I would like to synchronize my computer with an external camcorder recording so that I can know exactly (to the millisecond) when certain recored events happen with respect to other sensors logged by the computer. One idea is to playback short sound pulses or chirps every second from the computer that get picked up by the microphone on the camcorder. But the accuracy of a simple cron job playing a sound clip is not precise enough. I was thinking of using something like gstreamer, but how does one get it to playback a clip at precisely a certain time according to the system clock?