• State Resolved
  • Locked Locked
  • Replies 12 replies
  • Subscribers 45 subscribers
  • Views 1696 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TVP5150AM1 PAL Image Quality

David Collie
Prodigy 70 points
Other Parts Discussed in Thread: TVP5150AM1

I am using the TVP5150AM1 serialized via a channellink chip in one of my companies products.  We've been using the TVP for a while with colour and monochrome NTSC cameras without any issues.  We now have some customers that are using PAL cameras.  Unfortunately, we're seeing a stripe pattern across the images.  While the distortion to the image isn't terrible it is very noticeable when compared to other receivers we've tested.  The first image below is the raw data captured from the TVP encoder before de-interlacing or resizing.  The second image is a Piccolo Alert analog frame grabber.

 

 

I've been trying to adjust different luminance and chrominance control registers in the TVP in the hopes of improving the image quality.  I haven't had any luck.  The status registers show that the TVP has detected a PAL camera with no colour subcarrier.  So this part is working correctly.  I've also forced a black output and received a perfect black image.  Our board layout matches the recommended layout for the TVP chip.  We do not have anti-aliasing filters on the inputs though.  I'll have the parts in a few days to test that but I'm doubtful that noise on the input is causing this issue.  Both colour and monochrome NTSC cameras work flawlessly with our setup.

 

If anyone has any suggestions for debugging the issue or additional insight to working with PAL cameras it would be very much appreciated.

  • 0
    TI__Genius 15310 points

    Hello David,

    Could you let us know if you are using patch?  If you do, what is the version number?

    Regards,

    Viet

  • 0 in reply to Viet Dinh
    Prodigy 70 points

    As far as I know the firmware has not been updated by us.  The ROM Major version reported from register 82h is 04h.  The ROM minor version reported from register 83h is 00h.


    Regards,

    Dave

  • 0 in reply to David Collie
    TI__Genius 15310 points

    Hello Dave,

    You are currently using ROM version.  Can you use patch?  Attached is patch version 048CAA that fixed several issues in TVP5150AM1 include Vertical banding (what you see).  Can you try it out?

    Regards,

    Viet

    P5150A_048CAA.zip
  • 0 in reply to Viet Dinh
    Prodigy 70 points

    I've applied the patch and verified that registers 0x82 and 0x83 return 0x04 and 0x8C.  I still have the same vertical banding issue.

    Are there any other patches I could apply that might resolve this?

     

    Regards,

     

    Dave

  • 0 in reply to David Collie
    TI__Genius 15310 points

    HI Dave,

    I am sorry that you are still seeing problem.  Can you try it with a standard signal generator to see if it is source related?

    Regards,

    Viet

  • 0 in reply to Viet Dinh
    Prodigy 70 points

    I should be able to setup a signal generator in the next couple of days.

    I have verified that this is happening with two separate monochrome PAL cameras.  Both cameras have been tested with different receivers to verify their output.  The other receivers did not exhibit the vertical striping.

    Also you'll notice in the images I've posted there is black padding around the image.  The camera that produced the images actually has a sensor that is smaller than PAL resolution.  The camera therefore pads its output.  If you look closely you can see that the striping is present even in the black padded areas added by the camera.  If the striping was caused by the camera's sensor I wouldn't expect the striping to be present in the black padded area.

    I'm doubtful that the issue is related to the cameras themselves.

    I didn't see anything in the changes related to the patch that dealt specifically with vertical stripes.  Would it be possible to give me a technical overview of what the patch resolved relating to the striping?

    Regards,

    Dave

     

  • 0 in reply to Viet Dinh
    Prodigy 70 points

    Quick question regarding patching the TVP.  I applied the patch by following the directions in the pdf.  I used the c unsigned char array for the patch data.

    The order of registers operations are currently as follows:

     

    write 0x7F, 0x00

    write 0x21, 0x51,

    write 0x22, 0x50

    write 0x23, 0xFF

    write 0x24, 0x04

    write patch contents from c unsigned char array into 0x7E

    write 0x7F, 0x00

    write 0x21, 0x00

    write 0x22, 0x00

    write 0x23, 0xFF

    write 0x24, 0x04

     

    This appears to have worked and I can read the correct values from registers 0x82 and 0x83 ( 0x04 and 0x8C).  Is this all that is required to apply the patch?  I'm just trying to ensure that it has been applied correctly.

  • 0 in reply to David Collie
    TI__Genius 15310 points

    Hello Dave,

    Yes, if you read back the register 83h and it is 8Ch then you got the patch downloaded and it is running correctly.

    Regards,

    Viet

  • 0 in reply to Viet Dinh
    Prodigy 70 points

    One of the visual changes I've noticed is that the pixel values in the black padded area put out by the camera look significantly better if the automatic offset is disabled.  Writing 0x11 to register 0x01.  The first image below is with offset enabled and the second image is without.  The striping is still present but the pixel values are actually 0x01 for the black padded area as they should be.  With the offset enabled the black padded area will have pixel values from 0x0C to 0x14.

     

     

    Does this give you any ideas about what could potentially be causing the vertical striping?

  • 0 in reply to David Collie
    TI__Expert 6120 points

    Hello David,

    We're unable to reproduce the vertical striping problem you've reported.  Could possibly be some type of noise coupling issue in your application.  We don't recall ever seeing this issue before.

    Moving forward, please be sure to use the latest TVP5150AM1 patch code.  It is also highly recommended to always use an external anti-aliasing filter.

    Also, the automatic offset control "must" always be enabled.  The output black level is supposed to be 0x10.  With the automatic offset control disabled, the output black level may vary significantly from part to part.  Clipping in the video path may also occur.

    Regards,

    Jim

  • 0 in reply to James Nave
    Prodigy 70 points

       Thank you both for your help.  Installing the filter on the input resolved the vertical striping issue with PAL.

    Regards,

    Dave

  • 0 in reply to David Collie
    TI__Genius 15310 points

    Dave,

    This is great news.  Thanks for your feedback.

    Regards,

    Viet