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How to delay (and control) a composite video signal?

  1. May 24, 2016 #1
    Hey, I want to set my own delays to a composite video signal, for use of live video feedback effects (for visuals / art purposes). I am no electrician, but this can't be hard to do right? After searching a few hours online, I haven't come up with any device that I can buy which will do this. Is there any such device / how can I make my own "delay signal" device?

    All I would want control of is having 1 knob for example control the delay timings of a signal in milleseconds, with 1 composite video in and 1 composite video out of course. Can anyone guide me in the right direction?
     
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  3. May 24, 2016 #2

    berkeman

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    Typically this is done by digitizing the input analog signal, writing it to RAM with one process, reading it from RAM with another process, and writing it out to a DAC to make the output analog signal.

    There are certainly systems that can do this already, and you should be able to find them. The generalized ones with lots of delay capability will be expensive, though, and it sounds like you just need a simpler version.

    Do you really have to work with analog composite video signals? If you can just stay in the digital domain, you will save some money and get lots better quality. What are your signal source and your display device options? And how long of a maximum delay do you want?
     
  4. May 24, 2016 #3
    I can also use HDMI out on my Nikon camera, if I could control the delay of that signal that would be much better yes. Is it easier to construct / do devices for this exist for HDMI?

    Input options to my screen are plenty, HDMI / VGA / S Video / Composite. The range of delay timings I want control of would be something from 0 - 2 seconds.
     
  5. May 24, 2016 #4

    berkeman

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    I Goodled HDMI Video Delay Device, and got lots of hits. Here's the hit list:

    https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=hdmi video delay unit

    :smile:
     
  6. May 24, 2016 #5
    Hm, yeah I googled it a bit myself and see they are quite expensive. Given that it comes down to how much of it has to be put into ram, I can see why these things are expensive. Thats why I was hoping maybe composite video had something more simpler / cheaper, with less information to put into a buffer thus I could acheive longer delays..

    I think what I might do is use a capture card, stream the video source to my computer, then find some software that can delay the signal (since I have 16 gb of ram already on my laptop, but not sure of how long of a delay I can acheive with this given a HD 1920x1080 resolution).
     
  7. May 24, 2016 #6

    dlgoff

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    A really cheap way would, maybe, be by using video tape and the technique of Flanging.
    i.e. from the link, adjust the record & pickup head distance
    FLANGING5.PNG
     
  8. May 24, 2016 #7
    That also looks interesting, but I think it would then become a whole different project (plus I wouldn't know where to start).

    I have researched it more, and what I will do is buy a cheap composite video to usb device and use VLC to delay the video signal. Tomorrow I buy this little device, costs 10 euros and then start testing it. Maybe down the line I get an HDMI capture card and do the same, while still being able to control the delay signal.
     
  9. May 24, 2016 #8

    jim hardy

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    Wasn't it Les Paul who added a head to his tape deck and pioneered "sound on sound" ?

    I guess you'd have to reproduce the 3.58mhz color carrier? No wonder they use rotating heads.
     
  10. May 24, 2016 #9

    dlgoff

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    Not sure about Les Paul but yea, the color carrier would be problematic. That never occurred to me.
     
  11. May 25, 2016 #10

    jim hardy

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    Flanging ..... learned a new word
    from Don's link
     
  12. May 25, 2016 #11

    Averagesupernova

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    Since there are a lot of high (relative term I suppose) frequencies in NTSC even without the color subcarrier standard tape devices would not work. The general scheme was to frequency modulate the luminance information onto a carrier and feed this to a flying tape head. The color information was processed in some way also but exactly how escapes me right now. Even the audio in higher end VCRs was put onto the tape with the flying head. There was still always a stationary head for compatibility to lower end VCRs.
     
  13. May 25, 2016 #12
    Oh I have managed to work with long delays of up to 5 seconds using composite video to usb and Resolume as the effect software, and it works great! :)

    The quality is more then good enough for now, while I learn the techniques of how to film by playing around with it more. I have my own midi control mappings, and can delay the signal (or each rgb signal separately) by a simple knob. The quick access / ease of use is important with this live visual filming, because it is all about timing and working the delays (to get the right looking fractal pattern). An HDMI capture card will come afterwards, when I get better with my art ^^
     
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