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  1. #1
    Registered User
    Join Date
    Jul 2006
    Location
    Wieliczka, Poland
    Posts
    64

    Question LCD graphics problem

    I have a problem on N82 with LCD screen refresh rate (also checked on 5500, and almost same situation occurs). In my app I'm moving a bitmap from left to right with speed 30fps (one frame 33 ms, but I also tried slower). To visualize my problem I created small bitmaps similar to that I'm using in my app:
    img.gif
    On this image I'm moving small bitmap with background color TRgb( 128, 64, 0 ); and line color TRgb( 128, 0, 0 ); 3 times by 1 pixel in left direction. To move bitmap I'm using double buffering with offscreen bitmap and Direct Screen Access API and the same problem is when using anti tearing API (Direct Screen Bitmap).
    On first column I created bitmaps that reflects what I'm seeing on phone screen and on the second column how this should look like.
    FRAME 1 is a steady state
    FRAME 2 is bitmap moved left by 1 pixel
    FRAME 3 is bitmap moved left by 1 pixel
    FRAME 4 is bitmap moved left by 1 pixel
    FRAME 5,6,7 is a steady state

    On screen we can see some kind of streak or trace left by previous frame.
    I think differences between screen and memory is caused by low refresh rate of LCD. Using other colors for background and lines reduces this effect, but not solve problem.

    Is there any algorithm or method to avoid this situation?
    Last edited by mstrug; 2008-11-24 at 16:23.

  2. #2
    Nokia Developer Moderator
    Join Date
    Feb 2006
    Location
    Oslo, Norway
    Posts
    28,684

    Re: LCD graphics problem

    To be honest I do not know these two particular models. However other devices I know and use (3650, N80, N81, N91, N93, N95, E60, E90) refresh their screen from top to bottom, thus jitter/tear in horizontal lines can not occur. And I can get 71 FPS without any visible distortion.
    Are you sure about that your bitmap really has the right content?

  3. #3
    Registered User
    Join Date
    Jul 2006
    Location
    Wieliczka, Poland
    Posts
    64

    Re: LCD graphics problem

    I created simple bitmap and changed it in background bitmap of Scalable Screen Drawing example (Original link). Here is the sis file:
    ScalableScreenDrawing_S60_3rd_Ed_v_1_3_0.sisx
    and here is bitmap I used:
    background.bmp
    You can install and turn on scrolling background, and I'm sure you will see the unwanted motion-blur effect.

  4. #4
    Nokia Developer Moderator
    Join Date
    Feb 2006
    Location
    Oslo, Norway
    Posts
    28,684

    Re: LCD graphics problem

    I get USER-EXEC 3 panic with your code. However since it has turned out that you are using the scalable example, I agree, the scrolling jumps a bit sometimes. But it is not an issue of the devices, and it is not a motion blur, it is rather about dropped frames.
    Optimizing the code may help.

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