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HD quality, cable vs. D* TV?

1096 Views 13 Replies 10 Participants Last post by speters, Oct 22, 2004

speters

Discussion Starter · Oct 21, 2004

I recorded the Matrix Reloaded the other day from Comcast cable on my 30k. I noticed that there was alot of macro blocking ( I think this is the correct term) during the opening scene. I have had my 30k updated, so I know that this was not caused by the 30k. I was told that this was do to the low bitrate of cable. I was wondering if D* TV is any better? I want to start creating a catalog of HD movies. So I was wondering if D*TV is any better than Comcast?

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Chuck Mullen

· #2 · Oct 21, 2004

Just the opposite.

D* uses compression on some of their HD channels. Comcast has said they pass all HD feeds exactly as they are delivered to them.

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PRMan

· #3 · Oct 21, 2004

So, you won't get the macro-blocks, because D* already knows ahead of time that they are going to bit-starve it. Instead, you will get a resolution-reduced, color-reduced blurry picture that looks like a really good DVD instead.

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djdrock

· #4 · Oct 21, 2004

Quote:

Comcast has said they pass all HD feeds exactly as they are delivered to them.

I don't buy that a bit. Although I think that the PQ of cable is better that satellite for HD, I have seen HBO-HD on Comcast, and it is lacks to that of Insight Cable. Macro-blocking galore!

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RelDudeGOP

· #5 · Oct 21, 2004

okay at home i have comcast hdtv and at work (compusa) we have directv hdtv and comcast wins hands down in terms of pic quality....it's especially noticable during football games and other fast motion picture

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Ken H

· #6 · Oct 21, 2004

Quote:

Originally posted by djdrock
I don't buy that a bit.

Buy, not buy. It's the truth.

There are always exceptions when a cableco has over 22 million customers, but Comcast corporate policy is to pass HD image and sound quality intact.

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RelDudeGOP

· #7 · Oct 21, 2004

yup and that my friends, is why i love comcast....in a world where cable companies are the "bad guys" comcast is pretty freaking good

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djdrock

· #8 · Oct 21, 2004

Quote:

There are always exceptions when a cableco has over 22 million customers, but Comcast corporate policy is to pass HD image and sound quality intact.

That is interesting. Again, I am not a Comcast customer, but there is no way that all Comcast hubs are adhering to this policy. Recently, someone told me they recorded Full Metal Jacket off of HBO, and the total file size was around 6gb. He said it was basically unwatchable, although he could tell it was the HD xfer. Talk about downconversion...

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Barry928

· #9 · Oct 22, 2004

Quote:

Originally posted by RelDudeGOP
yup and that my friends, is why i love comcast....in a world where cable companies are the "bad guys" comcast is pretty freaking good

I left D* after 10 years for Bright House Networks cable because they do not re-compress the HD. Our local HD group even toured their headend and they showed us that they do not own any compression equipment. They explained during the tour that the payload is stripped out of the MPEG stream and re-wrapped in a QAM 256 jacket for delivery to our stb's.

This forced me to realize how much compression is done by the national networks to their own video upstream of cable or sat. Does anyone know what data rate arrives at the headend?

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mike greer

· #10 · Oct 22, 2004

I have both DirecTV and Comcast and there is no question that HD on Comcast is better than DirecTV. Comparing them side by side it's amazing how bad DirecTV can make HD look.

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John Mason

· #11 · Oct 22, 2004

Quote:

Originally posted by Barry928
I left D* after 10 years for Bright House Networks cable because they do not re-compress the HD. Our local HD group even toured their headend and they showed us that they do not own any compression equipment. They explained during the tour that the payload is stripped out of the MPEG stream and re-wrapped in a QAM 256 jacket for delivery to our stb's.

This forced me to realize how much compression is done by the national networks to their own video upstream of cable or sat. Does anyone know what data rate arrives at the headend?

Caught a short item in today's NY Times about my local Verizon phone company extending fiber-optic service into homes within parts of 6 Eastern states. Also prompted me to wonder, given fiber's practically unlimited bandwidth, what both SD and HD would look like if such bandwidth was used fully, compared to current video from my dual Time Warner and RCN cable systems. Assuming all-fiber systems took advantage of expanded bandwidth, all-fiber subscribers, or cable companies using other extended-bandwidth technologies , ought to deliver the same bit rates originating directly from programmers. Quality should match that available to those using big-dish (BUD) systems.

Some SD programming via my cable systems, such as weekday golf shows via USA, ESPN, or The Golf Channel, is way too fuzzy--drained of color and lacking resolution. Then, upconverted to 720p or 1080i on weekends by CBS/NBC/ABC, and with the expanded bit rates of H/DTV channels, the same golf matches appear with strong color and passable (not true HD) resolution on my 64" screen. The shift from quality to quantity and restricted bit rates (8-10 channels per 6-MHz-wide cable slot) appears to be the culprit. Time Warner Cable locally has indicated it uses rate shaping and statistical multiplexing with HD channels (presumably SD, too). But the inability to A-B compare pre/post signal manipulations prevents learning how image quality is influenced.

Also, while cable companies may not deliberately use special gear to further compress the already compressed video they receive, since MPEG-2 automatically minimizes higher frequencies (details) according to image variations, plus its allotted bit rate, perhaps a comparison of piping ~4 SD channels down each 6-MHz slot (~39 Mbps capacity at 256 QAM) instead of 8--10 or more would be interesting. (Note: MPEG-2 expert dr1394 here recently posted that standard video, presumably 720X480, is being deliberately filtered down to ~530X480. Can't find the post, but believe he said it was by the networks in order to approximate the image fidelity of their OTA SD. That, if true, is really remarkable! Also remarkable, as another current thead indicates, is the extent to which D* is limiting standard 1920X1080i HDTV to non-standard 1280X1080i video.) -- John

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Karyk

· #12 · Oct 22, 2004

I cannot tell a difference in PQ between Comcast HD and OTA HD, although it is somewhat hard for me to compare because of the DVI-HDCP implementation currently on the Comcast box (if I switch to another input I have to change channels on the Comcast box after returning to Comcast). If there is a difference, it's very slight.

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Ken H

· #13 · Oct 22, 2004

Quote:

Originally posted by John Mason
Caught a short item in today's NY Times about my local Verizon phone company extending into homes within parts of 6 Eastern states....

Also in progress by SBC in their service areas, and by someone else in another part of the country, who I can't remember right now.

Looks like the future is bandwidth unlimited. I like it.

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speters

Discussion Starter · #14 · Oct 22, 2004

Do others see the macro blocking I am talking about on Comcast? This was on HD HBO.

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