Editing controllers
Yuriy Mihaylovskiy

Not long ago TV materials were edited on the editing table by means of cutting and joining videotape into a ready video program. This gave birth to tape join term meaning edit between items. The process was rather laborious and difficult in realization and even in understanding. First films were edited depending on the program's primary content design, i.e. the events were simply set out in the necessary order. With time, methods of video editing have got complicated, rules of changing scenes, operating tempo-rhythm and tineness of subjects, etc. have appeared, and, as a result, a separate video editing science has formed. Special effects being only a dream, the editing science was based on knack to change correctly audio and video scenes. This is proved by outstanding, loved by millions, old video films, edited exclusively by method of videotape patching. Basic edit operations used in cinema production are assemble and insert. And today, modern cinematography and video production ground on these basic operations.

In 1980 first video tape recorders (VTRs) appeared in TV centers. These devices were capable of producing non-stop record or playback. Thanks to capability of VTR recording video material onto video tape a new edit method began to develop: by means of transfer from playing VTR (hereafter "slave") onto recording device (hereafter "master"). However, this method was not so simple, for the only possibility to realize qualitative joint was in-motion entry into recording from playback mode. Only in this case the record of tilt and linear tracks on magnet tape has the same phase as the earlier recorded video material.

One of the first electronic editing systems

First edit controllers were capable of assemble, video insert, and audio insert operations. They did not employ jog/shuttle control, as the lateral VTRs did not provide fragment search with view function.

Our flashback to cinematography and the first edit controllers was deliberate, for all the modern controllers use these basic principles. As the edit VTRs developed, the edit controllers became complicated and got new features and service functions. These very features will be highlighted in the review.

This permanent edit controllers' attribute plays a very important role in video edit. By turning the jug/shuttle wheel one can scroll the picture back and forward for searching the necessary fragment. The jug/shuttle performs several functions.

1. Frame review. In this mode, the operator, by rolling the jug/shuttle wheel, performs frame movement of videotape to the beginning or to the end, depending on the direction of the rotation. In professional systems, one has to roll the wheel to a quite big angle (more than 90°) to move one frame forward, which has made localization of the necessary frame easier and video tape recorder control flexible. The wheel's quick rotation for several turns causes quick frame change, up to 25 Fps (normal playback mode). Frame review mode is used for exact frame search.

2. Jet rewind. In this mode the operator can rewind the tape with speed higher than normal playback speed. When the wheel is in the middle ("zero") position, the tape does not move and the current frame is displayed. The tape is rewound to the end or to the beginning when the wheel is turned clockwise or counter-clockwise respectively. The more the rotation angle is, the higher the rewind speed will be. In case the rotation angle reaches its maximum (45°), the rewind speed will be the highest, its value depending on the concrete VTR modification. The mode is used for high-speed rough search.

3. Playback with variable speed. This mode can be used only by VTRs with auto tracking or slow motion functions. This mode operates the same way as Jet rewind, but the recorder's speed is proportionate to the angle of the wheel's turn, even while reverse playback. The range of play speed depends on the VTR's model. The mode is used for determining the necessary playback speed for its further usage in program edit.

Video edit is fully based on the time code, thanks to which each video material frame has its own number.

In order to perform edit operation it is necessary to enter time code of the key sections of "slave" and "master" into the controller's memory. The most necessary frames are the first "slave's" frame from which the recorded fragment starts, and the last "master's" frame after which the recording starts. For video insert modes it is also necessary to fix the point of the recording ending on the "slave" or "master".

Mark In and mark Out keys are used for fixation of the above-mentioned values in the controller's memory. The keys are to operate both in still-frame mode (if frame accuracy is important) and in motion (if marking is according to the subject tempo-rhythm) .

Controllers of higher level allow entering absolute value of time code using numeric keys panel. This may be more convenient than direct marking in case the initial material has been previously reviewed and time code values of key positions are known.

For more convenient edit it is possible to view the values of time code of all marked points and also the duration of edited fragment. Besides, the controller provides quick automatic underwinding to each marked point.

Playback speed change is a frequently used, vivid mode. This mode is used in video clips, video films, comedy and sports programs. For its realization the controller must not only play the initial material with changes in speed, but also perform record frame accuracy. Many controllers allow memorizing "slave's" record speed and, later on, performing preroll onto the automatically corrected number of frames. For example, if the "slave" slow-motion by 2 times is programmed, "slave" is prerolled by 2,5 s, "master" being prerolled by 5 s. If the reverse motion is programmed, "slave" will be prerolled to the end, but not to the beginning, as usual. The controller's software carries all counting of preroll algorithm and further synchronization, and the operator does not have to make any hand corrections or assist in this process.

Editing facility with "Kadr3P" VTRs

In the assemble mode the "master's" tape is supposed to be clean (even the saved record can be deleted). In this mode the controller produces only on-line entry into the record. Absolutely all tracks are recorded: video and sound channels, time code, control signals. This mode is good for video material composing in the order of topics arrangement in the finished program.

Insert mode is performed with already recorded video material only. This mode is designed for replacing video or sound fragment, already recorded onto "master", with other fragment. In this case, it is important that both, entry into and exit out of record are on-line. In the insert mode only video or sound information is recorded, while the tracks connected with synchronization are not recorded, being used as references for on-line exit out of the record. A good form is to record reference video picture with black ground before editing, while all further edit is being performed in the insert mode. With using professional video equipment it is possible to perform insert of video or any sound channel both separately and in optional combination. Insert of new time code is available for some technical tasks.

Audio split has to be mentioned as a special case of insert. Actually, this is the insert by video and sound, still locations of record beginning and ending of video and sound are different. This is a perfect creative way used for softening the sharpness of scenes change. For example, the street noise appears several seconds before a busy street scene changes an apartment scene.

This mode is necessary for visual evaluating the join accuracy. This is an important operation for the "master" record may be damaged because of incorrect marking. In case of video insert, it is important to see how Edit-out location will look like, for the earlier record must continue after it. Preview mode performs video edit imitation producing preroll, pre-edit playback. In the edit-in location the "master's" monitor switches into the "slave's" picture and/or sound. The monitor switches back into the "master's" picture and/or sound in position with the ending mark. This illustrates how the edit event will look like after the record.

This is the most important mode, owing to which record of initial materials into "master" is performed. The process is the same as in the preview mode, except "master" performs real tape recording.

Tape decks' characteristics being different, there often occur the situations where "master" and "slave" are not synchronous in the mode of preroll edit: "slave" is either ahead or behind "master". This causes an error in the joint. Several methods of the recorders' synchronization have been developed: two-, four-, and eight-field phasing, or color framing. In these modes, in the process of pre-edit playback the controller either hastens or slows down one of the recorders till the synchronization is achieved. For correct realization of this process the generator, whose sync pulses are used for phasing, must send video calibration signal to the controller. It is clear that all devices, taking part in the edit process, must be synchronized with the generator reference video signal.

Synchronization is not always performed successfully. If there is lack of preroll time for phasing VTRs, it is necessary to increase the time and make one more try. Usually, S-VHS video equipment requires preroll time of not less than 7 s, Betacam SP requires not less than 5 s. Digital VTRs get into synchronization more freely, thus they require 3 s preroll time.

Often it is necessary to increase preroll time in case of slow-, fast-motion edit, these modes being more complicated for synchronization.

The selection of synchronization mode also depends on models of the controllers and video tape recorders. Selection of the controllers and recorders' settings is often a creative process, requiring testing. Color framing, the most prevailing method, is the most optimal for any equipment.

Main imperfection of the classic two-machine editing is impossibility of using special effects in which two live scenes take part. Such necessity occurs during creative editing. Typical example is effects of smooth change of one live scene with another by any special effect, for instance "dissolve", "wipe" or "page curl". For realization of such editing type the system is added with the second "slave" recorder, video and audio mixers.

For this edit type more complicated controllers, employing A/B Roll mode, are used. They can synchronously manage two "slaves" as well as video and audio mixers. The controller manages basic video mixer modes: active video input selection, necessary effect selection, automatic effect start up, etc.

Process of preparing to A/B Roll editing mode is more laborious. Now edit event implies video image recording at once from two "slaves" that plays either simultaneously or in turns. First, marking of the necessary fragments' beginning and ending on both "slaves" and of record in-point on "master" is performed. As video mixer must perform transition from one "slave" to another during recording, data about video effect type and its duration must be entered into the controller.

In the preview mode it is possible to see how correct the "slaves'" marks are and to check if the effect and its duration is right.

Many edit controllers allow transition by sound separately from video.

Some controllers allow increasing number of VTRs taking part in editing. This may be necessary for solving the following tasks:

1. Quick selection of active "slave". With a big number of slave tapes it is convenient when each tape is easy of access for editing at a keystroke. This is especially necessary in cases when slave materials of several formats are used. This mode is supported by the following controllers: Sony BVE-2000 (up to 6 slave tapes), Panasonic AU-960 (up to 11 slave tapes), AJ-A900 and AG-A850 (up to 4 slave tapes).

3. Several "master" tape recorders. Such configuration allows getting several tapes with quality of the first recording.

As it was stated above, controller performs management of video and audio mixers via RS-422 interface is used for this purpose. Unfortunately, video mixers of different manufacturers have different command protocols. For instance, JVC RM-G870E controller manages KM-3000-protocol video mixers only and Sony PVE-500 controller manages Sony DFS-series mixers only. Some controllers (e.g. Panasonic AG-A850) support several types of video mixers, which allows developing more diverse schemes of editing areas.

In case of complex edit some additional devices, such as effect processors, sound tracks players, titling systems, etc., are needed. These devices are capable of starting-up by the command received through GPI interface. Professional controllers employ one or several GPI interfaces in order to be capable of starting a peripheral device in the necessary edit event moment. Some peripheral devices are capable of full controlling via RS-422 interface. Thus they can be connected to the controller instead of "slave".

Controller must manage VTRs and external devices via definite interface with a command system. For now, international RS-422 interface, employed in the professional equipment of all formats, is a professional standard. Command system is profound and thoroughly developed. Connection allows transmitting control commands, receiving feedbacks, getting time code value and control channel pulses. A small 9-pin connector is used for transmitting and receiving data. RS-422 interface includes both primary control modes commands and complex commands, performed only by professional equipment. Because of this only Professional-class video tape recorders are equipped with RS-422 interface.

Broadcast-class equipment also uses parallel control interface.

Some controllers use other control interfaces. For example, JVC equipment employs 12-contact interface (JVC RM-G800). First models of Panasonic equipment used 34-contact interface, some systems use RS-232 (Panasonic AJ-A250).

Domestic and semi-professional devices use LANC, 5-pin, DV interfaces.

Step-by-step technology of producing programs is frequently used by Broadcast equipment of Digital Betacam, D5 formats and equipment of HD formats for "master" edit of the highest quality level. First, primary video material is recorded into cheaper carriers (Betacam SP, DVCPRO, etc.) with time code. So called "rough-cut edit" (edit of low quality) is performed using equipment of the same format. Rough-cut edit can also be performed using non-linear edit system employing operation of edit decision list export. When edit is done, the received edit decision list is moved onto edit controller by high-quality edit area in order to perform editing in automatic mode using HD equipment. This allows, firstly, preventing expensive high-format recorders from large exploitation load the equipment is exposed to, and, secondly, saving time for the rent of expensive edit areas by reducing to minimum time for automatic-edit mode.

Computer-based controllers (e.g. BVE-2000, AU-960, etc) employ built-in hard disk drives for storing/exchange of edit lists. Hardware controllers (AJ-A900, AG-A850, AJ-LT85, AJ-LT95, PVE-500) use RS-232 interface for this purpose. It is possible to correct, print or archive edit list in computer. RM-G870E controller allows connecting printer for direct printing, although, unfortunately, it does not support import/export.

There are several protocols for transmitting edit list. CMX340 is the most universal format, supported by professional controllers and non-linear edit systems. This is how CMX340 edit decision list looks like:

Unfortunately, CMX340 format cannot transmit operations of non-standard speed playback. Also there is no indication of the mode used: assemble or insert.

A850 is far more informative format of edit decision list. Here is an example of A850:

One of the first electronic editing systems

The first group includes controllers managing one VTR. Actually, it is a remote control unit for managing VTR or other device, managed from outside (Panasonic AJ-A95).

The second group includes semi-professional edit controllers. All controllers using 5-pin or LANC control interface may be referred to this group. Such controllers have one peculiarity: they perform edit operation without preroll, starting "slave" and "master" from still-frame. In such method edit accuracy makes 0.±3 frames, synchronization stage being absent. However, these controllers are quite simple in exploitation and widespread among small news structures (AG-DV2700, DSR-30, etc).

The third group includes professional two-machine controllers. Their distinguishing feature is providing frame edit accuracy thanks to synchronization at the moment of pre-edit playback. The controllers differ from each other by additional service modes, but they all are capable of performing basic two-machine edit functions, displaying time code, providing comfort search and marking. Some controllers employ GPI programmable interfaces. JVC RM-G800, Panasonic AG-A350, Sony RM-450 controllers may be referred to this group.

The fourth group includes built-in two-machine edit controllers in VTRs or edit areas.

Here is the list of such controllers:

All controllers of this group are designed according to the approved standard. Thus, their performance capabilities are absolutely identical: edit assemble modes, video insert modes, any audio channels insert (depending on format there may be 2, 4, or 8 sound channels), separate video and audio marking, preview, edit. Some devices also employ trim and review modes. The peculiarity of built-in controller is that it is perfectly adjusted to "master" - its own tape deck and its control electronics. "Slave" control is performed via RS-422 interface.

The fifth group is A/B Roll edit controllers. These controllers are capable of managing at least three VTRs as well as video and audio mixers. Some controllers employ GPI interface. Controllers of this class must memorize edit decision list, allow its editing, program sound and audio mixers, set in-points for both "slaves". Panasonic AU-960, AJ-A900, AJ-A850; Sony BVE-2000, BVE-600, PVE-500, FXE-120; JVC RM-G860E, RM-G870E controllers refer to this group.

Other controllers may be referred to "Other" group. It will include controllers capable of performing specified, unique functions (for example JVC RM-G820E controller with Preread function). Other controllers, added into computer systems for easy-to-use edit, are also interesting.

In general, edit controllers have been successfully used in professional video production with Broadcast- and Professional-class equipment for many years. For today, there can be noticed an increase of popularity of non-linear edit systems, that have already ranked themselves in HI-FI materials production and require applying large number of effects, animation, and edit layers. However, linear edit with usage of edit controllers also has some advantages if compared with non-linear edit. There is an evident linear edit advantage when preparing short news topics, documentaries, sports programs, feature films, and other programs with large number of slave video tapes.

Linear edit is also preferable when edit is performed using high-quality Broadcast Digital Betacam, D-5 and high-definition (HDCAM, DVCPRO-HD, D5-HD) equipment.

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