A build of ffmpeg with many common audio and video codecs, including HEVC/VP9/AV1, as well as the Nvidia nvenc support.
Netflix's libvmaf support is also compiled in for running metrics on transcoded video.
It's best to make another docker container and copy the contents of /opt/ffmpeg from this container to your new container. This will make for a much smaller image. But you can also run it directly with
docker run -it offbytwo/ffmpeg
For an example of a smaller image that contains this (and other tools) see video-tools