Good news for Apple TV and the iPhone. Starting today, Apple TV owners can start watching YouTube content on their TV sets. YouTube content will also be available to the iPhone when it officially launches on June 29th.

Apple TV users can download a free update via the built-in software update option to enable a new YouTube content menu. An option to “check for updates” is listed under the Apple TV settings screen.

iPhone users will be able to enjoy YouTube’s originally-created content on their iPhones when they begin shipping on June 29. A YouTube player application on the iPhone will wirelessly stream YouTube’s videos to the iPhone over Wi-Fi or EDGE networks and play it on iPhone’s 3.5 inch display.

Both AppleTV and the iPhone will play YouTube content that has been reencoded into Apple’s h.264 video format. 10,000 of YouTube’s videos have been converted so far with the remainder expected by the fall. An Apple press release claims that h.264 was chosen “to achieve higher video quality and longer battery life on mobile devices.”

Reports coming out of WWDC 2007 say that one of Apple’s justifications of avoiding Flash video playback on the iPhone is improved battery life. The iPhone contains dedicated hardware capable of playing h.264 content, while Flash content would require more intensive use of the iPhone’s CPU, resulting in higher battery drain.