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UK audio tech specs in place for file-based shift

Delivery of UK TV programmes is set to go fully file-based from October 2014. In preparation, industry body Digital Production Partnership this week published version 4 of its technical standards, with guidelines for loudness and multichannel audio metadata.

File-based technology for television production and distribution has been a constant theme in the business over the last 10 years.

It has been a consistent presence at successive IBCs so it was fitting that the organisation driving the move towards tapeless, data-centric working in the UK, the Digital Production Partnership (DPP), used this year’s show to unveil the latest technical specification and announce that British broadcast will begin to go file-based for programme delivery from 1 October next year.

The DPP was set up in 2011 by the BBC, ITV and Channel 4 (C4) to inform and advise the broadcast industry on best practice for digital production and data-based distribution of material. The initiative is supported by other UK broadcasters, including Channel Five, Sky, UKTV, BT Sport and S4C, as well as independent production companies.

At the IBC session Mark Harrison (pictured first left), newly appointed chair of the DPP and controller of production for BBC North, described the organisation’s progress towards a unified file-based structure for UK broadcasting as a “rather happy roller coaster ride”. He added that while BT Sport was file-based from its recent launch and Sky “as on the way”, ITV and Channel 4 would be “ramping up” for full implementation over the year to 1 October 2014. Harrison observed that the BBC had “a bit of catching up to do” and would use the date as a starting point, with file-based delivery as its preferred means.

Audio was a relatively small part of the first DPP spec when it was published in March 2011. This document covered only tape-based operations and in sound terms concentrated on basic track lay-out. A file-based specification followed in February 2012, adding EBU R128 loudness control to track configuration guidance.

Version 4.0 of the DPP technical and metadata standards is based on the newly ratified AMWA (Advanced Media Workflow Association) AS-11 version 1.1 specification for MXF (Material eXchange Format) programme contribution. As well as R128, DPP v4.0 adds optional recommendations for the carriage of multichannel audio metadata in a programme file.

Kevin Burrows, chair of the DPP technical standards committee and controller of technical broadcast and distribution at C4, says the industry body was formed to not only bring broadcasters together but also manufacturers. “It doesn’t make sense for companies nowadays to support different standards because of tight profit margins,” he explains. “We’ve done a lot of testing and held a manufacturers’ day during IBC and had a lot of input, particularly with kit for interoperability.”

On the sound side Burrows says the main issue for broadcasters – and public service stations in particular – is ensuring all viewers can hear and enjoy the programmes. “There has been some concern from the hearing lobby about people not being able to hear dialogue properly,” he comments, adding that the loudness and multichannel aspects of the spec have been designed in part to address this issue.

The surround sound recommendations have three modes. Mode 1 has dialogue across the front three channels (left, centre, right or LCR); Mode 2 is for programmes with out-of-vision commentary or voice-overs, which are put in the centre channel; Mode 3 covers international or co-production material that has centre-only dialogue and where it is not possible for the UK broadcaster to prepare an alternative mix. Burrows observes that film soundtracks generally have centre dialogue but that “a lot of TV programme makers and broadcasters” want LCR.

All commissioned material has to conform to -23 as laid down in R123. This came into operation for UK broadcast at the beginning of September and Burrows says already there has been a drop in the number of complaints from viewers about variations in audio levels between programmes, commercials and promos. “R128 has made a difference but we’re not expecting it all to happen immediately, people need time to move across” he says. “Part of the problem is that we’re working with new commissions, which conform to R128, and old or archive programmes, which don’t. The problem will reduce over time and R128 will minimise it but there will always be an issue with not knowing what commercial might follow a drama with a wide dynamic range. There are also differences in how people are listening – on flat screen TVs with thin speakers or surround systems – and that has an influence as well.”

Burrows and his colleagues at the UK broadcasters are hoping agreement can be reached with US studios and TV producers to conform to common standards, so that programmes are more technically consistent. “We’ll never get to the point of universal standards,” he concludes, “but if we can cut down the number of formats that would be a start. It’s looking very hopeful.”