Recently, James Duke was experimenting with 10-bit (HDR) video in both Final Cut Pro X (10.4.2) and QuickTime Player and found some strange behaviors. So, he sent me several questions about how Apple is handling HDR material.
After doing some homework, I discovered there is no simple answer, but these answers are important if you are working with HDR.
1. Does QuickTime Player v10.4 in High Sierra play 4K 10-bit ProRes 422 HQ (both Rec. 709 and Rec. 2020 PQ) video as 10-bit or 8-bit?
Currently QuickTime Player plays ProRes as 8-bit.
2. Does QuickTime Player v10.4 in High Sierra play 4K 10-bit H.265 (both Rec. 709 and Rec. 2020 PQ) video as 10-bit or 8-bit?
On certain hardware, like current generation iMacs and iMac Pros, HEVC will play back as 10-bit.
3. In a Wide Gamut HDR – Rec. 2020 PQ 4K project on iMac (Retina 5K, 27-inch, Late 2015), does FCPX 10.4.2 clip viewer brightness on the iMac display to 100 nits, even though the iMac display has > 300 nits?
The iMac display is 500 nits, which is brighter than most SDR monitors. Final Cut Pro X uses the full brightness of the display when editing with HDR clips. It also uses ColorSync, which is a feature of macOS that enables apps to display images on different Macs with consistent color and brightness.
When working with high luminance HDR images, you may wish to display the raw values for images in the Final Cut Pro viewer. That preference can be enabled in the Preferences panel, within the Playback tab (the option reads: “Show HDR as raw values”). This option displays HDR footage in the Final Cut Pro viewer without clipping highlights, so the editor can see the full image while editing.
When working with HDR material, Apple recommends connecting an external HDR monitor and an IO device to view the full range of brightness in the image.
4. In a Wide Gamut HDR – Rec. 2020 PQ 4K project on iMac (Retina 5K, 27-inch, Late 2015), does FCPX 10.4.2 clip viewer brightness on the SECONDARY display to 100nits, even though the secondary display can be 300-1000 nits?
Currently the secondary desktop monitor is 100 nits. If you have an AJA Io 4K or Io 4K Plus, you can send the HDR video levels to a secondary monitor as video out.
5. In a Wide Gamut HDR – Rec. 2020 PQ 4K project on iMac (Retina 5K, 27-inch, Late 2015), with A/V Output connected to external HDR monitor through Thunderbolt to HTMI connector, will FCPX display full HDR video without clipping the brightness?
Does it require a third-party interface between Thunderbolt and the monitor with a special software/hardware handshake to display full HDR video without clipping? Is there a list of the certified interface hardware?
This requires an AJA Io 4K or Io 4K Plus to connect to an HDR monitor and display the full range of the Rec. 2020 PQ or HLG signal. Blackmagic also offers IO devices for HDR monitoring, but currently they’re limited to 8-bit video out unless you are using DaVinci Resolve.
NOTE: Either the AJA Io 4K or AJA Io 4K Plus will work. The only difference is that the Io 4K has a Thunderbolt 2 connection, while the Plus uses Thunderbolt 3.
SECOND NOTE: After I published this, James wrote to say he “contacted the developers at AJA. If I want 4:2:2 10-bit, I need AJA Io Plus, because only the Plus HDMI v2.0 chip can handle 4:2:2 vs 4:2:0 at 10-bit. Also, they say that Thunderbolt 2 to Thunderbolt 3 adapter will work, but to get 10-bits I am limited to 30 fps, which is Ok with me for now – all my videos are 30 fps.
Here’s a link to the AJA Io 4K. And here’s a link to the AJA Io 4K Plus.
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Larry adds: I’m sure these answers will evolve over time. I’ll update this article as I learn more. Thanks, James, for starting this discussion.
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