– Put the 4×3 video on v1
– Add a 3d warp effect and use the scretch properties to make it 4×3 with black bars at the sides
– now “step in” (bind this to your keyboard if you dont have it).
Once you step into the effect you will see your video on v2, with a blank v1 (the v1 represents the ‘black’ behind your movie). We are now going to fill that blac with something else. Place your background on v1 and make sure it’s identical length as the above v2 track.
Now “step out” and view your normal timeline — you should see your 4×3 video with the BG on the edges. If you need to add FX to the background at all, step back in and mess with it.
You can now add your title on v2 and carry on.