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TVP7002 video horizontal shaking

Steven Weng1
Expert 2200 points

Other Parts Discussed in Thread: TVP7002

Hi Sirs,

I have captured VGA input source via TVP7002.

I could distinguish what input resolution is and set the TVP7002 registers.

Everything seems OK but the captured video has horizontal-shaking at some VESA standard input.

After modifing H-PLL Phase Select register(0x04h in tvp7002),

For example 1080P60 VGA input,

I modified H-PLL Phase select register from 0x80 to 0x00 (180 degrees to 0 degrees)

The horizontal-shaking has improved!!

BTW, how to adjust the Phase select setting properly? any rules?

Thanks a lot!

Steven

  • 0
    TI__Mastermind 43875 points

    Steven,

    This is actually not a simple problem to solve.

    the TVP7002 can reliably lock to the horizontal sync pulses but there is no built in way to determine the correct sampling phase. This is really related to the video source and cable as much as to the TVP and you will need to determine exactly what your particular strategy/algorithm to obtain correct alignment and phase is.

    Please see the following post for more information...

    http://e2e.ti.com/support/data_converters/videoconverters/f/376/p/284760/1026283.aspx#1026283

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Expert 2200 points

    Hi Steve,

    Thanks a lot.

    As I know, it's a basic algorithm to obtain correct alignment that finds a non blanking pixel at each of the edges of the image.

    How about phase adjustment? Could you give me some directions?

    Thanks

    BR

    Steven

  • 0 in reply to Steven Weng1
    TI__Mastermind 43875 points

    Steven,

    There are lots of different ways thay different system developers implement, but basically something similar to the following...

    Monitor the left most pixel value then sweep the phase from min to max and look for the point when the pixel value appears becomes stable (this indicates that the sampling is looking at a part of the video that is not oscillating or in the over/undershoot region.

    Repeat the process for the right edge of the screen sweeping from max phase to min phase.

    The 'best' sample point is then likely to be the mid point between the two values.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Expert 2200 points

    Hi Steve,

    Very thanks for your help.

    It's useful for me. Thanks a lot.

    BR

    Steven