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Why HDMI over Coax for HDTV?

TVs & Video Components

TVs & Video Components
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Why HDMI over Coax for HDTV?

  • What I don't get is, why do I need HDMI or Component video to get the best HD picture possible for my HDTV?
    Here's the reason for my question: In my TV room I have digital cable and the set top box provided by my cable company has an HD tuner built-in.  I am currently running this to a digital CRT television and will soon be upgrading to a Samsung 52" LCD.  
    So how can an HDMI cable improve the quality of a signal that already comes from the coax?  Do cables not follow the laws of the "weakest link" principle?  In other words, won't the maximum quality be limited to the lowest quality component?
    Here's what else I don't understand.  On crutchfield.com in the learning section, it states that Coax and RF only carry a maxium of 350i resolution, but the cable that goes directly from wall into my 19" LCD HDTV in my bedroom, with QAM, shows me a beautiful 1080i picture. This is straight cable and does not go through a setop box.
    So both of these arguments confuse me as why HDMI does a better job than Coax.  
    Does the settop box increase the resolution of what was brought in by the wall cable?
    Apparantly my 19" Samsung does, so why couldn't I run Coax from wall to settop, the Coax from settop to my new 52" and get the same result as my 19"?

    Very confused.
    Thanks for the help.
  • I'm no expert either and when I first started to think about finally upgrading my gear after many, many years I was thoroughly confused as everyone seemed to say it doesn't matter much, go with what you like, and lots of other equally useless opinions.  But I still have the text I copied from one guy in another forum and maybe it will help you as well -

    ""HDMI offers digital audio in its cable and also allows HDCP material to be viewed. These are two big differences of component video and HDMI. For seeing if the picture quality in HDMI is better than component there is info on www.hdmi.com on that, here is one citing from that URL:

    Q. What are the advantages of HDMI over existing analog interfaces such as composite, S-Video and component video?
    Quality: HDMI transfers uncompressed digital audio and video for the highest, crispest image quality.

    All-Digital: HDMI ensures an all-digital rendering of video without the losses associated with analog interfaces and their unnecessary digital-to-analog conversions.

    Low-cost: HDMI provides the quality and functionality of a digital interface while also supporting uncompressed video formats in a simple, cost-effective manner.

    Audio: HDMI supports multiple audio formats, from standard stereo to multi-channel surround-sound.

    Ease-of-use: HDMI combines video and multi-channel audio into a single cable, eliminating the cost, complexity, and confusion of multiple cables currently used in A/V systems.

    Intelligence: HDMI supports two-way communication between the video source (such as a DVD player) and the DTV, enabling new functionality such as automatic configuration and one-touch play.""

    So it really boils down to what gear you have that takes advantage of what technology.  I still see many people insisting that component connections provide the same picture that HDMI does (except I think I've read you can't get 1080p except through HDMI, only 1080i through coax/component). But for audio, I think HDMI provides support for more audio formats and the quality of sound is pretty much the same for HDMI, optical and coax.



    [edited by: ldsheridan at 5:45 PM (GMT -5) on Mon, Oct 13 2008]
  • elcarlstono:
    So how can an HDMI cable improve the quality of a signal that already comes from the coax?  Do cables not follow the laws of the "weakest link" principle?  In other words, won't the maximum quality be limited to the lowest quality component?
    Don't confuse the media with the signal - that is, the cable with the information it carries.  The coax between the utility pole outside and your set top box or QAM-equipped TV is carrying a digital signal.  Your set top box converts that signal to something that can be used by your TV, and your TV with the HD tuner does the same internally.  A digital set-top box that outputs an analog signal via coax will be limited by what the coax can do.  The same box outputting HDMI can send a digital, uncompressed signal.

    ldsheridan:
    I still see many people insisting that component connections provide the same picture that HDMI does (except I think I've read you can't get 1080p except through HDMI, only 1080i through coax/component). But for audio, I think HDMI provides support for more audio formats and the quality of sound is pretty much the same for HDMI, optical and coax.

    Component can carry up to a 1080i signal.  1080p is out of its reach because it doesn't have the bandwidth neccessary to carry enough information.  Some people prefer component over HDMI for 1080i and lower, but I think that depends on their equipment and preference.  The digital audio information in HDMI is exactly the same signal as what digital optical and coax offers.  It's the same digital data stream regardless of the transport media.  Component of course is video only.



    [edited by: JerSully at 9:54 AM (GMT -5) on Tue, Oct 14 2008] [edited by: JerSully at 9:53 AM (GMT -5) on Tue, Oct 14 2008]
  • THanks JerSully, I beleive your explanation that the settop box outputs coax in analog answers my question.

    Thanks for the responses all.

  • I know its 4 years later but your answer doesn't do it for me.  If the coax can carry a digital signal from the wall to the tv or "set top box" why can it not carry the digital signal to the blu-ray, xbox, ps3, etc?

  • It can, but the signal is scrambled. The box de-scrambles it . . .

  • It can. What was missed here is that the signal from the wall to the box is broadband and digital while the signal from the box to the TV in component video is baseband analog divided over three coaxial cables. There is no inherent reason why component video (or VGA for that matter) cannot perform as well as HDMI (there are some "manufactured" limitations that involve DRM). In other words, the above posts are comparing apples to oranges, and your mileage may vary depending on the source material.

    The bottom line is that there is nothing inherently superior about using a digital connection between the source component and your TV (in fact, HDMI is a pretty awful connection method, from a technical standpoint). There is some "crippling" being done in the interest of copyright protection.

    It should also be stated that the reason for the digital conversion in the CATV and broadcast arenas had more to do with conservation of bandwidth than with the user experience, and that you will see a greater improvement in your picture by switching from CATV to antenna than you can achieve by switching from component to HDMI cables.

    I'm pretty sure I covered a lot of this in depth in some of my earlier posts, if you are inclined to search them out.

         RESIma

  • I have a Tote Vision LCD 1510v monitor with  VGA, DVI, two different s-Video inputs (one 4 pin plus flat pin, other 8 pin), AV (the red white and yellow RCA inputs), and BNC inputs, with built in speakers which work with the av. I play my Xbox 360 on it in my [very] small bedroom. I use the av inputs and could use an HDMI to DVI adapter for hd video without sound, but i would like  the best of both worlds; hd video with sound. There are some forums that say some graphics pc cards will send audio over and hdmi to dvi cable, but I don't think the 360 is on that list. Is there any cable that will send audio and hd video from hdmi to ANY of the inputs on my monitor?