Sync-pop

A sync-pop is a 1kHz tone that is exactly one film frame in duration, used for matching picture and sound negatives together. The sync-pop must occur exactly two seconds (or three feet) before the first frame of picture (FFOP) in a film reel. If the picture negative contains a standard Academy film leader, the sync-pop on the sound negative will line up perfectly with the film frame displaying a "2" (if the leader is counting down in seconds) or the film frame displaying a "3" (if the leader is counting down in feet). The terms 2-pop and 3-pop are often used interchangeably with sync-pop depending on how the leader is counting down.

Accurate sync-pops are critical for matching picture and sound film elements together. It is standard industry practice to include sync-pops on all film-reel length sound elements for picture synchronization.