Editing B-roll (section)

==History==
[[File:B-Roll with 4 shots.png|thumb|Layout with 4 shots.]]
The term ''B-roll'' originates from a particular solution to the problem of visible splices in the narrow [[film stock]] used in [[16&nbsp;mm film]]. 35&nbsp;mm film was wide enough to hide splices, but 16&nbsp;mm film revealed the splices as flaws in the picture. To avoid this problem, the intended shots were spliced to [[Film leader|opaque black leader]], with the black leader hiding the splice. Two sequences of shots were assembled, the odd-numbered shots on the A-roll, and the even-numbered shots on the B-roll, such that all of the shots on one roll were matched by black leader on the other roll, in a checkerboard pattern (an alternate name for the process was "checkerboard printing".) Unexposed 16 mm raw print stock was [[Exposure (photography)|exposed]] twice, once to the A-roll, then it was exposed again to the B-roll.<ref>{{cite book |url=https://books.google.com/books?id=3NFAbjYD8MkC&pg=PA669 |page=669 |title=The Filmmaker's Handbook: A Comprehensive Guide for the Digital Age |first=Steven |last=Ascher |first2=Edward |last2=Pincus |publisher=Penguin |date=2007 |isbn=9780452286788}}</ref><ref>{{cite book |url=https://books.google.com/books?id=WRklp-TmfQkC&pg=PA108 |page=108 |title=Film Technology in Post Production |first=Dominic |last=Case |publisher=Taylor & Francis |date=April 26, 2013 |isbn=9781136049781}}</ref><ref>Spottiswoode, Raymond (1966), ''Film and its techniques''. U. Cal Press. Chapter 1, p 44.</ref>

Until the mid-1970s, news teams shot both main A-roll and secondary B-roll footage on 16&nbsp;mm film. [[Sound-on-film|Sound was integrated onto the film]] by way of a magnetic stripe at the edge of the film. The A-roll and B-roll scenes, shot at 24 frames per second, were converted to the television frame rate of 30&nbsp;fps using a [[telecine]] system consisting of two film projectors, one showing the main A-roll footage and the other showing the B-roll. The sound from the A-roll footage was used, or sound from narration or voiceover, while MOS images from the B-roll were intercut as desired.<ref name="Compesi and Gomez 2014"/>

In the 1980s, the term ''B-roll'' was adopted for [[linear video editing]] using at least two video tape machines. Traditionally, the [[Tape recorder|tape decks]] in an edit suite were labeled by letter, with the 'A' deck being the one containing the main tape upon which the main action material was shot. The 'B' deck was used to run tapes that held additional footage such as establishing shots, cutaway shots, and any other supporting footage. The sound was usually taken from the A deck alone, so that the B deck provided video without sound.<ref name="Irving and Rea 2014"/> As linear editing systems were unable to dissolve between clips on the same tape, an [[edit decision list]] (EDL) was used to mark clips as "A-roll" and "B-roll" to indicate source machines.