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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
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
Waveform of one frame (1/30th of a second) of 1khz sound
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 magnetic dubber, 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.
Whereas laying down bars and tone prior to program start establishes
1 frame of 1 khz audio
video and audio calibration levels on the tape, the 2-pop is primarily
used for picture and sound synchronization. Therefore, while the
loudness of the 2-pop may be the same as the bars and tone audio 2-pop's sound frequency and duration
level in use, this is not a requirement. The loudness level should be Problems listening to this file? See media help .
sufficient to be heard clearly.
Robert Berke Post Production Sound FAQ
Guide to Video Sync , ProSoundWeb