The same MP4 video is available in HD and UHD, but I can’t import the UHD version. I’m not sure what the file extension for the UHD one is, but I know it’s called HEVC (H.265). If this problem could be solved, that would be great — thank you.

aike what do you mean? Any resolution video is being supported in Frame Extractor.

What type of video are you having problems with? What is the file extension?