Using ADV7184 SCART Overlay with ADV7341, isolated pixels are faint

Hi,

I am using the ADV7184 back to back with an ADV7341, to add an RGB overlay over CVBS. I find that when pixels are isolated, with no adjacent pixels in the same line, they are considerably dimmer. This means that vertical lines appear dark and text is of inconsistent brightness.

I thought this may be the the encoder attempting to filter noise, so I experimented with various DNR gain levels and filters but I did not notice a difference.

Here is an example, note how the vertical and diagonal lines in the image are much darker than the horizontal lines.

Vertical and horizontal lines

Is there some way to avoid or mitigate this effect, and have all overlay pixels of the same brightness?

Thanks!

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  • Hi,

    ADV7184 fast blanking could be used to overlay with dynamic switching using the FB pin.
    For that to work both the RGB and the NTSC/PAL must have identical timings.
    It may be the reason by without setting the FB pin to a logic "1" for every pixel you want blended from RGB onto the CVBS.
    And also refer Pages 16-18 for more information the ADV7184 data sheet.

    Thanks,

    Poornima

Reply
  • Hi,

    ADV7184 fast blanking could be used to overlay with dynamic switching using the FB pin.
    For that to work both the RGB and the NTSC/PAL must have identical timings.
    It may be the reason by without setting the FB pin to a logic "1" for every pixel you want blended from RGB onto the CVBS.
    And also refer Pages 16-18 for more information the ADV7184 data sheet.

    Thanks,

    Poornima

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