Networking for live television production

By Marcel Groos

Hard disk recording has become common practise on live productions because of its obvious advantages: Multiple operators can access images instantly and simultaneously, providing replay and edit functions which never interrupt any recording processes that run on multiple channels in “loop-mode”: When the disks are full, the oldest frames are over-written. The operator uses “in” and “out” points to mark the scenes that are to be preserved. This protects the selected clips, as the recording process will jump whenever it comes up to an “in” mark. Several playback channels are used at the same time to search, cue and replay scenes, at any speed and without ever interrupting recording at any time. So also during fast paced sports such as ice hockey, no incident will go lost. The server technology available today has matured tremendously over the recent past. Servers have been SDTI networkable for real time exchange of content for a while. IT/IP based networking techniques have now also made their entry into the TV trade to facilitate integration with nonlinear editing and (large-scaled) archiving systems.

Server networks

When working with networked servers on a live broadcast production, that network must be extremely reliable. The servers themselves must also be robust, so that no single point of failure, such as power supply, board or hard disk, can cause the loss of current recordings or previously stored material. Modern servers can achieve this by using independent units networked together, each with individual RAID arrays and dual power supplies. For large multi-camera configurations as often used on sports, the server network must allow real time access to all sources by many users each with different objectives: One may be responsible for (super-) slow-motion replays, while another is building packages for expert analysis, highlights packages and closing music montages. Each user must be able to perform their own task without affecting any other user, yet all using the same images. A typical set-up consists of independent servers each with a configurable combination of record and playback channels. The individual servers can be connected via a high bandwidth SDTI network to allow any operator access to any material. The modular approach of this network can be expanded to suit the requirements any production, big or small.

The advantages of SDTI networking for live production, are in the simplicity of its set-up and immediate access to recording files. This enables playout or manipulation of any live source direct from any networked server, rather than first needing to copy to local storage. SDTI uses standard 75-Ohm BNC cables which are largely available in any studio or OB truck. The default data rate is 540 Mbps which accommodates between eight and ten real-time operations in SD. Fibre encoders may be employed to extend the geographic range to well over a kilometre, that will typically reduce the bandwidth to 270 Mbps but the network will remain fully operation under such circumstances. The SDTI network not only deals with video and audio, but also control information and bandwidth management, ensuring that simultaneous demands on the network are prioritised. Traffic related to a playout to air of media recorded on a remote server has a higher priority than transfers for archiving. The SDTI networking hub “NetGuard” adds an essential level of reliability and quality of service to the system. The overall condition of the network and the status of each of the 7 branches are clearly displayed on the front panel. NetGuard as such is a convenient supervision tool, particularly when interconnecting servers that are spread over different production trucks and studios. A disconnected loop is isolated automatically and instantly from the rest of the network. This condition is signalled by the indicators on the front panel, external signalling lamps and alarms can be connected. In practise this means that when several OB vehicles are teamed up for the coverage of a large tournament and some need to leave before the end of the event, then NetGuard permits their safe disconnection whilst the remaining crews stay fully operational. Inversely, can extra devices be added onto a system in operation without causing any interference to the current traffic.

The real world

This type of system has been a feature of most English League football coverage for the recently ended season in the UK. Before that, the concept had already proven its efficiency at the “Tour de France” bicycle race and the “Rolland Garros” tennis tournament. The scale of the coverage has ranged from a game recorded for Highlights where only 2 servers are networked and the focus of the operation has been to produce instant replays as efficiently as possible, to a large event like the FA Cup final and the CBS Super Bowl in the USA: there have been a total of 20 XT-servers of different kinds in use, some operating in Supermotion mode but most in High Definition. All servers were sharing content via 3 SDTI networks that were put in place, each of which was backed by its own XFile archiving unit. Back in Europe, for the English FA Cup Final two distinct areas of production are required Presentation and Match coverage. A total of 10 servers were networked together for this operation, allowing the operators assigned to produce Highlights and Analysis packages (for studio discussions) for the Presentation aspect of the event to access all camera angles recorded on all servers.

Archiving

In the past when using isolated disk recorders on a production, once the live event has ended, the focus of attention turned to the archiving of the footage from the hard disks. This involved transferring lots of content to tape in real time and producing written logs. Now, with a networked server system, metadata is added to material at the time of recording. The XFile automatic archiving unit is detecting clips being created anywhere on the network and places back-up copies onto its removable drives. This process occurs in the background and with low priority as to not disturb any live on-air transfers. The MXF format is employed so that any third party database can interpret the information. At the end of the event the drives can be removed and transported back to the Studio, were the content can be re-instated via an SDTI connexion to an XT-server for further postproduction work. It is also possible to view the sequences directly from the disk within a windows environment. Metadata defined during the live event are associated with the footage and can be used for searching. This includes original timecode, camera number, rating and keywords that may include, for example, the team, score and player. Media can also be exported to a nonlinear editing system or archived to some mass storage device.

NBC covering the 2004 Olympic Games in Athens

NBC and its affiliates have broadcasted a total of 1,200 hours of coverage of the Games. The heart of the NBC broadcast was an EVS network at the International Broadcast Center (IBC) which consisted of edit and broadcast rooms. Each edit room was used to perform advanced editing and quick turnarounds for programs that aired. The remote venues covered the events live and created hundreds of clips of the action as it occurred. The coverage was then sent to the IBC edit rooms for the editing prior to broadcast to air. As a piece was completed on an XT-server, a copy was made via the network to another server for a back-up during broadcast. These finished pieces then resided on the appropriate servers in the broadcast rooms that eventually aired that particular item. The NBC Playback control room was also utilizing the SpotBox-XT, which was integrated with the vision mixer to provide direct control to the graphics and effects. The SpotBox-XT was tied to the SDTI network, which allowed clips to be placed there easily through the network. The XBrowse located at the IBC was linked with Gigabit connectivity to the XFile units at both the Gymnastics and Athletics venues, each a kilometer apart. This connection allowed the operators in the IBC to access any footage that had been archived at these remote venues. This footage could then be pulled to the local storage of the XBrowse and used on any server within the XT network. This remote access allowed footage to be available to the editors without the need to wait for tape dubs to be created and brought back to the IBC, and without any loss of quality. The network of XT servers used the XFile Gigabit Ethernet gateway to interface with Isilon storage clusters that provided 10TB of near-line storage to the venue coverage. Clips from each day’s events were being archived to discreet folders so that material could be easily searched and restored as needed throughout the events. This same large archive of footage was linked to the IBC through the same Gigabit switch, allowing the direct access to the media. The Boxing and Beach Volleyball venues used the SportServer with CleanEdit NLE software allowing fast editing and quick turnarounds of finished pieces. The CleanEdit interface was especially versatile as it allowed editing from both content from XT-servers acquired through the SDTI network as well as MPEG-2 streams ingested locally at the Sport Server.

Material provided by EVS Company