Time Remap Filter

The Time Remap filter is the first filter that allows altering the timing of the underlying source clip. It maps clip time to output time.

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Limitations

  • It can only be added onto clips with NO B-frames. If you try to add it to such a clip, it shows the Convert to Edit-friendly dialog.
  • A proxy clip can mask the above check for B-frames and then export may be very slow or give bad results. However, it may also be a very convenient workaround for the check and dialog mentioned above if you are patient and confident to troubleshoot and fix problem areas upon export.
  • This filter cannot be disabled.
  • This filter does not support simple keyframes or filter trimming.
  • This filter can not be applied to tracks or the timeline output.
  • The audio waveform does not reflect any of the changes.

Usage

TL;DR

Filters > Time > Time Remap > Keyframes

Hold Ctrl to drag a keyframe vertical only or Alt to drag horizontal only except on macOS these are to drag vertical only or to drag horizontal only.

More Detail

The default setting for the Time Remap filter sets the output time equal to the clip time which results in no change to the clip.

The user can interact with the keyframes to change the time mapping. When the slope of the line is up, time is moving forward. When the line is flat, time is frozen (freeze frame). When the slope of the line is down, time is moving backwards (reverse). A steeper slope moves time faster.

When the speed is faster than 1.0, multiple clip frames can map to the same output time.

Parameters

Time

This is the output time of the current frame.

- and + decrement or increment by one frame at a time. You can click and hold these to repeat.

< Sets the speed between the previous keyframe and the current frame by adding a keyframe at the current time position if needed.

> Sets the speed between the the current frame and the next keyframe by adding a keyframe at the current time position if needed.

Enable pitch compensation

Enable this if you want the audio pitch to remain close to the original and not affected by speed. The quality is degraded especially for speeds less than 0.5 or greater than 2.0.

Image mode

The Image Mode allows the user to choose between selecting the nearest frame, or blending frames frames.

If 30fps footage is sped up to 2x, it effectively becomes 60fps footage but with half the duration of the original. In this example, the sped-up clip is twice the frame rate of the timeline. This means two frames of source fit into the duration of one timeline frame. The export engine has to choose what to do:

  1. Choose a single source frame that is closest to the timestamp of the timeline (nearest mode).
  2. Blend multiple source frames into one mash-up frame with averaging (blend mode).

Quick tip: “Blend” mode could be useful for timelapse videos where the action needs to be sped up around 8x or more. Instead of seeing people or stars or whatever flickering between unpredictable positions on the screen, Blend mode would average their movements and create connective trails similar to extreme motion blur. This makes it much easier to track where people are moving and gives a much more relaxed and artsy vibe to the video. This also means not having to do a long-exposure photo sequence with your camera then stitch the photos into a video later to get the same effect… instead, it can be done as a single normal video, which can serve the dual purpose of extracting clips you care about in normal speed, but motion blurring the rest of it for a timelapse.

Here’s why it works:

Nearest mode is the same as the frame drop-or-dupe method that the timeline has used for years to handle frame rate mismatches. If someone puts 60fps video on a 30fps timeline, it drops every other frame of the 60fps video to scale it down to 30fps. It selected the “Nearest” frame to the 30fps cadence.

Extending that concept, if someone takes a 10-second clip and goes to Properties > Speed > 5x so that it becomes a 2-second clip, Shotcut accomplishes the speed-up by dropping (ignoring) four frames then displaying the fifth.

If the Time Remap filter is set to Nearest mode, then the usual dupe-or-drop method described above continues to be used. For the exported frame below, I took a 10-second countdown and did a Time Remap to 2 seconds in Nearest mode (same as Properties > Speed > 5x) then exported:

But here is (almost) the same frame when the Time Remap filter is set to Blend mode:

Instead of ignoring four frames and showing only the fifth, the five frames are now averaged together. This causes a gradient in the circular swipe pattern, because the dark bottom-left swipe was on the screen longer than the upper-left, therefore it went darker when averaged.

The faster the speed-up, the more frames that will be blended together.