As with the Commonwealth Games Showcase network, we have once again been working with Jisc in order to do this and as such the sites, spanning the UK, are connected via the Janet network. The requirements of the subsequent productions have been more modest than the R&D Commonwealth Games Showcase and since we no longer have the 100Gbps kit, we have dropped the connectivity to Janet down to 10Gbps (and one site to 1Gbps). This is still huge compared to normal BBC production standards. For example, the Edinburgh Festival Fringe venue had connectivity, but it was non-resilient and only 100Mbps (or 100 times slower than the Janet connectivity). Incidentally, the Commonwealth Games network was also non-resilient, so having these two operating in parallel improved the site resilience.

In the Commonwealth Games Showcase, we used powerful workstations running prototype IP Studio software to undertake software encoding of the video, audio and metadata. This worked for demonstration purposes, but for live productions like the Scottish Referendum and the Edinburgh Festival Fringe, it is important to have production-ready equipment. For this purpose, we developed and licenced a product called Stagebox. Stagebox follows much of the thinking behind IP Studio, but crucially is available as an off-the-shelf product complete with support from the manufacturer. It features a field-programmable gate array (FPGA) that is used to hardware compress bi-directional video using the AVC-Intra 100 codec, whilst transporting embedded audio, analogue audio, camera control and more. Given the plethora of signals transported, a single Stagebox can be used to replace several other devices. In the case of the Edinburgh Festival Fringe, each Stagebox provided bi-directional HD video links and used the bi-directional analogue audio as talkback lines, all using a single box.

The Stageboxes already deployed in London Broadcasting House are of an older hardware design with a smaller FPGA (in transistor count) compared to the newest ones deployed in Edinburgh. This caused some asymmetries in the topology, because when run with Forward Error Correction (FEC) the older devices can only send or receive video, not both, whereas the newest ones can run FEC in one direction with bi-directional video streams.

We found that we needed FEC in the Edinburgh to London direction, due to a small amount of packet loss and/or occasional excessive packet delay across the network. Further investigation would have allowed us to tune various parameters on both the Stageboxes and the network to remove all sources of packet loss, but for a temporary installation it was easier to turn on FEC and correct the errors. The use of FEC meant that we required double the number of Stageboxes in London compared to Edinburgh as shown on the illustration above.

In line with what we did in the Commonwealth Games Showcase, the video and audio was transported around the network using Source-Specific Multicast (SSM) so that feeds can be received anywhere on the network whilst using the bandwidth as efficiently as possible. This enabled us to create a monitoring point in our South Lab as well as provide the received video streams to BBC Scotland in Glasgow.

As is often the case, having ample bandwidth to site allowed the BBC to do more; for example it allowed high quality video feeds courtesy of Stagebox and it allowed us to undertake various trials, including the 4K Nearly Live demonstration. By way of comparison, each video stream from a Stagebox was over 100Mbps, which is more than the entire bandwidth of the existing connectivity into site, and we sent two of these streams in each direction. Partly due to the increased bandwidth, the Stageboxes would have produced higher quality video than the existing devices, which is something that may have been noticed when sent straight to transmission, but would have been even more noticeable if there had been any post-production work undertaken on the footage.

Officially these Stagebox video links were the reserve links, but having proved reliable they were used for a live television programme, namely BBC Breakfast.

The Edinburgh PoP was connected by Jisc shortly before the Festival, remained in place for the duration, and after a successful event has since been disconnected again. We would like to thank Jisc for their continued support throughout this and several other projects. Without them the underlying network that supports so many of our use-cases would not be possible. On a future and related note, we are looking at running a longer-term 100Gbps trial for IP Studio work with Jisc – watch this space for updates on this as the plan develops!