Apple today released QuickTime 7.6, which includes a number of performance, compatibility, and security updates. According to the support document for the release, the update includes the following changes:

Video:
- Improves single-pass H.264 encoding quality
- Increases the playback reliability of Motion JPEG media

Audio:
- Improves AAC encoding fidelity
- Audio tracks from MPEG video files now export consistently

Application Support:
- Improves compatibility with iChat and Photo Booth

The update, which weighs in at 72.3 MB and requires OS X 10.4.10 or later and a 400 MHz G3 processor or later, also includes a number of security fixes.

Sources: Macrumors , Apple