Full change log is as follows:
Addresses an issue in which audio is not output when playing some video content.
Addresses an issue in which video is not displayed when playing some content.
Audio output setting
Adds an audio output setting for switching to 16-bit audio for compatibility with some TVs and AV receivers.
Live FF/RW improvements
Improves the performance of fast-forwarding and rewinding live events.
Addresses an issue in which the description information is not displayed for some movies.
YouTube video order
Addresses an issue in which YouTube subscription videos were not ordered by date.
To update your Apple TV, from Settings –> General , hit “Update Software”, followed by “Download and Install” to get to the latest build.
Optionally, you can also download the firmware file from the link given below and update Apple TV using iTunes.
Download Apple TV 4.2.2 (8F305)