The term "aspect ratio" refers to the shape of a television image. Older, square-shaped television sets had an aspect ratio of 1.33:1, meaning they were 1.33 times wider than they were tall. Newer LCD and plasma TVs have an aspect ratio of 16:9, or 1.85:1. For Comcast cable users who have recently upgraded to an LCD or Plasma TV, you will have to adjust the aspect ratio on your cable box to make sure you are seeing television programming in the proper aspect ratio.
Press the "Menu" button on your Comcast remote control.
Use the directional arrow buttons on the Comcast remote to select the "Setup" menu. Press the "OK" button to enter this menu.
Use the arrow buttons to select the "HDMI" category. Change the setting that reads "4:3" to "16:9."
Use the arrow buttons to select the "SD" category. Set it to "Off."
Press the "Exit" button on your remote control to exit the menu. Your Comcast cable box's aspect ratio will now be properly adjusted to match the ratio of your television.
Though television is now being broadcast exclusively in a digital format, not all programming will be broadcast in the 16:9 aspect ratio. If you encounter a show that does not completely fill your screen, don't panic. The black bars on the left and right side of the screen are normal.