Posted by Martin Nicholson on , last updated
Video is big and takes a lot of capacity to carry it on a network. Traditionally broadcasters send large teams and vast quantities of kit to event locations so that the production can be handled on site. This enables them to have many camera feeds available and to mix between them to make a polished production, while only sending a small number of production feeds back to base for further production and transmission.
Instead of sending large teams and vast quantities of kit to event locations, what if broadcasters used IP cameras and had enough network capacity such that all camera feeds could be brought back to production centres across the country? These production centres could be different for different workflows: for example audio production could take place in one location and video production in another. This is exactly what BBC R&D is doing for the Commonwealth Games in Glasgow courtesy of a state-of-the-art national network.
The network that BBC R&D and our partners have created for the BBC R&D Commonwealth Games Showcase features 100Gbps connectivity in three cities across the UK. To put this capacity into perspective, 100Gbps is 1000x faster than the fastest readily available consumer broadband, which is around 100Mbps depending upon the location. This capacity is required because there are many camera feeds required and each one must be sent in high quality to ensure that it is still of a good quality by the time it has been heavily compressed for viewers at home.
The three cities in the network are Glasgow, Salford & London and each is connected to the state-of-the-art Janet network at 100Gbps. Within each city there is onwards connectivity to other sites at either 40Gbps or 10Gbps. Most of this high-speed connectivity is running over dark fibre optic links. Virgin Media Business has provided seven of these fibre links with individual fibre lengths ranging between 1km and 43km.
Cisco have loaned some of their high-end network equipment for this project. We are using the ASR 9000 platform as the core router that interconnects with Janet. We are using the Nexus 3000 series switches as the main layer-3 site switch throughout the network. We are also using some Catalyst 3560e series switches at layer-2 for where there are large numbers of 1Gbps hosts.
A UHD camera position in The Hydro
There are three Glasgow sites where BBC R&D has located cameras for the Commonwealth Games Showcase: Celtic Park, Hampden Park and The Hydro. The video production takes place in the public demo space in the Glasgow Science Centre; the audio production takes place in BBC premises in London. The production stream is received in the BBC R&D South Lab in London where the encoding takes place that feeds Digital Terrestrial Television (DTT) and is also available for IP streaming using MPEG DASH. See this blog post for more details on the UHD DTT and IP streaming.
To transport the video and audio around the network we are using Source-Specific Multicast (SSM) so that feeds can be received anywhere on the network whilst using the bandwidth as efficiently as possible. Using multicast allows all the feeds to be available on-demand at any site, which in turn enables video/audio production to take place centrally at one site or independently at multiple sites. Each video stream is compressed to around 1Gbps, which helps to ensure that the video remains in high quality throughout the production chain and thus looks the best it can when it finally reaches viewers at home. In the longer term our intention is to work towards using uncompressed video, which is around 12Gbps per UHD video stream, but to control the costs we are using light compression in these technical trials.
The UHD video production taking place in the Glasgow Science Centre
With the support of our partners, we were able to fix several initial problems with the network and since then the performance of the network has been exceptional. We are seeing no packet loss across the entire network, enabling the IP Studio team and the numerous other BBC R&D teams to demonstrate their exiting technologies as part of a high profile live event watched around the world on the BBC.
BBC R&D would like to thank our partners Cisco, Janet, and Virgin Media Business for their continued support throughout this project. Without them the underlying network that supports all the BBC R&D demos would not be possible.