If you're using a matrix system, sometimes they are not 1080 compatible, which is what the Apple TV default to. You might need to change the resolution in your settings. There are two ways to do this.
- Hold MENU and VOLUME DOWN for 5 seconds, then release.
- Your Apple TV will switch to a new resolution every 20 seconds.
- Select OK to choose a resolution or CANCEL to quit.
- Go to Settings
- Go to Audio and Video
- Go to TV Resolution and change