Test & measurement in a changing world

During this period of transition, when both analogue and digital solutions have to work together, test and measurement devices are playing an increasingly crucial role in ensuring compliance.
Analysis, Delivery & Transmission
Analysis, Delivery & Transmission


During this period of transition, when both analogue and digital solutions have to work together, test and measurement devices are playing an increasingly crucial role in ensuring compliance.

While all the hot talk in the industry is about "tapeless workflows" and "file-based architectures", the reality is very different. Virtually every broadcaster in the world today has to bring together a mixture of analogue and digital audio and video, and make them all work well together. This means that the proven and accepted standards are more important than ever - and you need good test and measurement equipment to ensure compliance at every step of the way.

It is important to remember that, whatever you do to the signal downstream, you acquire in analogue form. Camera CCD or CMOS chips are analogue devices. The same goes for audio: microphone capsules are analogue devices. At the point of acquisition, you have to know the signals you are recording are getting the best out of the recording medium. Camera matching, colour gamut, video black and white levels, audio phase, perceived loudness: all these and more are vital.

Today, we also have an unrivalled ability to change the image in digital post-production. Every edit system has a colour corrector (Apple's Colour has functionality to rival a da Vinci or a Pandora, and it is given away free!). Graphics systems can overlay multiple layers of effects, text and artwork. Producers are increasingly demanding a distinctive look for their programmes and, while software can create this at the click of a mouse, just because it creates a mood in the edit suite does not mean it can be broadcast.

Therefore, it is still important to have good test and measurement in the edit suite. These are the places where illegal colours can be created all too easily, and if you leave it to a downstream legaliser to catch them, then you are not going to like the results. Modern test equipment focuses on making it easy for the operator to appreciate the technical limitations of the broadcast chain by making errors very obvious indeed on the main monitor.

Even if you are capturing and processing pristine digital signals, there is still the archive. Many channels depend on old content, news operations frequently have to use archive footage to put today's stories into context and sport loves to compare performances over the years.

No archive content is going to be a match for today's pristine digital productions, especially as we move to more and more HD content. But we owe it to our viewers to make it look as good as we can. That means taking particular care with calibration to ensure we achieve the best possible quality.

The next consideration is that even all-digital systems have their challenges for test and measurement, because there are many sorts of digital connections.

While in an ideal world we would maintain SDI all the way from the camera to the home, in practice we have acquisition compression, mezzanine compression for servers (and maybe a different compression for nearline archives), and perhaps a manufacturer-specific codec to make the edit system run more smoothly. Finally, of course, there is the transmission codec when we cram the signal into a few megabits per second for broadcast.

As part of the system alignment and integration process, at the very least, engineers need to track signals through this path to see just what the signal degradation is. Signal generators now routinely include pathological test signals to highlight where it is under particular stress.

Finally, there is a move from realtime video and audio paths to delivering content as files over IP circuits. While the benefit of IP is that you are more or less guaranteed that what you put in at one end you will get out of the other, a broadcaster still has to perform quality control checks on the incoming content, to ensure that the producer is working to the same high technical standards.

As the content is arriving as a file faster than real time, it makes sense that the technical quality control checks should also be performed on the file itself, faster than real time, and automatically without the need for a human operator unless there is a problem. Test manufacturers are developing software-based processes to achieve this.

So the conclusion must be that the industry continues to need good quality test and measurement devices, which are carefully tailored to meet the specific needs, skills and knowledge of the staff at each stage of the content chain.

Engineers need highly portable - but still comprehensive and very accurate - instruments with them at all times. For fixed installations, on-screen displays may be more appropriate than conventional instruments. Editors and designers need simpler tools which make it very clear if they are exceeding the parameters of a good signal. Ingest operators need support from automated tools. And everyone needs to have confidence in the accuracy and reliability of each device.

Steve Nunney is managing director of Hamlet

Testing times for Hamlet

Hamlet has developed a standardised, all-digital test platform that is used in its fixed appliances - the MonitorScope which has the traditional half rack width form factor and an integral colour LCD screen, and the DigiScope which rasterises the output to be routed to any convenient video or computer monitor - and its portable devices the Flexiscope and its smaller brother, the MicroFlex.

This platform has application modules to define functionality and connectivity. At present, there are modules available for SD component and SDI video; SD and HD SDI; and SD and HD SDI with built-in test signal generation.

For file-based infrastructures, Hamlet offers ReelCheck, an automated quality control device running under Microsoft Windows. A similar suite of software is also available as the Vidscope Plus with realtime monitoring of multiple parameters and displaying up to six windows simultaneously on screen. Both can have Photo Sensitive Epilepsy filters installed.

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