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Published: 2008-02-27 - 17:05:28
Home Theater : Ask The Expert

PC DVI Output Won't Display via HDMI on HDTV Projector - Why?

By Chris Boylan

Question:

Dear Expert,

I have run into a problem running my computer into my Denon receiver--which acts as a switcher for all of my HD sources. It is linked to a projector. I have used a DVI to HDMI cable to an input that I know is active, with no results whatsoever. I assume that the signal coming from the computer (HP Media Center) is digital and that it would mesh with an HDMI adaptor. Any suggestions for a fix?

Thanks.

-Tim C.


Answer:

Hello, Tim,

Without knowing the specifics of your video card, Denon receiver model and projector model, I can only make a few generic suggestions.

First off, DVI (Digital Visual Interface) actually comes in three flavors - DVI-A, DVI-D and DVI-I.  DVI-D is virtually identical to the video component of an HDMI signal but DVI-A (analog) is more like a VGA connection.  DVI-I is a hybrid connector that supports both digital and analog outputs (but not necessarily at the same time).

You cannot adapt DVI-A to HDMI with a cable or simple plug adapter- it needs an active analog to digital signal converter (a box that gets plugged in to the wall or batteries for power).  These are not usually cheap.  You can convert DVI-D to HDMI with a simple adapter.  To figure out which DVI output you have, check your PC manual or take a look at the DVI jack itself and compare it to the pictures on wikipedia.

Try to simplifiy your connection for test purposes.  Does your projector have DVI input?  If so, plug the computer directly into the projector with a DVI to DVI connection and see if the results are any different.  If the projector does not have DVI then try the same thing with your DVI to HDMI cable plugged directly into the projector.  If the results are different then it may be a handshake issue caused by the receiver being in the middle.  Also, try using a different display (assuming you have another display with an HDMI input) and see if the behavior changes.  This will rule out (or rule in) the projector itself.

If you're using a laptop with a built-in screen, make sure you have toggled its switch to support external monitor output instead of the internal LCD screen (I think that's Function-F5 on an HP laptop).

Make sure you have selected a screen resolution that is supported by your projector (right click on desktop and go into "properties... settings").  If your screen output resolution is set to 1366x768 but your projector only supports 640x480 or 800x600 or 1024x768 then you will probably not see any output.  Check your projector manual for details on what screen resolutions are supported via the HDMI input.

Even if you've done everything right (DVI-D output, proper DVI to HDMI cable used, output resolution is one that is supported by the display, Denon receiver is switching the signal properly, etc.), it's still possible you would get no output when trying to view PC content on a projector via HDMI.  Some displays (flat panels and projectors) simply do not support computer signals from their HDMI inputs.  If this is the case, then you'll need to use VGA or DVI-A to connect the computer to your projector instead.

Hope that helps.

Regards,

-Chris


Follow-up Question:

Thanks for your thoughts and willingness to help with the investigation.  Our combined opinion after much testing is that this problem is not merely a physical connection mishap but, rather, one that will take an electronic intervention to fix. Now who wants to spend $200 on a device to change DVI to HDMI--well, not this elderly fixed-income home theater devotee.

Follow-up Answer:
Yeah, I thought it most likely that the HP PC's output was DVI analog and not DVI-digital. This is why it can't be converted to HDMI without a new piece of electronics.  But if your projector has a VGA (computer) input (which most do) then you can solve the problem with a simple, inexpensive DVI-A to VGA adapter and a long VGA cable.

Here's an inexpensive DVI-A or DVI-I to VGA adapter.

And here's an inexpensive high quality VGA cable (25 feet long).

So for about $30, you should be in business (assuming your projector has a VGA input).  If you can get by with a shorter cable, then you can spend less on the VGA cable.

If you solve the problem this way, then you'd use the Denon receiver for audio only for this particular device and select the projector's VGA video input when watching something from the PC.

Hope that helps.

-Chris

 

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