A Digital SNG Encoder

Advances in broadcast technology have brought the relative cost of implementing high-quality digital satellite newsgathering (DSNG) solutions within range of mid-sized call-letter station budgets. At the core of such earth-to-satellite transmission systems is the MPEG-2 encoder. Live feeds (baseband video) acquired at the remote site are encoded in a compressed signal that is modulated and converted for transmission via satellite link.

A clear understanding of the design and specifications of encoding systems can help broadcasters choose the right solution for their needs. The purchase or deployment of a DSNG system requires consideration of a variety of factors, including purchase and deployment costs, speed of integration and deployment, encoding quality and format, available bit rate, interactive communications, dish size, deployment location, future broadcast plans and other details specific to each broadcaster.

Because DSNG gear is used in mobile applications, the encoder must be compact, reliable, efficient and capable of providing maximum functionality within a very small package. It must be lightweight and easy to deploy, transport and set up for immediate coverage capability—this is especially true for flyaway units. In more dangerous environments, a less costly system is ideal. However, for everyday operation under more or less normal newsgathering conditions, the system’s flexibility and quality of encoding and transmission will be more important factors.

Video for live remote coverage is typically encoded with analog composite, SDI, AES/EBU and SDI embedded inputs. The SDI option provides the source encoder with a smaller processing load and thereby helps to maximize quality. More demanding live events, such as sports and concerts, require a higher bit rate so that content, once transmitted, processed, manipulated and broadcast, maintains the quality expected by the viewer at home. For these types of broadcast, a bit rate of 6 to 8 Mbps provides the necessary lossless 4:2:2 feed.

With improvements to MPEG-2 video encoding, the cost of acquiring and transmitting high-quality feeds has dropped significantly. The technological enhancements and reduced bandwidth requirements also have contributed to lower operational costs. Going forward, broadcasters have the option of using non-DVB store-and-forward solutions based around H26L, H264 and VC1 encoding techniques.

To move from an MPEG-2-based encoding solution to an MPEG-4 or VC1 solution is not yet feasible because the majority of today’s user base still relies on MPEG-2 systems for reception and processing. Some of today’s MPEG-2 encoding solutions incorporate an upgrade path to the advanced encoding scheme. Broadcasters with this built-in capability will be able to move to new standards quickly and easily as more and more alternative reception systems are deployed.

By using a primary encoder as a multiplexer for a secondary feed, DSNG operators can convert a single channel per carrier (SCPC) system to a multi-channel per carrier (MCPC) system. With encoding systems that can be daisy-chained, operators can save the cost of an external multiplexer while setting the ground for future growth though the addition of new channels. A limitation that is inherent in this type of solution is that a failure in one of the units will break the entire chain connected to it to. Some vendors have introduced a solution to this problem as they enable passive loop-through of ASI so the chain will not be affected by failure of a single unit.

While proprietary scrambling solutions may be appropriate for a large dedicated network, smaller operations will benefit more from implementation of an open standard, such as the basic interoperable scrambling system, or BISS. Because BISS is widely deployed, as opposed to propriety systems, broadcasters have many more choices in selecting the gear for their digital newsgathering systems.

The modulation schemes most commonly available in encoding systems are QPSK, 8PSK and 16QAM based on DVB-S standard. Because QPSK is the most robust, it is the scheme of choice for transmission and reception of compressed video feeds. As a result, equipment required to handle this scheme tends to be less expensive. So, while the less-robust 8PSK offers superior bandwidth usage, the cost of transmission and reception gear outweighs this benefit.

In fact, most systems supporting 8PSK also support a QPSK modulation scheme. The 16QAM scheme, on the other hand, has very little use because it has yet to demonstrate a viable combination of reliability and cost-effective pricing. More flexible encoding and receiver systems do allow for an upgrade path to 8PSK and 16QAM ensuring future compatibility. The cost of this upgrade, however, may not be worth extending the device’s useful life.

The new DVB standard, DVB-S2, is the latest iteration of the DVB modulation standard. The potential bandwidth savings and usefulness of DVB-S2 in feed transmission make it worthwhile to select a system also capable of upgrade to this new and very efficient standard.

Until recently, encoder solutions did not combine encoder, modulator and upconverter technologies in a single box. While separation of key functions can provide some level of protection against failure, the downside in terms of size, weight, power and efficiency is too great not to consider on integrated system.

In terms of frequency selection for this unit, the broadcaster can choose from IF (intermediary frequency), L-, Ku-, or C-band. IF is the most common output choice for internal and external modulators, which interface with the upconverter to enable conversion to the main broadcast frequencies: C-, Ka-, Ku- or DBS-band.

Use of the L-band option in an encoder allows for the conversion to satellite frequency, with the datacoms combined before the signal is converted to Ku- or C-band, and this process eliminates the need to integrate the COM signals later or transmit them via a second transmission chain. The combined method of handling datacom signals is most effective for “always-on” systems such as those supported by large networks with dedicated satellite space. Occasional-use broadcasters, on the other hand, may have access to a free secondary channel just large enough to handle separate datacom transmission.

Scopus Video Networks’ CODICO E-1720 MPEG-2 DVB DSNG encoder is a compact, lightweight and extremely power-efficient system with integrated state-of-the-art telemetry that simplifies operation so that journalists can manage operation without the assistance of an SNG operator on location. Within a 1-RU enclosure, the system features intuitive, menu-driven controls and incorporates both IF- and L-band outputs for upconversion.

With the L-band output and MPEG-2 codec, the Scopus E-1720 provides double duty in enabling transmission of audio and video converted for 4:2:0 or 4:2:2 satellite transmission, thereby maximizing the small amount of available space in flyaway units, mobile vans and trucks. In addition to the satellite output, the Scopus encoder provides output of a full transport stream. IF- and L-band outputs as well as monitoring output enable the operators to integrate the units to their specific needs.

The E-1720 also allows users to make a very cost-effective transition from QPSK to 8PSK/16QAM through a simple software upgrade. In addition to providing broadcasters with advanced encoding capabilities, the E-1720 offers ease of use and simplifies the process of satellite newsgathering. The Scopus unit also supplies 24 volts and a 10 MHz clock that enables DSNG operators to use a small, cost-effective block upconverter that requires such inputs to be modulated on its RF input.

The newly developed UE-9217/8 DSNG encoder from Scopus supports DVB-S2 as well as DVB-S technology in a versatile platform enabling future upgrades toward advanced encoding schemes such as H.264. Because H.264-encoded material matches optimal MPEG-2 video quality at just half the data rate, the UE-9217/8 allows users realize both improved video quality and reduced bandwidth requirements.

Scopus encoding systems can be cascaded to provide broadcasters with a future-proof video compression solution while enabling ASI loop-through to retain the chain integrity. The robust UE-9000 universal encoder series, housed in a 1-RU chassis, can be used in either open- or closed-loop statistical multiplexing system architecture. With up to four MPEG-2 video channels, as well as IP and ASI outputs, the unit offers up to eight stereo audio pairs and power consumption of less than 30 watts per channel.

In addition to energy savings, the system’s dense, modular architecture supports cost-saving cascading of up to 16 channels through ASI input, eliminating the multiplexer cost and utilizing the passive ASI loop-through for cascading redundancy. Hardware-ready for DVB-S2, the UE-9000 features a satellite modulator and L-band upconverter for DSNG or fixed applications. The UE-9000 and Scopus’ other encoding systems can be managed remotely by SNMP or via an intuitive Web-based user interface or locally from the unit’s front panel.

Broadcast technology continues to advance, with better solutions for encoding and transmitting audio and video bringing greater efficiency and flexibility to broadcast operations of all sizes. The Scopus CODICO E-1720, E-9217/8 and UE-9000 systems represent a versatile range of encoding products able to meet the unique needs and high performance standards of virtually any station, network or media group.

Kobi Horin is the encoders product marketing manger for Scopus Video Networks.