Editing > Timewarps > Creating and Modifying Timewarps in the Timelines >
Editing Timewarps with the Channel Editor

Using the Channel Editor, you can:

- Create a variable speed timewarp by animating the speed channel.
- Change the duration by trimming the timewarp.
- Add a trail.
- Animate Mix, Trail and Timing values.
- Set the sampling option.

To access the Channel Editor:

1. Double-click a timewarped segment.

   The speed and timing curves are shown in the Channel Editor of the Timewarp Editor.

(a) Speed curve(b) Timing curve

For the timing curve, the source clip frame number is mapped along the X, or horizontal, axis. The range is from 0 at the origin to the total number of frames at the top of the graph. You cannot add frames to the source clip in the Channel Editor.

The result clip frame number is mapped along the Y, or vertical, axis. The range is from 0 at the origin to the total number of frames at the right of the graph. You can add frames to the trail of the timewarp.

Speed Curves and Timing Curves

Timewarps are created by modifying the timing of the source clip or by changing the playback speed of the source clip. When you change a clip's timing, you are essentially changing the time that it takes for a clip to reach a given frame. For example, in a 100-frame clip, you could adjust the timing so that only the 50th source frame is reached by the end of the clip's 100 frames. This effectively halves the clip's playback rate. A negative playback rate can be achieved by reversing a clip's timing curve (by changing the value at the last keyframe to the value of the first keyframe and the other way around).

A steeper timing curve results in a faster playback rate.

Adjusting the clip's speed has a different result. Setting the speed to 200% doubles the playback rate. A speed value of 50% plays the clip at half speed (or in slow motion). A negative speed value corresponds to playing the clip in reverse (where a -100% speed value creates a clip that plays back at the normal rate, but backward).

In the Channel Editor, notice that the speed curve and timing curve are, by definition, dependent on each other. You cannot change the speed without affecting the timing. Any action performed on one curve results in a corresponding action on the other. If you add a keyframe to the speed curve, a keyframe is automatically added to the timing curve at the same frame.

Changing the Timing of a Timewarp

Edit the timing curve to adjust the timing of the timewarp. You can adjust the speed of the timewarp independently of its duration. For example, if you are satisfied with the duration of your edit and want to modify the speed of an element without changing the overall duration of your clip, adjust the timing curve without changing the position of the first and last keyframes. It is recommended to adjust either the timing curve or the speed curve for a given timewarp. It can be difficult to control the result when keyframing both curves.

The timewarp speed updates dynamically as you edit. Use the positioner to scrub the timewarp and see the results of your edits or click the button in the playback controls.

Mix and trail values do not update dynamically.

Creating Variable Speed Timewarps

Variable speed timewarps contain animated speed and timing channels. You can create custom timewarp effects by adding and modifying keyframes for the timewarp.

To create a timewarp with a variable playback rate:

1. Select a segment in the timeline, then press Ctrl+T to create a timewarp.
2. Double-click the timewarped segment.

   The Speed channel in the Timewarp Editor is automatically selected.

3. Move to the desired frame and set a keyframe.
4. Move the keyframe or adjust the value.
   NoteThe timing curve also moves as you adjust the speed curve.
5. Set and adjust more speed channel keyframes as needed.
6. Click Return.

   The timeline appears with the timewarp selected. The variable timewarp is identified in the timeline by a “*” in place of the segment's head and tail information.

7. Display Result view and click the button to view the timewarp effect.

Trimming a Timewarp

Trim timewarps to change their length. This is useful if you change the speed of a timewarp and want a different length, in frame, or out frame.

You can trim timewarps in the timeline or in the Timewarp Editor. The Trim button in the Timewarp Editor is the same Trim button as in the Timeline menu. Its on or off state is carried over from one menu to the other, and it must be enabled to trim in either location.

Trimming timewarps is the same as trimming any element. If you cannot trim all the repeating frames out of a timewarp that has been reset, it is likely due to a Ripple setting constraint. Change the Ripple setting, if necessary, to trim out the unwanted frames.

NoteOnly the frames you see on a timewarp are rendered. Head and tail frames are not rendered. Use the Timeline Process option in the TL Utility box to render head and tail frames that you reveal when trimming a timewarp.

The Channel Editor also contains a Trim box for trimming timewarps.

(a) Trim box in point (b) Trim box out point

The left and right borders of the Trim box represent the in point and the out point of the segment being timewarped. Head and tail frames appear outside the box.

Use the Trim box handles to trim the timewarp.

(a) Rec In handle(b) Rec Out handle

Use the Trim Lock box to determine the effect of trimming in the timeline and in the Timewarp Editor.

(a) Trim Lock box

Select: | To:
--- | ---
Lock Off | Trim the in point or out point of the timewarp without locking any frames in position.
Lock One | Lock the frame on the current in point or out point when trimming a timewarp.
Lock Both | Lock the frames on both transitions when trimming the in point or out point of the timewarp. This is useful for changing the speed and duration of a timewarp while respecting the in point and out point.

The following diagram shows the effect of trimming a timewarp's out point when the curve is locked and unlocked (using Lock).

NoteA freeze frame occurs if part of the timewarp curve is moved outside the source's in or out point while trimming or editing the timewarp curve. You can also move an entire timewarp curve outside the in and out points.

To trim a timewarp in the Timewarp Editor:

1. Expand the Timing channel to display the Trim box.
2. Enable Trim.

   Trim handles appear on either side of the Trim box.

3. Set the Trim Lock box to Off, Lock, or Both.
4. Drag one of the Timewarp Trim box handles.

Note When timewarping a virtual source, there are no source limits.

Adding a Trail to the Image

You can add a trail to the image that precedes and/or follows the moving object:

- A pre trail mixes the frames that follow the current frame with the current frame. In the final clip, the image trail precedes the object.
- A post trail mixes the frames that precede the current frame with the current frame. In the final clip, the image trail follows the object.

The number of frames used in the mix is set with the pre trail and post trail timing curves. Since you can change the shape of the timing curves, the Trail values can be varied in the clip. When you use a pre trail or a post trail, the mix value is not used.

Setting the Fall-off for the Trail

The Weight field specifies the fall-off for the image trail. The Pre and Post field each have one Weight field.

- When the Weight is set to 100%, there is no fall-off. The first image in the trail has the same intensity as the image in the current frame.
- At 0%, the image in the current frame is at 100% intensity and the first image in the trail is at 0% intensity.

To add a constant pre trail or a post trail:

1. Select a segment in the timeline and then press Ctrl+T to create a timewarp.
2. Double-click the segment to access the Timewarp Editor.
3. If needed, adjust the speed of the timewarp using the Speed channel and the mix value in the Mix field.
4. Select Trail from the Timewarp Processing option box.
5. Set the pre trail value in the Pre field. Set the post trail value in the Post field.
6. Set the fall-off value for the trail in the respective Weight fields.

To add an animated pre trail or post trail to a segment:

1. Select a segment in the timeline and then press Ctrl+T to create a timewarp.
2. Double-click the segment to access the Timewarp Editor.
3. Enable Auto Key.
4. Select Trail from the Timewarp Processing option box.
5. Set the pre trail value in the Pre field. Set the post trail value in the Post field.
   NoteYou can also set these values in the Channel Editor.
6. In the Channel Editor, expand the Trail channel.

   Curves for the pre trail and/or post trail appear for channels where a value was set.

7. Add keyframes to the curve(s) and move them to animate the effect.
8. Set the fall-off value for the trail in the Weight channel. Each Pre Trail and Post Trail channel has one Weight channel.
9. Animate the weight curves if needed.
10. Click the button in the image window to preview the result of applying the trail curve to the source clip.
11. When you are satisfied with the results, click Return to return to the timeline.