The mysterious 12th iPhone application button has been revealed. It is YouTube. According to Steve Jobs, “the iPhone delivers the best YouTube mobile experience by far. Now users can enjoy YouTube wherever they are-on their iPhone, on their Mac or on a wide screen TV in their living room with Apple TV.” Videos posted after Apple’s announcement at D5 regarding YouTube on Apple TV, have been encoded using H.264. YouTube plans to convert their entire catalog to H.264 to allow playback on the iPhone and Apple TV. Currently around 10,000 videos will be available by June 29th, and Apple has posted a YouTube demo to their iPhone QuickView page. Today Apple also launched the YouTube player in their Apple TV via software update. Looks like Google CEO Eric Schmidt joining the Apple board had some significant impact.