Notice of Meeting - ACES Gamut Mapping VWG - Meeting #15 - 6/4/2020

Discussions - ACESNext VWG – Gamut Compression/Mapping
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Here’s the meeting notes, sorry for the delay, don’t let me derail the convo - I’ll reply to some things separately with my pipeline thoughts.

  • BlinkScript and DCTL will be the versions we keep in the super-repo and get parity on for testing, and then create the CTL towards the end as a deliverable
  • @Thomas_Mansencal will connect with @Alexander_Forsythe to move the super-repo into the AMPAS git repository instead of Colour
  • @nick demoed a dark noisy image to show the algorithm’s effectiveness on negative numbers - both on the version that maps from infinity and @jedsmith’s latest that intersects one.
    • Group’s consensus is that dealing with all-negative pixel values resulting from the black level being set at the average noise floor value is out of scope for this group and belongs to the IDT realm.
  • Thomas has the spectral values (official) for ColorCheckerSG chart
  • Are there different values used in television?
    • SMPTE color bars?
    • DSC Chroma du Monde
  • @matthias.scharfenber : the colorChecker 24 makes the most sense, it’s what gets put in front of cameras on set and is also used in IDT generation
  • Matthias is experimenting with per-channel thresholds. Thomas pointed out that in this case the per-channel limits would need to compensate for any differences between the thresholds.
  • Discussion around where this algorithm lies in the pipeline, and whether or not it should be required
    • Thomas proposed right before the RRT
    • @carolalynn proposes as a part of the AP0 to AP1 transform
    • Mapping should be opt out, but have old transforms available for possible edge cases and archival for posterity
  • How should we be evaluating our algorithm in a display referred context?
    • RRT/ODT, but also other (simpler?) display transforms.
    • Thomas pointed out limitations of 3D lut based transforms
    • @joseph pointed out Dolby’s 2D transform experiments - do we have more info in these?
    • Qualitative or quantitative evaluation, or a balance of both?
    • We should be testing on sequences too
      • Fabian and Martin’s submissions, 2-3 seconds worth each as AP0 exrs
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