Velocity envelopes are used to change the speed of a video event over time. For example, you could use a velocity envelope to play a clip in slow motion.

This feature is available only in the full version of Vegas.

Each video event in your project has a specific duration that is not changed by velocity envelopes. Therefore, if you decrease the speed of a ten-second video event by 50%, only five seconds of video will be shown. On the other hand, if the speed is increased 200%, the ten seconds of video will play in only five seconds. The remaining five seconds of the event will be filled either with a freeze of the last frame or with ten additional seconds of video content from the media file.

Right-click the video event and choose Insert/Remove Velocity Envelope from the shortcut menu. A velocity envelope is drawn on the event.

Drag the envelope up to increase the playback speed of the event, or drag down to decrease its speed.

Setting a velocity envelope to a negative value will cause the event to play in reverse. Video events can only be reversed if there is media to reverse: an event cannot be reversed past the beginning of a media file. An event that has been reversed will play backwards until it gets to the first frame and will then hold that frame for the duration of the event.