It seems that what you want to do can be really simple. You can make that jpg file you call a mask as transparent as you want. Try this: Highlight that jpg on track 3. Place the mouse cursor at the top of that jpg on track 3. Slowly move the cursor down and see that the opacity is 100%. Drag that horizontal line down to reduce the opacity to somewhere between 0 to 70% so you can see the clip on track 1.
Go to the transition room and put either the slide or shove transition at the beginning of that jpg and change the duration to half that of the jpg. Place a shove transition only at the end of the jpg and increase the duration to meet the other transition on the left. That should do it.
Did you want only the sea life and not the ocean bottom to show in that jpg? You can try chroma keying for that.
There are many ways to do what you are after. Others users do this different. Hope that this may be enough to get started. Let us know if any of this might help.
This message was edited 1 time. Last update was at Nov 30. 2015 16:51