You Call This HD?

Yet when he tuned in Sci Fi HD for a recent episode filmed in high definition, the image was soft and the darkest parts broke up into large blocks with no definition. Explosions, he said, were just dull.

"It kind of looked like they took the standard definition and just blew it up," said Swanson, a 33-year-old graphic designer and videographer who subscribes to Comcast's (Nasdaq: CMCSK) TV service. "I couldn't really tell if what I was seeing was really better than what I saw on regular television."

As cable TV companies pack ever more HD channels into limited bandwidth, some owners of pricey plasma, projector and LCD TVs are complaining that they're not getting the high-def quality they paid for. They blame the increased signal compression being used to squeeze three digital HD signals into the bandwidth of one analog station.

Pushing the Limits

The problem is viewers want more HD channels at a time when many cable and satellite providers are at the limits of their capacity, said Jim Willcox, a technology editor for Consumer Reports magazine.

"They have to figure out a way to deliver more HD content through their distribution networks," he said.

Compressing the signal is cheaper than costly infrastructure upgrades to increase capacity. Satellite TV providers -- including DirecTV Group (Nasdaq: DTV) and Dish Network -- also have the option of launching satellites to boost the number of HD channels on their systems.

While information is nearly always lost when signals are compressed and then uncompressed, the process can theoretically be made unnoticeable to eyes and ears -- and Comcast says it should be.

However, some viewers say they can see it. Willcox said complaints about compression have been showing up on Web forums, including the AV Science Forum, a site for serious audio visual enthusiasts.

"It's not exclusively Comcast, although Comcast, being the largest cable provider, is probably the largest target," he said.

Bit by Bit

Derek Harrar, a Comcast senior vice president in charge of video, said the company recently began using new technology on some channels to compress three HD channels into the bandwidth of one analog station. Other channels continue to get the previous 2-to-1 compression.

In a posting on the AV Science Forum, Ken Fowler of Arlington, Va., compared Comcast signals with those on Verizon Communications' all-fiber-optic network , which doesn't have the same capacity limitations. Fowler found the higher-compressed HD stations, including Sci Fi, Animal Planet, the Discovery Channel, the Food Network and A&E, fared particularly poorly.

He analyzed the signals by recording them on a digital recorder, then transferring them to a personal computer for analysis. He found there was much less data, measured in bit rates, flowing to some channels than others.

For example, Discovery's bit rate was 14.16 megabits per second (Mbps) on Verizon's FiOS system but only 10.43 Mbps on Comcast; A&E HD was 18.66 Mbps on FiOS compared with 14.48 Mbps on Comcast. The FiOS system didn't offer Sci Fi HD, which Fowler's testing showed at 12.59 Mbps on Comcast.

He found the signals from the major networks and ESPN weren't getting the increased compression.

In an interview, Fowler said he reran his analysis about two weeks ago and found "basically the same thing."

Some Improvement

Philadelphia-based Comcast wouldn't identify specific signals that are 3-to-1 compressed, and a Sci Fi channel spokesperson referred questions back to Comcast.

Harrar said the company works to make sure any new compression technology is invisible to consumers, but Comcast is "constantly monitoring our network and making adjustments" for best picture quality. The company has been rolling out the new compression technology at different times around the country.

In fact, postings on the AV Science Forum from early April suggest the Comcast network has improved in some places.

There are other reasons a high-definition picture can appear subpar: The source image might not have been recorded in HD, or the television's settings, the viewing angle and even the ambient lighting in the room could be the cause.

New York-based Time Warner Cable has avoided many of the criticisms aimed at Comcast, although the companies are technologically similar and face the same capacity limits.

Time Warner spokesperson Alex Dudley attributed it to his company's testing procedures. He said that before Time Warner rolls out new technology that may affect image quality, it sets up two identical televisions in a lab, one with the old signal and one with the new. Technicians make adjustments until the pictures can't be told apart.

"The testers are our engineers who we call 'golden eyes,' who have a proven track record of picking up subtle differences in picture quality," he said.

Verizon's FiOS doesn't compress the signal once it receives it, and Willcox said it's considered the picture quality "benchmark." However, Verizon said the system is growing but is now available only in parts of 17 states and has just over a million subscribers -- compared with more than 24 million for Comcast.

Possible Solutions

He said two possible solutions are on the horizon, an improved version of compression, called "MPEG-4," and something called "switched digital video."

Comcast and Time Warner Cable have introduced switched video on a trial basis across their networks. In concept, it's like on-demand videos. The company sends only the channels the viewer is watching, instead of all the channels at once.

However, switched video has its own issues, including possible slower channel switching times and compatibility problems with digital video recorders.

Willcox said cable providers can't afford to ignore quality complaints. Many customers are already picky about quality after paying US$800 to $3,500 for an average-size, HD-ready LCD television.

Swanson, the "Battlestar Galactica" fan, is sticking with Comcast for now.

"It hasn't gotten bad enough for me to consider changing," he said.