The biggest advance in QuickTime is the presence of the H.264 video codec (compressor/ decompressor). Just as music files based on the AAC audio codec in iTunes sound better than MP3 files of the same size, video files based on the H.264 video codec look better than those based on other codecs. More specifically, H.264 gives you the same quality as MPEG-2 video at one-third or one-half the data rate.

You’ll particularly notice that advantage in the new iChat, which produces muchimproved video and supports multiperson chats. The QuickTime Player itself also adds some nice features. Full-screen controls A let you play, pause, stop, fast-forward, or rewind, as well as adjust volume and scrub through a movie—all while remaining in full-screen mode. Previously, you had to switch out of fullscreen mode to make such adjustments.

Keep in mind, though, that you’ll need to purchase the Pro version to access fullscreen viewing. QuickTime’s new A/V Controls window b lets you determine how fast you jump back or forth through a movie’s frames. A new Playback Speed slider slows down playback to half-speed or makes it move up to three times as fast.