In Blackbird, you can apply blur effects to video tracks for various purposes such as redaction of faces and logos for news and social media, or for stylized imagery. Here's how you can set up a blur on a video clip:

Select the Video Track: 

Right-click on the video track that you want to apply the blur effect to. This will bring up a context menu with various options.

Access the Video Effect Control Interface: 

After right-clicking on the video track, click on the video effect icon. This action will launch the Video Effect Control Interface.

Apply the Blur Effect: 

In the Video Effect Control Interface, click on the "Blur" button at the top. This will apply a Gaussian blur effect to the entire video frame, effectively blurring the entire clip. Additionally, a blur sub track will appear under the clip on the timeline, indicating that a blur effect has been applied.

Adjust the Range of Blur (Optional): 

If you only want the blur effect to affect a specific range of the video, you can trim the sub track. Right-click on the sub track and drag the trim points to adjust the range of the blur effect. This will target only the selected track, which is the blur sub track in this case.

Apply Blur to Specific Section (Alternative Method):

Alternatively, you can razor or break the clip into the desired range using the edit point button. Place the edit point at the start and end of the section you want to apply the blur effect to, effectively splitting the clip. Then, apply the blur effect to that specific section of the video.

Using these methods, you can easily apply blur effects to video clips in Blackbird for various editing purposes, whether it's for redaction, stylization, or other creative effects.