2-pop – one frame visual and audio mark 2 seconds before first frame of action. the audio is normally a -20db 1 khz tone. The visual can be a number of things from a white frame, bars, or a text card. The white frame or bars are my choice for visual reference to audio on playback.
The tail pop is the same, except that is can be placed anywhere at the end of the project, after last frame of action, it does not have to be 2 seconds after. But where ever it is place, it should be noted correctly in corresponding documentation. Placing sync pops is still highly recommended and can help in both maintaing sync across editing platforms and transfers of material in a project path.
It can also help to troubleshoot any sync issues that may arise. These sync markers are frankly more important on low budget projects where you may run into personnel that may more readily make a mistake from lack of experience.
You can also utilize the 2-pop within a count down at the beginning of a reel or project. Count downs can start at 10 seconds or 5 seconds and offer a “count” at the full second mark, ending on the 2-pop.
I use them in all my picture and sound work.
Used in television production and filmmaking post-production, a 2-pop is a 1 kHz tone that is one frame long and placed 2 seconds before the start of program. It is a simple and effective method of ensuring synchronization between sound and picture in a video or film.
A 2-pop is typically placed at the end of a visual countdown. Only the first frame of the “2″ is shown, and the remainder of the 2 seconds prior to the program is black. This provides a unique point of reference where the frame-long image and frame-long sound should align, similar to the way a film clapperboard is used to generate a synchronization point.
For example, in a video program the first frame of action (FFOA) starts at one hour (typically timecode of 01:00:00:00 in the US, and 10:00:00:00 in the UK), preceding that, 1 frame (or the 2-pop) of tone would be placed at timecode 00:59:58:00 or exactly 2 seconds before first picture.
A 2-pop is useful whenever picture and sound are handled separately. For example, projecting work-in-progress in the pre-video days involved a film projector linked to a magneticdubber, onto which the separate soundtrack reel was loaded. Aligning them by the 2-pop would ensure proper synchronization during playback. A modern scenario would involve sending a soundtrack to a separate facility for a sound mix. The returned product is a computer audio file which then needs to be synchronized again with the picture.