Kevin Wheatley: We have some Pull Requests to discuss and questions about what should be in the configs for SDR displays in HDR. My PR was merged into a separate branch. There are still some things to fix due to my misunderstanding of how the intrinsics work in OCIO. I also made a cut and paste error which need investigating.
Doug Walker: The CPU unit tests were failing due to algorithm changes. Cuneyt has undated the reference values to use for GPU testing.
Cuneyt Ozdas: But the values were affected by the error, so maybe they were right. I'll double check. I also want to see if we can reduce the threshold size for the tests.
Kevin Wheatley: Alex's work is relevant to that.
Alex Fry: I've update my tool, so you can point it at two OCIO builds, and it renders a directory images with both and produce delta E statistics. It burns those into the frame and also adds them to EXR metadata. I have seen high deltas in dark areas, and lower ones in bright low saturation values where I can see a difference. So I don't 100% agree with the metric. Overall the two renderings are effectively identical. I want to work more on the tool. I haven't uploaded all the images, as people can generate them locally.
Doug Walker: Do we need to make a determination if the algorithm is similar enough there are no concerns.
Alex Fry: It needs more eyes on it.
Nick Shaw: Have you looked at it in HDR?
Alex Fry: Yes. But I want others to look.
Carol Payne: You wouldn't have to upload all the images. Just some selects for people to look at.
Doug Walker: Given the CPU path changed with Cuneyt's PR, should we merge that so it's what's Alex uses to generate test images?
Kevin Wheatley: I checked and it was my mistake.
Cuneyt Ozdas: I'll update the reference values, which currently mostly agree between CPU and GPU, except one inverse with a huge difference, so should be easy to find.
[Alex showed one image with a single pixel high delta]
Alex Fry: In this 4000 nit rendering you can see this one pixel is noticeably different.
Kevin Wheatley: That's probably on the edge of a decision branch and one going each way.
Doug Walker:: Are there other tests people think necessary?
Alex Fry: I should add the CLF test image to the repo.
Kevin Wheatley: Some values in that should be clipped by the transform.
Doug Walker: The 1000 nit Rec.2100 PQ display includes an SDR 100 nit Rec.709 view, like the CTL. Why only that one?
Nick Shaw: I suppose that's the default HDR display people are expected to have.
Carol Payne: Should it be in the 2000 or 4000 nit displays? As Nick said on Slack, it lengthens the flat list in Nuke. But I think the Studio Config should a a reasonable default set.
Doug Walker: I'll add that to our configs repo. I proposed the HDR 1000 nit active view be highest priority, and the default display sRGB.
Kevin Wheatley: Or should it be BT.1886?
Carol Payne: A random computer monitor will be sRGB. It's the default in many apps.
Doug Walker: In the next few days GPU will match CPU. Then we can do the 2.4.2 review. Eric can test the HLSL. We have no HLSL unit tests.
Kevin Wheatley: One scale I made in CPU but not yet GPU is the tone scale going from A, not J. I can point you to where that is.
Cuneyt Ozdas: Should we make the final PR to main now so people can look at it?
ACES Output Transforms VWG
Meeting #182, February 26th, 12pm PT
[Meeting Recording]
Attendees
Meeting Notes