h265 to h264 transcode -> No NVENC capable devices found


I am having difficulties in using the NVEnc capabilities of my GTX970. I want to transcode some h265 videos to h264 (so they play nice on the raspberry pi 3).

Most of the time I have no issues, but from time to time, ffmpeg will complain that No NVENC capable devices found.

It puzzles me, as h264_nvenc is available for the GTX970 (I am aware hevc_nvenc is not), but for some videos it works, some other does not.

The full error message I receive is:

[h264_nvenc @ 0x55b80d12ff00] No NVENC capable devices found
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

I have played with size, bit rate and rate and I can’t find a suitable combination that will make ffmpeg happy.

I am completely lost now as I fail to understand why it fails.

Try adding -loglevel verbose so you get more information.