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Clue Data

Beyond the razor-blade: HHB's innovative CLUE system provides an answer to the digital editing dilemma. Paul Gilby pieces together the story.



At present digital recording falls firmly into two distinct fields: that of multitrack digital and that of stereo digital mastering. Multitrack digital is still far too expensive for all but the top flight professional studios and even they often use hired machines. But digital stereo mastering, with units such as the Sony F1 and 701ES, offers the quality of digital audio at a price almost anyone can afford.

THE DIGITAL DECISION



However, the real problem that exists for the majority of F1 and 701 users is that of editing. And it's this point alone that is holding back a lot of people from going 'digital'! For those who have no experience of these systems, let me outline the problems.

Point one: you don't ever cut the tape with a razor blade, so obviously this presents an immediate problem if after a session you decide that you want to change the running order of the tracks.

Point two: because of the way in which the sound signal is digitised and recorded on tape, any attempt to execute drop-ins results in a very audible click. So, when faced with these two major obstacles, it's no wonder that some people have, perhaps not through choice, been unwilling to buy a digital system even though the obvious benefits of greatly improved sound quality are so desirable.

ENTER THE CLUE



With all the benefits offered by digital recording, it's not surprising that someone would eventually develop an editing system that would enable you to overcome the problems.

The CLUE (Computer Logging Unit and Editor) has been developed for that very purpose by HHB Hire & Sales' technical division and provides one of the most realistically priced systems to date. It would be unfair to say that it is the only system, as Sony themselves have the DAE 1100 Digital Audio Editor but at £15,000 plus, it's out of reach of all but the few and is actually the system used for the preparation of Compact Disc masters.

However, at £4100 the CLUE system isn't cheap either, but this is not just a technological advance on the razor blade and splicing block. The facilities of CLUE go beyond the requirement of simple editing, for as the name implies, it is also a logging machine.

As you can see in the main photograph, the system comprises a computer, which is Apple software compatible and a rackful of various pieces of equipment. Sitting on top of the rack are a couple of Sony SLF1E video tape recorders which in this application are being used to record the digital audio. The rack itself contains at the top, a Sony PCM-701 ES digital audio processor which is responsible for all the digital audio conversion; below that is the main CLUE hardware which is housed in a 4U box and comprises two disk drives, level and routing controls and the main computer board.

This set-up represents CLUE with its minimum equipment configuration. So, having described the hardware we can turn our attention towards what you can do once the software is up and running.

The system is divided into two sections: logging and editing.

As a logging system, CLUE will give you very precise information about what is on any particular tape and where it is. Logging can be performed either while making a recording, which is obviously important if it's a live session and you need to mark the start of each song for later examination; or you can log any previously recorded material by playing it through and marking points of interest as you go.

WHICH MENU?



The whole CLUE software system revolves around a series of screen menus which tell you precisely what is happening, when it happened and what courses of action are available to you at the time. So, if you're logging a tape, the screen display would look something like the one in the colour photograph.

The data shown is quite straightforward and lists the tape number you're working on, the take recorded on that tape, its start time and take length. Below is the name of the song and immediately underneath is an area for comments about the particular take you're working on. The rest of the screen contains areas that show details of any 'marks' placed during a logging session and alongside these marks are the various position times. You can go back and select any mark position and CLUE will automatically locate the point on tape and do one of two things when it finds the point. It will either locate a mark and stop ready for further action on your behalf or it will automatically go into a play mode if instructed to do so. This is particularly useful when you wish to rehearse the same section of music over and over again.

At the bottom of the screen is a prompt area telling you what action is available ie. Fwd means forward, Back means backwards etc. These commands are easily remembered mnemonics so that you can quickly learn the system and then by hitting the appropriate letter key on the computer the command will be executed.

Finally, on the bottom line is all the relevant timing information. Count gives you an indication of the position from the beginning of the tape which you will have set to zero at the start; Time is set at the beginning of each take and gives you the local time within a take whilst Left gives you a readout of the tape duration in hrs-mins-sec left to run. This is particularly useful when trying to assess whether or not you can squeeze that last song on tape!

Within the various menu options there are a number of possibilities but CLUE, as the name suggests, will always make you aware of the situation. Any data generated by the user, be it song titles or 'marks', will be remembered and stored on floppy disk for later retrieval. CLUE always knows where it is on tape, due to the use of a control data track which the system records onto the video cassette tape on one of the normal analogue audio edge tracks. So, because the track has unique code along its length, the software is able to reference any song or take data to a counter number and through control of the video tape transport wind the tape in any direction to locate a particular position on tape.

For those of you who would like to work with SMPTE code, you can obtain a special card to insert into the main circuit board that enables any external machines to be locked via SMPTE directly with the digital audio.

As mentioned earlier, CLUE is more than a logging unit. With such powerful and accurate control of the tape transport system, a whole series of musical parts from all over a tape may be typed in, then the system will move between the various sections and play them through in the predetermined order. Effectively reordering the material. There is, however, a delay between parts as CLUE shuffles around the tape looking for the relevant sections.

When you approach this sort of use you are not that far off a full-blown editing condition. We mentioned previously the difference in attitude towards the editing of video as opposed to traditional analogue tape. The most notable difference is that with ordinary tape you can mark up the section of tape to be removed - say a false start to a song. Having done that, a smart bit of razor blade work on a block and you can cutout the offending piece. However, the story is very different with video editing.

EDITING BY NUMBERS



All editing with video tape systems is always performed with two VTRs (videotape recorders). This is because there is no tape cutting and, consequently, each part of the song you want to assemble has to be transferred in the correct sequence and pieced together.

Now, if you adopted this technique with analogue tape you would start to lose audio quality as a transfer to another tape puts another generation of tape noise on the recording. But we're dealing with digital audio here and, as we know, you can transfer as many times as you like digital-to-digital and there's no quality loss.

So the mechanics of the situation go something like this. You place your source tape in a VTR and dedicate that as the master source machine. You then put a clean tape in another VTR which will be known as the copy recorder. Having done this CLUE is now in control. Find the take you want to transfer and locate its beginning. You now put the copy recorder into record mode and by responding to the CLUE menu prompts you make a perfect transfer across to the copy recorder in real time(!). So, if the section is five minutes long that's how long it takes. Then locate the next section to be transferred. It's at this point that the system as an editor comes into its own. If you're purely interested in reordering the track sequence of a recording then it's a straightforward matter of moving the copy tape on a few seconds to give you the required gap between songs. However, if you want to actually edit, things get a little more interesting...

CLOSE TO THE EDIT



Technically, there are a number of quite complex things happening. Practically-speaking though, the procedure is that you locate the sound to be transferred. This is done by roughly finding the point where you wish the edit to start and then using the cursor left/right arrows to adjust the sound until you finally home in on a suitable point. CLUE likes the edit point to be just prior to a transient in the sound. This fine searching is done at an extremely precise level - literally a frame at a time, so you can therefore get down to one twenty-fifth of a second accuracy on edits.

When you have chosen the precise edit points on both the source and copy VTRs, you can check them for compatibility by listening to the sound at that point and if they are fairly similar you're likely to get a good edit. To perform the edit you first of all select from the menu the edit prompt and then respond to further prompts of Analogue or Digital. At this point you could choose analogue and take advantage of being able to process the sound through an external effects unit ie. stereo reverb. However, this means that the sound is first taken back into an analogue form for the processing to take place. So, to get the best transfer and edit you select digital mode and CLUE does the rest.

The procedure is as follows. After pressing igital, CLUE backs up the source recorder by about 6 seconds and puts it in pause mode, noting the counter pulses. Then the copy recorder is set in the pause mode. Approximately half a second back from the edit point a mark is set and the copy recorder's timer is set to zero. Both the source and copy recorders are then released from pause mode and just as they reach the correct speed, the software notes the position of the edit about to arrive and on the exact frame it switches the copy machine into record and the transfer begins at the precise point you selected. This whole procedure is performed automatically by the system and gives you an idea of the level of sophistication CLUE is capable of achieving.

APPLICATIONS



Obviously anybody who has the money and is working with digital recording is going to find the CLUE system invaluable. But what of its broader uses?

As the quality of digital recording is so high, CLUE would be well suited to archive sound purposes, not only for the quality and editing functions but also for the automatic logging of the sound data held on floppy disk. Any sound could then be found very quickly by accessing a library disk, placing the correct tape in the machine and then letting it do all the searching. And as the system is computer controlled, the usual facilities of a computer printout are also available for a more permanent record of sounds on catalogue. The same is true of a collection of digitally recorded samples for loading into a sampling keyboard.

At the 8 track studio level, the cost of a CLUE may be prohibitive, yet there are some people with a commercial mind who have researched their local studio activity and seen an opportunity to provide a low-cost digital editing service to all of the local studios who are now moving towards digital mastering.



Previous Article in this issue

Soundcraft Series 200B

Next article in this issue

Time For SMPTE


Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.

 

Sound On Sound - Nov 1985

Donated & scanned by: SOS Publications Ltd

Review by Paul Gilby

Previous article in this issue:

> Soundcraft Series 200B

Next article in this issue:

> Time For SMPTE


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