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Composite Video Input — Parallax Forums

Composite Video Input

ry.davidry.david Posts: 63
edited 2009-08-24 02:46 in Propeller 1
I am tossing around another idea for my project. I would like to have a composite video input and then record it directly to an SD card. Could anyone point me in the right direction, as I am assuming I need a dedicated IC to interface with.


Thanks!

Ryan

Post Edited (ry.david) : 8/22/2009 1:10:59 AM GMT

Comments

  • LeonLeon Posts: 7,620
    edited 2009-08-19 16:48
    Do you mean "composite" video?

    Leon

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  • ericballericball Posts: 774
    edited 2009-08-22 01:01
    Just for clarification - composite is everything combined into a single wire while component is at least 3 separate wires.

    Even without considering the input requirements, the current speed record for fsrw is around 2MB/s (100MHz clock).· With NTSC that's max 130 samples per line, maybe 140 if you have deep enough buffers to stream continuously during both hsync & vsync.· Pretty low res.· And that would just be B&W.· If you're sampling color too, divide by two or three (depending on whether you want 2:2:2 or 2:1:1 sampling).



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    Composite NTSC sprite driver: Forum
    NTSC & PAL driver templates: ObEx Forum
    OnePinTVText driver: ObEx Forum
  • ry.davidry.david Posts: 63
    edited 2009-08-22 01:08
    Yes, I had meant composite - sorry for the confusion...

    @ericball,
    Thanks for the input. This is assuming uncompressed input, correct? I am wanting to take apart a cheap camcorder, or something that records to SD, and see how it is done.

    Thanks!
    Ryan
  • ericballericball Posts: 774
    edited 2009-08-22 13:09
    ry.david said... Yes, I had meant composite - sorry for the confusion...

    @ericball, Thanks for the input. This is assuming uncompressed input, correct? I am wanting to take apart a cheap camcorder, or something that records to SD, and see how it is done.
    Yes, this is uncompressed.· Camcorders have dedicated chips which compress the data (typically quite heavily).· Their write speed is also limited by the SD card.· The Propeller isn't fast enough for real time video compression because it lacks a hardware multiplier.


    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Composite NTSC sprite driver: Forum
    NTSC & PAL driver templates: ObEx Forum
    OnePinTVText driver: ObEx Forum
  • ry.davidry.david Posts: 63
    edited 2009-08-23 14:27
    Okay... thanks for your time Ericball
  • RaymanRayman Posts: 14,848
    edited 2009-08-23 21:16
    You might want to search for "stupid video capture" in this forum... There's code and a circuit there to do very basic video capture in B&W...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • Ken PetersonKen Peterson Posts: 806
    edited 2009-08-24 02:46
    We did a project where we sampled composite video and displayed it on a VFD. It was crude and the image quality sucked, but it worked. I used a separate parallel A/D chip and a sync separator to do it because the delta/sigma A/D was too slow. I think we sampled 106 points per line.

    One problem we had was that we were sampling color video, and we didn't have a good comb filter in the circuit - only a low-pass filter. The amplitude of the chroma component is significant compared to the luma. I was running into a trade-off between a very noisy picture and a blurry picture. Also, the display we used had only 16 levels of gray, so a lot of detail was lost in the image. Needless to say we sort of abandoned that approach. Looking back on it, had we used a monochrome video source it may have looked a lot better.

    Ken
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