View source for 2-pop

{{short description|A brief 1 kHz tone}}
{{One source|date=August 2023}}
[[Image:2-pop_1frame_of_1khz.png|480px|right|Waveform of one frame (1/30th of a second) of 1&nbsp;kHz sound |thumb]]
Used in [[television production]] and [[filmmaking]] [[post-production]], a '''2-pop''' is a 1&nbsp;[[kHz]] tone that is one [[film frame|frame]] long and placed 2 seconds before the start of a program. It is a simple and effective method of ensuring [[synchronization]] between sound and picture in a video or film.<ref>{{cite book |last1=Jacobson |first1=Mitch |title=Mastering Multi-Camera Techniques From Pre-Production to Editing to Deliverable Masters |date=2012 |publisher=Focal Press |isbn=9781136057908 |page=369 |url=https://books.google.com/books?id=KMQqBgAAQBAJ&dq=2-pop+sync&pg=PA369}}</ref>
A 2-pop is typically placed at the end of a visual [[Film leader|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 television or video program the first frame of action (FFOA) starts at one hour (typically [[SMPTE time code|timecode]] of 01:00:00:00 in the [[United States|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. Alternately, in film post-production the leader starts at 01:00:00:00 (or 0+00 feet if using feet and frames as is common in the United States), the 2-pop starts at 01:00:06:00 (or 9+00), and the first frame of action (FFOA) starts at 01:00:08:00 (or 12+00).
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 [[Reel-to-reel audio tape recording|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.
== Sample sound ==
{{Listen|filename=2-pop_1frame_of_1khz.ogg|title=1 frame of 1 kHz audio|description=2-pop's sound frequency and duration|format=[[Ogg]]}}
Whereas laying down [[bars and tone]] prior to program start establishes 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 level in use, this is not a requirement. The loudness level should be sufficient to be heard clearly.
==References==
{{Reflist}}
== External links ==
*[https://henrirapp.com/what-is-2-pop/ What is 2-Pop & How is it used?], Henri Rapp Recording
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[[Category:Television terminology]]
[[Category:Film and video technology]]
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