Trimming MP4 with MPEG Streamclip

An excellent feature of MPEG Streamclip is trimming MP4 video without re-encoding. This is great for preserving high quality compression when you simply need to cut down the video duration.

STEP 1: Scrub to your in point "Go To Keyframe" edit option to lock to next I-Frame and set in point. Do the same for your out point. This prevents the pixel smear you would see from cutting on P or B-Frames.

STEP 2: Click File -> Save As... to write new file with a clean MP4 wrapper.