CUDA not working for many DVDs

[mjd]

I am trying to rip some old TV shows from DVD (Specifically, 'Matlock', if it matters). For some reason, even though CUDA is enabled, the rip does not invoke it and thus it takes twice as long (and makes my computer run hot because the CPU is carrying the whole load). Last week I was ripping another series ('Murder She Wrote') and on some DVDs, some episodes would use CUDA and others would not. Again, there was no pattern. What is it that makes the ripper decide whether to use CUDA? I have an NVIDIA 1080 with current drivers.

I can send logs if that would help but there are several files generated in the log file. I am not sure which one(s) you need.

[mjd]

Adding more information: I played with this a bit more and found that CUDA does happen if I choose any of the h265 formats as output. I had been using h264. I am hopeful I will be able to use the h265 in my Plex server to play using a Roku on my 4K tv.