Problems with a PC HDMI Connection to a TV

Note to Insomniacs: You should continue looking for a better post if your goal is glorious repose. I recommend “A Tale of Two Emails”. However, it’s possible this posting might do the trick. If it does work for you, drop me an email when you wake up and let me know that it really did work.

General Note: This is the first in a series of many postings (in no particular order) on setting up an HDhomerun Prime device and using Media Center to replace the STBs in my house. I have literally spent hundreds of hours working on it, and have gained some knowledge which I would like to share.

I’ve spent the last few days trying to set up a home theater PC that hooks up to a Samsung LN40B540 40″ TV. I thought I’d share my experiences should anyone have similar issues. You probably won’t have the identical TV and laptop combination that I have, but I think what you read here will apply to most other TV/laptop combinations.

I have a tiny Acer Aspire 722 that I have completely rebuilt from scratch. It had a damaged motherboard and a non functioning display. I replaced the motherboard and surgically removed the display, making the laptop headless. This isn’t a detriment for my purposes. Unlike HP laptops, and like Dell laptops, this headless Acer shows the post screen and allows you to see the BIOS menu on an external monitor. Headless HP laptops that I have played with are useless as the post info is not displayed externally, and the monitor does not turn on until Windows has booted. The 722 is unquestionably dog slow, even with an SSD but makes up for this with a Radeon 6290 video card which manages to pump out smooth 1080p AS LONG AS the laptop is doing absolutely nothing other than running WMC.

The goal was to use the HDMI port on the laptop to connect to my Samsung TV. Windows Media Center would be used to connect to my HDhomerun Prime 3-tuner cablecard appliance and this setup would replace the Verizon FiOS STB.

What I thought would be a 15 minute “cruise” actually took much longer.

The Samsung HDTV has 4 HDMI ports. One of them is a special port, labeled on the back of the set as “DVI PC” and situated right next to a pair of associated RCA audio input jacks. Most HDTVs have this arrangement. And very importantly, the Samsung TV menu has this port labeled in the firmware as “DVI PC”. If you go into the TV menu, there is a screen that allows the user to change the label for all the inputs. You have to choose from a drop down list. Two items in that list are PC and “DVI PC”. This will be important later on. It might seem to be just a few labels but they can dramatically affect how that HDMI port behaves.

I first thought I could use any port, since my laptop really had an HDMI and not a DVI output. So I didn’t think it mattered. I used the first free HDMI port on the TV, and the result was horrible. The display was acutely overscanned, resulting in all 4 edges being chopped. I could not see the task bar, the leftmost column of icons. The overscan was identical on the top and right. Furthermore the fonts looked smudged and fuzzy and were barely readable. Using AMD Catalyst software, I could modify the overscan to make the screen fit, but wound up with a custom display mode that was something less than 1080p by about 10 percent. While it looked better, the fonts were still fuzzy.

I tried using a VGA connector instead of HDMI, as an experiment. It looked pretty good, and filled the TV display perfectly. VGA requires a separate mini jack from the headphone output to a mini jack input on the TV. This also worked well. But now I had a thick VGA cable and a patchcord, instead of just one HDMI. Additionally and unsurprisingly, the live TV picture looked more like a 720p output, even though it was set to 1080p. A trained eye can spot the difference easily on a large screen TV. The VGA output (from the laptop) is converted to analog and sent to the TV where it is converted back to digital. This results in a noticeable loss of sharpness.

Then I retried the HDMI connection using the DVI PC port with the label “DVI PC”. Lo and behold, the W7 desktop fit perfectly on the TV display, in native 1080p. It looked crystal clear, with sharp fonts. But the RCA sound inputs on the TV did not work. DVI does not carry sound, hence the need for the sound cable just like VGA. I had assumed the Samsung HDMI port labled “DVI PC” was hardwired to ignore sound inputs thru the HDMI cable, so I was resigned to using sound cables. But the sound didn’t work. I could get it to work for a while by going into control panel -> sound and disenabling the headphone jack. But it wouldn’t work on the next reboot. I used an ipod to send an audio signal to the RCA inputs and it still would not work. This indicated that the problem was with the TV and not the laptop headphone jack. Those sound inputs were simply not working as designed and documented. A great picture is useless without sound. So I had to find a way around this problem.

On a lark, I started playing around with the HDMI firmware labels on the Samsung. There were two labels for PC inputs, DVI PC and PC. The HDMI port I was using was labeled as “DVI PC” on both the back of the TV and the firmware. When switching the firmware labels from PC or “DVI PC” to anything else, you could actually see the screen size change to overscan and the fonts become smudgy. I found this fascinating.

I then tried the label PC instead of “DVI PC”, because I wondered what the functional difference was between PC and PC-DVI in the label drop-down list. There had to be some difference between them, otherwise why would there be two similar but not identical entries? I also changed the default sound device on the PC from the Conexent analog sound to the AMD HD sound because I had a hunch the difference had something to do with the sound. And sure enough, the sound then came on thru the HDMI port.

The lesson here is when setting up an HTPC using HDMI, it’s very important to use the proper HDMI port on the TV and to make sure the port label is properly set, because the firmware label can affect the behavior of the HDMI port.

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