Changes restart the stream — the receiver resets automatically (new
session id in the frame headers; that's the fountain protocol's gift).
Images and videos are re-encoded on the way in, to 90% of the max
payload; re-encoding video runs in real time, so a 40-second clip takes
40 seconds. Anything still over the limit after that is refused rather
than started.
Max screen brightness helps. The stream loops forever — stop when the
receiver says done.