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Interlaced Graphics

Andrew Poole
Intellectual 570 points
Other Parts Discussed in Thread: OMAP3530

Hi,

I am using OpenVG to provide a graphics solution for Analogue TVs. My problem is that I see interlace flicker when outputting the video to a TV due to the intensity of a pixel on field 0 being significantly greater or less than the intensity of the pixel on field 1. I realise this is a 'feature' of interlaced scan monitors but after seeing graphics on TV and menus on DVD players etc, it must be possible to get a clear image free from any interlacing flicker.

Does anyone have any ideas on how to achieve this?

  • 0
    TI__Mastermind 43875 points

    Andrew,

    The only way to get rid of the flicker is to apply an anti-flicker filter.

    Basically this will effectively soften/smear the image vertically so that there are not any sharp differences between the 2 fields.

    This results in a loss of vertical definition, but does help reduce the flicker.

    Interlace flicker is usually only an issue when the display is a CRT based display and it is not usually an issue for modern displays based on LDC, plasma etc...

    the following wiki page does a good job of showing the implications.

    http://en.wikipedia.org/wiki/Interlaced_video

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Intellectual 570 points

    Hi Steve,

    Thank you for the quick reply. I take it the anti-flicker filtering is something that has to be applied external to the OMAP3530? Or is there a setting of the DSS that will apply such a filter? (I am using a CRT based display).

    Thanks,

     

    Andy

  • 0 in reply to Andrew Poole
    TI__Mastermind 43875 points

    OMAP has a filter built in which can be used (actually it is the same hardware as the scaler).

    It can only be used on the video path though, so if you are using a color indexed graphics mode you cannot use the filter.

    If you are using any of the other frame buffer formats (RGB or YUV) then you can actually use a video path in place of the graphics path and then utilize the scaler to do anti-flicker filtering.

    You do need to understand that the filtering is effectively done before blending, chroma keying etc... so if you are using any of those features the resultant image may still contain high frequency vertical components.

    BR,

    Steve