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Connecting DVI to HDTV

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Old 10-10-2004, 09:37 AM   #1
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Default Connecting Computer DVI to HDTV

I get PMs and questions about connecting a computer video card output to an HDTV quite often. It came to me that a series of threads that deal with this proceedure and the issues involved would be helpful. This thread will deal with the connecting of a computer video card with DVI outputs to an HDTV with a DVI input.

Also for you strictly technical guys out there, I do take a little poetic license to try and simplify the subject somewhat.

Introduction
The reason many TV manufacturers include a DVI connection in addition to component video was not to allow the connection of a computer. The main reason was to allow the exchange of video information in a digital format rather than analog. The DVI interface came into being due to the LCD and plasma flat panel computer monitors and projectors, and later DLP and LCOS (D-ILA) displays and projectors. Since these are fixed pixel devices an interface that would present a digital value for each pixel rather than an analog signal level made sense.

The DVI interface answered the question of, "Why start out with a digital array of pixel values then convert them to an analog signal to send to a monitor only to have the analog signal reconverted back to digital?" With the DVI interface the possibility of the signal remaining all digital is possible.

The DVI interface was also given interaction capabilities between the video card and the monitor. This allowed the computer to inquire of the monitor what the resolution and timing that it supported and then via software in the computer set the video output accordingly. This capability is actually the essence of the DVI interface, the ability to tell the source what signals the monitor will display. The earliest DVI-I interfaces were actually just VGA analog signals with the digital link to allow the information to be exchanged between the computer and the monitor. There is a cable available to convert a DVI-I output from a video card to a VGA input on a monitor.

The DVI connection that is most desirable for fixed pixel devices is the DVI-D, dual link connection. This is the connection that most HDTV manufacturers use primarily for compatibility reasons.

Adoption of DVI for HDTV Signals
Since the computer was able to ask the monitor to supply information concerning its signal capabilities, as well as other information, the consumer electronics industry saw this interface (and later the HDMI) as a possible answer to the copy protection issue that had prevented HD movies from being made available for broadcast in HDTV. The entertainment industries were concerned with copy protection and insisted on a method of preventing cloning of their movies. The HDCP protocol was developed and the DVI became the first interface to have HDPC implemented. This allowed the broadcasters to "raise the HDCP flag" that would prevent a recording device connected to the DVI output from recording by shutting off the output. As long as a monitor only device was connected the output was enabled.

Computer Output Compatibility
Many people think that because there is a DVI connection on their HDTV that it should be a matter of connecting a DVI cable between the two and presto! We have computer video on our HDTV screen. Well I'm sorry to say this is not the always the case, in fact rarely.

There are exceptions to this, primarily plasma, LCD displays and projectors. These are generally higher cost display units that are built with the connection of a computer in mind, but most HDTVs are not built with the connection of a computer. Computer monitors today will accept a vast range of video signals. Refresh rates from 50Hz to 120Hz are typical for most computer monitors, whereas most HDTVs will only handle 59 to 61Hz refresh rates. Horizontal scan ranges are also reduced compared to a computer monitor. Here is my HDTV information returned by MonInfo, a utility that can be downloaded and run to get information from your HDTV via the DVI connection:

Quote:
Monitor
Windows description......... Plug and Play Monitor
Manufacturer description.... R40W46
Manufacturer................ LG Electronics
覧覧覧覧覧覧覧覧覧覧覧覧覧覧
Plug and Play ID............ GSM0101
Serial number............... (n/a)
覧覧覧覧覧覧覧覧覧覧覧覧覧覧
Manufacture date............ 2003
EDID revision............... 1.3
Display type and signal..... Digital
Sync input support.......... (n/a)
Screen size................. 710 x 400 mm (~34")
Power management............ Not supported
Color characteristics
Display gamma............... 2.20
Red chromaticity............ Rx 0.640 - Ry 0.340
Green chromaticity.......... Gx 0.300 - Gy 0.690
Blue chromaticity........... Bx 0.138 - By 0.038
White point (default)....... Wx 0.270 - Wy 0.365
Timing characteristics
VESA GTF support............ Not supported
Horizontal scan range....... 31-45kHz
Vertical scan range......... 59-60Hz
Video bandwidth............. 80MHz
Timing recommendation #1.... 1920x1080 at 30Hz
Modeline................ "1920x1080" 74.250 1920 2008 2052 2200 1080 1084 1094 1124 interlace +hsync +vsync
Timing recommendation #2.... 720x480 at 60Hz
Modeline................ "720x480" 27.000 720 736 798 858 480 489 495 525 -hsync -vsync
Standard timings supported
720 x 480 at 60Hz - LG Electronics
1920 x 1080 at 30Hz - LG Electronics
Note that the 30Hz indicates these are interlaced timings.

The reason HDTVs have such narrow response is a cost issue. Most people who buy an HDTV do not want to pay the extra $2k or so required to expand the response to allow the computer timings.

What Is Possible
But there are many reasons to connect your computer to your HDTV, even though it will not be a big screen duplicate of your computer monitor. Slide shows of digital photos, DVD viewing and group web surfing are just some of the possibilities, but I find it will not replace my computer monitor.

To find out what is possible for your HDTV the first step, after the connection of the appropriate DVI cable, would be to download and run MonInfo. This utility will tell you what resolutions your TV will display. I have found that this is not the only resolutions, but the recommended by the manufacturer. For example my LG will also display 1920x540 at 60Hz which is the progressive scan counterpart to the 1920x1080 at 30Hz. It is probably not recommended by LG due to the aspect ratio issues.

It is important to know what is possible for your particular HDTV because serious damage can be done to your HDTV if non viewable signals are sent to your TV. If while trying out different resolutions and timings you hear a high pitched noise from your TV, remove the signal or turn off the TV immediately.

Recommended Steps To Get Started
First of all you will need to have a computer monitor connected as well as your HDTV. Since the majority of resolutions that can be displayed on your monitor will not be displayable on your HDTV, you would be operating blind and that just will not work. Some video cards have both a VGA output and a DVI output and if yours is this type, then you can hook up your monitor to the VGA output. If your computer monitor is a DVI unit then you will need a DVI distribution box, like the DTronics DD-12P, for example.

Start by setting your computer to 640x480 and get a stable picture. This should be no problem. Most likely the 16:9 resolutions of 720x480 and 1920x1080 will not be listed with the standard video drivers. In order to be able to set custom resolutions it will be necessary to download a program called powerstrip, which is available here: PowerStrip - English and the home page to read up on the software is here: http://entechtaiwan.net/util/ps.shtm

Most likely without the powerstrip software you will go no further. Some video cards have some HDTV drivers for their latest and greatest cards, but if you have an older card - 6 months old even - you will need powerstrip. In the end, you may need to get a newer card anyway. Even if you get a newer card that supports HDTV resolutions, you may still need powerstrip to tweak the display to reduce the overscan. See Overscan thread for more information.

This is a fairly complex issue to get your computer connected to your HDTV successfully, but with some persistence it can be done.

Last edited by rbinck; 01-19-2006 at 02:33 PM. Reason: spelling
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Old 10-29-2004, 05:07 PM   #2
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Default ATI radeon mobility 9700 DVI-I to Samsung DLP 5085EW HDMI

Thanks for the help. I used powerstrip and Moninfo as you suggested and now I can see my computer screen image from a Dell Inspiron 9100 on my TV! Prior to making the adjustments, I has overscan issues with the desktop image and an extremely squished DVD image when trying to watch a movie. The DVD image through DVI is incredible but I am not sure if it is better than thorugh my progressive DVD player through components. More fun over the weekend I guess. I tried two different resolutions suggested through Moninfo 1280x760p at 60hz and 1920x1080i at 30 hz and cannot tell any difference between the two. Is one better for movies and the other for text? Anyway, I hae learned a lot from you and the other posters. Thanks for the help.
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Old 11-01-2004, 01:20 PM   #3
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GREAT Post!

Once I get my HDTV I'll have to come back to this.

Do you have any idea how this will work hooked to a Mac?

Thanks
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Old 11-07-2004, 01:40 PM   #4
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Default Is there a way around the HDCP

I have a first generation Plasma monitor I used as a tv which worked great until the cable company started using HDCP. Now my dvi connections work for 5 seconds and then go blank. Is there a way to make it work, ie a filter or some devise that would get my picture back? Thanks for your input.
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Old 11-08-2004, 03:32 PM   #5
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I had the same problem with my Voom box. I ended up just using the component connections.

As far as the Mac question goes, it will depend on the video card capabilities of the Mac. Video cards need to be capable of HD resolutions. Only certian video cards will work for the PC with the ATI Radeon being the ones most used.

Last edited by rbinck; 11-10-2004 at 10:54 AM.
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Old 11-22-2004, 03:48 PM   #6
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Great information so far but I am still having issues with getting mine to work.

I have a pundit which has built in dvi video and using powerstrip doesn't seem to support the 1920x1080 at 30Hz (1080i)

I have been trying to research video cards so I can purchase one which will provide the best output for either component or dvi 1920x1080 at 30Hz interlaced, does anyone have a recomendation? I would prefer a pci but if there aren't any a AGP will be fine. I would also prefer to spend less than 120$ as well.

Please help.
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Old 11-22-2004, 04:28 PM   #7
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I use an ATI 7500 pci which has both a VGA and a DVI-I output. Also a composite video out. It works very well as I use the VGA for my computer monitor and the DVI for my HDTV. You will need a monitor in addition to the HDTV as all of the desktop will not end up on the HDTV due to overscan and you need the monitor to be able to get to the bottom menus.
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Old 11-23-2004, 09:10 AM   #8
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Default ATI said none of their cards would work

Are youy sure the ATI 7500 pci will support 1920x1080 at 30Hz (1080i)? I would love that solution but am afraid to buy any more products until I am sure it will work. (I have already spent 100$ for special cables, adapters, etc with no success.)
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Old 11-23-2004, 11:02 AM   #9
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Yes I use this card with the powerstrip software to set the 1920x1080i 30 timings. Make sure it is the PCI version, not AGP. The PCI version has a VGA and a DVI output and is capable of extended desktop use if desired.

The multirez software that ATI supplies will not do the interlaced timings, that is why you must use powerstrip.
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Old 11-23-2004, 12:58 PM   #10
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thanks
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Old 11-23-2004, 02:14 PM   #11
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Default HDMI 1 vs 2

I have the Panasonic PT60DL54 (DLP)on order. It has one HDMI input. My concern is that I will either have to choose whether to hook up my cable box (which will have a HD DVR) to the HDMI or my DVD (which I have not purchased yet...). I was told that I could just use the cable box with the components and not lose much HD quality and use the DVD with the HDMI and get superior quality. My other choice is to purchase an IR switch box and have both the cable box and DVD hooked up. Alternately, would I be better off with the Toshiba 62hmx84 (DLP) which has 2 HDMI inputs?
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Old 11-24-2004, 10:31 AM   #12
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Eaglevet, see: HDMI Input Quandry
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Old 12-09-2004, 09:43 AM   #13
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Hi I am new here and I got some questions. Anybody tried the newer nVidia driver that support HDTV modes from a Quadro FX 200 card?

My card has two DVI-I out so I would be using this with a Samsung TXP-2670WH but was wondering if there would be an overscan problem. Is powerstrip really necessary for this to work? Will powerstrip support dual monitor setup (computer monitor and HDTV)?

The nVidia driver certainly has a HDTV mode out and the Quadro FX card supports 1280x720 res at 75hz. It won't be my main computer display since I am retaining my 19inch computer monitor but would be evaluating SD and HD video authored (MPEG2) on the computer.
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Old 12-12-2004, 12:21 PM   #14
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Ok I was able to connect my Quadro FX 200 card DVI-out to the HDTV at both 1920x1080 and 1280x720 resolution without problem. The only issue now is the way WM9 HD videos gets cropped (from within the window) when viewed on the HDTV. Overall its pretty good only for presentations but not as a replacement for the computer monitor. The NFL games though are wonderful on it
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Old 12-12-2004, 02:19 PM   #15
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Powerstrip will only solve a little of the overscan problem that is causing the cropping of your picture. It may be that nVidia has some software simular to the ATI software that creates a resolution within a resolution to solve the cropping.


The better solution is to try and get into the service menus of your TV and set the height and width to eliminate the overscan for the input you are using for your computer. Be sure to write down the parameter and the factory setting if you try this so as to be able to get back to the original values. I don't know where to send you for the service menu codes. You may be able to google for them.
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