Why is any other cable than coax needed for HDTV?

2377 Views 22 Replies 18 Participants Last post by Rick_R, Nov 16, 2010

JasonR

Discussion Starter · Nov 9, 2010

Ok, this may sound like a stupid question, but I was thinking about this today. If your cable box is connected to your cable company by a cheap coax cable, then why all of a sudden do you need an expensive component or HDMI cable to go the extra couple of feet from your box to the TV? Even if HDMI or component is capable of higher bandwidths, wouldn't it still be limited by the coax that it traveled over to get to your house? Also, same thing with OTA broadcasts. The signal travels from your antenna to your TV over coax, and OTA HDTV is generally considered to be higher quality then compressed cable signals anyway. Now I can understand video coming from an HD source like a Blu-Ray player needing HDMI, because it's displaying 3D in full 1080p and it's not limited anywhere in the transmission by coax, but for cable TV and other providers, I can't understand why anything more than coax is needed. Can anybody enlighten me?

1 - 20 of 23 Posts

Kal Rubinson

· #2 · Nov 9, 2010

All the signals on the incoming coax are combined into a single data stream. HDMI has multiple lines to convey the various video/audio/handshaking/clock lines needed.

Also, who says it is expensive? Use these: http://www.monoprice.com/products/pr...seq=1&format=2

joed32

· #3 · Nov 9, 2010

I think it was to make copy protection possible if they decided to implement it. You are correct about OTA going straight to your TV and carrying an HD signal and it could be used if they had chosen to make it that way.

John Mason

· #4 · Nov 9, 2010

It's also the difference between digitally compressed material (MPEG2/4), which greatly limits the bandwidth requirements, versus uncompressed video needing more bandwidth. And video is delivered into homes on RF carrier signals that need shielding from electrical interference more than analog or digital signals piped between components in homes. -- John

gbynum

· #5 · Nov 9, 2010

Quote:
Originally Posted by joed32 /forum/post/19458613

You are correct about OTA going straight to your TV and carrying an HD signal and it could be used if they had chosen to make it that way.

Indeed, with many (most/all?) cable systems, clear QAM is available with HD programming. The problem with using RF, either 8VSB or QAM, is that a "receiver" in the cable box must (re)modulate the signal. Of course, they *could* offer all programming in clear QAM.

And if we get to DVD players, BluRay or not, this modulation would have to take place. I am unaware of any modulator that will do 1080p in any form for under $500.

These features will likely occur given time.

a_day_without_me

· #6 · Nov 9, 2010

1. You don't need an expensive HDMI cable

2. They wanted to add in copyright protection

3. New cable requirement = more profit

walford

· #7 · Nov 9, 2010

The digtial RF signal coming into your cable box is compressed by a factor of about 50:1 The cable box has to decode and completly decompress the signal so it can be sent as a video signal to your TV over HDMI/DVI or Component. High quality 6-10 foot HDMI high speed cables are available from the spoers of this forum such as MonoPrice Cables for less then $15.

mtallent

· #8 · Nov 9, 2010

Compression is really not the issue, if the QAM signal was not encrypted, then the HDTV with a QAM tuner would have no problem with only a coax cable connecting it to the cable signal. The cable box is needed to insure that you pay for the programming you watch, that is its main function.

Mike T

RosevilleHT

· #9 · Nov 10, 2010

gbynum, I wish this was the truth for all cable providers. Check out Comcast's project Calgery to find out how we got screwed out of clear QAM HD channels.

Tschmidt

· #10 · Nov 10, 2010

Communication protocols need to balance cost of media vs cost of modulation/demodulation. RF modulation is relatively expensive in order to make optimum use of RF and cable bandwidth. HDMI on the other hand is low cost point to point connection using low cost drivers and receivers.

Ken H

· #11 · Nov 10, 2010

Quote:

Originally Posted by RosevilleHT

gbynum, I wish this was the truth for all cable providers. Check out Comcast's project Calgery to find out how we got screwed out of clear QAM HD channels.

I don't think you understand what he was saying. All (most all) cable providers have local channels in clear QAM.

You didn't get screwed out of anything you were paying for. You did perhaps lose channels you weren't paying for.

Needing a box to get the channels you pay for is no different than what DirecTV, Dish Network, or AT&T U-verse require. At least Comcast still provides local channels without a box, which is more than what most other providers give you. And, the cableco's that still pass channels in the clear will soon be changing that, too.

Times change as technology changes.

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billybobg

· #12 · Nov 10, 2010

Quote:
Originally Posted by Ken H /forum/post/19463350

Needing a box to get the channels you pay for is no different than what DirecTV, Dish Network, or AT&T U-verse require.

I've no problem paying for what I view. It would be nice not to have that extra piece of equipment at every tv. We have rooms where we watch on a limited basis. Being charged for a box in the guest room or the home gym where they are used an hour a day carries a high cost/benefit ratio. I know its my choice to have this "luxury", but there was a time when extra sets were not an excuse to charge more. You just split the signal and used the tuner on the tv.

Ken H

· #13 · Nov 11, 2010

Quote:

Originally Posted by billybobg

I've no problem paying for what I view. It would be nice not to have that extra piece of equipment at every tv.

Those concerns should be directed at the content providers, not at the carriers; they are the ones concerned with security, and they are the ones who made the cableco's encrypt content.

Quote:

Being charged for a box in the guest room or the home gym where they are used an hour a day carries a high cost/benefit ratio. I know its my choice to have this "luxury", but there was a time when extra sets were not an excuse to charge more. You just split the signal and used the tuner on the tv.

Like I said, this is no different than if you had a DBS or fiber provider, and times change, even for cable subscribers. Comcast provides a standard box and two DTA boxes for free after the digital migration, for all expanded basic subs. Additional boxes are 1.99 a month in most areas.

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Sheer Lunacy

· #14 · Nov 11, 2010

Short answer is, it isn't. Using the industry-standard Serial Digital Interface for professional applications, that coaxial cable can easily carry 1080i/30fps 4:2:2 component video, with 8 channels of embedded audio.

The thing is, SDI is completely in the clear. It can be amplified, redistributed, recorded, whatever. The businessmen who keep ramming copyright extensions through Congress don't like that idea, so they combine to constrain the general public to use something they can control.

coyoteaz

· #15 · Nov 11, 2010

SDI could have been extended to include support for encryption. HDCP is not tied to any particular interface.

Making a fancy new standard (or more accurately, tacking a new connector on DVI and adding support for audio) resulted in $10000 per manufacturer per year fees, plus 4 cents per device in royalties for the HDMI Licensing cartel.

Glimmie

· #16 · Nov 11, 2010

Quote:
Originally Posted by coyoteaz /forum/post/19470085

SDI could have been extended to include support for encryption. HDCP is not tied to any particular interface.

Making a fancy new standard (or more accurately, tacking a new connector on DVI and adding support for audio) resulted in $10000 per manufacturer per year fees, plus 4 cents per device in royalties for the HDMI Licensing cartel.

I have said that in the past as well. But there is one argument the HDMI proponents make - SDI is unidirectional so there isn't any handshaking. Hmmm, I guess I see their point.

There is optional encryption on HDSDI when feeding digital cinema projectors. The handshaking is handled through a standard ethernet connection. I guess that would be too complex for residential use.

Sheer Lunacy

· #17 · Nov 12, 2010

Quote:
Originally Posted by Glimmie /forum/post/19473215

I have said that in the past as well. But there is one argument the HDMI proponents make - SDI is unidirectional so there isn't any handshaking. Hmmm, I guess I see their point.

In a studio setting, with either SDI or AES/EBU (digital audio), it's not unheard of to link the equipment in a "round robin" fashion. With each component having a cable going in & a cable going out, & being allowed to read & modify the bitspace reserved for intercommunication, it's possible to do all kinds of things.

In a home setting, however, that doesn't make a lot of sense. In a lot of cases, you would basically have a source component & a sink component, & the loopback cable would serve no purpose at all other than carrying the handshaking information. If you had multiple sources & sinks, & maybe a record-playback component such as a PVR, or that sort of thing, it could begin to look better than having a bunch of HDMI connexions jacked into one component.

Desert Hawk

· #18 · Nov 12, 2010

Quote:
Originally Posted by Ken H /forum/post/0

Those concerns should be directed at the content providers, not at the carriers; they are the ones concerned with security, and they are the ones who made the cableco's encrypt content.

Are you saying that Disney has a clause in it's contracts that prohibits a cable system from carrying ESPN HD in clear QAM? Are you sure about that? No doubt the contracts with cable companies require that the signal be secured to prevent reception by nonsubscribers, but I doubt that it specifically requires encryption. Traps would secure the signal from reception by nonsubscribers just as well as encryption.

Ken H

· #19 · Nov 12, 2010

Quote:
Originally Posted by Ken H /forum/post/0

Those concerns should be directed at the content providers, not at the carriers; they are the ones concerned with security, and they are the ones who made the cableco's encrypt content.

Quote:
Originally Posted by Desert Hawk /forum/post/19475050

Are you saying that Disney has a clause in it's contracts that prohibits a cable system from carrying ESPN HD in clear QAM? Are you sure about that? No doubt the contracts with cable companies require that the signal be secured to prevent reception by nonsubscribers, but I doubt that it specifically requires encryption. Traps would secure the signal from reception by nonsubscribers just as well as encryption.

Back up.

I'm absolutely 100% sure the content owners would withhold their product if providers did not take measures to prevent illegal use. This has been communicated to me from a number of reliable sources. The specifics are not the issue.

McDonoughDawg

· #20 · Nov 12, 2010

Quote:
Originally Posted by Desert Hawk /forum/post/19475050

Are you saying that Disney has a clause in it's contracts that prohibits a cable system from carrying ESPN HD in clear QAM? Are you sure about that? No doubt the contracts with cable companies require that the signal be secured to prevent reception by nonsubscribers, but I doubt that it specifically requires encryption. Traps would secure the signal from reception by nonsubscribers just as well as encryption.

How much would "traps" would cost to be put into place? And to manage after that? I can't imagine it being workable in the real world.

1 - 20 of 23 Posts

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