If you are using HDMI our or AirPlay mirroring from an iPad you will notice that the displayed image on your TV is not filling up the entire screen.
This is because of how AirPlay mirroring works - it is trying to fit the entire screen of the iPad inside of the TV screen without cropping or cutting off any part of it. The natural result is an area of black bars on the right and left sides.
If you're trying to achieve full screen playback over airplay these are you options right now:
1. If available, use an iPhone or iPod touch 5th gen. That will correctly render 16:9 images to your TV.
2. Use the zoom feature on your TV to increase the image size