Non-linear editing system

A non-linear editing system (NLE) is a video (NLVE) or audio editing (NLAE) digital audio workstation (DAW) system that performs non-destructive editing on source material. The name is in contrast to 20th century methods of linear video editing and film editing.Non-linear editing is the most natural approach when all assets are available as files on video servers 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, without needing to play or scrub/shuttle through adjacent footage to reach it, as was necessary with historical video tape linear editing systems. It is now possible to access any frame by entering directly the timecode or the descriptive metadata.
The NLE method is similar in concept to the "cut and paste" techniques used in film editing or in IT. 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.

Video and audio data are first captured to video servers, other hard disk-based systems, or other digital storage devices. The data are either direct to disk recording or are imported from another source (transcoding,digitizing, transfer). Once imported, the source material can be edited on a computer using application software, any of a wide range of video editing 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. This is one of the biggest advantages of non-linear editing compared to linear editing.

Professional editing software records the editor's decisions in an edit decision list (EDL) that is exportable to other editing tools. Many generations and variations of the original source files can exist without storing 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).Generation loss is also controlled, 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 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 Blender3D, can be downloaded as free software; and some, like Microsoft's Windows Movie Maker or Apple Inc.'s iMovie, come included with the appropriate operating system.

A multimedia computer for non-linear editing of video may have a video capture card to capture analog video and/or a FireWire connection to capture digital video from a DV camera, with its 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.

Linear video editing

Linear video editing is a video editing post-production process of selecting, arranging and modifying images and sound in a predetermined, ordered sequence.^[1] Regardless of whether it was captured by a video camera, tapeless camcorder, or recorded in a television studio on a video tape recorder (VTR) the content must be accessedsequentially.^[2] For the most part video editing software has replaced linear editing.

Until the advent of computer-based random access non-linear editing systems (NLE) in the early 1990s "linear video editing" was simply called "video editing".

The first widely accepted video tape in the United States was 2 inch Quadruplex videotape and traveled at 15 inches per second. To gain enough head-to-tape speed, four video recording and playback heads were spun on a head wheel across most of the two-inch width of the tape. (Audio and synchronization tracks were recorded along the sides of the tape with stationary heads.) This system was known as Quad, for quadruplex recording.

The resulting video tracks were slightly less than a ninety-degree angle (considering the vector addition of high-speed spinning heads tracing across the 15 inches per second forward motion of the tape).

Originally, video was edited by visualizing the recorded track with ferrofluid and cutting it with a razor blade or guillotine cutter and splicing with video tape, in a manner similar to film editing. This was an arduous process and avoided where possible. When it was used, the two pieces of tape to be joined were painted with a solution of extremely fine iron filings suspended in carbon tetrachloride, a toxic and carcinogenic compound. This "developed" the magnetic tracks, making them visible when viewed through a microscope so that they could be aligned in a splicer designed for this task. The tracks had to be cut during a vertical retrace, without disturbing the odd-field/even-field ordering. The cut also had to be at the same angle that the video tracks were laid down on the tape. Since the video and audio read heads were several inches apart it was not possible to make a physical edit that would function correctly in both video and audio. The cut was made for video and a portion of audio then re-copied into the correct relationship, the same technique as for editing 16mm film with a combined magnetic audio track.

The disadvantages of physically editing tapes were many. Some broadcasters decreed that edited tapes could not be reused, in an era when the relatively high cost of the machines and tapes was balanced by the savings involved in being able to wipe and reuse the media. Others, such as the BBC, allowed reuse of spliced tape in certain circumstances as long as it conformed to strict criteria about the number of splices in a given duration. The process required great skill, and often resulted in edits that would roll (lose sync) and each edit required several minutes to perform, although this was also initially true of the electronic editing that came later.

In the USA, the television show Rowan & Martin's Laugh-In was the first and possibly only TV show to make extensive use of splice editing of videotape.

VIDEO EDITING

Video editing is the process of editing segments of motion video production footage, special effects and sound recordings in the post-production process. Motion picture film editing is a predecessor to video editing and, in several ways, video editing simulates motion picture film editing, in theory and the use of linear video editing and video editing software on non-linear editing systems (NLE). Using video, a director can communicate non-fictional and fictional events. The goals of editing is to manipulate these events to bring the communication closer to the original goal or target. It is a visual art.

Early video tape recorders (VTR) were so expensive, and the quality degradation caused by copying was so great, that 2 inch Quadruplex videotape was edited by visualizing the recorded track with ferrofluid and cutting with a razor blade or guillotine cutter and splicing with video tape. The two pieces of tape to be joined were painted with a solution of extremely fine iron filings suspended in carbon tetrachloride, a toxic and carcinogenic compound. This "developed" the magnetic tracks, making them visible when viewed through a microscope so that they could be aligned in a splicer designed for this task.

Improvements in quality and economy, and the invention of the flying erase-head, allowed new video and audio material to be recorded over the material already recorded on an existing magnetic tape and was introduced into the linear editing technique. If a scene closer to the beginning of the video tape needed to be changed in length, all later scenes would need to be recorded onto the video tape again in sequence. In addition, sources could be played back simultaneously through a vision mixer (video switcher) to create more complex transitions between scenes.

Editor in linear VCR suite

There was a transitional analog period using multiple source videocassette recorder (VCR)s with the EditDroid using LaserDisc players, but modern NLE systems edit video digitally captured onto a hard drive from an analog video or digital video source. Content is ingested and recorded natively with the appropriate codec which will be used by video editing software to manipulate the captured footage. High-definition video is becoming more popular and can be readily edited using the same video editing software along with related motion graphics programs. Video clips are arranged on a timeline, music tracks, titles, digital on-screen graphics are added, special effects can be created, and the finished program is "rendered" into a finished video. The video may then be distributed in a variety of ways including DVD, web streaming, QuickTime Movies, iPod, CD-ROM, or video tape.