The H.264 decoder: a long-lived ffmpeg child framing its output by the declared size.
The frame size and the callbacks.
The ffmpeg binary.
Its release (decides the arguments).
Optional
Starts the process (tests pass a fake).
Writes one access unit.
Ends the decoder; no failure is reported for it.
Discards the frames of every unit written so far as they come out.
Stops reading frames, so the decoder blocks (back-pressure).
Reads frames again.
The H.264 decoder: a long-lived ffmpeg child framing its output by the declared size.