[mythtv-users] Colour/contrast

Graeme Wilford gwilford at gmail.com
Tue Sep 12 10:12:36 EDT 2006

On 12/09/06, Tom Lawton <tlawton at gmx.de> wrote:
> Hi,
>   I've been using mythtv for a while on a PC setup and finally have
> had permission to connect it up to the proper TV. I'm watching DVB in
> the UK, using an Intel Core Duo HTPC (Intel graphics 945GM, using
> i810 driver, connected via d-sub VGA to an LG 37" LCD TV).
> My main problem is that the picture isn't as good as using the TV's
> own tuner. Part of this is probably the TV's various enhancement
> algorithms, which don't seem to be active on the RGB input; but there
> are other problems. Reds particularly can look almost luminous, and
> hilights often look bleached.
>   With MythTV I can adjust the brightness (currently on 43%) but
> reducing it just makes the picture look dark. I can adjust the
> contrast (currently on 19%) but it makes the picture look overdone,
> or very weird if it's reduced. Attempts to change colour or hue just
> make it jump to '-1%' and won't actually do anything.
>   Any advice on sorting out the picture quality?

This isn't a solution but may shed light on the colour/hue, try running:
% xvinfo |grep XV_

make sure that $DISPLAY is set to your Xserver feeding the VGA
(usually :0) to avoid querying a remote Xserver that you happen to be
displaying on...

I see this on an ATI 9100 IGP:
[mythtv at mythtv1 ~]$ xvinfo |grep XV_
      "XV_DEVICE_ID" (range 0 to -1)
      "XV_LOCATION_ID" (range 0 to -1)
      "XV_INSTANCE_ID" (range 0 to -1)
      "XV_DUMP_STATUS" (range 0 to 1)
      "XV_SET_DEFAULTS" (range 0 to 1)
      "XV_AUTOPAINT_COLORKEY" (range 0 to 1)
      "XV_COLORKEY" (range 0 to -1)
      "XV_DOUBLE_BUFFER" (range 0 to 1)
      "XV_OVERLAY_ALPHA" (range 0 to 255)
      "XV_GRAPHICS_ALPHA" (range 0 to 255)
      "XV_ALPHA_MODE" (range 0 to 1)
      "XV_BRIGHTNESS" (range -1000 to 1000)
      "XV_CONTRAST" (range -1000 to 1000)
      "XV_SATURATION" (range -1000 to 1000)
      "XV_COLOR" (range -1000 to 1000)
      "XV_HUE" (range -1000 to 1000)
      "XV_RED_INTENSITY" (range -1000 to 1000)
      "XV_GREEN_INTENSITY" (range -1000 to 1000)
      "XV_BLUE_INTENSITY" (range -1000 to 1000)
      "XV_SWITCHCRT" (range 0 to 1)
      "XV_GAMMA" (range 100 to 10000)
      "XV_COLORSPACE" (range 0 to 1)

See what range XV_COLOR and XV_HUE give you on your i810.

Me at google | MythTV blog: http://mezzanines.blogspot.com/

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