BBC Pioneers Live IP Production in Ultra HD: The Workflow
The BBC prides itself on pioneering media technology, and its renowned research and development team has come up trumps again with what it claims is a world first live UHD production produced and transmitted in an entirely IP domain.
The trial is planned to take place during the Commonwealth Games, a quadrennial international multi-sport event hosted in Glasgow for two weeks from July 23.
It extends the BBC's trial of UHD live feeds from the World Cup in Brazil delivered simultaneously over conventional digital terrestrial and IP networks. The first of three matches delivered in the format for these tests airs on June 28.
From Glasgow, Scotland the BBC intends to replicate the Brazil trial by sending UHD signals across DTT and IP networks in partnership with telco BT and infrastructure provider Arqiva with the feed compressed in HEVC. This will again test the quality of service to a home environment.
This time around though BBC R&D is leading a major test which will see it not only produce the UHD content in a series of outside broadcasts in IP, but also route the signal to a special screening area accessible to the general public.
“We're setting up an R&D experiment to try and create a live multi-camera UHD programme from the Commonwealth Games using IP production techniques, IP processing and IP transmission,” explained John Zubrzycki, BBC R&D section lead.
The workflow will be as follows: 4K signals at frame rates of 55p from four Sony F55 cameras will be taken into mulitcore PCs containing video processing cards for conversion into IP. With no professional cameras capable of IP output as yet (vendors like Sony plan to include an IP interface in a range of its products including cameras beginning in 2015) connectivity will be by via existing HD-SDI cable. The PCs will be placed close to the camera to get the signal into IP as soon as practical.
The data will be fed over Virgin Media's dark fibre network, which links the Games' venues around Glasgow to an IP-operated production gallery built by the BBC at the Glasgow Science Centre.
Within the exhibition centre, members of the public will be invited to see the results encoded in production format H.264 and in HEVC, the proposed compression format to the home.
A sound mixer and commentator for the output will be based in London so that production collaboration over IP can be tested working in several locations.
To facilitate this, data will be transported from Glasgow to BBC R&D in London and to a second gallery at MediaCity in Salford near Manchester over the Joint Academic NETwork [JANET] at 100Gb/s. An additional network layer will be provided by 100Gbps Cisco switchers.
“Not all of that capacity will be used for data but it will give us some important lessons about how the network behaves handling live Ultra HD high bitrate signals,” said Phil Tudor, principal technician on the project.
It will test the 4K signal at mezzanine compression levels of 1.5Gbps and 100Mbps for HD. “This approach is not intrinsically about bitrates, since the system has inherent flexibility to be configured for any bitrate you want,” said Tudor. “The beauty of IP is its scalability as opposed to the rigidity of 3G SDI.”
Again, the production codec choice of H.264 is “an implementation detail” for this test. “IP production can handle many different formats on the same infrastructure whether optimised for Ultra HD, HD, or lower resolutions,” says Zubrzycki.
Indeed a key part of the workflow will see 4K source media but a simultaneous working resolution of HD and lower, adjusted to the suitability of the production device.
“It's not always appropriate to send a 4K signal to a multiviewer, for example, or a tablet where the size of screen is a fraction of full-screen Ultra HD,” said Tudor. “It will be 4K in and on the network, but there will also be an HD feed and a sub-HD proxy so that content is suitable for different devices.”
The suite of technologies that BBC R&D has put together for this test is dubbed IP Studio, a project that began life in the labs two years ago.
BBC R&D describes IP Studio as an open source software framework for handling video, audio and data content, composed of off-the-shelf IT components and adhering to standards like IP packet synchronisation protocol IEEE1558.
The requirements of an all IP studio are demanding: among them are high bit rate low delay streaming, timing and synchronisation, distributed configuration and control, real-time data, flexible reuse of processing, and access to production content and information.
“This is not a complete system,” stressed Tudor. “It is research designed to feed into the BBC's future broadcast strategy and standardisation efforts [of video over IP being made by the EBU and others]. We will learn a lot about the way multiple 4K cameras interact over IP and about the way live the network performance with live Ultra HD.”
Further demonstrations of IP Studio are planned to incorporate return channel interactivity and third party data.
However, while there is unstoppable industry momentum away from transport protocols like SDI and toward using commodity IT and packet-based networks in TV production, migration is matter of years not months.
“Broadcasting whether over by satellite or terrestrial is still the most economical solution to deliver programming,” asserts Carl Hibbert, Futuresource Consulting head of broadcast, content & services. “There's no way either the economics or the guarantee of a quality of service is there yet there with IP. Whether it's a 5 or 10 year horizon has yet to be determined but in our view there will be a hybrid DTT and IP broadcast infrastructure for some time to come.”
BBC R&D Controller Matthew Postgate says his department works to a 20 years plus horizon. “I think that reflects our desire to make sure all audiences have access to a service they expect of us. That said, our audiences are increasingly less homogenous.”
The BBC has other factors constraining a wholesale move to IP. While a quarter of UK homes enjoy superfast broadband of 30Mbps (according to regulator Ofcom), service in rural areas in particular remains patchy. Smart TV consumer uptake is rising with 60-65% of people who own a smart TV connected to an internet service (Futuresource), but it's far from a 100% penetration of smart TV sets necessary for a publically funded organisation like the BBC.
“Not everyone can receive an IP signal and not everyone wants to consume on-demand,” points out Hibbert. “Some 97% of viewing of BBC channels is still live at the point of broadcast so before we all get carried away with video over IP there is still a massive and crucial role for linear play.”
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