Starts the process at once. A failure to start is reported through OnFailure, never thrown.
Whether the process is still taking input.
What the decoder last wrote to stderr, for the log.
Ends the process; no failure is reported for it.
Stops reading the decoder's output, so ffmpeg blocks writing it (back-pressure from a full frame queue).
Reads the decoder's output again.
Writes one unit of the elementary stream. The pipe buffers what ffmpeg has not read yet, so a decoder whose output is paused (see PauseOutput) holds the compressed backlog, which is small at the avatar's bitrate.
One supervised decoder child process.