This will make it play at twice its usual speed. Your rate should not be
negative nor exactly zero. You can set a rate to e.g. 1e-6 if you want to
in practice stop the video; once you change it back to normal speed,
-the next frame will resume playing.
+the next frame will resume playing. Be aware that changing the rate may
+make the audio behave unpredictably; there are no attempts to do time
+stretching or change the pitch accordingly.
Finally, if you want to forcibly abort the playing of a video,
even one that is blocking on I/O, you can use (since Nageru 1.7.2)::