Assuming you need to prolong a movie as it is too short.

There is a way to do this using only Quicktime Pro. Let’s say you want to stretch it to twice the length. Just follow this guide, press the keys exactly as suggested:

• Create a new empty movie from File>New player.
• In your source, Ctrl + A, Ctrl + C.
• Swith to the new empty player, Ctrl + C, Ctrl + V. This gives you a movie twice the length, but everything doubled.
• In the new player do Ctrl + C, Ctrl + V. Then press delete.
• Now switch back to the source player and press Ctrl + C again.
• Switch back to the new player and this time from the Edit menu select “Add to selection & scale”.

This causes your pasted movie to be stretch (scaled) to the length of the new player, which we made double.