How to Use Motion Tracking Pixelate in Kdenlive

This article provides a step-by-step guide on how to automatically obscure moving objects, such as faces or license plates, in Kdenlive. By combining the “Motion Tracker” effect with the “Hide Region” filter, you can easily pixelate sensitive information in your videos without manually keyframing every frame. Follow along to learn how to set up the tracker, apply the pixelation effect, and map the tracking data for a seamless, automated result.

Step 1: Apply and Analyze the Motion Tracker

Before you can pixelate a moving object, you must first capture its movement using Kdenlive’s built-in motion tracking tool.

  1. Drag your video clip onto the timeline.
  2. Open the Effects tab, search for Motion Tracker, and drag the effect onto your video clip.
  3. In the Project Monitor, a rectangle will appear. Resize and position this box directly over the object you want to pixelate (such as a face or logo).
  4. Go to the Properties panel for the Motion Tracker effect.
  5. Select your preferred tracking algorithm (the default KCF or DaSiamRPN usually works best).
  6. Click the Analyze button (the play icon within the effect settings) to analyze the clip. Kdenlive will track the object and generate keyframe data.

Step 2: Apply the Hide Region Effect

Once the motion data is recorded, you need to apply the effect that will actually pixelate the video.

  1. In the Effects tab, search for Hide Region and drag it onto the same video clip.
  2. In the Hide Region properties, change the Type dropdown menu to Pixelate (you can also choose “Blur” or “Obscure” depending on your preference).
  3. Adjust the Width and Height parameters in the effect settings to match the size of the object you want to cover.

Now you must apply the tracking data to the Hide Region effect so that the pixelated box follows the moving object.

  1. In the Motion Tracker effect panel, click the menu icon (usually represented by three dots or a burger menu) and select Copy Keyframes to Clipboard.
  2. Go to the Hide Region effect panel.
  3. Click the menu icon next to the Geometry parameter (which controls the position and size of the pixelated box).
  4. Select Import Keyframes from Clipboard.
  5. In the dialog box that appears, make sure the offset and mapping options are aligned, then click OK.

The pixelated region will now automatically follow the path of the tracked object throughout the duration of the clip. You can play back the timeline to verify the alignment and make manual adjustments to the Hide Region’s size if the object moves closer or further from the camera.