Connecting your KnoppMyth box to a HDTV

With a high-definition television, you can get a much better, much-higher-resolution display of your MythTV material than with a standard TV-out port. An HDTV is effectively a computer monitor, capable of running in both progressive and interlaced modes, at resolutions up to 1080 horizontal lines of resolution.

Here are some of the steps involved.

1. Determine how you will connect your computer to your HDTV. Not all HDTVs have DVI inputs; not all MythTV computers have DVI outputs. Even if your HDTV has DVI inputs, some apparently aren't meant to work with computer outputs. (I'm unclear on whether that can be overcome with proper modelines)

So, best case scenario is: your video card or on-board video has DVI output, your HDTV has a computer-compatible DVI input, and all you'll need is a DVI cable. If your HDTV will accept an analog DVI input, your computer doesn't need a DVI output: you can get a VGA to DVI cable that will work.

Worst case scenario is still not that bad, and involves converting your video card's VGA or DVI output to an analog component signal. Most (all?) HDTVs support HD component inputs.

The two VGA to component converters I see mentioned most frequently are the Audio Authority 9A60, and the Key Digital KD-VTCA3. Another offering is from Crescendo Systems, which seems to have a following on AVSForum. ATI also sells a DVI to component adapter for its All In Wonder cards. (note the ati converter will not work with linux, at least not till ATI releases a driver that supports it.)

A few sources for these converters online are http://www.pacificcable.com, http://www.digitalconnection.com/, http://www.copperbox.com/, and http://mythic.tv ... PacificCable?.com, DigitalConnection? and CopperBox also sell the appropriate component cables for connecting the converter to your HDTV. The converters themselves are $105 to $178, including shipping.

2. Read read read. There is a ton of information out there, primarily on how to use a Windows program called Powerstrip. There is a similar but less-functional program that is included with KnoppMyth called xvidtune. You might be able to do much of this with xvidtune if you have a very good understanding of modelines and how to generate them, as well as technical specs of your video card and your HDTV.

Some of the better tutorials out there include:

http://www.digitalconnection.com/Support/cliffnotes_17.htm
http://www.htpcnews.com/main.php?id=powerstrip_guide_1
http://www.ramelectronics.net/html/powerstrip.html
http://wilsonet.com/mythtv/mythhd.php
http://www.linuxis.us/linux/media/howto/linux-htpc/video_card_configuration.html

3. Add a new modeline to your XF86Config-4 file.

First, connect a regular VGA monitor to your MythTV box before trying out new modelines. It's a much better idea to destroy a $100 monitor with a bad modeline than a $3000 HDTV.

There are three ways of potentially getting a new modeline that works with your HDTV: the lazy-but-hope-you're lucky way, the Powerstrip way, and the do-it-yourself Linux way.

3a. Lazy-but-hope-you're-lucky way: use someone else's modeline and hope it works for you. In Jarod Wilson's excellent HOWTO on connecting to an HDTV, he includes a link to his XF86Config file, and says that others have had good luck using his settings. Note that you should probably not use his file as-is: the first time I tried to do so it killed my mouse and keyboard. Therefore, edit your XF86Config file (located at /etc/X11/XF86Config-4) and use only his "Monitor" section, adjusting vendor and model name appropriately.

Another excellent description is in the Linux HTPC HowTo by Brandon Beattie. He has a page on the configuration of modelines for ATSC (HDTV) modes and resolutions. The modelines worked quite well on a Pioneer projection HDTV with VGA input.

There are also forums at the AVS website (http://www.avsforum.com/) and the Powerstrip website (http://www.entechtaiwan.net/forums/) where people have posted their modelines for their model of HDTV. If your model appears there, their modelines may well work with your video card.

3b. Using Powerstrip. You have to use Windows to go this route. As Jarod recommends, your best bet is to pull your hard drive that has your MythTV/Linux install on it, put in a different hard drive, and install Windows, the latest video drivers, and Powerstrip on it. Use Powerstrip to load and try out various preset HDTV settings. Once you find some that work, you can copy the settings to your clipboard, then paste them into a text document. Powerstrip builds an XF86-compatible modeline that you can copy and paste into the XF86Config-4 file. Get the text file onto a USB flash drive, or email it to yourself, then swap the Windows drive with your MythTV install, restart your computer, and edit your XF86Config-4 file with the new modelines you've generated.

A slightly different experience: Using my Windows XP computer, I connected the TV to DVI and left the monitor connected to normal VGA. In Display Properties, check the "Extend Desktop" checkbox, then use PowerStrip? to modify the TV setup. Getting a working configuration in Windows took almost no time. Note that X and the nVidia driver expects a ModeLine? divisible by 8. My initial ModeLine?--which worked fine in Windows--failed in X for this reason. Bump the Vertical Total and Horizontal Total in PowerStrip? to get to a ModeLine? divisible by 8 that works in Windows, and it should work in X, too. At least, that's my experience. --Dan Wolfgang, April 6, 2006

From personal experience, this method is very annoying with a small form factor MythTV box. :-/ Obviously, if you have enough room in your box, you can easily leave the Windows drive installed, or you can even set up a dual-boot system.

3c. Do it yourself modelines. You can probably build modelines via Linux, but it also requires a thorough understanding of your video card's capabilities as well as your HDTV's capabilities (my HDTV did not have very good documentation on its sync and refresh rates), not to mention how a modeline works. To read more about how modelines work...

http://en.tldp.org/HOWTO/XFree86-Video-Timings-HOWTO/
http://www.mythtv.info/moin.cgi/ModeLinesHowTo
http://www.mythtv.info/moin.cgi/ModeLinesHowTo_2fDoItByHand

As mentioned before, there is a program called xvidtune that can adjust your X modeline on the fly, as well as let you paste a modeline into it. Once you have adjusted all the settings appropriately, it will list out the corresponding modeline. Enter that info into your XF86Config-4 file. There is also a program called videogen that can generate a modeline. There are even online scripts can build a modeline for you...

http://xtiming.sourceforge.net/cgi-bin/xtiming.pl

Once your modelines are in place via methods A, B, or C above, try them with your monitor. If they work, then try them with your HDTV. Start with "simple" modes, like 480p, then work up to 540p, 720p and 1080i.

As with all the other pages out there, a word of warning: incorrect modelines can and will burn out a TV set's electronics! Be sure and turn off your TV ASAP if a modeline doesn't work. Or, to save all that turn-on and turn-off stress, quickly switch the TV to another input and switch it back when you're ready to test again. Refer to /var/log/XFree86-4.0.log for what the problem might be.

4. Tune your settings. The biggest problem at this point is usually overscan. Too much of the screen may be clipped off left, right, top, or bottom. If you can tweak your modeline with xvidtune or Powerstrip, you should be able to adjust for overscan a bit.

However, many people just run in a lower resolution within the appropriate timings. The Jarod Wilson and htpcnews links found above discuss how to do this: it basically involves leaving the overall timings alone, and just reducing the pixels visible within that timing. For instance, where my 960x540p timing had too much vertical overscan, using the same timing with a 960x480 resolution worked perfectly.

Modeline "1280x720@60" 73.78 1280 1312 1592 1624 720 735 742 757