Low Framerate in OCIO workflow

[MutinyFX]

Computer: Core i7 3.GHz | 64G RAM | RTX 3080
AE: 23.2 (build 65) CUDA enabled

Monitor: BenQ 4k

ISSUE:
When trying to preview 4k+ footage using the OCIO color managed workflow, the max preview playback speed seems to be reliant on the "magnification" or scale of the comp window. At 25% it plays at 23.976fps, at 50% it plays around 15fps it plays at around 6fps. This is REGARDLESS of the quality. It happens at quater, half or full quality. When the color display space on the comp window is set to none, everything plays correctly. When it is color managed to say sRGB or Rec709 the playback framerate drops. If the color space is set to none and an adjustment layer using Open Color IO is used, it plays back just fine. This seems to be a CPU related post process effect using the internal OCIO that is clunky and unnecessary. It is only using 65% of the CPU however can't seem to playback the video at the speed needed. This happens on ALL of our machines regardless of processor or GPU configuration. It seems to be ok with 1080 footage however we can not find any setup that works with 4k. If there is no work around for this, it seems to be a bug or highly inefficient code for handing OCIO. 

[Chetan Nanda · Accepted solution]

Please check if Hardware acceleration for Composition is enabled in Preferences,

 

[MutinyFX]

Thank you! That solved it. I guess I assumed that the Mercury GPU on/off option controled the UI too.