Getting into Video (Part 4)
In the fourth part of this series, David Mellor looks at the Fostex 4030/4035 synchroniser system, and how it is set up and operated.
These days, most audio and musical equipment can be bought straight off the dealer's shelf, taken home, plugged in and used without any problems. You may increase your chances of getting the best out of it by listening to expert advice and taking care over the installation, but you can be confident that when you plug an XLR cable from one piece of equipment to another, the audio signal will travel in pretty much the way you expect - nine times out of ten, at least!
However, when it comes to interfacing the mechanical, as opposed to the audio, functions of the various audio and video recorders in studio use, the situation becomes much more complicated. For example, how is the capstan speed of your multitrack controlled: by voltage or by frequency? What is its rate of tach pulses at play speed? Are the tally signals positive or negative? You don't know the answers? Well, neither do I, so it is time to call in the experts...
Fostex have a reputation for producing high performance equipment at low cost. It may not be the absolute ultimate in professionalism, but then again, it doesn't cost the earth. The Fostex synchroniser system, however, is a very professional collection of gear - it is widely used in TV production facilities where equipment cost is far less important than functionality and reliability, and it doesn't only work with Fostex tape recorders. The system can connect to virtually any video or audio recorder in current production that is capable of being synchronised.
When it comes to setting up a synchroniser system, it doesn't pay to go to a discount dealer who will only see the equipment as far as the boot of your car. This equipment needs to be installed by someone who knows what he or she is doing, in order that it will interface properly with your equipment, whatever its make. Note that this is not just down to model numbers. Proper machine interfacing takes account of the current state of performance of your particular machine - whether it is up to standard, or has suffered a good deal of wear and tear.
I was fortunate to have Harman UK's Richard Wear set up a demonstration Fostex system for me with my own equipment. I can see that it would be possible to set up a system using only the manuals and a bit of savvy, but I would definitely not recommend it - pay the list price, and have an expert do it for you.
The basic Fostex synchroniser is the model 4030. For very simple applications it can be used by itself, but it is more commonly seen with the 4035 controller which makes setting up and operation much more straightforward. The 4030 is a two machine synchroniser, with master and slave interfaces for the connection of two audio or video recorders. You can use it with a domestic VCR (video cassette recorder) or a more professional VHS or U-Matic machine - the video would be the master and your multitrack the slave. Of course, the Fostex E16 - or any of the Fostex range - are ideal for use with this system, but you can, as I said, use virtually any synchronisable multitrack recorder, if you have the appropriate interface.
The connection of the equipment is shown in Figure 1. Note that with a domestic VCR there would be no transport control connection and you would be operating as a 'code only master' (described later). Let's assume for the moment that this is the case.
With the 4030 properly set up, the multitrack recorder will chase the timecode coming from the audio track of the video cassette and keep perfect sync once it has found the right place. If the timecode on the multitrack tape does not match that on the VCR at points which should correspond - and this will probably be the case - then an Offset can be entered so that they both run in step.
In simple terms, that is what the 4030 does, but its simple appearance belies its capability. To get the best out of the 4030 you need the 4035 controller, which can access all of the 4030's various functions. Think of the 4035 as the bridge of a ship and the 4030 as the engine room - one is where the captain gives the commands, the other provides the motive power.
Although I have said that setting up is a matter for the specialist, particularly if non-Fostex recorders are involved, it will help demonstrate exactly what goes on in the synchronisation process if I go through the main topics in the procedure of setting up the 4030/4035 to work with an E16 and VCR.
Firstly, there are some DIP switches to be set on the rear of the 4030, to select whether 'frame lock' or 'sync lock' (explained later) will be applied, and whether the 4030 will be configured to work with a B16 or an E16, or another type of recorder.
That part is simple. An aspect of the system's operation that is a little more complicated is that of tape damping - the 4030/4035's control over the ballistics of the tape recorder and the mass of the tape. When a 10½" reel of tape is hurtling at full wind speed it acquires, as you will appreciate, a certain amount of momentum. If it was heading towards a locate point and the synchroniser issued a stop command exactly when it passed that point, then obviously it would wind past, probably by several metres of tape. It would then reverse and similarly overshoot, then wind forwards and overshoot, until it gradually homes in on its destination and comes to a halt.
This is not a good way of working. It would be better to tell the recorder to slow down before the locate point, how much before depending on the speed of the tape. The 4030/4035 does this by issuing a series of short fast forward and rewind commands to slow the tape down. The rate at which it does this is adjusted by the Damping control on the rear panel of the 4030, or by entering a value from the 4035. The optimum setting is that at which the recorder stops in the shortest time, without overshooting.
To synchronise a multitrack recorder to a master, the 4030/4035 finds a rough match between the timecode values, then slews the slave's capstan speed up or down until it comes into a precise lock. Consequently, the 4030/4035 needs to 'learn' the capstan characteristics of the particular multitrack that it will be driving as part of the set-up procedure. This process needs a tape already striped with timecode - the tape is played, and timecode is sent to the 4030. The 4030 will now automatically learn the tach rate of the recorder (the frequency at which tach pulses are sent out at play speed), which is obviously proportional to the tach rate at wind speed. In fact, the 4030 does this automatically the first time a tape is played after power up, each time it is used.
Next, the Servo Offset (a trimmer on the rear of the 4030) is adjusted until a back-panel LED illuminates to indicate that the transport is moving at half speed. The Servo Gain (another trimmer) is then turned until another LED comes on to show that the transport is going at twice the normal speed (a precise indication of the speed can be obtained from the 4035's display). After this, the 4030 will automatically run through a series of different tape speeds, during which it actually learns the capstan characteristics of the slave machine. It takes several minutes, but it is only done during the initial set-up, or when you change machines.
Once these procedures have been accomplished, the rest of the setting up is easier, and is concerned with specifying which of various modes of operation the system will use. To handle this programming, the 4035 has so-called 'second level' functions in which the buttons take on different meanings from their normal transport-related ones. A plastic overlay is provided so that you can see what these meanings are. Let's look at a few of the functions...
Midnight mode. If timecode on a tape or video cassette crosses the witching hour - 00 hours: 00 minutes: 00 seconds: 00 frames - then there could be a problem when it comes to locating times on opposite sides of zero. For instance, if the tape is at 0 hours 10 minutes and you wish to locate to 23 hours 50 minutes, do you wind forwards 23 hours and 40 minutes, or wind back 20 minutes? The answer is obvious to you and me, but not to the machine - unless you tell it that it is to work in midnight mode, and to expect timecode crossing zero.
Code-only master. If a domestic VCR is used, transport commands issued to the video master cannot be passed on by the synchroniser to the slave machine - because the VCR will only output code. The 4035 needs to know that the master is 'code only', and will not be transmitting direction and tach information.
Play to park. This is for when you need the machine to stop at precise locate points. A typical situation would occur with a VCR when it changes from wind to play. In wind, the tape is taken away from the head drum and positional information derived from tach or CTL pulses. When the tape is laced up, an error might occur which puts the position several frames out.
With play to park set to On, the tape will wind to just before the locate point, go into play, and find the correct position accurately from timecode. (Play to park is not possible with a domestic VCR).
Slave park point. When running in lock, if the master is stopped then the slave will stop also. If the master is put into play again without winding forwards or backwards, it will issue code only after a short interval, perhaps around a second. This means that the slave machine, if it is a reel-to-reel recorder running at 15ips, now has more than a foot of tape to catch up. But by setting the slave's park point to be slightly more than one second ahead of the master's park point, this problem never arises - when code starts again, the slave tape should be at the right point. It is only useful when the master and slave are already nominally in the same position and you intend to play from that position, but it saves time and speeds up the work.
Once the setting up is complete, which could take up to a couple of hours, you are ready to start synchronising. Let's look at what useful functions the 4035 offers.
First and foremost, the front panel has a large LED timecode display which can show master code, slave code, offset (difference between master and slave timecode values) and editing information. To the right of this are three LEDs which show when master and slave code are being received and, most importantly, when a successful lock has been achieved. To the right again are LEDs to indicate which of the three slaves - yes, this small unit can look after the transport and synchronisation of a master and three slave machines - are ready for timecode lock. Four more LEDs show which of the machines are in a state of record readiness, and are therefore willing to respond to record commands issued by the 4035.
Moving down to the bottom left are three buttons which select the type of lock that the system will use. I haven't touched on this aspect of operation so far, so let me now offer a few details:
Frame Lock is where timecode values on master and slave are compared number for number, allowing for any offset. Frame Lock has to be used to achieve proper synchronisation with both machines in the correct place. This is a 'tight' lock, and therefore any wow and flutter on the VCR will be faithfully followed by the slave.
Sync Lock means that the machines will run together and keep the correct speed, but the 4030/4035 will not bother to check the timecode numbers. Sync Lock is not as tight as Frame Lock and induced wow and flutter will be less.
Auto Lock is the most commonly used mode. Frame Lock is employed until sync has been achieved. Thereafter Sync Lock is used.
The rest of the 4035's controls fall into three groups: numeric keypad and trim buttons; Zone Limit, Auto Play/Return/Record; transport controls. Users of the Fostex 4050 autolocator will find themselves on familiar territory, but will be surprised at how much quicker the 4030/4035 is at operating their favourite multitrack.
The transport controls will operate all the video and audio machines in the system, except where a domestic VCR is used. The record function works too, on any or all of the recorders, so there is no need to touch the machines except to select the correct track(s) to record on. Automatic punch-in is possible also.
The Locate button works in conjunction with the numeric keypad and the nine position memories. Zone Limit sets the range of timecode values within which work will take place, to prevent tape coming off the spool. Auto Play sets the machines into play as soon as a locate point has been reached. Auto Return in conjunction with Auto Play can cycle the machines between two points. Pre-roll sets the number of seconds before a locate point that the machines will actually stop. These few seconds are necessary for sync to be achieved when the machines start up again.
Let us now look at this system in use, returning to the case of a domestic VCR, or code-only master. I shall assume that the project in hand is to add music to a video, a copy of which you have been given on a VHS cassette with timecode recorded on the audio track, and that you have a reel of multitrack tape to hand which has already been striped with code.
Having loaded the video and threaded the multitrack tape, the first problem you will probably find is that the code on the video starts at 10:00:00:00 - common TV practice - and the code on your audio tape starts at 00:00:00:00. You will therefore need to enter an offset so that your music can start at the beginning of the reel. (It is best to allow for 30 seconds to a minute of timecode before the music to give the machines time to lock, plus a good margin.)
Now you are ready to record any music that takes your fancy. You can use the 4035 to control the multitrack while you are doing nothing but recording, but when you want to check sync with the video, or record in sync, you will have to use the video's controls (or remote controller) with Chase Lock enabled on the 4035. This is, unfortunately, a very slow way of working because when you are synchronising, the 4030/4035 never knows where the video is unless it is playing. During wind mode, the multitrack just sits and waits for some timecode to come into the system before catching up.
The obvious step forward is the acquisition of a better VCR than a standard domestic model - one that can be slaved to the 4035. The major manufacturers of video equipment (JVC, Sony and Panasonic) all have something suitable in their range. For my tests, JVC were kind enough to lend me a CR6650, which is a U-Matic machine; though for the project described here, a suitable VHS recorder would do just as well. Fostex make an interface to connect the JVC CR6650 to the 4030, which consists of a smallish box and cabling with the appropriate connectors, and there are similar interfaces available for most suitable VCRs.
With the full master/slave capabilities of the 4030/4035 in operation, you can really motor along. All transport functions are now controlled from the 4035, so when you press 'Rewind', both machines rewind and locate together. Press 'Play', and the multitrack will quickly come into lock with the video. At first it is disconcerting to hear the music slew up and down in pitch as the capstan speed changes, but it is soon over and you do get used to it.
Adding a stereo centre track timecode machine to our system brings further advantages and further complication. Although one 4035 can control up to four machines at once (one master and three slaves), you need one 4030 for each slave. So the use of an extra stereo machine entails having an extra 4030, a cable splitter box, and masses of ribbon cable.
With a synchronisable stereo recorder such as the Fostex E2 or E22, you are in a position to mix while synchronising to video, and to replay the stereo master afterwards to check that the lock is OK. It is possible to mix without the extra synchronising equipment, but you would have to replug the 4030 into the E2 to check the tape. Also, with the extra machine, it is now possible to spin in extra material - sound effects, perhaps - synchronised with the correct offset.
What I have described here is a basic system - there are further additions one could make to improve efficiency and performance. The lone composer may not need them, but any studio which aims to be video-capable should certainly be up to date with what is on offer.
The final part of this series will look at a few such items, in the form of the Fostex 4010 advanced timecode generator/reader and the 4011 VITC generator/reader. There will also be hints on timecode system installation and on the various kinds of audio and video machines that can be used in this way.
(Fostex) Harman UK Ltd, (Contact Details).
(JVC) Bell & Howell Ltd, (Contact Details).
Gear in this article:
Feature by David Mellor
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