Sync and Video : Working with Video in Pro Tools : Video Track Controls and Indicators : Frames View

Frames View
In Frames View, video data is displayed as pictures in the video track. These pictures are computed based on the video image, and scale according to your track zoom and height settings. They allow you to easily find a scene or sequence in the video track.
 
Frames do not display properly if you change zoom settings during playback. Black frames are drawn until playback is stopped. You should stop playback before changing zoom settings if you want to view frames.
If video pull up or pull down is enabled, frames do not change position.
Frames View Performance
When using Frames View to view video content in the video track, your computer may exhibit reduced or sluggish performance. If this happens on your computer, hide the video track or switch to Blocks View.