Performance problem in DR17 Studio

I am working on an iMac Pro (2017) 3.2 GHz 8-Core Xeon W, 32 GB, Radeon Pro Vega 56 8 GB.

When I play a single clip (H.265 1920x1080 60FPS, Audio AAC, 44100 Hz, Mono) in DR17 Studio (17.0 Build 39) in Edit-Page, I see CPU usage between 80-90%. When I play the clip in Fusion-Page, the CPU load is over 200% and the clip cannot be played smoothly. I am not using any effect and the video file is on the internal Macintosh SSD. Is this performance normal, is my computer too slow to play a clip at 60FPS in DR 17? If I play the clip with Quicktime Player, I only have a CPU load of 6.5%?

xeon server CPUs does not have quicksync like a i-core
and without quicksync is H265 the most sophisticated codec for any computer.

so transcode to prores will be your best option

[Peter Chamberlain]

moved to the Resolve forum

I think the codec is not the main problem here. I rebooted the computer and then did some tests. Here are the results:

https://www.dropbox.com/s/o823jh4rx00uz2x/Dr17_Test.pdf?dl=0

All clips have the H.265 codec. The first thing to notice is that the 4K clips require another process "VTDecoderXPCService", which causes a high CPU load. After generating the opimized media, this process is completely omitted. Interestingly, with optimized media, the CPU load is also basically about 25% higher, while the GPU load remains about the same. The main problem is clearly the 30FPS and 60FPS clips in the 24FPS timeline. Especially with the 30FPS clips no smooth playback is possible and with optimized media the playback of the 30FPS clips gets even worse! Interestingly, 60FPS clips play back basically fine in a 24FPS timeline, even though they cause a good 20% higher CPU load compared to the 30FPS ones. In a 30FPS timeline, playback is perfect for all clips, with optimized media causing a good 25% higher CPU load here.

Obviously, the conversion from 30FPS to 24FPS is the main problem. This does not work well. Converting 60FPS to 24FPS does cause a slightly higher CPU and GPU load, but it works fine. Optimized media doesn't help either, in fact it's like optimized media actually makes the CPU load and playback in the 24FPS timeline worse. The only thing that helps is to convert the clips to the correct timeline format before importing them into DR. I think that maybe something is not quite right with the conversion from 30FPS to 24FPS, possibly it is a bug.