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The VARITIME DIGITAL SYNC GENERATOR
Written for Bjarne Laesoe by Brian Aird (published in IBE May 1997)
As system designers know, seldom does one piece of equipment cater for all real-world configurations. However, the Philips PT 5210 VariTime Digital Sync Generator can provide a perfect match for a remarkably wide range of applications. This is achieved with over one hundred possible configurations with its many well thought out options and standard features.
The VariTime product is manufactured, along with other test and measurement equipment by Philips TV Test Equipment located in Brondby, near Copenhagen. An extensive range of test and calibration products are made including the industry standard colour analysers and video pattern generators, used by broadcasters and set makers all over the world.
The VariTime Concept
Philips' VariTime is so named since it is designed with the multiple delays of digital television installations in mind. It allows signal and reference black outputs to be timed in fine steps over the length of the data sequence relevant to each output. SDI black and test signals can be timed with 37.5ns resolution over a +/- one field range, whilst analogue black burst and test signals are timeable in half subcarrier steps over a +/- four field sequence for PAL and +/- two field sequence for NTSC. Analogue colour black or black burst, is routinely used for timing purposes even in digital installations, where processing delays are often of the order of several fields.
The VariTime is effectively a dual standard SPG since, analogue and SDI outputs can be selected as a mixture of 525 or 625 simultaneously.
There are numerous VariTime model variants depending on the functions required and options selected. In fact over one hundred possibilities exist, making Philip's VariTime the most versatile digital sync generator ever made.
All versions allow for analogue genlock and the lowest model in the range has only two independently timeable black bursts. However, for a small editing suite where multiple timing planes are not required, a version is available with one timeable black burst and seven parallel black bursts.
The main features are as follows:-
The main options are as follows:-
Philips have a flexible attitude towards their clients needs, and are willing to customise some of the test signals generated, providing sufficient specification details are provided at the time of order.
For example, although most stations will undoubtedly possess logo generators, Philips can burn a simple text message into a chosen test pattern, (for example a station name can be included in the Philips circle test pattern). In addition, in order to satisfy the needs of simple installations, Philips are considering providing a simple EBU/FCC BARS output for customers who do not need a comprehensive range of test signals. Philips are working on a solution where the menu for each of the pairs of SDI black outputs will also include colour bars.
The unit is menu driven with eight main menus and over fifty sub menus. Eight instrument presets have been provided to ease the task of changing configurations for different set-ups, each of which can be named.
An RS-232 remote interface gives access to all functions and each parameter of each output may be adjusted remotely. In addition complete set-ups can be uploaded or downloaded by a PC or another VariTime unit. In a multiple SPG installations, the ability to copy set-up data including set-up names either from a Laptop or from a maintained 'hot' spare unit is very powerful in implementing unit replacement or upgrade with the minimum of operational disruption.
Positive Status Reporting
In order to simplify integration into fault tolerant system designs, Philips has implemented the signal integrity circuitry into the unit itself, instead of a changeover unit. The circuitry, which monitors all outputs directly, has been implemented in dedicated hardware and is independent of the main SPG CPU. Moreover, positive affirmation is required that all outputs work. In the absence of such a signal the changeover will switch to the back up SPG. The advantages of this approach are reduced complexity in the change-over design and improved reliability. It is considered very unlikely that a faulty unit would continue to send a positive status signal, in addition since each SPG has its own status check circuitry, the back up SPG can be monitored continuously in the same way as the main SPG and an appropriate alarm given to the operator. Other competing systems may only monitor the main SPG.
The simplest need is for one SPG with BB and Bars, and as we have seen this is accomplished with the base model, the PT 5210/00, whilst the addition of the PT 8604 will provide for multiple BBs.
A more complex installation is represented below where three slave SPGs are genlocked to a master SPG. Black burst genlocking is standard, whilst an SDI genlock feature is provided with the PT 8606 option.
Although digital mixers with autophasing inputs are now commonplace in serial digital component systems, multiple system-wide timing planes in modern, multi-channel television stations with multiple studios, transmission suites and post production areas or Master-Slave studios and interconnected OB Vans have created the need for individually timeable references from a fault tolerant dual master SPG/changeover sub-system (fig 4 refers). Providing no analogue test signals or SDI black outputs are required, then eight independently timeable black bursts can be provided by VariTime.
With the PT 8605 AES/EBU audio option digital silence and reference tones with stereo markers are available. The digital audio may be embedded in the SDI video outputs. The digital audio 48Kz reference silence is the same value for both standards. This allows for standards conversion with AES/EBU digital audio without non-sync audio failure, as shown in (fig 5).
A longitudinal timecode output on a balanced XLR is provided with the PT 8607 option providing vertical timecode is present at the analogue genlock input.
EDH Testing with Philips Digital Video Analyser
The integrity of serial digital data paths may be checked using the serial black EDH test signal available from either VariTime test generator options.
Philips now have the PT 5474 digital video analyser to partner the VariTime SPG . This multi-format, 525/625 analyser for serial digital component/composite working allows for real time measurement of key parameters such as serial jitter, signal amplitude, colour levels, and EDH error. Alarm setting is provided for all parameters and indication can be made both locally and at remote stations. Extensive error logging on a printer or 3.5" disk drive is possible and an analogue RGB output is available for monitoring. Options include a frame buffer to ease data analysis.
The unit is a self contained half-rack wide unit with a touch screen LCD and is ideal in new installations or as a replacement for analogue waveform monitors during system upgrades.
The Digital Video Analyser has been designed with ease of use in mind and supports a full range of simulated analogue waveforms. All the digital video tests are performed continuously and provide real time, on-line measurements with external and internal alarm notification when user defined limits are transgressed. Internal alarms take the form of front panel LEDs and an internal speaker, whilst external alarms are via a GPI output that permits both major and minor levels of user notification.
A separate monitor can be used to indicate RGB and NTSC/PAL colour space violations and any non-recommended value errors. (Question:- Is this the same as vectorscope and waveform monitor - will there be a lightning display? - Brian)
Analogue systems will be able to take advantage of the one rack unit Philips PT 5463 video signal analyzer. It is a combined waveform monitor, vector scope and analyzer based on a rasterizer and uses a standard picture monitor for display. Ease of use is ensured by on-screen pull down menus and six custom set-ups can be programmed for frequently used measurements. A stereo audio display for both level and phase is provided and includes user definable reference levels. A print out facility is provided and a Windows based software package permits full instrument control and performance documentation.
Modern complex digital television systems demand synchronisation in multiple standards and for long and short delays. VariTime, with its high flexibility, is the perfect match for a multitude of system applications.
The dual standard VariTime digital sync generator and the new digital and analogue Video Analyzers are good examples of a new breed of market-led technology products designed to be leading examples in their class.
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