EVAL-ADV7842-7511 Noise Interference lines

Hi, I have a EVAL-ADV7842-7511 Board which I'm using to decode CVBS signal from a Laserdisc player.

I have an issue where I'm seeing faint diagonal lines across the image. These are present on all of the input formats 10Bit, 24Bit and 36Bit and is also present on the s-video input. 

It it looks almost like interference. I've tried multiple cables and players and all produce the same results.

Any idea what is causing this?

many thanks

ken

Parents
  • I also had the problem of diagonal interference lines with the scripts. Turns out that the script didn't enable the anti aliasing filter. So I just had to enable them:

    4C 05 0F

  • Hi vhs_inter. I enabled the anti aliasing filter by changing to "0F" like you said. After I made the change the lines/noise immediately went away. My laserdisc player was idle so I had a black image on my tv which made it easy to see the change. I'm viewing a letterbox widescreen laserdisc, and once I push play I can see the noise again in the upper & lower areas of the black bars. Is it possible that once a signal is introduced, it disables the anti aliasing filter? or do you think it's just the source material of the analog laserdisc?

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    •  Analog Employees 
    on May 10, 2021 2:00 PM in reply to clashradio

    Hi,

      Please let us know, which part are you using whether -P part or Non-P part.

      Have you verified with laser disk source and sink by connecting directly (i.e Back to Back/ Direct Connection ) without board ?

    Thanks,

    Poornima

  • Hi poonima,

    My board is Non P.

    I do not get any lines or video noise when connecting the laserdisc player directly to a tv monitor. However, when connecting direct to a tv, I use CVBS from the player. When I have the 7842 board in the chain, obvisoluy I'm using HDMI output which seems a little brighter and maybe easier to see any noise that's inherent in the video source. When I lower the brightness I can't see the noise depending on how low I adjust..

    One trick that's helped is turn in the anti aliasing filter on by using code 4C 05 0F. It would be nice if I could find another register to lower the video noise.

    Thanks~ Jason

Reply
  • Hi poonima,

    My board is Non P.

    I do not get any lines or video noise when connecting the laserdisc player directly to a tv monitor. However, when connecting direct to a tv, I use CVBS from the player. When I have the 7842 board in the chain, obvisoluy I'm using HDMI output which seems a little brighter and maybe easier to see any noise that's inherent in the video source. When I lower the brightness I can't see the noise depending on how low I adjust..

    One trick that's helped is turn in the anti aliasing filter on by using code 4C 05 0F. It would be nice if I could find another register to lower the video noise.

    Thanks~ Jason

Children
  • 0
    •  Analog Employees 
    on May 11, 2021 4:37 PM in reply to clashradio

    Hi,

     Y shaping filter block is a programmable low pass filter with a wide variety of responses. It can be used to selectively reduce the bandwidth of the luma video signal. For example in some video sources that contain high frequency noise, reducing the bandwidth of the luma signal improves visual picture quality.

     Please note that if the input signals in CVBS format, the luma shaping filters play an important role in removing the chroma component from a composite signal. YC separation must aim for the best possible crosstalk reduction

     So Please configure the Y & C filter into manual mode and try several different setting and let us know the result.

     Refer Page 114 at  https://www.analog.com/media/en/technical-documentation/user-guides/UG-214.pdf

     Please create new thread, Since it is difficult for tracking.

    Thanks,

    Poornima