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about LCD noise issue on DM355

YHLShareware
Intellectual 830 points

All,

I used MVL 2.6.18 kernel. I connected a LCD panel (640x480) to DM355 using PRGB interface. When I run encode demo in DVSDK package (display captured data on /def/fb/3, display osd data on /dev/fb/0), I found some noise existed in LCD screen. I have run the “writeb 20000020 0 10”, but I have still noise issue. Any help is much appreciated. Thanks.

BR, Jeff

  • 0
    TI__Mastermind 37340 points

    have you seen this article (pretty new): http://wiki.davincidsp.com/index.php?title=DM355_HD_Display

    It does an exellent job of describing this sort of scenerio.

  • 0 in reply to Juan Gonzales
    Intellectual 830 points

    Juan,

    I  have checked that document, but I only display VGA resolution(640x480) on LCD screen, i think it consumed less DDR bandwidth, right? That document is only for HD display (720p or 1080i). Thanks.

    BR,

    Jeff

  • 0 in reply to YHLShareware
    TI__Mastermind 37340 points

    Jeff,

    You are correct, just wanted to make sure you were not attempting one of the VGA capture, HD display scenerios. 

    Can you describe your system a little bit more, specially with regards ?  Are you doing any resizing... what refresh rate are you displaying at (just to get a feel for DDR2 usage)?

    Also, if you can post a pic of the noise you are seeing that would be great.

  • 0 in reply to YHLShareware
    TI__Mastermind 41665 points

    YHLShareware said:
    I  have checked that document, but I only display VGA resolution(640x480) on LCD screen, i think it consumed less DDR bandwidth, right? That document is only for HD display (720p or 1080i).

    Just a note on this, even though the document focuses on the HD displays you can see the same sort of artifacting it is trying to avoid in lower resolution displays, even the out of the box DVSDK demo can show artifacts on a NTSC display (load it up and hold enter on the terminal to load the CPU and you may see such noise, at least on earlier releases before PBBPR was being adjusted). In general if you can adjust the PBBPR register and perhaps the TC RDRATE register as discussed in that document you may be able to improve performance on your display fairly quickly, however if that does not resolve the noise you may also have to start removing things like OSD windows or the attribute window as these use a lot of memory bandwidth.

    Of course if your noise is not random horizontal lines on the display that appear relative to system load than you may be looking at some other issue with your display, if you could post a picture of your output as Juan suggests that may help in the diagnosis.

  • 0 in reply to Juan Gonzales
    Intellectual 830 points

    I used 3 tasks like VGA capture, VGA display, mpeg4 encoder. I can see some short black or white line in horizontal on screen. Thanks.

     

    BR,

    Jeff

  • 0 in reply to YHLShareware
    TI__Mastermind 37340 points

    Did you already adjust the PBBPR register like Bernie suggested; I assumed that your comments referencing "writeb 20000020 0 10" were related to PBBPR.  If not, the first thing I would try is adjusting PBBPR.

    The system description above seems reasonable.  You can try to disable OSD to see how that impacts DDR bandwith, also if you are using resizer to do deinterlacing (like our demos do by default, but can be avoided by -d option), I would try disabling this.