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06.01.2004
Originally featured on BroadcastEngineering.com
Satellite broadcast technology

Satellite-based technology has become incredibly important to the broadcast industry, where the primary techniques of direct-to-home (DTH) and contribution/distribution (C&D) are employed throughout the world. In recent years, advances made in these methods have improved efficiency, and broadcasters are keen to move forward to use these technologies. However, there are issues, both financial and technical, that govern deployment.

The use of satellite bandwidth is expensive, so the requirement to get more bits/Hz transmitted and received at a lower cost is paramount. By using video compression techniques such as MPEG-2, broadcasters have been able to reduce bandwidth requirements and make multichannel DTH transmissions more efficient. However, technological and regulatory changes have made it possible for satellite, cable and telco operators to compete in providing a wide range of services, such as video-on-demand, interactive TV and, the most recent catch phrase, triple-play (voice, video and data). All are requiring new compression techniques, but a move to MPEG-4 or Windows Media 9 will introduce significant costs in terms of moving away from systems already in place.

Price, more than ever, remains a key element in decision making. More for less is the ideal, and the use of compression techniques that allow more content to be pushed down a channel is a priority. It will not be long before the pressure is on broadcasters to supply interactive TV and video-on-demand. So where is the technology progress?

MPEG-2 technology

MPEG-2 technology has, over the last few years, been steadily improving to produce today’s broadcast-oriented high-quality video compression products, but it suffers a price performance tradeoff. This balances image quality and end-to-end delay (latency) with bit-rate optimization to make the most of expensive bandwidth. This is particularly true of 4:2:2 encoding compared to 4:2:0. The relatively expensive but high-quality 4:2:2 has traditionally been used for contribution to maintain the highest signal quality and allow for degradations that occur in post-production processes prior to broadcast, whereas 4:2:0 is mainly used in distribution systems, due to the low cost of receivers.

Recent developments in statistical multiplexing have allowed further bit-rate reductions. Dual- and triple-pass systems combine seamless interoperation between established preprocessing, complexity estimation and statistical multiplexing techniques, providing a flexible method for managing compressed digital streams while optimizing bandwidth — up to 18 channels per transponder. These systems also offer the flexibility and control to manage the bit rates and priorities of individual programs in order to improve the quality of the output streams. MPEG-2 as a compression standard has been the enabling driver of the success of digital television broadcasting, but as it is beginning to reach the theoretical limits of its capabilities, other technologies will succeed it. The two main candidates are MPEG-4 and Windows Media 9.

MPEG-4 and Windows Media 9

MPEG-4 has been promoted extensively over the past 24 months, but while it has interested the technical community, there has not been much evidence of commercial success in its use within the broadcast sector, at least up to now.

Prior to standardization (Part 10, AVC, JVT, H.264), MPEG-4 was best suited primarily to webcast applications. But with the release of the new profile, MPEG-4-10 will become a viable future alternative for the broadcast industry, thanks to features that have led to a dramatic reduction in bitrate. MPEG-4-10, however, requires significantly more processing power than MPEG-2. It will, therefore, come with a steep price tag compared with today’s MPEG-2 systems, and this will affect both the head-end and receiver unit cost. Because MPEG-4-10 will use expensive media processing chips to handle immense computational loads, consumer-based MPEG-4 decoders will also initially be priced significantly higher than today’s MPEG-2 set-top boxes (STBs).

Nonetheless, we are now seeing application success for MPEG-4, where the promise of cost-saving through bandwidth reduction is being experienced in satellite news gathering, program contribution feeds and content backhaul projects.

The huge number of deployed MPEG-2 STBs is the barrier that may hold back the move to the next-generation video compression standard, since today’s DTH receivers will not support any of the new advanced standards. Moreover, moving to a new standard may require change throughout the network. Changes in a wide range of hardware may be required, including encoders, multiplexers, modulators and other equipment associated with the broadcast chain. As for the Windows Media 9 platform, it improves on earlier versions of Microsoft’s digital player and server technology on a number of fronts. It features better audio and video quality at any bit rate, as well as the first 5.1-channel surround sound codec for IP streaming. It can be used to create live and on-demand audio and video content and comes with an updated streaming server in Windows. For businesses, the technology includes improved media management features. For consumer media, the system is updated for speed and seamless playback to create a more TV-like experience on the PC.

In C&D, the move to new standards could be simple, as it is based on professional equipment with limited deployment. In contrast, DTH is based on the consumer STB in the subscriber’s home. Here the expenses are enormous, the variety of units is great, and universal replacement would be almost impossible due to the cost. MPEG-2 will inevitably be replaced by new standards in the coming years; this transition will be gradual, and systems will probably support several standards at once. There is some confusion in the market as to which standard to adopt.

Many are waiting to see which technology picks up the greatest momentum. It is widely recognized that both MPEG-4 and Windows Media 9 offer superior performance over older standards in areas most important to broadcasters, in both DTH and C&D environments. Only time will tell how painful the transition to the new technologies will be.

Nick Cahill is product manager - broadcast for Sematron UK.



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