Unable to use it with NixOS and Intel Graphics HD

[blackheaven]

I'm struggling to use it with NixOS unstable:

$ webcam-filters --input-dev /dev/video0 --output-dev /dev/video3 --hw-accel-api vaapi --background-blur 50
failed to find and enable element 'vaapijpegdec'
failed to find and enable element 'vaapimpeg2dec'
failed to find and enable element 'vaapih264dec'
failed to find and enable element 'vaapih265dec'
failed to find and enable element 'vaapivc1dec'
failed to find and enable element 'vaapivp8dec'
failed to find and enable element 'vaapivp9dec'
unable to find a suitable input format
Aborted!
$ webcam-filters --input-dev /dev/video0 --output-dev /dev/video3 --background-blur 50
unable to find a suitable input format
Aborted!
$ export LIBVA_DRIVER_NAME=iHD
$ webcam-filters --input-dev /dev/video0 --output-dev /dev/video3 --hw-accel-api vaapi --background-blur 50
failed to find and enable element 'vaapijpegdec'
failed to find and enable element 'vaapimpeg2dec'
failed to find and enable element 'vaapih264dec'
failed to find and enable element 'vaapih265dec'
failed to find and enable element 'vaapivc1dec'
failed to find and enable element 'vaapivp8dec'
failed to find and enable element 'vaapivp9dec'
unable to find a suitable input format
Aborted!
$ export LIBVA_DRIVER_NAME=i965
$ webcam-filters --input-dev /dev/video0 --output-dev /dev/video3 --hw-accel-api vaapi --background-blur 50
failed to find and enable element 'vaapijpegdec'
failed to find and enable element 'vaapimpeg2dec'
failed to find and enable element 'vaapih264dec'
failed to find and enable element 'vaapih265dec'
failed to find and enable element 'vaapivc1dec'
failed to find and enable element 'vaapivp8dec'
failed to find and enable element 'vaapivp9dec'
unable to find a suitable input format
Aborted!

Even if I have v4l2loopback and my hardware acceleration configured:

$ lsmod| grep loopback
v4l2loopback
videodev

I also tried with docker:

$ docker run -it --device=/dev/video0:/input-dev --device=/dev/video3:/output-dev ghcr.io/jashandeep-sohi/webcam-filters:master --background-blur 50
docker: Error response from daemon: error gathering device information while adding custom device "/dev/video3": no such file or directory.
ERRO[0000] error waiting for container: context canceled

NB: it would be grep to document how to install it at system level.