locked
Flickering when changing multiple display settings

    Question

  • Hi folks,

    there is something that has been bugging me for quite some time now. When I plug in an HDMI cable to connect my laptop to my TV (assuming the display settings are set to something like: "Duplicate"), my laptop screen gets black and the audio stops playing for a second, before the image is displayed on both screens.

    When pressing Windows Key + P to change the display settings and changing to something like "Computer only" or "Display only" the same happens again: Both screens get black for a second before the image shows up again on the selected screen.

    My question is (without any knowledge of the underlying technology): Is it possible to make this a smoother experience, like letting the PC make up its mind beforehand and then smoothly switching the screen that has to change while leaving the screen that doesn't have to change untouched, so that no more flickering occurs?

    This would be much more 21st Century and make connecting a TV a real joy!

    Does anyone have a better understanding of the technology to explain why it is currently behaving as it does and whether there might be ways to change it?

    Sunday, October 16, 2011 5:32 PM

Answers

  • Hey Plot-paris,

     

    I see the same behavior when changing between displays (I tested using the Windows + P shortcut to change between Extend, Projector only, etc.).

     

    Here is a general overview of what is happening behind the scenes.

    Your TV is constantly waiting for a signal with the display of No Signal or similar. Once a signal is received the TV is told what resolution that signal is coming in. If the resolution is within the limits of what the TV can display it displays the image.

    Your laptop has a video card either integrated or dedicated that provides a video signal to your laptop screen (which is essentially a connected monitor). The HDMI output is a second connection to your video card.

    When the resolution or display configuration (Monitor only, Duplicate, Extend, Projector only, etc.) changes, the video output must stop sending the current signal and send a new signal with the new resolution information to all display devices connected at that time that will be used (laptop screen and TV in this case). This is where you see the screen go blank for a moment as one signal ends and another is made.

     

    Hope that helps.


    Steven
    Saturday, October 22, 2011 11:41 PM
    Moderator

All replies

  • Are you running Windows Developer Preview when the flickering occurs?
    Have you updated your video drivers to the latest Windows 7 drivers from the manufacturer's website?
    Is User Account Control enabled or disabled?

     


    Marilyn
    Sunday, October 16, 2011 8:15 PM
    Moderator
  • I am indeed running Windows Developer Preview. But the exact same behavior also happens with Windows 7. Actually it is not so much a flickering (maybe that was a bad choice of words by me), but simply the screen turning black and the audio stopping for a brief moment during the transition.

    So its actually not a big deal and nothing that will reduce usability at all. Its just my aesthetic mind crying out. It simply would be so much cooler, if the transition went smoothly (so if I switched from "Computer Only" display setting to "Duplicate", I would never loose the image on my laptop screen, not even for a fraction of a second...) 

    Sunday, October 16, 2011 8:58 PM
  • You may be seeing the User Account Control (UAC) when the dsiplay turns black.
    Disable the User Control Account settings to see if it makes a dfifference.

    Go to Start screen, type in User Account Control. Click on Settings.
    Click on "Change User Account Control settings".
    This brings up the UAC dialog box. By default, it is set to: Notify me only when programs try to make changes to my computer.
    Move the slider down to Never Notify. This setting is not recommended, but I want to see if this is what is making your screen go to black.

    Then test with your HDMI cable and connect to your TV.

    Please reply back with an update on your status.


    Marilyn
    Tuesday, October 18, 2011 8:28 PM
    Moderator
  • Tried it with changed User Account Control settings. Didn't change anything. The screen still turns black for about a second...
    Wednesday, October 19, 2011 10:10 AM
  • Hello, Marilyn,

    I thought as though setting UAC to Never Notify would render any Metro app unusable, I am wrong?

    Thank you.


    Well this is the world we live in And these are the hands we're given...
    Wednesday, October 19, 2011 11:04 AM
  • You are correct about disabling UAC and Metro Apps. I was just troubleshooting to see if UAC was causing the flickering and black screen as the User was connecting to a TV. I didn't recommend keeping UAC disabled.
    Marilyn
    Thursday, October 20, 2011 2:50 AM
    Moderator
  • Hey Plot-paris,

     

    I see the same behavior when changing between displays (I tested using the Windows + P shortcut to change between Extend, Projector only, etc.).

     

    Here is a general overview of what is happening behind the scenes.

    Your TV is constantly waiting for a signal with the display of No Signal or similar. Once a signal is received the TV is told what resolution that signal is coming in. If the resolution is within the limits of what the TV can display it displays the image.

    Your laptop has a video card either integrated or dedicated that provides a video signal to your laptop screen (which is essentially a connected monitor). The HDMI output is a second connection to your video card.

    When the resolution or display configuration (Monitor only, Duplicate, Extend, Projector only, etc.) changes, the video output must stop sending the current signal and send a new signal with the new resolution information to all display devices connected at that time that will be used (laptop screen and TV in this case). This is where you see the screen go blank for a moment as one signal ends and another is made.

     

    Hope that helps.


    Steven
    Saturday, October 22, 2011 11:41 PM
    Moderator
  • Thanks for the good explanation, Steven.

    So the problem lies with the graphics card redrawing the whole screen (sometimes even in a different resolution). Then the only way would be to get the graphics card keep the current image while simultaneously redrawing the new one and only switching images, once everything is ready... And thats probably too complicated to achieve, I guess?

    So I will have to wait a few more years for my bright, zippy, screen changing future... ;-)

    Tuesday, October 25, 2011 5:38 AM