EDIT2 - a case story

Non-linear editing

There are many non-linear editing systems on the market, most of which handle the job in similar ways. The description of non-linear technology given here is intended to be general in nature, but is based on our close working knowledge of the ///FAST silver. system which is the heart of EDIT2. Other systems differ in many details from silver - but the principles are generally the same.
The non-linear system requires that all video and audio material which is required for the editing process be digitised from the acquisition format (videotape) to the digital format (in our case MPEG2). Besides video and associated audio, the system can import data in many digital audio and graphics formats for integration into the production. The raw material is first logged, during logging the material is defined in many separate clips which will be digitised separately. NLE systems include tools for modifying the digitised clips when they are used in the project - for instance adding echo or other audio effects, converting video to monochome or colour processing, and adjusting video levels. As such processing is time-consuming, many digital suites include traditional processing tools which are used to treat the signal during the digitising process - between the VTR and the computer.
	The digitised clips may be sorted in many different ways - we sort according to the reel number of the raw material for the project. When all raw material is digitised, the editor and production team have complete overview and instant recall of every clip in the project. A current project at Channel 6 Television involves material from over 200 reels of videotape, resulting in over 30.000 clips in the project, from which a series of programmes are edited.
Even with digital compression technology, video data at broadcast quality demands a large amount of storage space and substantial processor resources for handling transitions and effects.Most NLE systems allow the raw material to be digitised at a lower resolution, thus allowing for more material to be available during the editing process, after which, the specific clips which are used in the timeline are redigitised at a higher resolution, before the finished programme is played out to videotape or digital storage for archiving and copying.
The clips are then dragged or copied onto a timeline - a graphical representation of the programme, on which video and audio clips are laid in several layers in relation to a horizontal timebase. Transition effects are added to determine how clips on the same layer, or on several layers, are combined. The timeline is not a master copy in the traditional sense, but a list of which clips will be played back in which order. Changes are simple and reversible.
All NLE systems have some finite limitation on how many video, graphics and audio data streams they can handle simultaeneously in realtime. Our ///FAST silver. system can handle 2 video, 1 graphics and 8 audio tracks in realtime. Those sequences, which exceed the realtime capabilities will be rendered so that during playback, the system will play the rendered files instead of having to handle multiple layers in excess of its capability. Some NLE systems have to render most of their transitions, and in many systems - even systems from prominent manufacturers - rendering can lock up the system resources so that editing cannot proceed until rendering is complete. The ///FAST silver. system handles rendering in the background, permitting editing and playback of adjacent sequences to continue in the foreground.
Whilst non-linear systems bring high end results within the grasp of even entry-level users, the migration towards computer-based systems has reduced the general level of expertise available both inside the production environment and from many systems suppliers. Given that most NLE systems draw on hardware and software components from several unrelated suppliers, the user must often be able to resolve issues the cause of which may not be immediately attributable to the product from the supplier with the greatest overall understanding of the system. In contrast to a traditional linear suite, which could continue to function without an important piece of equipment, the non-linear suite can be grounded by something as simple as a virus or a wrongly configured mouse driver.
Non-linear digital editing The advantages	Non-linear digital editing The drawbacks
Reduced hardware investment Software upgradeability Fast operator learning curve Low maintenance "First generation" signal quality Ability to modify the edited programme Retrieveability of project data Accurate repeatability of effects Ease of language versioning	Dependence on integrated system Dependence on operating system Software/hardware compatibility issues Need for a backup strategy High cost of media storage Delay of digitisation process Susceptibility of critical production chain to general networking and virus problems Lack of in-house support expertise
It is on such issues that the void between the dedicated non-linear hardware and software manufacturer, and the manufacturer(s) of the workstation becomes clear. Our system - ///FAST silver. is sold as a software package and a plug-in device with external active breakout boxes, to be installed by the regional distyributor or end-user in a workstation of their choice. This product - like many NLE systems - is easiest to install in non-compliant clone systems which do not necessarily offer the quality of materials, manufacture and technical support associated with brand-name workstation systems. Unless the end user is very critical in his or her choice of workstation and storage platform, the all-important hardware will become the weak link in the system. As the cost of investment in NLE systems continues to fall, the user expects equivalent savings in the cost of the hardware platform. However, it is important to judge the cost of the hardware platform in relation to the cost of investment in the whole facility, and not just the NLE bundle, otherwise an edit suite costing several hundred thousand dollars may be grounded by a clone workstation costing less than two thousand dollars.