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Black line on the Output from the ADV7282-M

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This FAQ was generated from the following discussion: Black line on the Output from the ADV7282-M

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Anonymous
  • Dear expert

            Our back end process can't do I2P process,I disabled ADV7282-M I2P function,

    A balck line shown in a field.

             You can get video(3.0MB) from following address link:

             https://www.sendspace.com/file/xlrigl

  • Dear expert

    Local Analog engineer Bob Gao sent me some pictures.
    It showed that image had 507 lines whether ADV7282-M output BT656-3 or BT656-4 format based 480P.

    Everything is normal in free-run mode,but there is a black line at botton of image when using a extern analog camera,DVD device or TV Pattern generator.
    I want to make sure that if this issue has occurred after I2P process.
    Register 0x12 states that sometimes the ADV7282-M receives CVBS video of non-standard horizontal line length,so an error occurred during the I2P process.

    How can  I confirm?

  • Dear expert

          Could you recreate this issue in the lab?

           I think it is difficult  to implement a detection mechanism in back end processor.

           I'am checking it,thanks!

    •  Analog Employees 
    in reply to guoyuanyuan@longcheer.net

    Hello Yuanyuan Guo,

    Thanks for reading those registers. Register 0x12 states that sometimes the ADV7282-M receives CVBS video of non-standard horizontal line length. This may be related to your issue.

    You may be correct in this issue being due to a screen resolution issue. I will run some experiments in the lab to see if I can recreate your issue.

    Note that when a CVBS source is disconnected from the ADV7282-M it will output a few frames of video of non-standard length (i.e. greater than 576 lines lines of video) until it enters free-run mode. These non-standard line lengths can sometimes cause input buffers on the MIPI receiving device to overflow.

    I would advise implementing a line counter or similar control loop, to prevent issues in your back end processor.

    regards,

    Robert

  • Dear expert

         I think this may be parameters settings issue, I did a set of experiments as follows:

         In order for the receiver to correctly receive video data, It is necessary to tell  the szie of  video data,also included video data + blanking data in platform side(receiver).

        

    ADV7282-M output format      video data        video data + blanking data       test results

               BT656-4                          1440x487                     1728x525                       Images is displayed correctly(no 10lines dark and  a black line) ,but  a error is receiver has received the 507 lines.

               BT656-4                          1440x507                     1728x525                       there is a black line at botton of image,no any software error

               BT656-3                          1440x487                     1728x525                      more than 10 dark lines at top of image,and  a error is receiver has received the 507 lines

               BT656-3                         1440x507                     1728x525                       10 dark lines at botton of image,no any software error

               Image is displayed correctly in the first set of experiments,and only has a software error.

               The ADV7282-M outputs 487 lines of video in BT656-4 progressive NTSC mode,Why receiver does receive is 507 lines? I initialize ADV7282-M wiht parameters of "I2P AUTODETECT CVBS Single Ended In Ain 1, 480p/576p MIPI Out", Is it related to this settings?          

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