Difference between revisions of "Video display card"
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Revision as of 17:57, 15 August 2006
Video display cards provide the graphical output for MythTV and modules (compared to video capture cards which provide input). 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.
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
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.