Just got started with Watermark Master today and it looks promising.
The only problem is that when we add watermarks to existing .flv files and the video output stays the same (to an .flv file) we receive several audio errors such as:
“audio stream not found” and
“sound filters initialization failed”
software automatically selects the codec “Sorenson H.263” when selecting .flv for the output. So, I'm not sure why everything works flawlessly except for audio output.