Non-linear editing

"NLE" redirects here. For the standardized test, see National Latin Examination.

A non-linear editing system (NLE) is a video editing (NLVE) or audio editing (NLAE) system that can perform random access on the source material.

Non-linear editing

Non-linear editing for film and television postproduction is a modern editing method that involves being able to access any frame in a video clip with the same ease as any other. This method is similar in concept to the "cut and glue" technique used in film editing from the beginning. However, when working with film, it is a destructive process, as the actual film negative must be cut. Non-linear, non-destructive methods began to appear with the introduction of digital video technology.

Video and audio data are first digitized to hard disks or other digital storage devices. The data is either recorded directly to the storage device or is imported from another source. Once imported they can be edited on a computer using any of a wide range of software. For a comprehensive list of available software, see List of video editing software, whereas Comparison of video editing software gives more detail of features and functionality.

In non-linear editing, the original source files are not lost or modified during editing. Professional editing software records the decisions of the editor in an "Edit Decision List" (EDL) which can be interchanged with other editing tools. Many generations and variations of the original source files can exist without needing to store many different copies, allowing for very flexible editing. It also makes it easy to change cuts and undo previous decisions simply by editing the edit decision list (without having to have the actual film data duplicated). Loss of quality is also avoided due to not having to repeatedly re-encode the data when different effects are applied.

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. With the edit decision lists, the editor can work on low-resolution copies of the video. This makes it possible to edit both broadcast quality and high definition quality very quickly on normal PCs which do not have the power to do the full processing of the 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 (focussed on the professional market), can be downloaded free of charge, and some, like Microsoft's Windows Movie Maker and Apple Computer's iMovie come included if you buy the appropriate operating system.

A computer for non-linear editing of video will usually have a video capture card for capturing analog video or a FireWire connection for capturing digital video from a DV camera, as well as video editing software. Modern web based editing systems can take video directly from a camera phone over a GPRS or 3G 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.

Various editing tasks can then be performed on the imported video before it is exported to another medium, or MPEG encoded for transfer to a DVD.

History

The first truly non-linear editor, the CMX 600 [1], was made in the early 1970s by the CMX Corporation, a joint venture between CBS and Memorex. It recorded & played back black-and-white analog video recorded in "skip-field" mode on modified disk pack drives the size of washing machines. These were commonly used to store data digitally on mainframe computers of the time. The 600 had a console with 2 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 which were superimposed as text over the preview video. The left monitor was used to display the edited video. A Digital PDP-11 computer served as a controller for the whole system. Because the video edited on the 600 was in black and white and in low-resolution "skip-field" mode, the 600 was suitable only for offline editing.

Various approximations of non-linear editing systems were built in the '80s using computers coordinating multiple laser discs, or banks of VCRs. Computer processing advanced sufficiently by the late '80s to enable true digital imagery, and has progressed today to provide this capability in personal desktop computers.

An example of computing power progressing to make non-linear editing possible was demonstrated in the first all-digital non-linear editing system to be released, the "Harry" effects compositing system manufactured by Quantel in 1985. Although it was more of a video effects system, it had some non-linear editing capabilities. Most importantly, it could record (and apply effects to) 80 seconds (due to hard disk space limitations) of broadcast-quality uncompressed digital video encoded in 8-bit CCIR 601 format on its built-in hard disk array.

Non-linear editing with computers as we know it today was first introduced by Avid in 1988 with the Avid/1, the first in the line of their Media Composer systems. It was based on the Apple Macintosh computer platform (Macintosh II systems were used) with special hardware and software developed and installed by Avid. The Avid/1 was the first system to introduce modern concepts in non-linear editing, such as timeline editing and clip bins.

The video quality of the Avid/1 (and later Media Composer systems from the late 80s) was somewhat low (about VHS quality), due to the use of a very early version of a Motion JPEG (M-JPEG) codec. But it was enough to be a very versatile system for offline editing, to revolutionize video and film editing, and quickly become the dominant NLE platform.

Although M-JPEG became the standard codec for NLE during the early 1990s, it had drawbacks. Its high computational requirements ruled out software implementations, leading to the extra cost and complexity of hardware compression/playback cards. More importantly, the traditional tape workflow had involved editing off tape, often in a rented facility. When the editor left the edit suite he could take his confidential video tapes with him. But the M-JPEG datarate was too high for systems like Avid on the Mac and Lightworks on PC to store the video on removable storage, so these used fixed hard discs instead. The tape paradigm of keeping your (confidential) content with you was not possible with these fixed discs. Editing machines were often rented from facilities houses on a per-hour basis, and some productions chose to delete their material after each edit session, and then redigitise it again the next day, in order to guarantee the security of their content. In addition, each NLE system had storage capacity limited by its hard disc capacity.

These issues were addressed by a small UK company, Eidos plc (which later became famous for its Tomb Raider video game series). Eidos chose the new ARM-based computers from the UK and implemented an editing system, launched in Europe in 1990 at the International Broadcasting Convention. Because it implemented its own compression software designed specifically for non-linear editing, the Eidos system had no requirement for JPEG hardware and was cheap to produce. The software could decode multiple video and audio streams at once for real time effects at no extra cost. But most significantly, for the first time, it allowed effectively unlimited quantities of cheap removable storage. The Eidos Edit 1, Edit 2 and later Optima systems even allowed the editor to use any Eidos system, rather than being tied down to a particular one, and still keep his data secure. The Optima software editing system was closely tied to Acorn hardware, so when Acorn stopped manufacturing the Risc PC in the late 1990s, Eidos stopped selling the Optima system; by this time Eidos had become predominantly a games company.

Another leap came in the late 90s with the launch of DV-based video formats for consumer and, more importantly, professional use. With DV came IEEE1394 (Firewire/iLink), a simple, inexpensive, accessible and native way of getting video into and out of computers. The video no longer had to be converted from an analog signal to digital data - it was recorded as digital to start with - and Firewire offered a very straight forward way of transfering that data without the need for additional hardware or compression. With this innovation, editing suddenly become a more realistic proposition for standard computers with software-only packages. It enabled real desktop editing producing high-quality results with a fraction of the cost of other systems.

More recently the introduction of highly compressed HD formats such as HDV has continued this trend - making it possible to edit HD material on a standard computer running a software-only editing application.

Avid has held on to its market leading position, but faces growing competition from other, cheaper, software packages, notably Adobe Premiere in 1992, and later Final Cut Pro in 1999. These three competing products by Avid, Adobe, and Apple are the foremost NLEs, and often referred to as the A-Team[2].

Avid is still considered the industry standard, with the majority of major feature films, television programs, and commercials created with its NLE systems. For example, Avid products - including technologies from its Digidesign audio division, and Softimage 3D animation subsidiary, were used in the creation of every film nominated in the Best Picture, Directing, Film Editing, Sound Editing, Sound Mixing, Visual Effects, and Best Animated Feature categories of the 77th Annual Academy Awards, held in 2005. In addition, Avid systems were the overwhelming NLE choice of the 2004-2005 Primetime Emmy Award nominees – with more than 50 shows in eleven major categories created on one or more Avid systems.

Quality

One of the primary concerns with non-linear editing has always been picture and sound quality. The need to compress and decompress video leads to some loss in quality. While improvements in compression techniques and disc storage capacity have reduced these concerns, they still exist. Most profressional NLEs are able to edit uncompressed video with the appropriate hardware.

With the more recent adoption of DV formats, quality has become an issue again: DV's compression means that manipulation of the image can introduce significant degradation. However this can be partially avoided by decompressing DV before making alterations and keeping the resulting video in an uncompressed format, thereby avoiding quality loss through recompression of the modified video images. Ultimately it depends on the DV Codec being used. Sony's Vegas DV codec, for instance, has been touted as able to endure up to 50 generations of recompression (in the same codec) until compression artifacts become noticeable to the average human eye.

DVCPRO HD has been shown to endure five generations of recompression before perceptual changes occur; though, even 15 generations of recompression only displays modest compression-related loss under 3x magnification.

The range of user-friendly editing tools has given inexperienced people access to editing at high quality for the first time.

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