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Reading Video [NTSC] [VGA] [DVI] [HDMI] — Parallax Forums

Reading Video [NTSC] [VGA] [DVI] [HDMI]

Mag748Mag748 Posts: 269
edited 2012-07-27 08:51 in Propeller 1
Hello,

I am wondering how possible it would be to read an incoming video signal. I am only concerned with a very small number of the actually pixels coming in, because I am planing on mapping this incoming video signal to a set of LEDs. So ideally I would like to have an HDMI or DVI port connected to the Prop, and be able to ready the pixels in the, lets say, top 10 rows and leftmost 50 columns. Since the prop is able to create video of this low resolution, is it able to read the type of video?

Thanks,
Marcus

Comments

  • RaymanRayman Posts: 14,826
    edited 2012-07-26 14:53
    Phil has posted an NTSC capture routine that works with fairly simple external circuit.
    That would probably be the easyiest way to go.

    It may be fairly easy to low resolution capture VGA, I'm not sure...

    DVI and HDMI would require a dedicated decoder chip. But, the output of that chip may be fairly simple to connect to a Prop and capture at reduced resolution.
  • lanternfishlanternfish Posts: 366
    edited 2012-07-26 14:54
    There are a number of threads that deal with this or similar projects. I don't have time to search for them but they are there.

    I was working on a similar project a couple of years ago but the person who was funding it went in another direction and I didn't do any further development.Basically the prop would read a 800 x 600 VGA signal and decimate it to 400 x 300 before outputting it to an led strip. This required a video DAC and dual port SRAM (acting as a frame buffer). If I can locate the code and any other info (archived somewhere) I will put it up for you to look at.

    Cheers
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-07-26 16:30
    Post #4 of my index has a list of Propeller machine vision links. Some of them would apply to this application.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-07-27 07:21
    Mag748 wrote: »
    I am only concerned with a very small number of the actually pixels coming in, because I am planing on mapping this incoming video signal to a set of LEDs.

    Do you need the color information?

    If not, you could use Hanno's method of capturing a NTSC signal.

    I used Hanno's method to do something similar to your goal. Rather than displaying a small portion of the image with LEDs, I used pixels distributed throughout the image to create a very low res image with LEDs from the NTSC signal.

    Here's a picture of my LED array showing what is being "seen" by a small B&W video camera.

    attachment.php?attachmentid=80519&d=1303582009

    The small camera is held by my fingers in the top left of the photo. It's not easy to see, but the word "HI" is both on the whiteboard and displayed on the LED array.

    Not a very practical way of displaying a video image, but it sure looks cool (to me anyway).

    There's a little more information about this project here. I'm pretty sure I've posted code for this project somewhere. The program is probably called "MecanumVision" with the date as part of the progam's name. Let me know if you'd like to see the software (it is very very messy), but can't find where it's posted (I don't recall myself where I posted it).
  • Mag748Mag748 Posts: 269
    edited 2012-07-27 08:51
    lanternfish,

    This is very similar to what I am trying to accomplish, although I will not need any decimation as the source signal will be formatted specifically to map to the LEDs.

    Rayman,

    I was thinking that it would be nicer not to have to deal with analog signals at all, so I will look into your idea of a dedicated HDMI/DVI interface chip.

    Duane,

    I will need color as I am controlling RGB Leds. Your project looks very cool though. I will let you know if I am interested in see the code you created for that project.

    Thanks,
    Marcus
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