Overview of Tape Editing Methods

Assemble and insert editing are terms that originate from linear, tape-to-tape editing systems. Originally, videotape was edited physically by cutting and splicing at the boundaries of magnetic tracks on tape. This was not only cumbersome, but difficult to do precisely because video tracks are incredibly small and can only be seen when magnetic ink is applied to the tape. The invention of electronic editing allowed editors to edit by copying selected portions of source tapes to a new master tape.

Three methods of electronic editing exist, each with increasing precision and quality:

About Assemble Editing to Tape

An assemble edit records all video, audio, timecode, and control track information onto tape starting at the In point of the edit. Whatever signal was on the tape previously is replaced. By definition, this means there must already be some signal recorded on the tape (even if it’s only 10 or 15 seconds at the head of the tape) so you can set an In point.

When an assemble edit stops, there is a signal break at the Out point between the new signal and the previous signal already on tape. Thus, the In point of an assemble edit maintains a smooth control track signal, but the Out point always has a break. Since you can always cover up the last Out point break with the In point of a new edit, assemble editing gets its name from the fact that it is used for quickly assembling footage together in a linear fashion. However, you cannot replace a shot in the middle of the tape without creating a signal break at the Out point.

About Insert Editing to Tape

An insert edit allows you to individually replace video, audio, and timecode tracks on a tape, using In and Out points. Insert editing is frame accurate and never creates breaks in the control track. For example, you could record new music to audio track 1 while keeping the existing video track and audio track 2 intact. This requires a precision, professional deck. (For more information, see About Tracks on Videotape.)

Note: This term is not at all related to making an insert edit in the Timeline; insert editing is a tape-to-tape editing term that predates nonlinear editing systems.

To perform an insert edit, your tape needs to have a signal already recorded on it. You can prepare a tape for insert editing by blacking the tape, which means recording control track, timecode, and a black video signal. You can also perform insert edits on any tape with an existing, unbroken control track. Having timecode on the tape is also necessary to set In and Out points for the edit. For more information about blacking a tape using Final Cut Pro, see Stage 6: Preparing Your Videotape with Black and Timecode.

Important: DV devices do not support insert editing because the tracks are too narrow to be precisely replaced. DVCAM and DVCPRO formats support insert editing because they use wider tracks.

About Tracks on Videotape

Most professional videotape formats have one video track, two or more audio tracks, a timecode track, and a control track.

About the Control Track

Unlike the other tracks on a tape, the control track serves a purely practical function: to make sure the tape plays at exactly the same speed it was recorded at so the signal is output correctly. A control track is a series of electronic pulses on your videotape that the VTR follows during playback, speeding up or slowing down the capstan (motor) as necessary for consistent playback. These pulses are almost like electronic sprocket holes that regulate videotape playback speed.

Insert editing allows you to replace individual video, audio, or even timecode tracks, leaving the other tracks intact. The control track is never replaced during insert editing. When you perform an insert edit, the VTR uses the control track to play back the tape at the proper speed while recording new video or audio tracks.

When the control track is broken, you may see the video signal jump or look unstable for a few seconds. This happens because the VTR relies on a consistent control track to control the speed of the deck’s motor. A missing or inconsistent control track causes the motor to change speed drastically, which means the video signal isn’t read at the proper speed of the tape, and so the image is not scanned properly. Control track breaks may not always be noticeable, but they are unacceptable in a professional environment.

About the Timecode Track

Timecode is also recorded onto a separate track on non-DV tape formats. Timecode allows your computer to control your camcorder or deck and import or export frame-accurate video clips. When you’re using the Print to Video command, abrupt breaks can cause subtle gaps in the timecode track. Although these happen less often than control track breaks, they can cause problems in a professional environment.

Requirements for Assemble or Insert Editing to Tape

Before you can edit to tape:

  • Your video equipment must support either FireWire or serial RS-422 remote device control.

  • Your deck must support recording; you cannot perform edits on play-only decks.

  • Your camcorder or deck must support insert editing, if you wish to do that type of editing.

For details about the capabilities of your video equipment, check the documentation that came with it. For more information about equipment requirements for output to tape, see Output Requirements.