By Philip Bird and Khalid Butt
While digital satellite news gathering (DSNG) has only recentlydeveloped into a true force, it has enjoyed a steady rate of acceptance over the last 20 years. This advancement of technology can be noted through a timeline of major news events that relied on satellite news gathering systems.
SES ASTRA satellite control room in Betzdorf, Luxembourg. ASTRA provides more than 1000 TV and radio channels plus IP-based content to more than 91 million European homes. Photo courtesy of SES-ASTRA.
Its roots can be traced back to 1982, during the Falkland Islands conflict between Great Britain and Argentina. All news gathering from this crisis was sent from the site via UK Ministry of Defense analog links and time-shifted anywhere up to 24 hours. These were the first real images we had from an SNG situation.
By the early ’90s, broadcasters were generally using analog equipment to send reports back to the studio, for example the Gulf War. Over the next decade, digital equipment found its way into the mix: The Balkans conflict in the mid-’90s saw a hybrid of digital and analog SNG equipment in use, while by the end of the decade during the Kosovo crisis, DSNG equipment was the norm.
This history of news gathering at 20 years old has undergone a complete evolution from using links provided by outside organizations through analog and digital units owned by broadcasters. In 2002, it’s a lock that every single piece of satellite-based news gathering equipment is digital.
A 5RU start
DSNG gear really began to come into focus about six to seven years ago, with the introduction of a 5RU satellite encoder from NTL. This unit was comprised of an encoder, monitoring receiver and a modulator. It was intended primarily in flyaway applications, and the European market was the first to embrace the digital realm of SNG technology.
The interior of a DSNG vehicle from Skyways Communications. Skyways uses five TANDBERG Television E5500 DSNG encoders between three of its trucks. Two such encoders are installed in the left equipment rack of this truck.
The U.S. market at this point was more willing to hold onto its analog equipment for a while due to the cost and availability of satellite transponder space. Many large networks at the time had transponder bandwidth booked and paid for with long-term leases, so the drive to go digital came after those payments expired.
With its focus primarily on local coverage, news gathering in the United States did not emphasize international news. Therefore, American broadcasters were satisfied with their microwave ENG gear. With European news carrying a stronger international focus, broadcasters in that region began installing DSNG encoders in mobile vans. The United States followed suit several years later.
Through technological development, satellite encoders have come down in size and have become more effective over the years. Along with these changes came smaller and more effective units. Space is always at a premium in an OBV, so even the modulation scheme to be used can be a consideration if there’s a difference in required space. For instance, while a QPSK modulator may fit in a 1RU space, it may take 2RU to accommodate 8PSK or 16QAM.
This DSNG vehicle from First Call Uplinks also employs two TANDBERG Television E5500 DSNG encoders.
While 16QAM is not as applicable to DSNG because mobile vehicles do not feature large enough dishes to support this modulation scheme, 8PSK has become more important recently — particularly when there are multiple camera angles for uplink to the satellite. In addition, when using a wider bandwidth with a higher data rate, a higher order modulation scheme such as 8PSK is required to fit that data rate within a standard satellite bandwidth.
GlobeCast provides SNG and mobile production for sports, news and special events coverage. It owns and operates a fleet of mobile transmission and production trucks for instant deployment across Europe and to hot spots around the world.
The benefit of adding modulation directly into the DSNG encoder is a space saving strategy, but it also eliminates the need to establish an interface between the encoder and the modulator if they were separate units. In that event, the units would need to be configured so that the bit rates match, or the modulator would have to be put into a bit-rate adaptor mode, causing some of the available bit rate on that link to be useless. Integrating the modulator and encoder into the same unit is a general industry practice, as a much cleaner result is provided.
Enter MPEG encoding
Recent trends in DSNG equipment have continued to evolve. Contribution quality video, at 4:2:2 MPEG, is available in many DSNG units throughout the industry. One trend is creating the ability to multiplex other services into the encoders.
AsiaSat now serves more than 50 television networks and broadcast companies, as well as wholesale news agencies, offering more than 100 news, sports, music, movies, general entertainment and educational programs. Shown here is AsiaSat’s Satellite Control Center in Hong Kong. It is housed in the Causeway Bay headquarters and linked by communications lines to the Tracking, Telemetry and Control station in Stanley.
If broadcasters are using top-level encoding along with multiplexing services via a remux card, then they can fit many more channels in a given bit rate, or at a much higher quality using the same number of channels in that same bit rate.
Another advantage of adding a remux card is the elimination of the entire mobile studio at the site. Typically, these large mobile studios feature a full-size studio-mixing desk, and the producer of the program would be on site to mix numerous video sources and uplink them as one completed program.
With a remux card, all cameras can be uplinked back to the studio, eliminating the need to have the director and artistic crew on site. The reduction in equipment allows the necessary units to be installed into a much smaller vehicle, opening the door for better access to a news site. National news networks in the United States, for example, often use this approach: An event in New York City or Washington often does not leave enough room to park the mobile vehicle and set up next to the event.
Based in London, Europe*Star provides a full range of services throughout Europe, Southern Africa, the Middle East, the Indian Subcontinent and South East Asia. Shown here is Europe*Star’s satellite control center.
Though referred to as news gathering, this term encompasses more than news. Sports programming in particular is an important element in mobile broadcasting, and very demanding when it comes to MPEG encoding. Any program with fast motion, camera panning and multiple zooms can be problematic, so using top-quality encoding technology creates far superior quality images for uplink. Broadcasters using a remux card with relatively narrow transponder bandwidth can quite comfortably send four channels over 20Mb of transponder space.
Voice communications
Mobile broadcasters have become increasingly more interested in establishing stronger communications between the DSNG vehicle and the home studio. The issues here revolved around simple barriers, such as not being able to communicate to the studio once the vehicle has reached its destination. Often these sites are outside of cell phone coverage areas, adding an extra layer of difficulty to the vehicle’s situation.
This is one of the problem areas in DSNG addressed in recently introduced solutions. IP information can be embedded in an MPEG transport stream to allow data to be uplinked from the vehicle back to corporate headquarters. In response, corporate headquarters can access a back channel to broadcast information over the same satellite and back to the van. With a 2-way IP link between the central studio and the DSNG truck, equipment within the truck can be connected to the corporate network. This includes Voice Over IP to allow a telephone to be plugged into an IP return.
The SNG truck for the 21st Century will be a complete program generation center and not just a news contribution truck. Two-way IP connectivity, coupled with high-quality DSNG encoding units, are the key ingredient. Extending the range of the corporate network over a 2-way satellite link into the DSNG vehicle is a completely new concept that is just beginning to be fully realized, and will open up new possibilities as to how news reports are put together in the future. Once a corporate LAN is established inside the vehicle, journalists are able to begin accessing video material from the studio library. This extends the journalist artistically to build a complete news report using live clips from the site of the event, library clips, and contributions from journalists in other trucks throughout the world.
Motion estimation
In regards to encoding, full motion estimation is important. MPEG is made up of three different frames: I, B and P. The B frames, which are bi-directional predicted, are the frames that provide maximum compression. Unfortunately, they also are the frames that most commonly introduce errors into the picture if proper motion estimation is lacking. Therefore, the greatest benefits from B frames are most noticeable when the motion estimation is pixel perfect. During motion estimation, each frame of a picture is broken up into macro-blocks, which are 16x16 pixels. Instead of rebroadcasting all information within those 16 pixels, motion estimation allows you to broadcast just two numbers representing a magnitude and direction. These numbers communicate to the receiver where to place the macroblock to achieve maximum compression.
It’s widely known that noise is the biggest killer of high-quality encoding. A clean feed sent into the compression engine is an absolute necessity. MPEG finds random motion and high-frequency content — which is how noise appears — difficult to encode, so anything that can be done to remove that noise significantly increases the end quality.
Wherever the DSNG industry heads from here will be vitally important to the length of its successes. Looking at a multi-channel environment these days, news and live events are becoming an increasingly large proportion of the total output, and images are what drive news programming. And as 2-way IP connectivity becomes fully realized, the possibilities are endless: From remote control of vehicle equipment from the studio to complete automation of the truck, the future of the DSNG industry is going to be incredibly interesting.
Philip Bird is encoder product manager and Khalid Butt is product manager for TANDBERG Television.
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