BBC R&D’s John Zubrzycki was in the audience at Broadcasting House to see the opening ceremony shown in Super Hi-Vision (SHV) on a 7680 pixels by 4320 pixels 8-metre wide screen and with 22.2 multichannel 3-dimensional sound system. The combined effect was more like telepresence than TV. John and the rest of the audience were left feeling they were viewing the stadium through a glass window.
The SHV pictures coming from the Olympic stadium are the culmination of 4 years hard work and collaboration between the BBC and NHK’s Science and Technical Research Labs. NHK’s work on a TV system where the resolution exceeds that of the eye and where the screen is big enough to fill your field of view began in the 1980′s.
Almost every piece of SHV kit in the world has been brought to London for the Olympics. There are three cameras (the only three operational units in existence) in the Olympic Park. They are connected to NHK’s Outside Broadcast vehicle, where images are recorded and simultaneously sent to the SHV Production Centre at BBC Television Centre.
Audio is taken care of in a separate truck provided by SIS Live that’s fitted out with a mixing desk and a small NHK 22.2 multi-channel sound system. Audio feeds are coming from NHK’s own mics and shared mics dotted around the Olympic Park. The audio is also being fed to Broadcasting House, where it is edited and refined.
The SHV pictures and surround audio are sent uncompressed at 24 Gbit/s via diverse fibre over eight wavelengths.
At Studio 0, TV Centre, there are editing, storage, transmission and pre-view facilities. Picture editors work on a downconverted HD proxy. The resulting EDL drives one the two SHV editing stations on site (one for the UK & US feeds, the other for Japan), where the content package can be further refined. At 16 x HD resolution, they’re not working in real-time. The NHK production team and a BBC editor are able to edit a new content package overnight ready for showing the next day. A dedicated SHV graphic station is used to add captions and make up titles sequences.
Sound is edited in the Studio 0 gallery, which has been kitted out with a 24 speaker array surrounding the audio mixer operator arranged three heights: floor, mid and ceiling, and one speaker directly overhead.
The edited audio package is previewed in Studio 12 (the old Drum Room for Studio 0, pictured), which has its own 22.2-channel sound system and an 85-inch LCD display. The room only seats seven, but does a good job of recreated the immersive experience that SHV can produce in the home.
Edited packages are transferred to a solid state recorder/player for transmission to the theatres, with second machine for backup. A playout machine uses sixteen P2 recorders working in parallel.
The whole operation is run jointly by the BBC and NHK, with hourly transmissions from 11:55am. Content from the playout machine is sent to a bank of audio and video encoders, with each audio channel encoded at 384 kbit/s using AAC and the video encoded in sections using H.264 encoders giving a total of 280 Mbit/s. Coded signals are transported on a pair of Transport Streams (TS) to a pair of TS/IP converters to produce a pair of IP (Internet Protocol) data streams for each theatre at about 350 Mbit/s in total. Two data streams are produced because the total bit rate is too high to be carried on one Transport Stream. Unicast UDP (User Datagram Protocol) is used to transmit the data to the theatre in the UK and USA with some Forward Error Protection (FEC to guard against minor data packet loss. In Japan, Multicast is used with the option of extra FEC.
The transmissions to Glasgow and Bradford are carried to the theatres over Janet (Joint Academic Network), with the final link to the BBC studios in Glasgow over a link provided by BT. Geant2, Internet2, Sinet4, and GEMnet2 research networks coordinated by NTT are used for the links to the USA and Japan.
At the theatres, the signal is decoded and displayed on 250-inch or 300-inch screens using projectors with 8k resolution and the audio sent to the 22.2-channel audio system.
Setting up these theatres took several days, and special attention was needed to set up the audio system to ensure that the channel order was correct, then the relative levels and delays needed to be set. Fine adjustments were required to the speaker positions and angles to ensure the best sound reproduction.
Andy O’Dwyer of BBC R&D at the control centre in TC Zero, where Stagebox video links connect all the display venues with the OB at the Olympics and the Television Centre.
This has been a project long in its preparation, with first test transmissions of a live pop gig by the Charlatans from London to Tokyo in September 2010. Network tests across the UK and from the UK to Japan started in winter 2011/12. The network link to the National Media Museum had to be upgraded from 100 Mbit/s to 1Gbit/s. In Glasgow, BT provided a link from Glasgow University. Soak testing of the link has been going on for several months, during which several problems were found and solved. As I finish writing this post, we are into the fourth day of the Olympics. The links have been reliable, with only one glitch that has occurred during a show in the UK so far. Even so, we are investigating why there was a glitch. We have shown that IP networks can be made to reliably carry high bit rate time critical video and audio, but care is need in the way the links are set up. It is not clear to me that all the interaction mechanisms on IP networks are well-understood; an area for further research, perhaps.