To mask a section of video using Adobe Premiere Pro, you can create a mask shape as a new title and apply the "Track Matte Key" effect to your video clip. This will make the affected area of your video appear cut out, blackening the background around the selected area. You can also reverse the mask, displaying all areas except those selected.

Step 1

Add the video you want masked to a new project in Premiere and drag the video clip onto the timeline.

Step 2

Press "Control-T" to create a new title. Leave the default settings and Press "OK."

Step 3

Select one of the shape tools and draw your desired mask's shape on top of the video. You can also use the pen or line tools to create a custom shape. The shape's color does not matter as long as it has a single, solid color.

Step 4

Close the title window. You don't need to save first. Your shape will appear in the project's clip bin.

Step 5

Drag the shape onto the V2 track on the timeline. Drag the edge of the V2 track to the right to match the length of your video, or as far into the video as you want to mask.

Step 6

Open the Effects tab. Open the "Video Effects" folder, followed by the "Keying" folder.

Step 7

Drag "Track Matte Key" on top of your video clip on the V1 track.

Step 8

Open the Effect Controls tab. Expand the Track Matte Key section if it isn't already open. If you don't see this section, make sure you have the V1 track selected.

Step 9

Change the "Matte" drop-down menu to "Video 2." Leave "Composite Using" set to "Matte Alpha."

Step 10

Play your video in the preview window to see the clip masked by your shape.