This is when you copy only the “good” parts of a tape over to a new tape. Assemble editing systems often include titlers (character generators) or special effects generators to make the videos more fun to watch. A/B roll editing is when we edit from two or more video sources.
An A/B roll system often includes a digital mixer, to let us cut, fade, dissolve and wipe from source A to source B. Insert editing is when we splice in a different scene, or video only, into the middle of an existing video tape. Only very expensive, high end editing decks are capable of insert editing.
Today, linear editing means deck to deck. The quality of your linear editing is dependent on the editing capabilities of your decks. For the best results, you need special editing decks with flying erase heads, special editing jacks, pre-roll and time codes.
This includes VTRs, ATRs, Disk-based media, and effects channels. The model for non-linear is hard to stretch to cover more than one or two things happening at once.
There are 7, 8 or 9 separate video sources rolling during some shots – this requires the resources of a powerful digital switcher, a critical component of a linear edit bay. When you see the fancy effects with moving pictures being wrapped around a solid shape, or being flown around the screen, those are generated in real time on a linear system. If they can be generated at all on a non-linear system, it may take minutes or hours to render a few seconds of effects.
There are many applications that have just minutes to finish the show before going to air. Last-minute shots have to be incorporated quickly, and there just isn’t the time to go through the preliminary steps to do the job in a non-linear way. In the non-linear world, all the source material has to be copied onto a dedicated computer. 20 hours of raw footage equals 20 hours of copying (at least).