Most vision mixers are based around the preview bus and the program bus, each of which has it’s own monitor.

• The program bus is the main output feed, i.e. the vision which is being recorded or broadcast. Whichever source is on the program bus is said to be online.
• The preview bus is used to select and preview the source which is about to be put online.

Note:  The preview bus does not have to be used — sources can be cut online without being previewing if desired. However the preview is normally necessary for any visual effects such as transitions, as the effect is constructed from the preview and program sources.

The main purpose of a vision mixer is to create a master output for a real-time video recording or broadcast. Typically vision mixers are used for live events, or any event where multiple sources need to be mixed in real-time. Vision mixers can also be used to create various visual effects, from simple mixes and wipes between sources to advanced composite effects.

The main concept of a professional vision mixer is the bus, basically a row of buttons with each button representing a video source. Pressing such a button will select the video out of that bus.

As a job, vision mixers are technicians who work at a console in the gallery or studio control room. They are responsible for controlling the vision mixing desk: the pictures viewers see on their television are the result of the work of the vision mixer.

Non-linear editing was not welcomed by everyone and many editors resisted the new wave. In addition, early digital video was plagued with performance issues and uncertainty. However, the advantages of non-linear video eventually became so overwhelming that they could not be ignored.

In the 21st Century non-linear editing is king and linear editing is widely considered to be obsolete, or at least primitive. This is an understandable attitude considering the advantages of non-linear editing, but we urge you not to be too judgemental. Linear editing still has some advantages:

1. It is simple and inexpensive. There are very few complications with formats, hardware conflicts, etc.
2. For some jobs linear editing is better. For example, if all you want to do is add two sections of video together, it is a lot quicker and easier to edit tape-to-tape than to capture and edit on a hard drive.
3. Learning linear editing skills increases your knowledge base and versatility. According to many professional editors, those who learn linear editing first tend to become better all-round editors.

Although the “linear vs non-linear” argument is often subjective and some editors will disagree with the statements above, there can be little doubt that increasing your skill base is a good thing. There is nothing to be gained by completely rejecting linear editing, and much to be gained by adding it to your repertoire.

Video and audio data are first captured 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.

A computer for non-linear editing of video will usually 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.

Digital nonlinear systems provide high-quality post-production editing on a desktop computer. However, some detail may be lost if lossy compression is used to store the images.

Linear Editing is basically mechanical process, in that it employs the use of Camcorders, VCR’s, Edit Controllers, Titlers, and Mixers to perform the edit functions. This editing technique is performed in linear steps, one cut at a time (or a series of programmed cuts) to its conclusion.

Linear Editing consists of three main categories:

1. In-Camera Editing: Video shots are structured in such a way that they are shot in order and of correct length. This process does not require any additional equipment other than the Camcorder itself, but requires good shooting and organizational skills at the time of the shoot.

2. Assemble Editing: Video shots are not structured in a specific order during shooting but are rearranged and uneeded shots deleted at the time of transfering (copying). This process requires at the least, a Camcorder and VCR. the original footage remains intact, but the rearranged footage is transfered to a new tape. Each scene or cut is “assembled” on a blank tape either one-at-a-time or in a sequence.

There are two types of Assemble Editing:

A Roll–Editing from a single source, with the option of adding an effect, such as titles or transitioning from a frozen image the start of the next cut or scene.

A/B Roll–Editing from a minimum of two source VCR’s or Camcorders and recording to a third VCR. This technique requires a Video Mixer and/ or Edit Controller to provide smooth transitions between the sources. Also, the sources must be electronically “Sync’d” together so that the record signals are stable. The use of a Time Base Corrector or Digital Frame Synchronizer is necessary for the success of this technique.

3. Insert Editing: New material is recorded over existing footage. This technique can be used during the original shooting process or during a later editing process. Since the inserted footage is placed over the unwanted footage some of the original footage is erased.