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Build your own embedded DVR

Discussion in 'Hobby Electronics' started by Miem, Aug 6, 2007.

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  1. Miem

    Miem Guest

    Hi,

    I wonder if someone tell me how to digitize and save/record composite
    color video data (and optionally audio) from a low-cost camera into
    compact flash or SD memory without using a PC.

    I know I can purchase COTS units like
    http://nservices.com/wireless3.htm
    http://www.brickhousesecurity.com/memory-card-dvr-video-recorders.html
    http://www.startechoutlet.com/product_404_detailed.htm
    http://www.pimall.com/nais/ultraminidvr.html
    http://www.eyespyli.com/dvr9800.htm

    But, I want to learn how to digitize and record composite video (as a
    hobby).

    Thx

    Miem
     
  2. Here you go, it's all been done for you with an AVR:
    http://www.circuitcellar.com/avr2006/winners/AT3267.htm

    Dave.
     
  3. kreed

    kreed Guest

  4. Miem

    Miem Guest

    But, I want to learn how to digitize and record composite video (as a
    Dear Dave,

    Thank you for your reply and for the URL.
    The AVR based image/video capture circuit on that URL is very
    interesting.
    It use OV528 (www.ovt.com) which is a JPEG compression chip designed
    for mobile phones and PDA's. My understanding is that it requires
    OVT's digital camera chips.

    How ever I want to be able to digitize/capture composite video signal
    from any ordinary video source such as low-cost cameras, VCR, etc.

    Do you know also any other circuit which can digitize composite video
    signals without needing a PC?

    Cheers,

    Miem
     
  5. kreed

    kreed Guest

    Sadly, this sort of thing is possibly in the realm of high density
    custom IC's these days and mostly intended for the PVR or DVD market.

    The only thing that comes to mind was in the late 80s or early 90's EA
    or ETI magazine made up a project involving still video frame capture
    PC card (probably of XT class). Because of the technology at the
    time, it would more likely have used discrete ICs and therefore
    should be easy to understand as a starting point for how video signals
    can be read into a computer/microcontroller and help you to build such
    a system for hobby use.

    Its very likely that this unit could be interfaced to a modern high
    performance microcontroller such as an AVR - and signals stored on an
    IDE hard drive thus avoiding the PC. (There are a number of circuits
    on the web for interfacing HDD's to microcontrollers - mainly for MP3
    based projects.)

    OR:
    You can buy PVR devices (usually with a set-top digital box built in)
    starting from about $250 or so at most electrical retailers such as
    retra-vision, betta, E-Bay etc. WES components also sell one. I
    would look for one with a composite video/audio input - or you may
    have to use an RF modulator. A very comprehensive remote control
    would also be good, to give you greater control over the functions of
    the unit if you want to try and interface it to a microcontroller or
    do other experiments with it

    What video format these devices store the info on the internal hard
    drive is unknown.

    I would consider buying one of these units and experiment with it.
    Unless you happen to google up some suitable project on the net - this
    is probably as good a starting point as I can think of

    There will likely be a custom IC that will do all the digitising etc.
    Read the part numbers of all the internal ICs and google them to find
    out more of how the system works. It would also be helpful to collect
    all the brand/model numbers of the available units, and see if you can
    buy a service manual with a schematic for these to help in your
    research.

    Major long-established brands (especially their more up-market models)
    like Panasonic, Sharp, Sony etc should be able to supply service
    manuals/schematics hopefully though they might cost a bit to buy.

    -------
    Another problem you may face in future is that AV may disappear as a
    standard. Proprieteary digital methods (like HDMI on PC's already)
    might take over as a standard method of sending video/audio signals,
    especially if "copy protection" based stuff starts being implemented
    by government regulation.
     
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