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The CMX 600 System could now record and play video. Its capacity was about five minutes of black and white video per Memorex disk pack and the system usually ran four to six drives per system thereby getting 20 to 30 minutes of storage. VP Martin Fletcher was readying the marketing campaign. Yves Faroudja was impressed.

Our marketing guy, Martin was a very sharp guy and he understood what the market wanted with regards the image resolution for editing.

Strobele recalls:

It was amazing to see it working as a unit for the first time even though it was strung out across a number of work benches. We had all of the audio and video coming off a disk pack in sync and sure it was a black and white image on a standard definition monitor but we were shouting and cheering.

Jerry Youngstrom recalls:

The skip field disk drive was a marvel but it was a real challenge for David Bargen and Jim Adams when edits had to be “assembled” into a broadcast quality tape. Probably more time was spent on that technical issue than any other in the CMX development.

There was more work to do because put simply, the original specifications weren’t a true list of what was required. For various reasons many things had been missed. We just didn’t know any better but despite that I started to think we might have a real success on our hands. As an engineer that’s what you strive for.

Bill Butler recalls how the team used resources like the Stanford Research Institute which was newly independent of the university:

In those first days we spent a lot of time at SRI, which was the seminal source for input/output devices concepts. We had to find a system that was appropriate for creative editors who were mostly terrified of computers, more used to pencil and paper for records and being able to see each individual frame.

Lon Priest wrote of early interface development.

Originally, the console was designed to be alive with push buttons marked 'splice,' 'dissolve,' 'forward,' 'reverse,' 'transport’. A push button for all the myriad of electronic orders needed to edit videotape. When it was determined this would be incredibly cumbersome, an idea was taken from the computer industry itself.

CMX used the CC light pen originally chosen by Adrian Ettlinger on the CBS’ Autocue lighting system and CBS RAVE system.

Joe Flaherty later explained:

At the tip of the light pen is a photocell that senses the control words and characters on the monitor when the light pen is pointed at them and pressed. The identification of the specific control word or character is determined by the timing of the light detected by the photocell relative to the sweep timing of the picture monitor display.

The pen was used to select editing tools from a superimposed Menu displayed on the console’s right hand monitor. The interface presented four function options:

Splices - Edit - Play - Scenes.

The CMX interface acted as an electronic equivalent of a film editing system. Single letters on screen could be tapped with the light pen to set the rushes in motion.

The letter F was used for fast, N for normal speed, S for slow and J for jog, one frame at a time was. A still-frame was selected by touching any of the hyphens/rectangles between the letters. These variable speed capabilities were breakthrough achievements by themselves.

The CMX digital team had expanded on the work of Ampex engineer Anthony Poulett who had experimented with recording and reproducing television signals with an altered time base effect.

The video rushes signals had been recorded to the Memorex discs at a predetermined head-to-medium writing speed, and could be played back at the same head-to-medium writing speed, single frame access or half head-to-medium speed.

When the editor selected the ‘Scenes’ option from the right-hand monitor, he was able to call up the various rushes material. He could then play a shot and chose the first frame he required. Then he pressed the light pen to the word ‘Splice’ and the chosen frame was instantaneously transferred to the left-hand monitor and spliced to the preceding material.

By selecting ‘Play’ on the right hand monitor material, the editor then played through the scene to select a desired exit point. The exit frame of the previous one scene was always present on the left-hand monitor and the entrance frame of the next scene on the right-hand monitor.

As an alternative to a direct cut, the editor could call up the Edit option which gave him the ability to add a transition such as a (fade,dissolve,wipe,matte) or a special effect of any length from one frame on.

The 600 had the option of splicing video only or audio only from the "Edit" option.

Jim Adams continues:

From the software side, the 600 was pretty straight forward. Disk drive positioning was well known, all of the video was 30 fps and the PDP-11 real time clock (RTC) provided timing interrupts at 60 Hz.

Dave Bargen worked out the timing to switch between the primary playback disks and the auxiliary at the various playback rates and I devised a satisfactory for the Edit Decision List (EDL) as we named it. This was nothing more than an ASCII formatted list of source material, in-point and out-point frame codes and the computed record points.

The operator could also specify whether the recording was to be audio only, video only or both, and if the video was to be switched or fed through an effects generator. The audio and/or video transition was provided within the 600, but no effects were simulated.

Some of the original material was recorded in color and was frame coded in what was known as 'Drop Frame Code'. This code periodically omitted two frames from the frame count. For the 600, this was a minor issue and I solved it easily with special add and subtract routines, not unlike leap year day counting.

Interestingly the CMX team realized that the editing system could be controlled by other devices. From their 1971 patent:

It will be appreciated that while the light pen character generator described herein is particularly suited to convenient operation of the disclosed editing system, other interface terminals could be utilized if desired, such as keyboard, push buttons, joystick, etc

While the CMX 600 unit was now more or less capable of recording and playing video and audio in sync for an editor to make edit decisions, its sibling system, the CMX 200 needed to be able to translate all of those decisions in order to control the high resolution videotape copies of the master material on analog VTRs and ATRs.

Dave Bargen adds:

The second product priority was the Assembler system to be called the CMX 200. It isn't talked about much, because it isn't as glitzy, but it was an integral part of the product plan from the outset. It would take the edit decision information from the 600, and control broadcast tape recorders to produce the finished program

Jim Adams began work on the 200 Assembler.

One of the features of the PDP-11 was the ability to use the input and output ready/busy signals as interrupts under software control. I therefore set up the frame-code ready signals as interrupts and was able to keep track of the location of each (playback and record) tapes.

I keyed off the Real Time Clock (RTC) to analyze the tape position while seeking the in-points for each insert edit and was able to cue the VTR by alternating between Fast Forward and Rewind commands depending on the distance the tape was from the pre-roll target point.

Once all tapes were parked, they were put into play and capstan plus or minus over-ride commands were issued to bring them into synchronization with the counting of the PDP-11 processor. Conceptually this worked very well, but a number of issues surfaced that impacted the operation of the system.

The first was the tape machines did not follow the commands from the processor. I brought this up to the lead digital engineer, W. King Anderson and he assured me that it was a software problem.

After stepping through my code and observing the reactions of the VTRs, I approached King once again and told him that the interface cards were not responding to multiple commands from the processor. King reiterated that even though there were no ready/busy signals from the interface cards, they were much quicker than the PDP-11.

He did ask me how quickly I might be issuing commands, and I told him they would be about 1.2 or 2.4 microseconds apart. This completely surprised him and he said the interface card would take 5 to 8 microseconds to process each command. I added software delays into my code until the cards could be modified with appropriate ready/busy signals.

With the tape machines responding, other problems were exposed: some edit points were occasionally off by a frame, other times the switcher did not respond to commands from the processor.

More insidiously, the PDP-11 would halt with a fault signal and had to be restarted. I reported the issue with the fault signal to both the CMX management and the DEC maintenance people and was assured that is was a software problem.

I began logging each time the fault occurred and it appeared to be very random. I again reported the problem and was told "Software Problem, fix it". After a couple of weeks of this, I set out to find the root cause.

Staying late one evening, I hooked oscilloscopes to the various interface cards and into the PDP-11 processor. After about six hours of testing, plus my logs from the previous weeks, I was confident that I had the root cause of the fault.

Most mini-computers had instruction sets that were all 16 bits (2 bytes) wide. The PDP-11 had different lengths (2, 3 and 4 bytes) for different instructions like most of the large computers. This is a very efficient use of program memory and allows for more complex instructions in the 4 byte instances.

I had obtained the home phone number of the product manager of the PDP-11 and I called him. I asked for him by name and identified myself and said him I had a hardware problem with the PDP-11. He asked if I knew what time it was, and I told him it was midnight in Sunnyvale, so it would be 3AM in Massachusetts.

To his credit, he asked me to describe my problem. I told him that I was using many fast interrupts to drive my software, and if I received an interrupt during the execution of a 4 byte instruction the PDP-11 would trap to a fault error. He thanked me, we hung up and I turned out the lights, locked the doors and went home.

When Adams arrived at work the next day, he was directed to Butler’s office. He walked in to see CMX management plus the regional manager and local sales and maintenance staff from DEC.

He was asked why he had "broken with reporting protocols" the previous evening.

I told them I had tried that twice and was told it was my problem and I should fix it. I never spoke to the DEC people again. I found out later that the Massachusetts engineers knew they had a problem, but I don't know if they knew the exact cause. Perhaps I helped them out with my phone call.

Adams spent the next two days removing all 4 byte commands from his program code and had no further hardware traps.

I did, however, still have bad insert edits and missing switcher commands. The insert edits were occasionally a frame late, and I attributed this to a mismatch between the frame counting of the PDP-11 and the record VTR. As I indicated earlier, the frame count scheme was not 30 fps but was slightly less. I had a frame counting routine in my software, so began to focus on that.

No matter how well I tracked my counter, I could not resolve this issue. After much time observing the video signals and my commands from the processor to the VTR and sleeping on this for many fitful nights, I had an 'A-HA' moment and deduced that the computer RTC had to be tied to the 59.94 Hz video synch and not to the 60 Hz power line.

I kludged (today called 'hacked') together a circuit to make the video synch pulse look enough like the 60 Hz signal that the RTC board in the PDP-11 would react to it. Voilà, all my timing problems were solved. It turned out that if the edit commands to the VTR were late in the frame, the VTR would delay the edit until the beginning of the next frame.

Also the switcher processor was performing internal tasks during the first five or so lines of the frame and would ignore any commands during that time.

I added enough software delay after each synch interrupt to adjust for this timing in the switcher. The VTR commands were now in lock step with the video synch, so were always at the onset of the frame.

Adams went to management with a request to design a new RTC board for the PDP-11 but was told that the clock problem should be solved in software, and there was no money to develop a new board.

Fortunately, I had a good buddy Bob Gilbert who laid out the interface card artwork for CMX. I convinced him to bootleg me a board, and worked out a design from the backend of the DEC RTC board and a synch stripper circuit from one of the video engineers. This board did work its way into the Bill of Materials so all 200's and follow ons had it.

Adams’ discovery, if it had been patented, could have given the company a major revenue stream when others entered the analog editing sphere.

CMX would have been in the driver’s seat for all future video edit systems. With these issues resolved, not in software but with hardware modifications, the 200 software development proceeded nicely and was soon ready.

CMX Systems was part of Memorex’s Information Group under manager John Del Favero. He briefly mentioned the progress of the forty CMX technical, marketing and administrative personnel.

“A prototype system was substantially completed at year-end 1970 and production and marketing of the product is anticipated in early 1971.”

Del Favero’s statement was somewhat misleading. The engineering teams were trying to iron out any significant bugs in the 600 before an NAB showing, knowing that the 200 would not make the trade show.

CBS editor Howard Smith continued to trial the editing system and give the development team valuable ‘real-world’ feedback. Smith started as an editor at the Hal Roach Studios in 1935 on the "Our Gang" films for Laurel and Hardy. He continued a lengthy feature film editing career, editing films like "Breakfast at Tiffany's" then moved to CBS to cut television shows like "Gunsmoke", "Get Smart" and "Gilligan's Island".

A third-party industrial design company had completed the editing console to house the system. When the first mockup of the console was delivered there was an immediate reaction. Jerry Youngstrom recalls:

Everything about it was wrong. The slope of the desk was wrong, the slope of the monitors to the desk was wrong. It was beautiful to look at but anyone who sat at it hated it! The editors who visited from CBS, the Memorex sales people. Everyone.

Youngstrom and Bargen called Ken Ferrin to help build a new console. Bargen recalls:

Jerry Youngstrom decided that the fastest way to work out the human engineering of the new editing console was to build a full-size mockup. I went over to his house one weekend and helped him build it out of plywood in his garage and on his driveway. It had adjustable tilt and height of the desk surface, monitors, etc. and was designed on the fly.

Youngstrom recalls:

After we finished up, we hauled it the 10 miles back to CMX. Over the next few weeks the very same editors from CBS who had disliked the original console sat at the new plywood monstrosity that now housed a functional CMX 600 prototype system. Using the increments that adjusted the desk and monitors we soon had all the parameters for the industrial designers to make a new console that everyone liked to look at and use.

Bargen continues:

The new editing console won a national industrial design award that year. The names of the controls on the screens and the logic of the operations were based on conversations with film editors and observation of them cutting film. The goal was to make it as easy as possible for a film editor to operate the new system.

By March of 1971, the 600 was functional, an impressive achievement for taking a new concept to working hardware in 10 months.

CMX hired a second programmer, Steve Foreman.

Adams recalls:

Steve proved to be a very competent programmer.He quickly picked up on my design philosophy for the two systems--including no 4 byte instructions <grin>. Steve accompanied me to CBS on a number of trips to get an understanding of how things worked in the field.

Steve Foreman recalls:

My first programming task in March 1971, was on the PDP-11 to devise a table to quickly remove a disk head from the software address calculation.The NTSC disks capacity was 5.4 minutes and PAL was 4.5 minutes video material in black and white. The software was loaded via an ASR-33.This was a very slow process. During my first week at CMX I had to observe the demonstrations from outside the editing suite at CBS and if the process hung, I was to reset the computer. This was a crucial part of the demonstration as the design concept was to have a minimum of buttons, knobs etc on the editing console so the editor would only be concerned with artistic activity.

A CBS camera crew recorded material of a jazz band performing in a studio, then shot a sequence of the 600 editing the performance. Bargen adds:

As (can) be seen in a close-up, the editor was quite nervous...because this was the first time he had worked with the system and because there was a lot of jitter in the light pen control. The demo tape implies that it was finished automatically on tape, based on the editing on the 600. That was the concept, but not the reality. The reason is that the assembler portion of the system, the CMX 200, which was to control the quad tapes, had not yet been built.

With the NAB trade show just weeks away and a demonstration tape prepared CMX began its publicity campaign. Joseph Flaherty and Bill Butler co-authored a discussion paper “Why Use Film?”, while marketing head Martin Fletcher ensured trade journals were briefed about a device that was ‘the most important development in television production since the arrival of videotape itself’.

New York Times journalist, Jack Gould reported:

Computer to save millions in film editing, due soon. A major technological advance in Hollywood’s methods of producing films and videotapes for television and motion pictures is only weeks away with commercial introduction of an electronic computerized system for editing visual material. Savings of millions of dollars are envisioned in the system that can store scenes of a drama photographed in seemingly chaotic disorder.

Upon demand the system produces a finished product in the logical narrative sequence of a director’s choice. The human hand never touches either the tape or film during the editing and the individual in creative control can choose between limitless versions of a given scene, repeatedly trying first one and then another and making deletions or insertions until he is satisfied.

Gould called the CMX a ‘fusion of tape recorders computer banks and magnetic disks’. It was obvious that the new workflow could bypass the time consuming and costly steps of traditional linear tape editing.

The system already has a nick name RAVE; Random Access Video Editor. Two major Hollywood studio heads have shown interest in acquisition of the system and representatives of foreign broadcasting companies have been attending private showings in New York.

In laymen’s terms the heart of the CMX system is ability to collect and file away all the separate takes of a film and make them instantly available for an editor sitting at a console of two screens to put in a coherent order. Operation of the system borders on the eerie.

The console operator can order up what he wishes to see. He presses no buttons nor pulls any switches. Rather he uses a pencil light which direct the system to record play back or edit.

Bill Butler continues:

From the engineering and technology challenge standpoint, it was exciting as hell. It was a great crew that started in January 1970 and 15 months later we presented a working model.

Cal Strobele recalls:

We knew it was new and novel. A smart use of existing technology but it didn’t seem it was earth shaking or industry changing at the time.

But it was.