Bitstream Basics: More Services Or Higher Quality?
There is an ongoing effort in the terrestrial broadcast, Direct-to-Home/Direct Broadcast Satellite (DTH/DBS) and cable industries to establish a set of operating guidelines that deals with what HDTV should look like, and what is really acceptable to the consumer. Is everybody reading off the same page? Not quite.
"As HDTV is starting to establish itself as a compelling value proposition rather than as a luxury item, there is a growing realization that a certain line can be crossed wherever compression occurs, and the service provider risks underwhelming consumers," says Bryan Willson, senior engineer of video products at Radyne Comstream. "In order to succeed, broadcasters need enough bits to make it all work."
Cable often starves its SD services at under 2 Mbs, and "they are getting away with it," he says. "At the end of the day, they have to make a decision about what is more important, more services or higher quality."
While encoding is going to experience big changes in the future, the question is when this migration to Advanced Video Coding or Windows Media 9 will actually take place. In the meantime, the focus is on satellite performance given fixed power configurations, new modulation schemes with new forward error correction techniques, and the pending launch of several Ka-band satellites, which will result in a lot more available capacity.
"The quantum leap that we will see with the adoption of DVB-S2, for example, is going to happen faster than most people realize especially when it comes to contribution links including DSNG in HDTV where we can provide both ends of the pipe," says Willson. "However, the DVB-S2 contribution model is still limited by what is happening downstream. This makes high-quality picture generation from the start so important given the likelihood that the images will go through a succession of compression."
HDTV content distribution for live events to theaters or digital cinemas is seen as a high growth opportunity in many regions. The 2003 Super Bowl and The 2002 World Cup were two recent special events where Tiernan encoders were used. And last summer, JVC and Radyne Comstream formed a partnership to address this live event market using the JVC DM- D4600U decoder and the Tiernan THE15A HD MPEG-2 encoder. Beaming high-quality HD imagery at rates of 70 Mbs is well within the range of the THE15A, which can operate at rates over 100 Mbs.
For customers with mobile HD/SD requirements, Radyne Comstream offers a flyaway earth station known as the Modular Integrated Broadcast Systems (MIBS), which is designed for HDTV services where rapid deployment is a vital concern.
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