Comcast Compresses HD - No One Shocked
This is Battlestar Galactica on Comcast
In a news item that should have all of the Audioholic audience thinking, "and?" - The Associated Press is reporting that Comcast and other cable companies are compressing their HD signals in order to deliver more content. We've been discussing this over at AV Rant for some time now and even have a listener who is contacting Time Warner's CEO directly to see what he has to say about it.
The "pass the buck" mentality was in full effect as Sci-fi, under fire in the article because of its soft HD picture, referred all questions to Comcast. Comcast admits that they are shoving 3 HD channels into the space of one analogue channel in some cases!
3 to 1!
Other channels are getting 2 to 1 compression though Comcast spokespeople wouldn't admit which channels are getting the increased compression. Don't worry Comcast - we can tell. The interesting part of this story is that some of the data being used to show how bad Comcast is compressing their channels was gathered from AVS. The post, which compared Comcast to Verizon FIOS shows clearly the picture differences between the two services. Verizon, with their fiber optic FIOS network, doesn't compress their channels at all but only serve about one million people in 17 states. Comcast serves over 24 million.
The problem, claim the cable companies, is infrastructure. There is only so much cable out there and people are demanding more and more HD content (I know I am). Compression is going to be a fact of life for those outside of Verizon's FIOS system though it doesn't have to be as visibly apparent as it is with some of the channels. While the AP suggests that poor HD picture can come from miscalibrated displays (true) or ambient lighting conditions (huh?), Comcast and Time Warner are working on solutions.
One of the solutions, switched video, only sends the channels that you are watching and not all of them at once. This could slow down channel switching times (meaning you can make a sandwich instead of just getting a beer while waiting for the channel to change), but it would increase available bandwidth. We wonder if it would be possible to effectively "delete" unwatched channels at the user's discretion so that favorite channels would have as much bandwidth available to them as possible. Other alternatives include instituting alternative compressions schemes such as MPEG4.
After paying $5000 for a TV and $500 for surround speakers, Joe Consumer expects to see a difference. If Comcast and others can't figure out how to get HD to their consumer's homes, we're going to see a greater and greater outcry. Bring it on, we say. Until the general public gets up and arms, all the complaining on the net will be for naught.
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First, understand that we're not talking about "3 to 1" compression. An uncompressed HD signal is 1.5 Gb/s, so any consumer HD MPEG-2 source, typically 10-20 Mb/s (and this includes digital cable, broadcast, satellite, Blu-Ray) will be more like 100:1 compression.
Your local TV station can fit 19.2 Mb/s in their 6 MHz channel. Most carry sub channels with weather, news, local programming, etc., and what's left for the HD signal is usually closer to 12-15 Mb/s.
Assuming your cable company is using 256-QAM modulation, they can fit 40 Mb/s in that same 6 MHz channel. So, even with 3 HD services in one RF channel, it's around 13.3 Mb/s, so it's about the same bit rate as the HD channel from your local OTA station.
stratman;404096
My friend swore up and down there was no PQ difference between Comcast HD and Direct TV HD, he goes and buys a 58" Panny, orders Comcast HD, compares my PQ (Direct TV HD) to his.......................he's getting rid of Comcast. He's not a techie or an A/V'er, just an attorney.........yet he could see the difference.
One possible reason for poor HD reception in some homes is that HD is sent over cable at a really high frequency. If your getting audio drop outs and pixelation then it can be result of weak signal on the high end. Low signal hitting your house from the plant, too many splits, old splitters that dont pass up to 1 gig, long lengths of cables and such will greatly effect your HD pics.
I dont want to start any arguments on here but that is what is going on in the system I work in. Other Comcast systems may not be so Comcastic.
And only if the broadcasters could figure out their end so I dont get cutouts in American Idol........
when the guy came to hook up I was watching ABC/HD ota and he asks so you already have cable? I ask him since when does time warner have any channel close to this quality. he started telling me about the hd package. i had him go get an hd box from the truck and hooked it up we toggled between my free hd and the pay hd. i think that even he was surprised at how much better the free hd was. he put the hd box back in the truck. i would like to have Discovery hd but i'm not paying 20 extra bucks for one semi hd channel.
