OS X Mountain Lion Bible

Editing Media Files

You can edit media files—essentially, cut pieces out or trim them—using the controls in QuickTime Player 10. To do so, choose Edit⇒Trim or press +T. The time bar changes to the trim slider, which show a sequence of stills for video and the sound waves for audio.

Drag the trim slider's thumbs on either the left or right side to trim from the beginning or end, respectively, of the file. You can start with one side and then move onto the other side. For audio files, you also can choose Edit⇒Select All Excluding Silence or press Shift++A to exclude the silent part of the file (this moves the trim sliders to exclude silence at the beginning and/or end of the file, but it leaves silence inside the file). Click Trim to complete the cut. (You can choose Edit⇒Undo Trim or press +Z to cancel the trim.)

When you're finished, click Trim to apply your cuts to the file. QuickTime Player makes a copy of your media file containing those edits. Close the file by choosing File⇒Close or pressing +W; in the settings sheet that appears, enter a name and choose a location to store the edited ...