A timewarp is an effect in which the speed of the action taking place appears faster or slower than when it was originally recorded. A freeze-frame effect, in which a single frame is repeated, is another form of a timewarp. Timewarps can have a constant or variable speed.

You can create timewarps in the EditDesk record timeline or BFX timeline, the Player, or by performing fit-to-fill four-point edits.

Using the Player you can create a timewarp by adjusting the playback speed of a source clip explicitly. When you edit the clip to the Record Area, it appears as a timewarp soft effect.

A fit-to-fill four-point edit is one in which you set the in and out points of a clip in the Source Area and of its destination in the Record Area. When Ripple is off, this results in a fit-to-fill edit. Here, the timewarp is calculated implicitly based on the difference between the duration of the source clip and its destination. There is no need to explicitly set values. A fit-to-fill edit is a convenient means to create a freeze-frame effect.

To create a timewarp in the timeline, use the Timewarp quick menu or the Timewarp Editor. Simple enhancements, such as blending frames to produce smooth timewarps, can be done using the quick menu. More complex effects, including variable speed timewarps and strobe effects, are created using the Timewarp Editor.

Timewarps whose values have been set implicitly take precedence over explicit timewarps. In other words, if you fit-to-fill a source clip for which a timewarp has been specified explicitly, the explicit timewarp is ignored. For example, if you reduce the playback speed of a clip by 50% in the Player, and then drop it into the timeline using a fit-to-fill edit, the 50% reduction is ignored.

A constant timewarp does not change over the duration of the clip. In the Timewarp Editor, the Speed channel is displayed as a straight line with one keyframe. A constant timewarp is commonly used to create a slow- or fast-motion effect. By adding keyframes, you can create a timewarp that varies over its duration. For example, you can create a clip that plays at its normal rate until a particular event occurs, decreases dramatically during the event, and then returns to normal for the rest of the clip. In addition, timewarps can have either positive or negative values. A negative value has the effect of reversing the clip.

A timewarped element's head and tail frames are determined by the speed and duration of the source. For variable speed timewarps, heads and tails are infinite; that is, source frames are reused infinitely, as determined by the timing curve. Note that only visible frames are processed. Head and tail frames are not.

Most of the timeline illustrations in this chapter are of the EditDesk record timeline. There may be some differences with those of a BFX timeline.