Nonlinear editing today

By Michail Lvov

The nonlinear editing already has firmly occupied their own positions in technological chain of TV production and broadcasting. These positions are steadily consolidated and expanded. It is no one specific mass media, which did not spare an essential attention to hardware and software of the digital nonlinear editing. The journal “625” is not an exception. The articles about this subject are constantly appeared on its pages, and the last from those articles was issued in previous number and is dedicated to the most modern nonlinear editing systems. So hardly makes sense in this article to sink in technical fine points of the modern hardware. It is better to pay attention to some general questions concerning digital nonlinear editing.

Well, what must provide an abstract card, intended for digital nonlinear editing? First, this is intake of source video material into computer. Probably, this is the main purpose of that equipment. Warning question about output of the edited program, I shall say that such task originally was not raised. The first nonlinear systems were used for off-line editing, and output product was not a program, but the EDL (Edit Decision List), which was carried out into controller of the linear editing system, where the final stage of this job was carried out. Along with improvement of the cards, rising of computer efficiency, increasing of the hard disk capacity and lowering of disk price the output of video from station of the editing to videotape or another carrier became available, and this is the second. The third, the card, aside from input/output, must allow realizing the control of peripheral equipment, for instance, a video recorder, from which the transfer of video to computer disks is executed and to which the edited program is produced in consequence. Hence, aside from video and audio interfaces it is necessary to have availability of the control port. Usually this is serial port such as RS-232/422 or similar. Probably, these are three the most total tasks, which must carry out by any abstract card intended for digital nonlinear editing.

Let us consider each of them in detail. Since appearance these cards have fallen to the bloom of analog video equipment, that till present time the most wide-spread are the cards with analog interface such as composite, component or S-Video. Input of material can be realized either with compression or without it. All depend on tasks of editing station. In principle it is possible to consider that a possible degree of the compression is 5:1. If degree of the compression is higher then total quality of the signal is scarcely fit for the following broadcasting.

The possibility of the card functioning in real time is depended from card capacity. As a fact, at the last years, together with impetuous growing of computer output, many functions, earlier laid “on shoulders” of hardware, now are realized by software, particularly for DV format. But for video without compression or with small compression ratio is more preferably to use the card, in which the most important functions are realized by hardware.

As for idea of the building of the digital nonlinear editing systems, which integral part is a card of the input/output, here is clearly tracked several directions:

• Cards for standard computer with hardware realization of all the most important functions;
• Cards for standard computer with programmed realization of all the most important functions;
• Combination of the first two versions;
• Specialized hardware.

Development of digital video has contributed its own corrections in equipment for nonlinear editing. Digital interfaces, for instance SDI and IEEE 1394, were added to analog interfaces. Moreover, with development of information technology and their penetration in television it is more happen to speak not about re-recording of video and audio from tapes to disks of the editing station, but about duplication of the files. In fact, a recording/playing device forms not television signal already, but flow data (stream), which is transferred on computer disk with multiple rate under comparing with real time mode.

Today we can watch the real boom of the inexpensive interface cards IEEE 1394. Essentially, it is impossible this card to name as input/output video cards, since by means of these units are transferred not video- and audio signals, but simply a stream. But looking from another point of view, these units execute practically all main functions, which are peculiar to general cards of the input/output. They allow transferring the material on computer disks, to output an edited program on recorder back and to realize the recorder/player control. But they do not participate in processing of the video, transferred to editing station. In this case all are executed by application software. So and the price of the cards IEEE 1394 is low. However is existed a family of cards produced by different producers, in which this interface peacefully is coexisted with usual analog input/outputs that greatly increases the system functionality and alongside with digital source, allows to use any analog source as well. This can be necessary when we are dealing with old analog archive.

If try to predict the future of the cards for nonlinear editing, I’ll risk to suppose, that early or lately they will remain only in broadcasting control room (output) and in archives, containing old materials in analog type (input). I’ll try to motivate this point of view. As it was already mentioned, modern shooting and recording-reproducing equipment certain moves to file exchange that is obviously demonstrated by Panasonic (technology ING on the basis of the P2 cards) and Sony (recording on professional optical disk and the equipment line on this base). But until the broadcasting in its present form is saved, it is necessary to convert the data files to the standard TV signal, “comprehensible” to transmitting and receiving (subscribing) equipment. Well, with archives, I hope, all is clear. Until the last material from video cassettes was not transformed into file form, the need in traditional video equipment will remain and in the input/output card as well. On all rest stages of TV production these cards will change by a network, by the interfaces with big traffic capacity (for instance, IEEE 1394), by gates and the other equipment, which today it is sooner possible refer to computer, than to TV equipment.

But today this is only far perspective. The reality is based on continuation of development and appearance of new cards for nonlinear editing. The companies-producers invest in this the high financial and knowledge-based means, offering for user the more perfect systems.