Comcast acknowledges that it recently implemented additional compression of selected HD networks, but contends that its improved compression technology allows it to transmit three channels in the same bandwidth in which two were transmitted previously, without a loss of quality. Comcast's spokesperson adds that many comments about Fowler's AVS Forum post recognize that "our ongoing tweaking, if you will, and adjustments" are improving image quality.
Comcast isn't alone in looking to squeeze more HD into its cables. A Time Warner Cable spokesperson says that company is testing new increased-compression technology as well. On the satellite side, DirecTV and Dish Network are switching to a "more advanced compression algorithm," Putman says. Verizon FiOS, however, applies no additional compression to the network signals that it receives, a spokesperson says.
The HD broadcast format that a network uses can make a difference in the compression's impact. ABC and Fox are among those that use a progressive-scan format (720p), which Putman and other experts say tolerates compression slightly better than the interlaced (1080i) format used by CBS, NBC, PBS, and others.
Blu-ray Is the Benchmark
For consumers, the best HD experience will be with Blu-ray Disc content on a player hooked up to a display with an HDMI connector, which transmits uncompressed digital streams. "That's going to be the benchmark," says Symes.
If you're shopping for an HD service, Symes adds, "it's fairly a no-brainer: If you have FiOS or [AT&T's] U-Verse available, that's probably the way to go." Beyond that, so much local variability exists among competing cable and satellite services, he says, that the best idea is to ask friends in your area about their satisfaction levels.
But if you have an HD picture quality problem that you think is the result of overcompression, the best thing to do is to call your provider. Symes and Putman agree that overcompression and lowered quality will become an industry issue only when buyers who trade up to the biggest, highest-resolution screens notice and complain.
This story, "Is HDTV Compression Damaging Picture Quality?" was originally published by PCWorld.