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How does HDTV Go from Coax to HDMI to TV?

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Old 01-21-2011, 01:32 PM   #1
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Default How does HDTV Go from Coax to HDMI to TV?

Hopefully someone can enlighten me on this. I couldn't find an answer and it's really driving me insane.

The question is regarding HD def channels, which requires an HDMI cable to view. I don't understand why we need an HDMI cable to view a HD channel, yet the source of the signal travels through a coaxial to reach your home. Coaxial is not HI DEF, am I correct? How does that exchange take place?

Anyway, I think you see what I'm getting at. Someone help me understand this!

Thanks.
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Old 01-21-2011, 01:42 PM   #2
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There is NO requirement/need to use an HDMI cable to view HD. HD was around before HDMI. Some HD TVs do not even have HDMI ports.

I can view HD on my plasma TV with NO HDMI connected; the video signal can be carried to the TV by coax-- or by other connections-- even USB . . .

Coax is not "Hi Def" It is not "Std. Def" It is a coaxial cable that carries a signal-- it can be a signal that is contains hi def video, audio, almost anything. You need only have a device connected that will "process" the signal. A modern HD TV can take a signal from a coax and display a high definition picture-- the signal can be from an antennae or from a cable TV system-- depends on what type of tuners the TV has. Cable boxes are just tuners that process signals from the coax and send the resultant digital data stream via HDMI cable (or other) to the TV for display.

http://electronics.howstuffworks.com/dtv.htm

Last edited by Rick-F; 01-21-2011 at 02:04 PM.
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Old 01-21-2011, 01:47 PM   #3
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Quote:
Originally Posted by ElJoker View Post
Hopefully someone can enlighten me on this. I couldn't find an answer and it's really driving me insane.

The question is regarding HD def channels, which requires an HDMI cable to view. I don't understand why we need an HDMI cable to view a HD channel, yet the source of the signal travels through a coaxial to reach your home. Coaxial is not HI DEF, am I correct? How does that exchange take place?

Anyway, I think you see what I'm getting at. Someone help me understand this!

Thanks.
HDMI cables provide Video & Audio via a single connector. The Coaxial is delivering the signal to your Cable box, it in turn, breaks down the signal to Video and Audio it is then sent to a single output HDMI ( which consist of approx 19 connectors) thus allowing Audio 5.1 and a Video signal signal to your display (via HDMI). Or you can connect a coaxial cable from your source to your TV for 2 channel audio and Video. and then either a digital Coaxial audio cable to your AVR audio inputs for 5.1 sound. Or your can connect your Video coax cable to your TV and the standard RCA type connectors to your TV, but that will produce 2 channel sound only.

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Old 01-21-2011, 01:49 PM   #4
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You can use component video DVI or VGA as well for HD.

But as far as coax (RG6), it only works for ATSC (OTA antenna), QAM (cable) or if a STB (cable box) is involved. But that is because there is a digital tuner in the TV or the cable/sat box that uncompresses and converts the signal. It can not handle the bandwith after the conversion from say the HD cable box to the TV.
Is this what your were asking about?
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Old 01-21-2011, 02:21 PM   #5
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I guess that somewhat answers my question. There are obviously tons of people out there that believe that you need HDMI cables to get an HD picture.

For example, I have a 42" 1080p Panasonic Viera, the picture is the same with coax or hdmi, but my picture still doesn't "pop" like I see in a lot of hi def TVs. I don't get it.

I thought it would definitely make a difference after going from coax to HDMI, but nothing. So is it my TV? And I do subscribe to HD channels from comcast.
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Old 01-21-2011, 02:34 PM   #6
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Originally Posted by ElJoker View Post
I guess that somewhat answers my question. There are obviously tons of people out there that believe that you need HDMI cables to get an HD picture.

For example, I have a 42" 1080p Panasonic Viera, the picture is the same with coax or hdmi, but my picture still doesn't "pop" like I see in a lot of hi def TVs. I don't get it.

I thought it would definitely make a difference after going from coax to HDMI, but nothing. So is it my TV? And I do subscribe to HD channels from comcast.
SAY WHAT??? Are you talking about using both HDMI and coax from the cable box and viewing HD channels, or are you talking about comparing coax strait to the TV's QAM tuner and HDMI from the cable box with HD?

If you are reffering to the 1st question, you definately do not have things set up correctly.. You will not see a major improvement at all with HDMI vs coax viewing SD, but you CAN NOT get HD with coax other than the way I described it above, so PQ via HD channels will be, well in HD with HDMI.. And Wayyyyyyyy better.

If the latter, you should see very little if any diff between HD via QAM and HDMI from the box (if settings are correct). HD via OTA (ATSC tuner) is usually the best from what I have seen due to less uncompression involved I believe.
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Old 01-21-2011, 02:36 PM   #7
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Quote:
Originally Posted by ElJoker View Post
I guess that somewhat answers my question. There are obviously tons of people out there that believe that you need HDMI cables to get an HD picture.

For example, I have a 42" 1080p Panasonic Viera, the picture is the same with coax or hdmi, but my picture still doesn't "pop" like I see in a lot of hi def TVs. I don't get it.

I thought it would definitely make a difference after going from coax to HDMI, but nothing. So is it my TV? And I do subscribe to HD channels from comcast.
One very important part of you setup is missing here . . . what is the other end of your HDMI cable (and the coax) connected to?

Using an HDMI cable does not assure you will see an HD picture on your TV. You need to be sure a HD signal is being sent to the TV. You need to be sure the TV is set/adjusted/tuned properly to display the HD picture.

Because you subscribe to HD from Comcast, I ASSUME you are using a set top cable box. Is it setup to output 1080i via the HDMI? Again having the STB and a HD subscription does not assure you are sending the HD signal to the TV.

If you see no difference between the HDMI between the TV and STB and coax between the STB & TV-- then something is not set properly.

Last edited by Rick-F; 01-21-2011 at 02:40 PM.
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Old 01-21-2011, 02:52 PM   #8
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Okay, I am kind of getting confused with all the different slang, but this how I have everything set up:

So the coax enters my home from outside and it hooks up to my comcast cable box. My comcast cable box connects to my TV via the HDMI cable.

So from the wall to the cable box coax, from the cable box to the TV HDMI.

Is that the proper way to set it up?
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Old 01-21-2011, 03:12 PM   #9
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Quote:
Originally Posted by ElJoker View Post
Okay, I am kind of getting confused with all the different slang, but this how I have everything set up:

So the coax enters my home from outside and it hooks up to my comcast cable box. My comcast cable box connects to my TV via the HDMI cable.

So from the wall to the cable box coax, from the cable box to the TV HDMI.

Is that the proper way to set it up?
Yes that is correct. And your box should be set to 1080i output..

What was confusing me/us is when you said you see no difference in HD PQ (picture quality) with either coax or HDMI.. Can you elaborate a bit further on that?
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Old 01-21-2011, 03:47 PM   #10
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Originally Posted by Bigloww View Post


Yes that is correct. And your box should be set to 1080i output..

What was confusing me/us is when you said you see no difference in HD PQ (picture quality) with either coax or HDMI.. Can you elaborate a bit further on that?
Sure. The box is set to 1080i. I've had this box for several months now. And the box and TV have been connected with coax all this time.

It's not until recently that I upgraded from coax to HDMI to connect the cable box to the TV. I haven't seen an improvement after changing to the HDMI cable. Does that make sense?
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Old 01-21-2011, 04:02 PM   #11
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Many cable and satellite companies distribute much of their content as encrypted digital data streams. The encrypted aspect is similar to the way diplomats and military personnel use secret codes to keep other organizations from reading intercepted telegraph or Morse code radio messages. Commercial TV distributors use encryption to limit subscribers to the channels the subscriber pays for and restrict their ability to record programs for illegal "pirate" duplication. The receiver (for digital satellite) or converter (for cable) strips away the encryption for "in the clear" relaying to the display.

A commercial TV distributor has the option to configure their receivers/converters (set top boxes) to require two way communications with a [b]single[b] display utilizing the digital communications standards associated with HDMI cables. If the HDMI cable were to be connected to a recording device the receiver/converter would reject the destination and degrade the images to standard definition. A similar degradation or refusal to relay the signal at all would occur if the receiver/converter detects multiple devices (two TVs or a TV and a recording device). If the distributor implements these controls a similar degradation might also occur over a component cable connection between the receiver/converter and the display.

The standards used for this content protection allow the distributor to turn that function on and off for individual programs.

As any coax connection between the receiver/converter and the display lacks standards to support content protection the receiver/converter is normally designed to relay a NTSC (thus standard definition) signal that connector. Similar limitations exist for the any receivers/converters equipped with composite and S-video outputs.
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Old 01-21-2011, 04:27 PM   #12
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Thanks for that lengthy explanation. If I understood you correctly, you're saying that depending on the number of TVs hooked up to the box, there may or may not be signal degradation to the standard definition. I only have one TV hooked up to the cable box, the only TV in the house. So that's probably not my case.

However, there is a splitter on the coax (before it reaches the cable box) that goes to my computer for internet service. Would this degrade the signal going to the TV?
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Old 01-21-2011, 04:38 PM   #13
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Sure. The box is set to 1080i. I've had this box for several months now. And the box and TV have been connected with coax all this time.

It's not until recently that I upgraded from coax to HDMI to connect the cable box to the TV. I haven't seen an improvement after changing to the HDMI cable. Does that make sense?
So, origianally you had your HD cable box connected to the TV via coax cable and set to channel 3 or whatever. And just recently, you upgraded your connection from the HD cable box from coax to HDMI??? And after this you see little or NO mprovement in HD PQ.. If so, there is something majorly wrong here. Either you are not setup correctly, or your not getting HD programming or not tunning to the HD channels....

And who originally connect the cable box to your plasma via coax? Was it you or the installer?
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Old 01-21-2011, 05:13 PM   #14
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So, origianally you had your HD cable box connected to the TV via coax cable and set to channel 3 or whatever. And just recently, you upgraded your connection from the HD cable box from coax to HDMI??? And after this you see little or NO mprovement in HD PQ.. If so, there is something majorly wrong here. Either you are not setup correctly, or your not getting HD programming or not tunning to the HD channels....

And who originally connect the cable box to your plasma via coax? Was it you or the installer?
Okay, so we're on the same page.

I got my plasma flat panel several months back. A few days later I walked in to the comcast service center to trade in my old box for a new hd box. Then I went home and hooked everything up myself.

I have no doubt that I'm tuning into the HD channels... because I can see them, and the only way you can see them is by being a subscriber. I have to rule that out.

I guess I have to play around with the settings on the TV. The picture looks nowhere near as good as when I play blu-ray movies. Could it possibly be that I have a low quality HDMI cable? I got the cable free from Comcast.
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Old 01-21-2011, 05:18 PM   #15
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Okay, so we're on the same page.

I got my plasma flat panel several months back. A few days later I walked in to the comcast service center to trade in my old box for a new hd box. Then I went home and hooked everything up myself.

I have no doubt that I'm tuning into the HD channels... because I can see them, and the only way you can see them is by being a subscriber. I have to rule that out.

I guess I have to play around with the settings on the TV. The picture looks nowhere near as good as when I play blu-ray movies. Could it possibly be that I have a low quality HDMI cable? I got the cable free from Comcast.
You should also check your Cable HD box most often they have to be "programed" for nec. settings,they must be set up in through their menu section to confirm necessary HD output.
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