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ADV7282A Flickering

Hello,

I are using adv7282a composite SDTV video decoder in my application.

The decoder hardware is designed according to datasheet references.

I fallowed the eval board scripts to configure adv7282a device, which we implemented is ;

:I2P - PAL In Ain1, YPbPr Out (576p EAV/SAV):
delay 10 ; Wait 10ms After Hardware Reset To Start I2C
42 0F 80 ; Reset ADV7282A
delay 10 ; Wait 10ms
42 0F 00 ; Exit Power Down Mode [ADV7282A writes begin]
42 52 CD ; AFE IBIAS
42 00 00 ; CVBS in on AIN1
42 0E 80 ; ADI Required Write
42 9C 00 ; Reset Current Clamp Circuitry [step1]
42 9C FF ; Reset Current Clamp Circuitry [step2]
42 0E 00 ; Enter User Sub Map
42 80 51 ; ADI Required Write
42 81 51 ; ADI Required Write
42 82 68 ; ADI Required Write
42 17 41 ; Enable SH1
42 03 0C ; Enable Pixel & Sync output drivers
42 04 07 ; Power-up INTRQ pad
42 13 00 ; Enable ADV7282A for 28_63636MHz crystal
42 1D 40 ; Enable LLC output driver
42 FD 84 ; Set VPP map address
84 A3 00 ; ADI Required Write [ADV7282A VPP writes begin]
84 5B 00 ; Enable Advanced Timing Mode
84 55 80 ; Enable the Deinterlacer for I2P [All ADV7282A Writes Finished]

But I have been struggling about getting the smooth and correct video output from the device.

I am facing with flickering at borderline test pattern and also while playing video,

but color bar and blue screen test patterns outputs are good.

I'm also adding video and images to this post to give you an idea.

Any help would be appreciated. 

adv7282aResults.zip

  

  • Hi,

    Please double check that you are using the recommended scripts, recommended schematics and layout.

    As per expert comment Unfortunately such jitter are expected from the ADV7280.
    There are two possible causes of these artifacts : interlaced to progressive conversion jitter or 2D comb artefacts.

    Interlaced to progressive conversion
    The I2P does contain a smoothing filter to minimise artefacts but some artefacts can still occur.

    2D Comb
    The ADV7180/ADV7182/ADV728x video decoders are designed to be low cost analog to digital video decoders and as such they only have 2D comb YC separation filters.
    2D comb filters are good at separating the luma and chroma information but artefacts such as the one you have highlighted are still possible.     

    Solutions :
    1) Use a deinterlacer in your back end processor rather than using the I2P block of the ADV7280. The backend processor will have to store an odd frame of video in a buffer, then store an even frame of video and then stitch these two frames together to generate a progressive field. This will minimise interlaced to progressive errors but will add a delay to your system.
    Be sure to introduce a line counter or similar software control to ensure that you do not get buffer overflows.
    2) Modify some of the registers in the ADV7280 to try and minimise 2D comb this artefacts for your system.
         Try reading the Chroma filter, Luma Filter, Chroma Transient Improvement, Digital Noise Reduction and Luma Peaking Filter, and Comb filter sections of the ADV728x hardware manual. You may get some improvement but you will never be totally able to remove 2D comb artefacts.

    3) Use an Analog Devices video decoder that uses a 3D comb filter e.g. ADV7842.
         3D comb will result in fewer artefacts output to the screen. However  a number of frames of video need to be stored      in an external SDRAM chip in order for the 3D comb filter to work. This will add a delay from inputted video to      outputted video.


    Thanks,

    Poornima

  • Hi ,

    Thank you for your quick response,

    I will check the 2D comb filters and test them again to minimize the artefacts.

    Also, I wonder why do I see the color bar test pattern correctly but not at the boundary box pattern

    and what are those reasons?

  • Hi,

      Your register configuration order seems differ from the reference script and also some register configuration missed from your end. Please configure according to the script exactly and let us know whether flicker issue has gone at 4774.ADV7280_CUST-VER.4.5.txt.zip - I2P - PAL In Ain1, YPrPb Out (576p EAV/SAV).

      Boundary Box Test pattern: Boundary box test pattern will display slightly differently on each system. This is because systems can be aligned slightly differently.

      Try programming the ADV7282A into free-run mode using the recommended free-run script and then write to User Map registers 0x8B and 0x8C.

       It is possible to compensate for this by writing to registers in the ADV728x. By writing to User Map registers 0x8B and 0x8C can move the white pixel border lines. Please refer below table,

      

    Thanks,

    Poornima

  • Hi

    I change the filters that you mantioned and nothing happened. I think adv7282a doing this filterings automaticly in the best optimized way.

    Also there are nothing about the 0x8B and 0x8C registers in the datasheet for borderline pixel movement.

    Datasheet link: adv7282a datasheet

    Even if this registers not exist in datasheet, I tried to change but not a single pixel movement happened.

    I think, I will try to implement other advices until find the solution.

    Thank you for advices.

  • Hi,

     Please refer below thread there Expert gave some suggestion regarding boundary box test pattern,

         https://ez.analog.com/video/f/q-a/8004/cannot-capture-from-adv7281-m-with-i-mx6q/12925#12925

    Thanks,

    Poornima