Apple's latest QuickTime Pro software, version 7, has an added "Export to Apple TV" option that is capable of creating high definition content in 720p format.
iLounge discovered:
Using the H.264 video compression codec, Apple TV supports 720p playback at 24 frames per second - the frame rate used by movies, not TV shows - at substantially higher bit rates than prior iPod- and iTunes-created videos. A 2.5-minute 720P sample we converted with QuickTime yielded a 4214kbps, 76-Megabyte file from a 5708kbps, 102-Megabyte original, suggesting that feature-length, 90-minute HD movies formatted for Apple TV will require around 3 Gigabytes of hard disk space.
The creep towards streaming HD content continues.

From: Sony to double BRAVIA LCD TV production for growing European demand