I'm trying to use MediaTranscoder to transcode UHD 2160p60 (aka 4K at 60 frames per second) video files. I've had good success transcoding from 2160p60 to 2160p30 (30 frames per second) on two devices I have: a Surface Pro LTE with a Core i5 CPU from 2018 and a desktop gaming machine with an Intel i7-5960X processor and an Nvidia GTX 980 Ti GPU.
Unfortunately, I've had less success transcoding from 2160p60 to lower bitrate 2160p60. It works fine on the Surface Pro but fails on the desktop machine. In that case MediaTranscoder.PrepareFileTranscodeAsync returns CanTranscode==false and FailureReason==Unknown. Based on the modules being loaded as shown in the debugger, I think MediaTranscoder is trying to use Nvidia's NVENC to transcode the file. NVENC for my GPU is supposed to support 2160p60 so I don't know why this fails.
Is 2160p60 output officially supported by MediaTranscoder? It seems to work on devices with Intel integrated GPUs with Quick Sync Video but not on devices with Nvidia discrete GPUs.