- Go to the clip properties and set the duration to something longer that will meet your needs. Maybe just make it way longer than you need. For example, if you are just going to double the speed, then reduce the length by half. But if you are going to use keyframes to make some interesting effects, maybe you don’t know how long it will need to be until you are done.
- Apply the Speed filter and adjust the keyframes to your liking
- Drag the right edge of the clip to trim it back down to the length were you want the effect to end.