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A comparison of bitrates between FiOS and Comcast reveals signals compressed up to 38%.  (Source: AV Science Forum)

Red Hot Chili Peppers live: crisp and clean on one side, a blocky mess on the other.  (Source: DViCE/AV Science Forum)
Comcast tries to fit three HDTV channels in the space of two

HDTV aficionados with Comcast service might be in for a rude awakening: the nation’s largest cable provider seems to have ratcheted up the compression on its cable HDTV signals.

A thread at AV Science Forum updated last Monday details what appears to be compression of up to 38%, allowing Comcast to deliver more HDTV channels per line while using the same amount of bandwidth. A side effect of this, however, means that HDTV’s pristine video is now jagged and muddy for Comcast customers, full of MPEG-style compression artifacts and stuttered movement:

For the most part, fine detail remains very good on static (non-moving) images with Comcast's added compression, but you do see reduced contrast, with more dithering artifacts (banding) between colors and objects. With some channels, it looks a bit like Comcast is taking a 24-bit image and reducing it to 18-20 bit. This tends to reduce the 'pop' effect in some images. The difference in 'pop' was quite noticeable on Food HD, despite the relatively small bitrate reduction.

The greatest differences are seen with movement. With slow movement on Comcast, the first thing you notice is added noise and a softer image, as fine detail is filtered from the picture signal. The greater the rate of movement, the more detail you lose and the more noise you see. With intense movement, you see more blocking and skipped frames. In VideoRedo, I noticed that a number of frames in the FiOS signal simply did not exist in the Comcast signal during motion intensive scenes. This may be responsible for the stutter and excessive motion blur seen with some video sequences on Comcast.

Still images comparing Verizon’s FiOS HDTV service with Comcast’s HDTV service, taken at the exact same time in the exact same broadcast, show Comcast’s images losing much of the legendary detail that HDTV is so well known for – in a screenshot  of the Red Hot Chili Peppers playing live in Milan, the Comcast image was almost completely stripped of all fine-grained detail; lead singer Anthony Kiedis’ textured wristband becomes flat and blocky, and the tattoo on his left arm made pixellated and blurry.

A request for comment was received by Comcast, but not replied to.

The purpose of Comcast’s increase in compression is unclear; however it would appear that the company is attempting to fit three HDTV video streams inside of one QAM (Quadrature Amplitude Modulation, Comcast’s DTV broadcast format) signal, as opposed to the previous two. In a bitrate comparison between each provider’s broadcast of the same show, the Verizon signal was recorded at 17.73 Mbps, while the Comcast signal recorded at 13.21 Mbps, a 34% reduction in size.

According to Ken Fowler, the A/V buff known as “bfdtv” at AV Science Forum, Comcast’s compression increase currently affects most customers that were not originally in Adelphia’s cable system, which Comcast purchased in 2005. Further, the increased compression only affects national networks like A&E or HBO; local TV signals are rebroadcast at whatever bitrate they were originally sent in.



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RE: Another sad move....
By NaughtyGeek on 4/1/2008 3:44:13 PM , Rating: 2
Well, I've been toying with switching to FIOS for quite some time and this will likely be the final straw. I actually was ready to move once but they upped my package for the same price but if they're going to give me DirecTVs HDLite BS, I'm done with them.


RE: Another sad move....
By FITCamaro on 4/1/2008 4:09:28 PM , Rating: 5
I think you're nuts if you've got the option to use FiOS and you're not. They couldn't sign me up quick enough if I had the option.


RE: Another sad move....
By theapparition on 4/2/2008 9:24:18 AM , Rating: 3
As a FIOS customer myself, and former Comcast subscriber, I can clearly say that they are Superior to Comcast. So much so, that when switching services, usually they give the "AOL" hard pressed sell to keep you as a customer, but when I told them I was going to FIOS, she just said "I understand".

Now, while I'm totally enamored with the FIOS service, here's the downside. Verizon is in it's infancy as far as TV is concerned, specifically service. They don't have their act together. I've had some issues.
When initially installed, they didn't turn on HBO and some of the cable boxes were the wrong type (more on this below). I wanted to swap boxes and get HBO turned on. After being on the phone for hours with multiple disconnects (wait, isn't Verizon a phone company?) they finally told me (compressing very long story) that they'd have to turn on HBO (take a few days??? WTF, comcast does it in a few minutes), and when that was complete, I could then open up another service record for my address to swap the box.

As for swapping the hardware, they do have local stores which I opted to do rather than pay for someone to come out and inconvenience my wife. I thought the exchange would be as easy as walking into the Comcast store. Far from it. I walk in, told them I wanted to swap hardware. He asked for a service number (mind you the phone rep told me to go to the store, without mention of a service number). I had to pick up a verizon phone in the lobby, call verizon, wait an hour, then get a service number so the guy can swap my box. Just not organized at all.

A huge plus with FIOS is that it offers a multi-room DVR, something that Comcast severely lacks. Here's the problem with the multi-room DVR functionality....it won't work with HD satellite boxes. I have 6 HDTV's in the house, with a 60" TV in the bedroom. Obviously, I wanted HD on that TV. But the HD box won't talk to the HD DVR. You have to have a standard box to get that functionality. So I had to swap a few HD boxes for standard ones to get that to work (wife's insistence since she likes to watch a lot of DVR TV in bed). This is supposed to be upgraded at some time in the future, but for now it really sucks that I can't have the best of both worlds.
FIOS uses Motorola hardware, which plain sucks. I came from Comcast's Scientific Atlanta boxes which were much better (Comcast uses Motorola in other areas).
I also had an issue recently where the multi-room DVR got "out-of-sync". The shows stored on the main DVR did not match up to the available stored shows on the satellite boxes. I had to reboot the network (Verizon's tech support) and everything got back into sync, but I also lost several shows on the main DVR. Pift, gone. I was not happy.

Still, they are getting better, but do have some growing pains.

Internet and phone service has been exceptional. It still blows me away when i start a download and it comes in at 2.5MB/s sustained. Vista SP1 took just a few minutes for the entire distribution! Gotta love that.


RE: Another sad move....
By winterspan on 4/1/2008 9:08:34 PM , Rating: 2
For once, I actually agree 100% with FITCamaro. You'd be bat-shit crazy to keep service with ANY cable or satellite provider if you have access to FIOS. Because of the fiber to your door, FIOS will always have a much better capacity for high bit-rate, minimal compression HDTV, more channels, more VOD options, etc. And the best part of all is the availability of ultra highspeed net access.

Don't listen to the misinformation from 'Cable' about DOCSIS 3.0. Bottom line is that the coaxial cable network is a shared medium, so if you live in a dense area with many subscribers, your average throughput will be nowhere near the stated "maximum" speed. This will be more prevalent now that average users are starting to use a lot more bandwidth than in the past. Joe sixpack is now streaming high-bitrate and even HD video from websites like NBC.com, BBC, Hulu, Netflix, iTunes, etc. Others are downloading large video podcasts or DVD rips and lossless music files from Bittorrent and P2P software at all hours of the day. Beyond just the home computer, you are also seeing video game consoles and standalone STBs offering movie rental downloads and online gaming.
With all of this traffic, it will be hard for cable to compete with Fiber-to-the-home FIOS service, even with DOCSIS 3.0 and other network enhancements.


RE: Another sad move....
By Cullinaire on 4/2/2008 1:46:09 AM , Rating: 4
"For once, I agree with FITCamaro" -multiple authors

should be one of the rotating quotes on the bottom of the page.


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