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DM648 to DM648 video losing four lines of video

Vasily9089
Prodigy 90 points

There are two DM648 in our device. Video Port (in display mode) of one DM648 is directly connected to Video port (in capture mode) of another DM648. Both video ports are configured to work with NTSC 720x480; BT.656 interlaced video streams. First DM648 captures a video frame, process/add some graphics in it and sends(displays) frame to the seconds DM648.

Now the problem: When second DSP receives/captures the frame from the first DSP - frame is OK,  except the four first lines of this frame are disappeared (frames starts from fifth line) and last four lines of the frame are filled with zero values.

What should I do to receive all lines of my video frame on the second DSP?

  • 0
    Expert 1200 points

    check your settings for the active image area on the digital input and output.

    check data at the start of the frame on the digital video bus, e.g. by writing test patterns into the leading few bytes.

  • 0 in reply to Alexander Stohr
    Prodigy 90 points

    Thank you. I changed default settings fldYStrt1and fldYStrt2 in VPORTCAP_Params for capture channel. And now it works OK.

    But I got another adjacent  question:

    When the second DSP receives a frame from the first DSP - value of each Y pixel containing 0x00 or 0x01 or 0x02...0x0F is replaced to 0x10 as well as each Y pixel containing 0xF1 or 0xF2 or 0xF3...0xFF is replaced to 0xF0. Which video channel does this replacement capture or display? Can I somehow disable this replacement?

     

  • 0 in reply to Vasily9089
    Expert 1200 points

    fast quick guess: BT.656

    its a digital video encoding format with only a clock signal. syncs are embedded by a set of rare and thus reserved values.

    if you want to circumvent such things you need to use HSYNC and VSYNC signals as well.