 12bit and the ITP 420 color space in the source file. This is not the case with a UHD disk, since only the mix of both layers can result in this. This is because the disc must be backwards compatible to hdr10.
At first I thought that it doesn't matter, since the output to the TV is always 10bit / YUV 420 and there are currently no 12-bit commercial screens out there. But more about that in a moment...
So the question arises what the monkey is doing there!? I thought if the picture on the TV looks like the original DV, I don't care what the source is or what DVDFab does. My first short ugly tests confirm that SL looks like DL but not like HDR10:
(dv demo disc 2018 - black demonstration)
You can see that the point is much too bright with HDR10 and the screen is not darkened as with DV. With DV, the display is off except for the small area. So the black demo doesn’t really work with HDR10. You can see the difference with the eye and the camera. In my opinion you can see there that the metadata for HDR10 is “static” because the brightness has been completely set for the video and the spot is too bright. The TV is on the DV standard picture profile without any changes. The same with the HDR mode … standard without changes. Local dimming is set to Medium in the standard profiles.
But since I can't take good pictures with my bad smartphone camera, I asked Toby. He has the appropriate equipment. He took some pictures with the same settings and the same conditions. The short answer is: Yes it is different! Here is the thread with the better comparisons:
https://forums.plex.tv/t/some-thoughts- ... ols/536340
If you look at the pictures, you can see that there are small color differences from the original. I think the missing color depth or primaries will be the problem. The Dolby Vision composer and display manager obviously makes a better colored picture from the 12-bit source of the EL even if the screen always gets 10 bit YUV 420.
I'm not sure about metadata. If these were really static, you would not see any differences to HDR10. That's not the case. So it is not an HDR10, which only triggers the DV logo on the TV. It is the 10bit baselayer which is expanded with useful dv data substream and thus comes very close to the original. In principle, DVDFab doesn't state anything else. BL+PRU = "single layer". I think it’s kind of a HDR10 and DV mix. DVDFab will extract the RPU substream metadata and discard the expanded color. Then he adds the metadata to the first 10bit HEVC layer and replaces or overwrites the static data. The differences to HDR10 could not be explained otherwise!?
So...
Is it like the original DV = no
Is it HDR10 with only DV logo = no
Is it better like HDR10 = yes
What the monkey does is the only way to create later a SL from a DL or a UHD disc. There is no other way as it is actually not possible to do this. So if you are dependent on single layer DV, you have an option to create a very similar experience afterwards, but you have to accept drawbacks in the color.
Thank you TobyX for your work and the effort involved!!! I think we have now largely closed the case...!?
greetings
KCX
The other bits in the equation is libx265 can also do some level of dolby vision manipulation. I would not be surprised that DVDFab is doing something similar to what libx265 is doing.