When high-definition TV enters the living room, it's been through the digital wringer.
Getting HD into a house or apartment is the television industry's biggest squeeze play to date. A cable or satellite operator only scores if it convinces all spectators that it has delivered a drop-dead gorgeous, real-as-life image — even if it has wrung out 99% of the data in the original picture.
And that technical illusion is now a high-stakes exercise, as DirecTV moves to beam down 100 or more HD channels from satellites and cable operators, from Comcast to Time Warner Cable, try to respond in kind, making use of switching and other techniques to match not just the quantity but quality.
“HD quality is becoming a battleground,” says Gary Traver, chief operating officer of the Comcast Media Center, which is trying to refine ways to compress high-definition signals in novel ways.
That's because uncompressed HD signals cannot economically be distributed by cable, telephone or satellite providers: They would eat up far too much bandwidth.
For now, the top-of-the-line HDTV signal standard in wide use is 1080i. That means 1,920 lines of 1,080 pixels each are painted on a screen to create a picture. Each frame, in this case, contains 50 million pieces of data. With about 30 frames needed each second to create a movie or show, that means 1.5 billion bits of video data would have to be delivered every second, if no compression took place.
That stream would consume bandwidth occupied by more than 400 digital standard-definition channels on a cable system. The stream also could not fit into typical satellite uplinks, which can beam at most about 80 million bits of data per second per channel (or transponder) into the sky.
So all HDTV channels must be compressed to some degree. It's a necessary evil. The bottom-line metric is the bit rate of compressed video.
The key question is: Which bits of the video signal can be taken out without viewers noticing that anything is terribly wrong? Take an HDTV signal down to too low a bit rate and it starts to show “artifacts,” industry lingo referring to blotches or blurs in a video image.
As such, video distributors make different decisions regarding how much compression to apply to a given HD signal — and that's often an element of carriage agreements, thus confidential.
The HD-quality issue is central in the fight among cable, satellite and telco operators to win new video subscribers. It has even prompted false-advertising lawsuits by DirecTV against Comcast and Cox Communications, as well as one by Time Warner Cable against DirecTV that was settled in August (“Competition in High Definition,” May 28, 2007, page 12).
Verizon Communications, meanwhile, has claimed that unlike many cable or satellite providers, it doesn't further compress the HDTV channels on FiOS TV. “We've definitely shown that there's a big gap between what the consumer expects in this space [on video quality] and what we can deliver,” said Verizon vice president of video solutions Shawn Strickland.
But delivering the “best” high definition is still as much art as science, as there is actually no absolute definition of what constitutes high definition.
“There's disagreement even among so-called industry experts about what exactly the bit rate should be for HD with any given type of content,” said Tandberg Television vice president of technology for compression systems Matt Goldman.
Here's a look behind the battle's front lines — at the squeeze play cable, telco and satellite operators are trying to execute in order to claim the highest quality picture on the market while also delivering the greatest quantity of HD channels.
