Revision as of 20:30, 22 January 2007

Adapting the frequencies

To use a TV screen as monitor, the 'Monitor' section in xorg.conf (usually in /etc/X11) should be adapted to allow refresh rates that can be understand by the TV encoder chip of your videocard. Normally this will be 60.0 Hz, also in Europe for the PAL TV-standard! I repeat, you need the value for the TV-encoder on the videocard. (in fact, the TV-encoder chip has internal instructions how to handle the rates for your TV. This is what TV-standards like PAL and NTSC are designed for ;-)

As sample I provide you with the 'Monitor' section of my xorg.conf:

Section "Monitor"
        Identifier   "Generic Monitor"
        HorizSync    30 - 50
        VertRefresh  60.0
EndSection

This will result in all common resolutions (1024x768, 800x600, 720x576 and 640x480) to work at the common frequency of 60Hz. Please note that TV standards understand resolutions at a 4x3 Aspect_ratio; For a discussion about wide-screen see below!

Wide-screen Television

Nowadays, many people have a wide-screen television set.

Compared to a computer monitor, where a wide-screen monitor also has a wide-screen resolution, the wide-screen TV uses always the same resolution. In fact, that resolution is always a resolution what is in fact a 4x3 Aspect_ratio resolution. The wide-screen TV set uses a technique called 'anamorphic imaging' to 'stretch' the actual image to a wide-screen view.

For people who want to know how this technique works, just power-on the wide-screen television, and look for a football/soccer game with a round ball. Press the buttons on your Remote Control to change the picture to wide-screen (real 16x9 Aspect_ratio!) format, and the ball becomes somewhat stretched; in fact it looks like if the ball is oval, or more like a rugby ball. Compared to that, a real 16x9 wide-screen broadcast with rugby will present you with a compressed (or 'sandwiched') ball if watched in the 4x3 Aspect_ratio setting of the television. That ball will look like a football/soccer ball instead...

Now back to our NVidia video-card: the TV encoder chip on the video-card always encodes an actual 4x3 Aspect_ratio resolution. If you want to enable a wide-screen view, just keep the 4x3 Aspect_ratio resolution setting, like 800x600 or one of the others mentioned above! Then select a theme which was designed for wide-screen use, normally a theme with a name which ends up in '-wide'. When viewed in the 4x3 Aspect_ratio setting on the television (or letterbox), the theme will look like 'sandwiched', smaller than it should be. Again as with the test explained above, please use your Remote Control to switch to the real 16x9 Aspect_ratio, and the theme will appear as if your television natively supports wide-screen. Thanks to the anamorphic technique which is used to stretch the compressed/sandwiched images back to their real size...

But, in short, don't try to get a wide-screen resolution working with TV out; just keep the standard 4x3 Aspect_ratio resolutions, and use a wide-screen time and the wide-screen button on the Remote :-)