I'm using Vegas Pro 20, trying to edit MOV video files from an iPhone, filmed in HEVC 4K 60fps with HDR enabled (I can post MediaInfo if needed, but I guess iPhones are popular enough that he video file properties are known). The Vegas project settings match the video files, and HDR mode is set to HLG.
Just dropping one of those video files into the timeline, with no editing, no video FX, no transitions, etc., and the preview window set to "Draft (Auto)", I'm getting less than 1 fps playback speed. Disabling Legacy HEVC Decoder slightly improves things and I get about 2 fps, but that's still unusable.
The computer is fast enough to handle the material: Ryzen 7 3700X, GeForce RTX 3070, 64 GB RAM. The same video files play fine in video players on the machine, and I also have DaVinci Resolve Studio installed which plays them back on the timeline just fine with a smooth 60fps.
I assume there's something wrong with my Vegas setup. I'm not currently expecting Vegas to meet Resolve's performance, but it shouldn't be *that* slow, right? What can I try to maybe improve the situation?
Thanks in advance for any help