OK - downloaded this app this weekend - loaded .avi file and .3gp file made minor changes and saved.
Despite numerous attempts, choosing a variety of encodings, the resultant clip had clear audio but
no video output. I loaded a .3gp file made no changes and saved it. Saved file was double the size
of the original but still no video. I was using VLC and WMP to try to play.
The only exception was .swf which played fine.
Any clues