Sync and Video : Working with Video in Pro Tools : Video Track Controls and Indicators : Video Track Type Icons

Video Track Type Icons
A video track displays a QuickTime icon, Windows Media icon, or an Avid icon depending on the type of video added to it. No icon displays when the video track is empty.
You can add any supported video to an empty video track, in which case the icon will update and the video track will play back only that type of video.