HD enthusiasts crying foul over cable TV's crunched signals

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 Corp.'s 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.

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 Inc. and Dish Network Corp. 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.

But 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.