The clip handle simply indexes the clip slots from 0 so the first clip slot is 0 and the next is 1 etc. It is a 16Bit channel to allow up to 65535 clips. Blank slots are included so say you have ClipA then a blank slot and then ClipB you will need to set the channel to 2 to play clip B. Clip A would be on 0.
The clips only play when you have play selected. So when the playback channel is set to clear screen, changing the clip handle will have no effect until you set the playback channel to play. When set to play the clip index will have imediate effect.
Please not that the channel order of the 16Bit channels are reversed to most moving lights. This will be changed on the next version but can make it difficult to write a personality.
Some clip types do not support looping so it is possible that if you change the format of your clips the looping will work. It is normally possible for me to get certain video formats to work if you send a sample clip to me at support@screenmonkey.co.uk.
Olie