Does your test and measurement equipment meet the grade?

Monday, July 09, 2012

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Nowadays it is unusual to find separate waveform monitors and vectorscopes; their capabilities have been combined to create modern waveform monitors for complete visual measurement, something Hamlet was the first to do.
Broadcasters have spent millions upgrading their transmission infrastructures to ensure they are able to offer viewers the highest quality television content, whether that is from analogue to digital, SD to HD or 1.5Gb/s to 3.0Gb/s. Such a huge investment means TV bosses want the source programming to be of the best possible standard both visually and audibly. According to Steve Nunney of Hamlet, to ensure this happens, any content received is rigorously tested and anything that does not make the grade will either be rejected or auto-corrected – neither of which a producer wants to happen.

Rejection means that the content maker needs to spend precious time and money putting these issues right. Given that we all know how cut-throat the broadcast production industry is, any company that has to do this more than a few times is not going to be around for long. The issue of auto-correction by a third party can be just as much of a nightmare for producers. For instance, if an ad agency creates a TV advert that falls outside the colour gamut required by a broadcaster, the broadcaster could decide to alter the colour levels so that it is in line with other content. This can result in the colour of a product being changed, which, as it is so closely connected to branding, is likely to infuriate the ad agency’s client and make them look elsewhere for future campaigns.

So, testing and measuring content is vital for the production and broadcast industry. What most producers are trying to achieve is an accurate, digital reproduction of real-world sights and sounds. In terms of vision, this means checking synchronisation, levels, timing, distortion and, as touched upon above, colour gamut. 

To ensure their visual parameters are correct, broadcasters will use a waveform monitor. Traditionally, a waveform monitor was a stand-alone oscilloscope which measured the level of a video signal against time. An oscilloscope enables the operator to assess, among other things, whether or not the colour gamut and analogue transmission limits have been exceeded. For testing the other visual parameters outlined above, the oscilloscope needs to be used in conjunction with a vectorscope. The vectorscope takes the colour information and displays it on an X and Y axis, revealing greater detail.

Nowadays it is unusual to find separate waveform monitors and vectorscopes; their capabilities have been combined to create modern waveform monitors for complete visual measurement, something Hamlet was the first to do. 

For sound, one of the many issues that producers have to contend with is the need to ensure that levels are consistent throughout and are not so loud as to cause distortion or so quiet as to be noisy. However, level metering is not actually very good at measuring the actual perceived loudness of sound, which depends upon the content and duration of sounds. Audiences are well aware of the issue of relative loudness, and have been complaining about it – particularly that adverts always appear louder than the programmes – for decades. This is now being recognised by broadcasters and international bodies, which have finally taken action, developing an accurate means of measuring perceived loudness, and drawing up specifications. Everyone is more or less agreed that ITU recommendations 1770 and 1771 are the world standard.

In stereo, the phase of the output needs to be checked, which is even more important for surround sound. Substantial out of phase audio makes audiences feel uncomfortable at the best of times and physically sick at worst. Channel separation and balance also need to be monitored.

In the past, ensuring that content made the grade both in vision and audio would require a range of test equipment and accompanying monitors. This has proven to be costly for producers, who not only have to pay for the equipment, they also need to employ or hire a number of specialists to operate it, waste large amounts of valuable space on storage and finally ensure that it is all maintained and operating as it should.

At Hamlet, we believe that carrying out test and measurement procedures should be as simple and as convenient as possible and this is the ethos behind everything that we do. This is epitomised in Hamlet’s compact and intuitive DigiScope DS900, which offers in one unit the capability of undertaking all the appropriate routine tests on any video format up to 3G-SDI (level A and B). This has been made possible through a modular approach that enables the DS900 take up to four digital input board modules in a half-width 1U cabinet.  The modules are capable of providing all tests, including digital eye pattern testing for front-line maintenance or serial digital and analogue combined enabling reverse compatibility. It will also take a test signal generator that produces high precision signals for 22 common tests, including pathological, bars, sweeps and multi-burst, with embedded audio tones.

The DS900 also has an audio module, which covers 16 analogue and AES/EBU audio inputs, recognising that multi-channel audio and multi-lingual capabilities are now a common requirement. Audio tests available include Dolby, and loudness to US Calm or EBU standards.

Due to the unique digital modular construction of the DS900, it can be installed immediately without 3G-SDI if it is not required, as this can always be added later with a software download when it is needed.

The DS900 frame includes a built-in multiviewer, allowing the operator to create exactly the configuration of test displays required for a particular project or production. With four inputs, a single DS900 could be used to align four cameras, for instance. The device can be controlled remotely or even over the internet, as well as with the iScope soft key touch screen controls on the front panel.

At Hamlet, we realise that many engineers would like the convenience and functionality of being able to analyse multiple tests on their own computer, which is why we came up with the VidScope-Plus QC. This suite of software applications runs on a standard Windows PC to provide a quality control workstation for live video – with a suitable capture card – or within a file-based environment. It enables six concurrent traces to be displayed onto any monitor, including waveform, vectorscope, parades, gamut and histograms. The VidScope-Plus QC also includes audio monitoring of up to 16 channels and surround sound, peak audio levels, loudness and frequency, as well as a variety of picture preview options. More than 40 repeatable QC time-coded logging tests can be programmed, allowing staff to work on other tasks.


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