What is 2-Pop and how is it used?
2-Pop is a term for a 1 kHz (1000 Hz) tone that lasts 1 frame inserted 2 seconds before the start of the program. Originally established as part of the SMPTE “Universal Leader”, it’s still widely used today. It’s used as a simple method to ensure sync between Picture & Sound in Post-Production for Film, Commercial, or Television Programs.
A 2-Pop is used anytime sound & picture are handled separately. A common situation where 2-Pop may be used would be sending the audio to a separate facility for a post sound mix then where the edit is done. One the work is done the audio needs to be synchronized again with the picture, by lining up the 2 pop with the video it ensures a fast reliable way to ensure sync.
2-pop is placed at the end of a visual countdown leading into the video. As the counter counts down, and reaches the 2 second mark a 1 kHz tone plays for a single frame. Only the first frame of the 2 second lead in is show, after that black video leading into the start of the video. This is especially helpful for playback purposes. In addition to lasting only one frame, the standard (though not a requirement) is a -20 db volume level for the 1 kHz tone.
Gets its name from the popping sound such a short burst of tone sounds like, and its placement at the 2 second mark before the start of a program, it certainly is a 2-Pop.
Listen to a 2-Pop
Here is an example of a 2 pop with a 2 second lead in, a 1 frame burst of 1 khz tone at the first frame 2 seconds from the end of the file in a 23.98 fps project.