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TVP5146M2: Color interference

saman mazrooie
Intellectual 640 points
Part Number: TVP5146M2
Other Parts Discussed in Thread: TVP5146, , TVP5150

Hello,

I have two board that use tvp5146 to decode the input PAL video and process it by DM6437 DSP,

I Changed the order of the video lines in the first board by DSP and do the same in the second board , it encrypt and de decrypt  the input video,

every things is ok  but there is something like color interference, The colors of each line do not appear to be independent and depend on the surrounding lines.

What do you think is the problem and what is the solution to it ?

thanks.

  • 0
    TI__Guru 65405 points
    Hi Saman,

    TI does not recommend using TVP5146M2 in a new design (NRND). Support for these devices is extremely limited as it is described at:
    e2e.ti.com/.../622064
    But could you give more details about your issue?

    Regards,
    Tsvetolin Shulev
  • 0 in reply to Cvetolin Shulev-XID
    Intellectual 640 points

    Hi Shulev,

    thanks for reply.

    by Changing the order of the video lines, the effect of the color of the previous lines are still exists.

    The colors of each line do not appear to be independent and depend on the surrounding lines.

  • 0 in reply to saman mazrooie
    TI__Guru 65405 points

    I had not seen such problem but the observed issue could be due to some display problem. It is not still clear enough for me what exactly you have mean with "Changing the order of the video lines".

    Regards,

    Tsvetolin Shulev

  • 0 in reply to Cvetolin Shulev-XID
    Intellectual 640 points

    Hi,

    "Changing the order of the video lines" means that for example i copy the video line 4 to line 8 and copy line 8 to line 4; we do for any pair of lines this method.

    it is not a display problem, There seems to be a filter that dependenced the color of different lines to surrounding lines. 

  • 0 in reply to saman mazrooie
    TI__Mastermind 43875 points

    If you mean that you swizzle the video image before encoding into the analog domain, then want to use the TVP5146 to decode the analog video back into the digital domain, then 'undo' the swizzling in the digital domain, then yes, this will cause an issue.

    The TVP5146 uses a 5 line comb filter to analyze the analog video, so if you re-arrange the video in the analog domain the comb filter will not be able to correctly filter video artifacts. Please review sections 1.2 & 2.2.2 in the datasheet for a little more information.

    You probably want to disable the adaptive filter and enable just the chroma trap filter. Note however that this will result is a lower quality decoding of the video, but in your specific application is probably the only real solution since the video lines being received are not actually in the correct order, so utilizing them in the filter will not work.

    Try changing the filter type in the luma processing control registers (sub address 07h, bits 6 & 7, sub address 08h bits 0 & 1, sub address 0eh bits 0, 1 & 2). It may also be necessary to disable the chroma adaptive comb filter in sub address 0dh, bit 3. You will need to experiment with all these registers to get the desired result for your specific application.

    This does also mean that you may actually be better using a lower quality (hence cheaper) decoder such as the TVP5150/51 family.

    Kind regards,

    Steve