Broadcasting comprises many individual departments, some of which once existed almost entirely unto themselves. Test and measurement (T&M) was very much of that ilk, hiding away in engineering workshops and only occasionally venturing out into the studios when something went wrong. Its near neighbour, quality control (QC), was also one removed from the main hurly burly of the broadcast centre, even though what it does is crucial to the technical acceptability of the end product – the programmes.
Both T&M and QC have now been brought closer into the fold with the advent of file-based workflows and, if proposals by the European Broadcasting Union (EBU) and, in the UK, the Digital Production Partnership (DPP) become reality, they will be right at the beginning of the production chain and not just at the distribution and transmission end. The EBU strategic programme on QC has spent the last two years sifting through more than 500 tests submitted by member public service broadcasters. The job of overseeing the distillation of this “massive list” into something more usable has fallen to Andy Quested (pictured above), whose day job is as head of technology for BBC HD and Ultra HDTV. In his role as chair of the EBU QC strategic group, Quested says “different groups of broadcasters have different takes” on the way to approach QC and how to define the tests. The long list has been reduced to approximately 160 tests, partly because some functions were found to be duplicated but under different names, while others have been rolled into a single test. The work so far was released at this year’s IBC as EBU Tech 3363, with the confirmed tests represented on a QC periodic table. Quested says these give an overview of procedures to test both base band audio and video and files containing base band material. “These divide into groups and are represented both horizontally and vertically,” he explains. “We have defined the importance of each test and where in the workflow each is done. If tests are made on base band material before it is wrapped as a file, you don’t have to process it again to generate a new file.” Quested says that in the days of tape the main criteria to check were: does it sound and look OK and does it play? How a programme sounds and looks is still the primary question the producer has to answer; but the rest of a modern broadcast media file, Quested adds, is the means of getting it to its destination, with information regarding the codecs and other technical data. The EBU QC tests divide into four groups: regulatory, absolute, objective and subjective. The hot audio quality topic of the last few years, loudness, falls under the absolute heading, as it is tightly regulated in some countries but comes under a voluntary agreement on targets and specification in others. But, as Quested points out, even without a universal regulation there are still standards to hit – EBU R128, ITU 1770, ATSC A/85. “If the target is -23 for R128 and something measures -27, then clearly it’s outside the spec and the metadata is incorrect,” he says. Quested describes the tests as a mix of the relatively simple to the more involved. “Some can be done by ear and eye but in many cases it’s the interpretation that is the difficult thing,” he comments. “Telephone distortion would not pass a straight technical test but it would come into the subjective group because it can be used creatively. We’re also looking at getting rid of every objective test – including lipsync – and either moving them up into absolute or down into subjective.” The EBU strategic group has been working closely with QC/T&M equipment manufacturers to incorporate the final definitions into new systems, so that all devices produce similar results. “This will be a first because everybody will agree on the definition of what is being tested,” Quested says. Despite the sophistication of today’s test and checking equipment, both base band and file-based, Quested says the ears and eyeballs of trained operators will still play a part in the QC process, especially for programmes sold internationally. The aim is that the bulk of QC will be done at post-production facilities, with broadcasters checking the metadata to see that all the tests have been carried out. The EBU strategic group on QC is now working on the last 60 or so tests, which Quested says are the more difficult ones. The complete list could be published by April or May next year. An extended examination of QC/T&M technology, with comments from leading manufacturers, will appear in the January edition of PSNEurope.