Difference between revisions of "Video display card"

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Revision as of 06:05, 26 January 2006

Video Cards

Video cards provide the graphical interface for MythTV and modules. A standard video card will output all display to a VGA port to display on a standard computer monitor. Most MythTV users are looking to have this display outputted to a television or other display device. This can be accomplished by either using a card that has integrated TV-out capabilities or using a VGA to NTSC/PAL (television) converter.


NTSC/PAL converter

I can recommend the TView Micro as a device that I have used with success with MythTV. Instead of relying on driver support and extra hardware to provide video out, I opted for this device which handles VGA resolutions and requires only a standard video card. If you find a video card with MPEG-2 acceleration or other features, it is easy to take advantage of them since you are not relying on any TV out capabilities, just standard VGA. --Kevin Kuphal

Display Quality

It has been noted on the mailing list at http://www.gossamer-threads.com/lists/mythtv/users/68744 that since the 0.14 release of MythTV there have been some fixes and enhancements for getting the picture quality of MythTV near the quality you see of your standard television:

There is a new filter added after the 0.14 release in CVS that
fixes an outright mistake for bttv luma. It also has parameters
that allow you to make further adjustments that you can't do for
the hardware cards. I've played with this over the past few months.
By comparing direct cable on one input and myth on another, I've
got the color reproduction almost identical. Even though the
myth input is a little fuzzier, the picture is otherwise as
vivid. To set these parameters, run your mysql client and
enter these two lines.

update channel set contrast=21500,brightness=37500,colour=32768,hue=32768;
update channel set videofilters='adjust=34:253:1.0:23:232:1.0';

If your worried that you might have to undo this, these will
reset the defaults:

update channel set contrast=32768,brightness=32768,colour=32768,hue=32768;
update channel set videofilters='';

Also, especially if you have an AverTV card, they tend to over-
saturate quite a bit by default. Hauppage tend to under-saturate.
If you have v4l2 support in your kernel, v4lctl can normalize
the chroma levels with Automatic Gain Control (AGC).

: bjm@moktoo ; v4lctl -c /dev/video0 setattr 'chroma agc' on
: bjm@moktoo ; v4lctl -c /dev/video0 list
attribute  | type   | current | default | comment
norm       | choice | NTSC    | PAL     | PAL NTSC SECAM PAL-Nc PAL-M PAL-N NTSC-JP PAL-60
input      | choice | Televis | Televis | Television Composite1 S-Video
audio mode | choice | lang1   | mono    | mono stereo lang1 lang2
bright     | int    |   37500 |   32768 | range is 0 => 65535
contrast   | int    |   21500 |   32768 | range is 0 => 65535
color      | int    |   32768 |   32768 | range is 0 => 65535
hue        | int    |   32768 |   32768 | range is 0 => 65535
mute       | bool   | off     | off     |
chroma agc | bool   | on      | off     |
combfilter | bool   | off     | off     |
automute   | bool   | on      | off     |
luma decim | bool   | off     | off     |
agc crush  | bool   | on      | off     |
vcr hack   | bool   | off     | off     |
whitecrush | int    |     207 |     207 | range is 0 => 255
whitecrush | int    |     127 |     127 | range is 0 => 255

If your output is missing "chroma agc" and some of the others
then you do not have v4l2 support.