Get Adobe Flash player
Quality is the best policy by Steve Nunney, Hamlet D espite all the changes in our industry at the moment – and maybe because of them – quality is more important than ever. HD has become the production standard norm. Why have audiences embraced HD so enthusiastically? Because it looks and sounds great. If you have a 42” or bigger screen in your home then the difference between SD and HD is obvious to all, and so HD channels have to maximise that benefit to get a commercial edge. Quality. Consumers expect to access content on multiple devices, from the small screens on smartphones right up to that 42” plasma. The sheer number of permutations of resolution, codec and wrapper – it can work out at thousands – makes it impossible to check each one before release. The only answer is to feed the best possible signal into the best possible transcoding farm. Quality. Stereoscopic 3D is still a niche, but an important niche. This is a difficult medium to get right. When it works, it gives the viewer a new and rich immersive experience. If it goes wrong it makes the viewer nauseous. Vomiting consumers tend not to be return customers, so you have to make sure that all the complex parameters are in the right place. Quality. I suspect you are beginning to get the message. So, if quality is so important, is responsible for the quality? The answer, of course, is everyone: if it is not perfect at the shoot then there is a limit to what you can recover downstream. But I would argue that the most important quality gatekeepers are the people in post production. The simple reason, is that it goes direct from the post house to the broadcaster. The first thing the broadcaster will do is run its own quality control checks and if it fails then it is bounced back to the post house for remedial work. This is work that is not on the budget and the cost is likely to fall on the post house because they were the last to handle it. It is the difference between a nice little earner and making a loss on a job. My first message, then, is that the post house should be doing its own QC on incoming material, and checking again during every process that can change the quality of the audio or video. 68 | TV-BAY MAGAZINE Audio Let us start to look at what we need to check and why with audio. This is an area where the move to digital has made life significantly harder, so we need to apply extra care. In the days of analogue audio, the odd excursion over the nominal peak level might get you a black mark from a QC engineer if it was noticed, but unless it was hugely over-modulated you would probably get away with a momentary high: analogue audio had a bit of headroom before the degradation became obvious. That is not the case in digital audio. 0dB is the maximum and if you go above that there are no bits to represent it. It is not a graceful degradation, it is a brick wall. Worse than that, running out of bits creates odd harmonic distortion, which is horribly obvious. As well as managing audio levels, you need to check phase correlation. Too much out of phase audio is very unsettling for the listener. Phase monitoring was relatively simple in stereo, but in 5.1 or more surround sound it needs a clever way of visualising it in a display to be able to see at a glance what is happening. The Hamlet solution is a unique “jellyfish” display which is informative and simple to understand. There is a new audio measurement which must be added now. Audiences have long complained about the differences in perceived loudness between different pieces of content, and particularly that the commercials always sound louder than the programmes. The industry has now taken action, and an accurate means of measuring perceived loudness has been defined. ITU recommendations 1770 and 1771 set out the world standard for loudness (the American CALM proposals basically follow the same technical parameters). Audio quality control should now include loudness monitoring, to ensure that your content has good impact without annoying the viewer. Broadcasters will include loudness in their ingest QC – they have to – and will reject if you sound too loud. >>