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Thread: Brightness?

  1. #1
    Junior Member
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    May 2008
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    Brightness?

    Just been going through the OpenWF Display spec and just noticed that there doesn't appear to be any API to control the brightness of a WFDPort (or rather the display hardware connected to a WFDPort of type WFD_PORT_TYPE_INTERNAL)? The closest I can see is WFD_PORT_POWER_MODE which allows toggling between WFD_POWER_MODE_ON and WFD_POWER_MODE_LIMITED_USE, which I guess could be used to "dim" the display.. have I missed something?

  2. #2
    Senior Member
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    Re: Brightness?

    Yes, we notice that too. Brightness, hue, saturation would be nice pipeline properties.

  3. #3
    Junior Member
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    Re: Brightness?

    I was thinking more along the lines of a port attribute to control the brightness of the LCD backlight. Do you mean adjusting the connected display's hue/brightness/saturation? Do you know if it is possible to signal such settings via DVI or HDMI? Or did you mean running the image through a hw filter and adjust the brightness/hue/saturation of the image data before it is sent to the display hardware?

  4. #4
    Senior Member
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    Re: Brightness?

    I was suggesting those properties for pipelines as some layers on display controllers support them. I'm less familiar with ports, but I have heard of backlights. I don't think the other properties I mentioned would be applicable to ports.

  5. #5

    Re: Brightness?

    Don't forget very useful gamma correction/targeting stuff.
    Can make a big difference in color-sensitive applications.
    Artistically oriented or graphic designer work.

  6. #6
    Junior Member
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    Re: Brightness?

    The spec allows you to set gamma correction to a port using the WFD_PORT_GAMMA.

  7. #7
    Junior Member
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    Re: Brightness?

    The OpenWF working group did not address the idea of display backlight control on purpose. It was discussed, but there are many different backlight arrangements and it was unclear whether the backlight controlling entity was the window system, the target user for the API. Due to this the working group decided that display backlight control was outside of the original scope of the API.

    If there is a strong feeling that control of display backlights should be part of this API, I would suggest creating a extension for such an addition. If the extension becomes a very common addition to an OpenWF implementation, then it may be included as an official part of the a future revision.

    FYI, none of the WFD_POWER_MODE_* values were intended to address the idea of backlight control. The LIMITED_USE mode was intended for use cases such as default clock display, which only needs to be updated occasionally. The display update hardware could be turned off most of the time and conserve power.

    Concerning color brightness, hue, & saturation, the gamma setting should be able to address some of these. Beyond that, again I'd suggest creating an extension so the working group can see what sort of additions would be needed and to see if these are commonly needed.

  8. #8
    Junior Member
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    May 2008
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    Re: Brightness?

    Yup, I guess it makes sense to not stick it in if it's not certain it belongs in OpenWF. Thanks for clearing the matter up, especially what WFD_POWER_CONTROL was designed for.

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