Default ffmpeg_wait to 0, which makes pyTivo skip the poll()ing and just
wait() for FFmpeg to finish. Since I've never personally seen FFmpeg get
stuck, IIRC. To Do: There's even more common code now.
New description for ffmpeg_wait. Could use expansion.
Tighter.
On the off chance that something actually tries to parse the sid as a
16-digit hexadecimal number...