Testing Video Transcoding with Docker

I’ve been playing with Jellyfin to stream movies and shows, and it’s a compelling, open source alternative to paid solutions like Plex. While there are endless ways to run it, I’ve settled on running a virtual machine in Proxmox with Jellyfin running in Docker, or in the native LXC container directly in Proxmox, which has far less resource requirements. One key to this is getting video transcoding working in this setup, while a VM has direct exposure to more of the underlying hardware to allow an easy passthrough to Jellyfin it gets tricker with LXC, and even Docker. To test that the passthrough is working I found a simple way to run FFmpeg in Docker to show if transcoding is setup correctly for the host to access and utilize the hardware. If you have a system you want to test out Intel’s QSV (Quick Sync Video), this is a way to do it.

There’s not much to setup, if you have the path available /dev/dri/renderD128 then Linux knows about your video card and can access the hardware.

Setup

Install Docker for your Linux distribution, and be sure to also follow the Post-install steps so your user can run Docker approprietly.

(NOTE to self, setup Docker in Rootless mode for greater security and post another howto here about the process)

Run it

Next up, copy the following command and paste it in your terminal, this will use Docker to pull the ffmpeg image, run it in a container, and have it try and do some test video transcoding using Intel’s QSV:

➜ docker run --rm \
        --device /dev/dri:/dev/dri \
        --entrypoint ffmpeg \
        ghcr.io/linuxserver/ffmpeg \
        -init_hw_device qsv=hw:/dev/dri/renderD128 \
        -hwaccel qsv -hwaccel_device hw -hwaccel_output_format qsv \
        -f lavfi -i testsrc=duration=3:size=1280x720:rate=30 \
        -vf 'format=nv12,hwupload=extra_hw_frames=64' \
        -c:v h264_qsv -f null -

The output from that will look something like this:

Unable to find image 'ghcr.io/linuxserver/ffmpeg:latest' locally
latest: Pulling from linuxserver/ffmpeg
3256fba51dcd: Pull complete
f6a4c3e338ed: Pull complete
5eb77ae98956: Pull complete
d662074283bf: Pull complete
ead2c5851e51: Pull complete
426dc410d532: Pull complete
281193377f04: Pull complete
744073494f37: Pull complete
27d26dfb2332: Pull complete
fa320a8bcf11: Pull complete
b9f43dc726ba: Pull complete
27d06c84b486: Download complete
5ec5d858b183: Download complete
Digest: sha256:96362b26bbe9ab836a619ccd49cf5258da9b2a22c8688317441aefb2bba4c6a0
Status: Downloaded newer image for ghcr.io/linuxserver/ffmpeg:latest

And finally once it’s downloaded and running, it will start the transcoding bit:

ffmpeg version 8.0.1 Copyright (c) 2000-2025 the FFmpeg developers
  built with gcc 13 (Ubuntu 13.3.0-6ubuntu2~24.04)
  configuration: --disable-debug --disable-doc --disable-ffplay --enable-alsa --enable-cuda-llvm --enable-cuvid --enable-ffprobe --enable-gpl --enable-libaom --enable-libass --enable-libdav1d --enable-libfdk_aac --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libharfbuzz --enable-libkvazaar --enable-liblc3 --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libplacebo --enable-librav1e --enable-librist --enable-libshaderc --enable-libsrt --enable-libsvtav1 --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpl --enable-libvpx --enable-libvvenc --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-nonfree --enable-nvdec --enable-nvenc --enable-opencl --enable-openssl --enable-stripping --enable-vaapi --enable-vdpau --enable-version3 --enable-vulkan
  libavutil      60.  8.100 / 60.  8.100
  libavcodec     62. 11.100 / 62. 11.100
  libavformat    62.  3.100 / 62.  3.100
  libavdevice    62.  1.100 / 62.  1.100
  libavfilter    11.  4.100 / 11.  4.100
  libswscale      9.  1.100 /  9.  1.100
  libswresample   6.  1.100 /  6.  1.100
libva info: VA-API version 1.23.0
libva info: Trying to open /usr/local/lib/x86_64-linux-gnu/dri/iHD_drv_video.so
libva info: Found init function __vaDriverInit_1_23
libva info: va_openDriver() returns 0
Input #0, lavfi, from 'testsrc=duration=3:size=1280x720:rate=30':
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: wrapped_avframe, rgb24, 1280x720 [SAR 1:1 DAR 16:9], 30 fps, 30 tbr, 30 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (wrapped_avframe (native) -> h264 (h264_qsv))
Press [q] to stop, [?] for help
[h264_qsv @ 0x5645ab5c0940] Using the constant quantization parameter (CQP) by default. Please use the global_quality option and other options for a quality-based mode or the b option and other options for a bitrate-based mode if the default is not the desired choice.
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf62.3.100
  Stream #0:0: Video: h264, qsv(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 30 fps, 30 tbn
    Metadata:
      encoder         : Lavc62.11.100 h264_qsv
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
[out#0/null @ 0x5645ab8b9dc0] video:41KiB audio:0KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: unknown
frame=   90 fps=0.0 q=33.0 Lsize=N/A time=00:00:02.93 bitrate=N/A speed=9.15x elapsed=0:00:00.32

And that’s it, if you see output like the above you can be sure that video transcoding is available and working on the host, plus Docker can access the hardware successfully.

Offline transcoding

In researching this I found a great GitHub project called Docker Transcode which will do, “Automatic conversion of all videos from the input folder to the output folder in H.265 (HEVC)”, so you won’t need Jellyfin to run it on the fly, which again is useful for reusing the same video files, but of course will take up more disk space in the long run.

Done

My long term goal with this work is to be able to share my Jellyfin collection with friends and family who are remote, but I need transcoding to work so they can have a reasonable video streaming experience as they would expect with Netflix or the like. No I don’t expect to run a Netflix style datacenter in my house (yet!) but as always, everything scales.