What is the deference between audio / video linear and non-linear editing systems?

Answer 1

Basically, it's the difference between a typewriter and a word processor. In the first one, you're actually assembling the finished product on the fly (e.g., typing out words on a typewriter); in the second, you complete the product in an electronic form in your computer before outputting the finished version of it (e.g., print it out to your printer).

A linear system usually consists of one or more sources (video tape players, usually), a recorder (video tape recorder, of course), and a controller that allows the user to precisely control the decks and preprogram edits. The person doing the editing essentially, step by step, copies the stuff from the sources onto onto a master tape in the recorder, by setting "in points" and "out points" to tell the source decks what portion of the footage is going to be copied, and to tell the record deck where on the master tape the footage is going to be copied to, as well as deciding which tracks of the source footage will be used (video only, audio only--usually left and right audio tracks can be split--or both video and audio). Because it's all physically being put on a tape, it's done in a linear fashion. Let's say that on your master tape, if you have a ten second clip of a bird followed by a ten second clip of a dog, then realize that you need fifteen seconds of bird, all you can really do is do those edits all over again--you redo the bird, record over part of the dog clip, then redo the dog clip at the tail end of the new bird clip.

In nonlinear editing, everything's done inside a computer before putting it out to a viewable format--one imports the material they want to use into the computer, edit the stuff in there, and when it's done, one just sends it out to DVD or videotape or whatever the final output product is. In the "bird and dog" scenario above, all one has to do is delete the 10-second bird clip from the timeline, and put the 15-second bird clip in (or even just manipulate the 10-second clip to make it longer); the dog clip will simply scoot down the five seconds needed to make room for the longer bird clip.