FCP intermittent brightness fluctuation on Apple Silicon during playback of Sony SLog3 XAVC-L MXF

[joema4]

Apple Feedback Assistant ID: FB9840048

When playing or skimming UHD 4k/23.98 SLog3/SGamut3.cine 8-bit 4:2:0 XAVC-L (Long GOP) MXF from a Sony FX6, there can be an intermittent brightness fluctuation unique to Apple Silicon. It manifests as an approx. 1-stop darkening in the viewer when the skimmer or playhead is in motion, then resumes normal brightness when stopped. Most users would describe it as “flickering”. The behavior is intermittent and does not always happen, however it should be reproducible in a few tries using the attached files.

Originally filed on 10-Jan 2022 as bug #FB9840048 using MacOS Feedback Assistant.

Other observations and boundary conditions:

• Behavior is unique to Apple Silicon and does not happen with the same files and version of FCP on x86.
• It does not happen if using 4k/23.98 10-bit 4:2:2 XAVC-I All-Intra material from the same camera, only XAVC-L which at 4k is 8-bit 4:2:0.
• I’ve observed it on 4k material from the Sony FX6 but it may also happen with XAVC-L MXF material from the FS5, FS7 and FX9 since those use the same codec. However I don’t have those in hand for testing.
• It does not happen if using optimized media.
• It happens whether media is imported within library or “in place”.
• It happens on a clip with no Fx and without built-in SLog3 camera LUT.
• It reportedly does not happen if using the S-Cinetone color profile, only with SLog3.
• It is not affected by selecting Rec 709 color space override in Inspector Settings tab.
• It happens whether skimming with mouse in Event Browser or using playhead on timeline with JKL commands.
• It happens whether viewer is set to Better Quality or Better Performance.
• Material is progressive, not interlaced.
• It does not happen if clips are externally re-wrapped using EditReady2 before import, but for some reason that negatively affects playback performance.

VERSIONS AND HARDWARE TESTED:

• M1 Max MacBook Pro 16, 64GB RAM, 4TB SSD, FCP 10.6.1, Monterey 12.1, Apple Pro Video Formats 2.2.2
• M1 Ultra Mac Studio, 128GB RAM, 8TB SSD, FCP 10.6.6, Ventura 13.4, Apple Pro Video Formats 2.2.5
• M2 Pro Mac Mini, 32GB RAM, 4TB SSD, FCP 10.6.6, Ventura 13.4, Apple Pro Video Formats 2.2.5
• Camera: Sony FX6, UHD 4k/23.98 XAVC-L Long GOP, 8-bit 4:2:0, SLog3/SGamut3.cine

STEPS TO REPRODUCE:

(1) Import attached file JDM0872.MXF; do not create proxies or optimized media.
(2) Skim clip in Event Browser to about the 1/2 point, roughly 1 min 27 sec.
(3) Repeatedly skim back and forth over that region, halting periodically with either mouse or keyboard.
(4) Behavior: Viewer will dim somewhat when skimmer or playhead is in motion, then brightness recovers when playback halts.

Test file: https://www.dropbox.com/s/e9moto7f6l28fu2/JDM0872.MXF?dl=0

[latenitefilms]

I can reproduce this on Final Cut Pro 10.7 sadly.