I had about 50 events in the timeline. After the editing was complete, I made the letterbox for the first event.
But I did not know how to put the letterbox to all events rather than clicking Even Pan/Crop button for each events.
How do you put the letterbox to all events simultaneously?
If this is the only "fx" done to your event, do a copy (CTRL+C), select all events to which the letterbox should be applied, right-click one of them, choose "Copy Event Attributes".
Actually there is a lot easier way - add it to "Video output FX" portion. Make it the very last thing in the chain. Keep in mind whatever you put here will *really* be added to everything video wise.
*EDIT* - Sorry - I see you are using pan/crop. Thought you were using something like the Zenote Letterbox plug-in. Well, do what I told you and try this - use the Cookie Cutter. Set it to "Square". Border at 0.50, Repeat X = 2, Repeat Y = 1. See if that works for you - adjust border as needed.
You can also drop a mask on a top track with a transparent area, this works very well, and applies to everything. If you use a TGA, it will render pretty quickly.
Cookie cutter is a great way to go too. I wonder what the render time difference would be between the tga and the cookie cutter? Curious minds wanna know.