When no GPUs are found, ffmpeg uses GPU_THREADS variable for CPU

[jeremysherriff]

When setting up my docker-compose environment, I only changed the THREADS count for CPU knowing that I had no usable GPU (I have an Intel iGPU).

Snippet:

    environment:
      - GPU_THREADS=5
      - CPU_THREADS=3

This configuration spawned 8 ffmpeg processes:

Log snippet showing no GPUs being detected and used:

root@mediabox:/volume1/docker/previews# docker compose up -d
[+] Running 1/1
 ✔ Container previews  Started                                                                                                   10.3s
root@mediabox:/volume1/docker/previews# docker compose logs -f
previews  | 2025/01/02 21:53:25 | ℹ️  - GPU Detection (with AMD Support) was recently added
previews  | to this script.
previews  | 2025/01/02 21:53:25 | ℹ️  - Please log issues here
previews  | https://github.com/stevezau/plex_generate_vid_previews/issues
previews  | 2025/01/02 21:53:25 | ⚠️  - Error initializing NVIDIA GPU detection NVML Shared
previews  | Library Not Found. NVIDIA GPUs will not be detected.
previews  | 2025/01/02 21:53:25 | ⚠️  - Error initializing AMD GPU detection: 'ROCM_PATH'.
previews  | AMD GPUs will not be detected.
previews  | 2025/01/02 21:53:25 | ⚠️  - No GPUs detected. Defaulting to CPU ONLY.
previews  | 2025/01/02 21:53:25 | ⚠️  - If you think this is an error please log an issue
previews  | here https://github.com/stevezau/plex_generate_vid_previews/issues
previews  | 2025/01/02 21:53:25 | ℹ️  - Getting the media files from library 'Movies'
previews  | 2025/01/02 21:53:32 | ℹ️  - Got 1813 media files for library Movies

My expectation was that I would see 3 ffmpeg processes only.

[stevezau]

Right now it defaults to falling back to CPU if the GPU is not available.. but you are right prob better to fail.

I'll fix this when i get time.

[jeremysherriff]

Ah ok, good to have confirmation that it's working as (currently) intended.

Potentially you could drop one of the variables, if you've got fallback working nicely there may not be a reason to have both?