Posted by Phil Layton on , last updated
BBC R&D recently announced our intention to trial the distribution of Ultra High definition programming over both DTT and IP and I would like to share with you some technical details of the trial.
BBC R&D is actively working on Ultra High Definition (UHD) with standardisation bodies and the World Cup gives us an ideal opportunity to practically test out some of that work. We set ourselves the goal of demonstrating an end-to-end live UHD broadcast over both a traditional DVB network and an adaptive bitrate delivery approach over IP. To do this we have partnered with Arqiva on the DTT side and will use existing super-fast broadband infrastructure for IP delivery. In a later post we will detail the chain we have constructed and the contribution from numerous other companies we’ve collaborated with and who have provided essential equipment.
The UHD production will be received in the UK from an H.264/AVC satellite contribution feed. For both DTT and IP we will be using Main Profile HEVC to compress the video to distribution bitrates that can be sustained within a DVB network and a super-fast broadband line. The frame rate being used is 59.94Hz as that is the standard in Brazil.
The DTT trial will be transmitted from Crystal Palace - channel 35 (London), Winter Hill - channel 37 (Manchester) and Black Hill - channel 35 (Glasgow). The transmissions are starting now and will carry live content on June 28th from 19:30 to 00:20 (BST), on July 4th from 15:30 to 20:20 and on July 13th from 17:30 to 00:20. As we are using the same T2 modulation parameters that are used for HD multiplexes the signal can be received on current consumer equipment. I’m not aware of any equipment which can decode the video though some existing HD models may tune the service and decode the audio.
The stream will use the latest DVB-DASH profile and is geo-IP locked to the UK only.
Our experience so far is that dedicated hardware is required to be able to decode Ultra High Definition HEVC encoded video. In conjunction with some consumer equipment vendors, we will be using some of the latest chipsets from the silicon suppliers.
Part of the experiment will be to understand the performance of the newly launched HEVC encoders so the video bitrates are very much subject to change but will end up at around 30-35Mbit/s.
BBC R&D has a long history of research in this area reaching back to our white paper back in 2004 and to our Super-Hi-Vision demonstrations during the London 2012 Olympics. More recently we have written about some of the challenges faced around frame rates and resolution.
Update: 28th Jun 2014
BBC R&D successfully transmitted the Columbia v Uruguay game tonight in UHD at a resolution of 3840x2160 over both DTT and MPEG-DASH. The video bitrate was approximately 35Mbit/s on both DTT and MPEG-DASH.
We were able to successfully receive and decode the DTT transmissions from Arqiva's Crystal Palace site at our research lab in London. Transmissions also took place from Winter Hill in Manchester and Black Hill in Glasgow. We used specially modified receivers from three major consumer equipment vendors, plus development boards from a chipset vendor. More details of DTT transmission and TV reception will follow later in the trial.
We also successfully decoded a two representation MPEG-DASH stream over the open internet at both our site and at the R&D site of a project partner. For decoding the MPEG-DASH streams we used development boards from different chipset vendors. One of the implementations uses software developed by BBC R&D.
The UHD coverage was up-linked from the Estádio do Maracanã in Rio de Janeiro by Eurovision. Globecast provided the downlink facilities and we used Ateme satellite receivers to decode the quad HD AVC/H.264 signal. I hope to describe more of the challenges of the contribution in a future blog post.
Update: 9th Jul 2014
The BBC is a very active contributor to DVB, the organisation which designs the television distribution standards in Europe. So we are very pleased that DVB released new and updated standards on the 3rd July 2014 to cover HEVC, UHD and MPEG-DASH around which we have based our trial.
The DVB Blue Book A157 (PDF) covers the use of HEVC within transport streams and the core UHD specification and will be standardised as an update to ETSI TS 101 154. DVB Blue Book A168 (PDF) provides the MPEG-DASH DVB profile that we are using.
On July 4th we used these technologies to cover the World Cup quarter final game between Germany and France. Staff at BBC sites at New Broadcasting House, Broadcast Centre, Pacific Quay and MediaCity were able to follow the game over DTT, whilst staff in Belfast, Cardiff and Bristol, with help from Broadcom, were able to watch coverage over DASH.
Another team at BBC R&D is actively contributing to the MPEG video coding standardisation and is working on the standardisation of MPEG-HEVC/H.265, one of the enabling technologies for our UHD trials.
The final game to be covered will be the World Cup final on Sunday 13th July.
UHD Production Training and Skills from the BBC Academy including:
This post is part of the Broadcast and Connected Systems section