Non-destructive editing is a form of editing signals where the original content is not modified in the course of editing—instead the edits themselves are edited by video editing software on a non-linear editing system (NLE).
A pointer-based playlist—effectively an edit decision list (EDL)—is used to keep track of edits. Each time the edited audio or video is played back or accessed, it is reconstructed from the original source and the EDL. Although this process is more computationally intensive than rendering each edit, changing the edits themselves can be almost instantaneous, and it prevents further generation loss as the audio or video is edited.
When videotape was first developed in 1956 by Ampex Corporation, the only way to edit was to physically cut the tape with a razor blade and splice segments together. While the footage excised in this process was not technically "destroyed", continuity was lost and the footage was generally discarded.
In 1963 with the introduction of the Ampex Editec, video tape could be edited electronically with a process known as linear video editing by selectively copying (or dubbing) the original footage to another tape called a "master". The original recordings are not destroyed or altered in this process.
Non-linear editing, originally developed in 1971 by CMX and now the most prevalent form of editing video and film, is also non-destructive: Un-edited original footage is digitized into electronic files stored digitally on a computerized disk-based system. The edited end-product (often referred to as a "sequence" or "playlist") is simply a series of digital files played back out of the editing computer. In this case, neither the original footage nor the digitized source files are destroyed in the editing process.