Non-linear editing (NLE) is a form of offline editing for audio, video, and image editing. In offline editing, the original content is not modified in the course of editing. In non-linear editing, edits are specified and modified by specialized software. A pointer-based playlist, effectively an edit decision list (EDL), for video and audio, or a directed acyclic graph for still images, is used to keep track of edits. Each time the edited audio, video, or image is rendered, played back, or accessed, it is reconstructed from the original source and the specified editing steps. Although this process is more computationally intensive than directly modifying the original content, changing the edits themselves can be almost instantaneous, and it prevents further generation loss as the audio, video, or image is edited.
A non-linear editing system is a video editing (NLVE) program or application, or an audio editing (NLAE) digital audio workstation (DAW) system. These perform non-destructive editing on source material. The name is in contrast to 20th-century methods of linear video editing and film editing.
Basic techniques A non-linear editing approach may be used when all assets are available as random-access files on video servers, on local solid-state drives, or hard disks, rather than recordings on reels or tapes. While linear editing is tied to the need to sequentially view film or hear tape, non-linear editing enables direct access to any video frame in a digital video clip, allowing editors to work faster and more efficiently without having to play or scrub/shuttle through adjacent footage to reach it, as is necessary with video tape linear editing systems.
When ingesting audio or video feeds, metadata is attached to the clip. That metadata can be attached automatically (timecode, localization, take number, name of the clip) or manually (players' names, characters, in sports). It is then possible to access any frame by entering the timecode or the descriptive metadata directly. An editor can, for example, at the end of the day in the Olympic Games, easily retrieve all the clips related to the players who received a gold medal.
The non-linear editing method is similar in concept to the cut-and-paste techniques used in information technology (IT)Evans, Russell. Practical DV Filmmaking. Focal Press, 2005.. However, with the use of non-linear editing systems, the destructive act of cutting of film negatives is eliminated. It can also be viewed as the audio/video equivalent of word processing, which is why it is called desktop video editing in the consumer space.
Broadcast workflows and advantages
In broadcasting applications, video and audio data are first captured to hard-disk-based systems or other digital storage devices. The data are then imported into servers, employing any necessary transcoding, digitizing or transfer. Once imported, the source material can be edited on a computer using any of a wide range of video editing software.
The end product of the offline non-linear editing process is a frame-accurate edit decision list (EDL), which can be taken, together with the source tapes, to an online-quality tape or film editing suite. The EDL is then read into an edit controller and used to create a replica of the offline edit by playing portions of the source tapes back at full quality and recording them to a master as per the exact edit points of the EDL.
Editing software records the editor's decisions in an EDL that is exportable to other editing tools. Many generations and variations of the EDL can exist without storing many different copies of the final product, allowing for very flexible editing. It also makes it easy to change cuts and undo previous decisions simply by editing the EDL. Generation loss is also controlled, due to not having to repeatedly re-encode the data when different effects are applied. Generation loss can still occur in digital video or audio when using lossy video or audio compression algorithms, as these introduce artifacts into the source material with each encoding or re-encoding. Codecs such as Apple ProRes, Advanced Video Coding and MP3 are very widely used, as they provide dramatic reductions in file size while often being indistinguishable from the uncompressed or losslessly compressed original.
Compared to the linear method of tape-to-tape editing, non-linear editing offers the flexibility of film editing, with random access and easy project organization. In non-linear editing, the original source files are not lost or modified during editing. This is one of the biggest advantages of non-linear editing compared to linear editing. With the EDLs, the editor can work on low-resolution copies of the video. This makes it possible to edit both standard-definition broadcast quality and high-definition broadcast quality very quickly on desktop computers that may not have the power to process huge full-quality high-resolution data in real time.
The costs of editing systems have dropped such that non-linear editing tools are now within the reach of home users. Some editing software can now be accessed free as web applications; some, like Cinelerra (focused on the professional market) and Blender, can be downloaded as free software; and some, like Microsoft's Windows Movie Maker or Apple's iMovie, come included with the appropriate operating system.
Accessing the material
The non-linear editing system retrieves video media for editing. Because this media exists on the video server or other mass storage that stores the video feeds in a given codec, the editing system can use several methods to access the material: Direct access The video server records feeds with a codec readable by the editing system, has a network connection to the editor and allows direct editing. The editor previews material directly on the server (which it sees as remote storage) and edits directly on the server without transcoding or transfer. Shared storage The video server transfers feeds to and from shared storage that is accessible by all editors. Media in the appropriate codec on the server need only be transferred. If recorded with a different codec, media must be transcoded during transfer. In some cases (depending on material), files on shared storage can be edited even before the transfer is finished. Importing The editor downloads the material and edits it locally. This method can be used with the previous methods.
Editor brands
The leading professional non-linear editing software for many years has been Avid Media Composer. This software is likely to be present in almost all post-production houses globally, and it is used for feature films, television programs, advertising and corporate editing. In 2011, reports indicated, "Avid is still the most-used NLE on prime-time TV productions, being employed on up to 90 percent of evening broadcast shows."
Since then, the rise in semi-professional and domestic users of editing software has seen a large rise in other titles becoming very popular in these areas. Other significant software used by many editors is Adobe Premiere Pro (part of Adobe Creative Cloud), Apple Final Cut Pro X, DaVinci Resolve and Lightworks. The take-up of these software titles is to an extent dictated by cost and subscription licence arrangements, as well as the rise in mobile apps and free software. , Davinci Resolve has risen in popularity among professional users and others alikeit had a user base of more than 2 million using the free version alone. This is a comparable user base to Apple's Final Cut Pro X, which also had 2 million users .
Some notable NLEs are: Adobe Premiere Pro Avid Media Composer DaVinci Resolve Final Cut Pro X and its predecessor, Final Cut Pro 7. Kdenlive Lightworks Shotcut Vegas Pro
Home use
Early consumer applications using a multimedia computer for non-linear editing of video may have a video capture card to capture analog video or a FireWire connection to capture digital video from a DV camera, with its video editing software. Various editing tasks could then be performed on the imported video before export to another medium, or MPEG encoded for transfer to a DVD.
Modern web-based editing systems can take video directly from a camera phone over a mobile connection, and editing can take place through a web browser interface, so, strictly speaking, a computer for video editing does not require any installed hardware or software beyond a web browser and an Internet connection.
History
When videotapes were first developed in the 1950s, 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, videotape could be edited electronically with a process known as linear video editing by selectively copying the original footage to another tape called a master. The original recordings are not destroyed or altered in this process. However, since the final product is a copy of the original, there is a generation loss of quality.
First non-linear editor The first truly non-linear editor, the CMX 600, was introduced in 1971 by CMX Systems, a joint venture between CBS and Memorex. It recorded and played back black-and-white analog video recorded in skip-field mode on modified disk pack drives the size of washing machines that could store a half-hour worth of video & audio for editing. These disk packs were commonly used to store data digitally on mainframe computers of the time. The 600 had a console with two monitors built in. The right monitor, which played the preview video, was used by the editor to make cuts and edit decisions using a light pen. The editor selected from options superimposed as text over the preview video. The left monitor was used to display the edited video. A DEC PDP-11 computer served as a controller for the whole system. Because the video edited on the 600 was in low-resolution black and white, the 600 was suitable only for offline editing.
The 1980s Non-linear editing systems were built in the 1980s using computers coordinating multiple LaserDiscs or banks of VCRs. One example of these tape and disc-based systems was Lucasfilm's EditDroid, which used several LaserDiscs of the same raw footage to simulate random-access editing. EditDroid was demonstrated at NAB in 1984. EditDroid was the first system to introduce modern concepts in non-linear editing such as timeline editing and clip bins.
The LA-based post house Laser Edit also had an in-house system using recordable random-access LaserDiscs.
The most popular non-linear system in the 1980s was Ediflex, which used a bank of U-matic and VHS VCRs for offline editing. Ediflex was introduced in 1983 on the Universal series "Still the Beaver". By 1985 it was used on over 80% of filmed network programs and Cinedco was awarded the Technical Emmy for "Design and Implementation of Non-Linear Editing for Filmed Programs."
In 1984, Montage Picture Processor was demonstrated at NAB. Montage used 17 identical copies of a set of film rushes on modified consumer Betamax VCRs. A custom circuit board was added to each deck that enabled frame-accurate switching and playback using vertical interval timecode. Intelligent positioning and sequencing of the source decks provided a simulation of random-access playback of a lengthy edited sequence without any re-recording. The theory was that with so many copies of the rushes, there could always be one machine cued up to replay the next shot in real time. Changing the EDL could be done easily, and the results would be seen immediately.