Getting black pixels on the right and the left of image on ADV7180 output

Hello,

we use an ADV7180 for getting digital image from analog PAL source (monochrome images). Test source is a Teletest Pro OZT1200 box, providing a video pattern with a grid.

Expecting digital format is 576 lines x 720 pixels. Image seems correctly received but we have a few unexpected constant black pixels (8bit hexa value near 10) on the left (6 pixels) and on the right (3 pixels). You can see the received image below, with vertical black bars on the left and right (areas have been red outlined by myself)

If we select a fully white image as source pattern, the pb is the same (still have the same nb of black pixels on the left and on the right of received image).

We have made a record of the source signal and the measured durations are always

for 1 video line = 64us

for active part in a single video line = 52.6us

for horizontal synchro part in a single video line = 11.4us

Could it be possible that the black pixels received on the left and right are part of the horinzontal synchro considered as active video part when converting ?

Also, as we use the ADV7180 without modifying default register values (the only command sent on i2c to ADV7180 is for selecting input in register 00 when starting video acquisition), could you tell me if this pb could come from a wrong setting of ADV7180 ? I have found in a document ADV7180 - Preliminary register settings recommandations Rev. PrA an example of CVBS autodetect script with many more i2c commands than perfomed by our application but I am a newcomer in video acquisition and do not understand if listed operations are useful for our acquisition process.

Thank you for your help.

  • +1
    •  Analog Employees 
    on Mar 23, 2021 2:50 PM

    Hi,

     Please make sure whether you are using PAL? Generally for NTSC input these black video being output at the left/Right of the screen.

     Also make sure with crystal clock (i.e) you are providing correct XTAL 28.6363,and your script selects 28.63636 crystal.

    Thanks,

    Poornima

  • Hello Poornima,

    thank you for this elements. Here are the checks made after your remarks about possible cause.

    For the video test box Teletest Pro OZT1200, its output is only CVBS PAL 1Vp-p, 75ohm, so no way to erroneously get a NTSC image (see https://www.teletest.tv/store/p4/Video_and_stereo_audio_test_generator_TELETEST_PRO.html).

    For the clock source XTAL, we use a TXC AM-28.63636MAGK-T, in a way that seems compliant with suggested arrangement of page 111 of ADV7180 datasheet (Rev J) = crystal close and on the same side of the PCB as ADV7180, with an expected capacitor loading value of 12pF (according to TXC), modified into 20pF after application of Analog Devices application note AN-1260.

    For the script, we do not write into register with address x1D, and ADV7180 indicates the default loaded value is right for selecting 28MHz external crystal

    So the problem seems to come from somewhere else. Could it come from another register setting ? As I said, our script only writes into register 0x00 for selecting active input channel, nothing else, all the others registers are left with default values.

    Thanks

  • Hello Poornima,

    thank you for this elements. Here are the checks made after your remarks about possible cause.

    For the video test box Teletest Pro OZT1200, its output is only CVBS PAL 1Vp-p, 75ohm, so no way to erroneously get a NTSC image (see https://www.teletest.tv/store/p4/Video_and_stereo_audio_test_generator_TELETEST_PRO.html).

    For the clock source XTAL, we use a TXC AM-28.63636MAGK-T, in a way that seems compliant with suggested arrangement of page 111 of ADV7180 datasheet (Rev J) = crystal close and on the same side of the PCB as ADV7180, with an expected capacitor loading value of 12pF (according to TXC), modified into 20pF after application of Analog Devices application note AN-1260.

    For the script, we do not write into register with address x1D, and ADV7180 indicates the default loaded value is right for selecting 28MHz external crystal

    So the problem seems to come from somewhere else. Could it come from another register setting ? As I said, our script only writes into register 0x00 for selecting active input channel, nothing else, all the others registers are left with default values.

    Thanks

  • 0
    •  Analog Employees 
    on Mar 26, 2021 1:05 PM in reply to expleo_tcou31

    Hi,

      Could you please try writing the 0x00 to User Sub map 2, register 0x84 and let us know the result.

      Please check with other sources also.

      If possible could you share your register dump.

    Thanks,

    Poornima

  • Hello Poormina,

    when you ask me to "check with other sources also", do you mean to set register 0x84 with values 0x01, 0x10 and 0x11 ? I should be able to run it this afternoon, so you will have it tomorrow.