what is analog and digital video?

Discussion in 'Amateur Video Production' started by Andrei, Sep 12, 2004.

  1. Andrei

    Andrei Guest

    Hi, I would like to know a good explanation about analog and digital
    video, is there a web site that explains it well? for dummies?
     
    Andrei, Sep 12, 2004
    #1
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  2. Andrei

    Will Dormann Guest

    Analog vs. Digital...

    Think cassette tape vs. CD
    VHS vs. DVD
    Hi8 vs. DV

    With the digital formats, you can transfer the bits from one medium to
    another without any loss. Transferring an analog format to another
    medium is lossy. So when you "capture" DV video from your camcorder,
    it's really just doing a digital transfer. With analog video, the data
    is sent over the wire in analog form and then digitized by your capture
    card.


    -WD
     
    Will Dormann, Sep 12, 2004
    #2
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  3. Andrei

    PTravel Guest

    Analog means that values are represented by a signal scaled to the value,
    e.g. if a component of a scene is bright, the video signal recorded is
    strong. If a component of a scene is dark, the video signal recorded is
    weak. When copies are made of an analog signal, degradation is
    introduced -- signals aren't recorded at exactly the same strength, and
    false signals from the recording process can be introduced which distort the
    signal.

    Digital means that each component of the scene is represented by a number
    representing a discrete quantization, e.g. very bright components may be
    represented by the number 255, and very dim components by 0. When digital
    video is copied, it is nothing more than copying the set of number from one
    medium to another. Since each number is discrete and copied exactly, there
    is no degradation of the underlying image, and no noise is introduced that
    can cause distortion.

    In a nutshell, analog video uses varying signal strength to represent
    brightness. Digital video uses discrete numbers to quantize brightness.
     
    PTravel, Sep 12, 2004
    #3
  4. Like somebody said among the other replies here the analog video signal is
    sampled and converted into 8bit numbers which gives 255 levels.

    Prior to conversion, however, the video signal is split into three signals
    which together constitute the necessary information for describing an analog
    color video signal. Each of the three signals are then sampled in various
    ways depending on the type of digital system you want. In miniDV and DVCAM
    (most common in consumer and semipro cameras) the three signals are sampled
    with 8 bits(255 levels) for brightness and 4 bits(15 levels) each for the
    two color information signals (PAL).

    Peter
     
    Peter O Sjostrand, Sep 13, 2004
    #4
  5. I believe all the video components are sampled at 8-bit
    resolution, both NTSC and PAL. The difference is how
    *often* the samples are taken (thus affecting the overall
    bitrate). See "4:1:1" (NTSC) vs. "4:2:0" (PAL), etc.
     
    Richard Crowley, Sep 13, 2004
    #5
  6. Andrei

    Andrei Guest

    What confuses me is when an analog camcorder records then I connect to
    the computer throw a capture card it transforms it into digital
    signal?, when I think in a computer I think that every video recording
    inside its digital, its right? or an analog video captured in a pc its
    still an analog video?

    Thanks
    Andrei
     
    Andrei, Sep 13, 2004
    #6
  7. (Andrei) wrote in
    Yes, the capture card or external capture device converts the
    voltage levels (the analog signals) into numbers (binary values,
    digital values, whatever you'd like to call them) and that's what
    gets onto your hard drive.

    So everything in the computer is digital, just as you surmised.

    With digital cameras, the conversion to digital happens in the
    camera and the digital values are written to tape (or whatever
    storage medium is used in the camera). In this case "capture" is
    really "transfer", and the numbers are copied to your hard drive as
    numbers.

    Part of the secret is how the numbers are organized into files, and
    so on, but let's not go there until we've had a chance to rest :)

    HTH,
    gino

    <SNIP>
     
    Gene E. Bloch, Sep 13, 2004
    #7
  8. Andrei

    DavesVideo Guest

    aberdich said:
    still an analog video?>>

    Well, at one time there were analog computers, so I guess if you have one of
    those you could. :)


    Dave
    http://members.tripod.com/~VideoDave
     
    DavesVideo, Sep 14, 2004
    #8
  9. aberdich said:
    "DavesVideo" wrote ...
    Even at their prime, analog computers couldn't handle even a tiny
    fraction of the bandwidth of ordinary baseband video. I remember
    a very sophisticated one that filled two rooms at USC in the early
    1960s. It did play a mean game of astro-blaster (or whatever it
    was called).

    OTOH, my Sony SEG-2000 switcher is a completely analog
    video "computer". :)
     
    Richard Crowley, Sep 14, 2004
    #9
  10. Would you believe me when I tell you they are still used in
    state-of-the-art tanks to work out where the target is?
    That's something else than video-editing eh? :)

    cheers

    -martin-
     
    Martin Heffels, Sep 15, 2004
    #10
  11. Andrei

    DavesVideo Guest

    state-of-the-art tanks to work out where the target is?
    That's something else than video-editing eh? :)>>

    Interesting. I worked in Target recognition and tracking for quite a few years.
    10 years ago, it looked like it was heading toward all digital.


    Dave
    http://members.tripod.com/~VideoDave
     
    DavesVideo, Sep 15, 2004
    #11
  12. Maybe the Germans are a bit slow developing new technology ;-) But to
    be more accurate, they use a mix of analog and digital computing.
    So do we have to call this, hybrid computing?

    cheers

    -martin-
     
    Martin Heffels, Sep 15, 2004
    #12
  13. Andrei

    DavesVideo Guest

    Martin Heffels said:
    be more accurate, they use a mix of analog and digital computing.
    So do we have to call this, hybrid computing?>>

    As a mater of fact, that is what it is called.


    Dave
    http://members.tripod.com/~VideoDave
     
    DavesVideo, Sep 16, 2004
    #13
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