News editors want pictures, regardless of where the reporter is located. And they want live links with the reporter to drop into the newscast. When reporting from war or disaster zones, it is unusual to have a wide bandwidth fibre link from the local telco. Instead, satellite backhaul provides the primary route back to the newsroom.
News can stand a poorer quality picture for breaking news, with higher quality pictures available when facilities can be set up on-site. When satellite newsgathering first started, the only way to operate was with a large dish mounted on a truck. Although an SNG truck will still deliver the best quality for planned events, developments in satellite technology have enabled reporters to transmit live reports with just a laptop and a similar size antenna.
With any satellite newsgathering, the primary trade-off is weight vs. bandwidth. The three choices are an SNG truck, a flyaway and broadband global area network (BGAN). Quite clearly, portable systems exclude the truck, leaving the choice between a collection of flight cases or a single carry-on size case for the BGAN.
The flyaway has long been the option to cover breaking news in remote locations where uplink trucks are not available. As an event breaks, a broadcaster must arrange for the flyaway to be sent to the location and arrange a link budget with the satellite service provider. Depending on the location, there may be C-band or Ku-band availability.
A single thread system for initial coverage could be three flight cases. If an event needs continuing coverage, more equipment could be sent to provide redundancy and higher power uplink for better video quality. This could include trucks. A lightweight terminal with a 1m dish transported as two carry-on bags can stream around 1.5Mb/s, sufficient for a head-up. Heavier 2m or 3m dishes can uplink 8Mb/s, which is fine for an SD application and even better for HD if using MPEG-4 AVC coding.
Even when a truck is available, the situation can be too dangerous for such an obvious vehicle, whereas a flyaway can be more easily concealed. It can be transported in more discrete pickups and vans. And to get to a location quickly, a flyaway can be carried as checked baggage. To qualify, each item must weigh less than 32kg. Air freight can add 12 to 24 hours to the journey. And all air transport becomes more difficult as security increases.
Conventional satellite backhaul systems have become smaller and lighter. The basic components are a video encoder, a modulator, an upconverter, an HPA, plus the antenna and its controller. The crew would also have all the video equipment to carry.
Deskilling the operation
With increasing 24-hour news stations, and the demand for live interviews, it is becoming harder and more expensive to assemble skilled engineering crews to man flyaway systems. There is a general move to deskill the operation so that a reporter can operate much of the equipment. For example, with an antenna controller remote, the QAM, QPSK or DVB-S2, or FEC can be set without requiring the reporter to possess specialized skills.
DVB-S2 modulation is a new coding and modulation scheme that offers real advantages for SNG, especially for HD backhaul. Broadcast Engineering will look at DVB-S2 in more detail in the January 2007 world edition.
The first job is to set up the antenna and aim it at the correct satellite. The antenna controller uses GPS to calculate the azimuth and elevation, and the satellite parameters are stored in the controller's database. Once the satellite has been acquired satisfactorily, the encoder and modulator can be set up and configured remotely. The final task is to hook up the video and audio connections, and the system is good to go.
Store and forward vs. live
The best way to use available bandwidth is to cut a story, store the clip and forward it slower than real time to base. This is fine for the reporter filing stories in the traditional agency sense. More and more, television news wants a live interview with the reporter. This rules out store and forward for the live insert, but it is still valid to backhaul the main story. The latest laptop controllers make it easy to mange the live or store and forward operation without technical knowledge.
Full screen or SIF
News presents conflicting demands. There are many broadcasters looking to move to HD production. On the other hand, they want pictures from anywhere in the world, live, and at an instant. This generally means low bandwidth. To achieve that, pictures are scaled one-quarter-size SD (CIF or SIF) and the video frame rate halved. These soft, blocky and jerky pictures do not sit well in an HD news program.
Two technical developments have eased the problem of meeting the editors' demands. One is improvement in compression; the other is new satellite services for land mobile.
For many years, MPEG-2 has been the mainstay of satellite backhaul. Data rates of 1.5Mb/s to 15Mb/s can be used, depending on the dish diameter and available capacity. The encoding profile can be configured to give low latency encoding — a must for two-way interviews. Recently, more efficient compression algorithms have been developed. For example, MPEG-4 AVC (H.264), while still in its infancy, is becoming popular. There are also proprietary formats that have been designed to maximize efficiency for specific applications. One example is Streambox's ACT-L3 codec. This is optimized for low bit rate video encoding, with up to four times the efficiency of MPEG-2. It is designed for interlaced video and can code SD resolution, 30fps at 500kb/s down to 64kb/s for quarter-size pictures at lower frame rates. AVC provides the efficiency gains that enable either full frame rate over BGAN, or HD over larger flyaway systems.
A new laptop with the latest dual-core processor can easily encode video in real time for live streaming using a software codec like AVC or ACT-L3. The same laptop can carry a nonlinear editor to cut material for filed reports. The camera is simply plugged in using FireWire, and Ethernet connection feeds data to a BGAN terminal.
A simple user interface allows a reporter to link a laptop editor or camera live to the studio via a BGAN terminal.
It is difficult to report from war zones, so news editors are always looking for ways to get reporters in the front line, and to make live reports. Natural disasters also present challenges because it can take a few days to get a flyaway in position.
For these reasons, broadcasters have looked to mobile communications technology. Many of these systems can only carry voice and low bit rate data. Another more recent option is mobile ISDN service. With 64kb/s video, quality is poor, but offers immediacy to a breaking story that voice-only reports cannot. Using two links in parallel, it is possible to stream 128kb/s, at which point the quality starts to become acceptable for news.
Satellite providers offer a number of services for occasional use. (See Table 1.) Many of these can be used for newsgathering. The first service of interest to broadcasters was the global area network, with mobile ISDN at 64kb/s. This has proved popular for videophones in hostile locations, but can only deliver low frame rates at low picture sizes. Some operators connected two channels together to get a more respectable data rate of 128kb/s.
Now, Inmarsat BGAN, operating in L-band (1.5GHz to 1.6GHz), provides a global, high-speed data and voice service through an antenna the size of a laptop computer. BGAN provides an IP connection up to a maximum of 492kb/s, but for newsgathering, a guaranteed bit rate of 256kb/s for streaming is more important.
At the newsroom, a server receives and buffers the incoming video and converts it to a studio friendly format like SDI. The servers are also used to build the video file in store-and-forward applications. BGAN is bidirectional, so the reverse feed can be used for the anchor to talk to the reporter.
New technology is supporting news organizations to get to the story quickly and to file live reports immediately on arrival at the scene. BGAN provides a flexibility that can get pictures within hours of an event. The picture quality will suffice for a head-up, and is a step forward from the voice over a still picture of the reporter. Once a flyaway arrives, and a transponder is available, more detailed coverage can start.
Many news operations are now looking at equipping stringers with BGAN systems. This means that most parts of the world can be reached in a matter of hours. The reporter grabs the case and jumps in a taxi.
Compression codecs have been tweaked to get encoding delays as low as 50ms, an important parameter for two-way links. End-to-end BGAN systems have a latency of just one second. Developments like MPEG-4 deliver more efficient compression for low data rate circuits like BGAN or backhaul HD at SD bandwidths.
Smart control systems have made it possible for field operations to be deskilled. Systems like BGAN can be operated by the reporter and cameraman. Lightweight flyaways need a basic set-up to acquire the satellite, but then an engineer at base can take over.
New technologies through the delivery chain are delivering better quality pictures, with the immediacy demanded by breaking news, and at the quality required as news operations transition to HD.
Table 1. Progression of portable news systems
Satellite ISDN BGAN Lightweight Flyaway Large Flyaway Size Briefcase Carry-on case Checked baggage Freight Live video stream 64kb/s 256kb/s 1.5Mb/s 8Mb/s to 15Mb/s Resolution? SIF/CIF SIF/CIF/SD SD SD/HD Ship and set-up time Hours Hours One day Two days Note: ISDN and BGAN can use tandem systems to double the bit rate.
Get the TV Tech Newsletter
The professional video industry's #1 source for news, trends and product and tech information. Sign up below.