While watching a video in QuickTime: Hold the option key. Options such as speed and playback rate (the jog shuttle). Well as the volume, bass, and treble levels. Quicktime Player For Mac Adjust Player Speed Slow Speedįor any QuickTime movie with an audio track, you can adjust the right/left balance, as.Quicktime Player For Mac Adjust Player Speed Slow Windows 10.Quicktime Player For Mac Adjust Player Speed Slow Windows 7.