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Handling TVP5150AM1 color flickering

Other Parts Discussed in Thread: TVP5150AM1, TVP5160, TVP5146, TVP5147

I am developing an UVC solution using TVP5150AM1. I am successfully getting NTSC video but there are color issues. When there's white text on black

background visible amount of color flickering and false color  happens as seen from the image.

I've tried lowering saturation with considerable success but color quality is then sacrificed. Also, I have a pull-up resistor on pin 27 and after startup I enable VBLK so it should probably not be and issue. Is there something else I can do? I am using comb filters enabled by default

  • This is a limitation of the NTSC/PAL composite video signals.

    There are some things you can do to mitigate the problem but it is a fundamental issue of CVBS.

    If you need higher quality then you can switch to a higher quality video decoder. If white on black text (or other primarily static images) then you would really need to use a 3D comb filter (such as the TVP5160). Other options are the TVP5147 or TVP5146 depending on the quality level you need.

    Google "ntsc color leak", "ntsc color bleed", "ntsc color artifacts", "ntsc cross color" etc... for more information.

    Fundamentally though it is caused by the same frequency band being used to carry both luma information (sharpness) and modulated color information. The complementary issue is called "dot crawl" where color transitions cause luma transitions which appear as moving, or "hanging" dots at color transitions.

    You can try switching to a chroma trap filer setting but you will loose some sharpness.

    BR,

    Steve

  • Tried trap filter but results were even worse. Will probably consider decoder with 3D comb filter if I can find one that is recommended for new designs


    Thank you

  • Yep, a trap filter is the simplest filter but in some applications its characteristics are more suitable.

    There is always a trade-off between spatial characteristics, temporal characteristics, luma, chroma, cost, size etc...

    BR,

    Steve