Apple TV 4.2.1 Update Now Available. Fixes Screen Flickering And Other Issues
Apple has released Apple TV firmware update 4.2.1 (iOS 4.3.1 - build 8F202) for Apple TV second-generation to fix a number of issues, including screen flickering, waking from sleep, and audio output.
Addresses issues that may cause the screen to flicker or display incorrect color on some older TVs.
Wake from sleep
Addresses an issue where Apple TV may not wake up from sleep.
Addresses an issue where audio may not be heard on some TV models after switching from another input.
Stability and performance
Apple TV Software Update 4.2.1 includes stability and performance fixes for Apple TV.
You can install the new update by choosing Software Update on your Apple TV.