Copyright Michael Karbo, Denmark, Europe.


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    Chapter 21. Analog video

    While it is relatively simple working with video sequences from a webcam or a digital camera, it is much more complicated working with analog video signals.

    Clutter and teasing

    I have for a long time liked the figure of speech ”life is too short for video-editing on a computer”. It expresses, maybe, an anxiety which is a little exaggerated; but there is no getting away from the fact that, the transmission of – especially analog – video to a computer can be very troublesome indeed – the first time you try it, anyway.

    You mess about with hardware devices, which are difficult to get started. There are cables all over the place, Windows crashes, and it all seems rather confusing. But now I have said that, then it is a really good feeling, the first time a home video is burnt onto a video CD and can be shown on the television. And you think, ”well, that wasn’t so difficult after all”.

    In a later section, I will show you how easy it is to work with digital video in a DV format; this is a completely different and much more simple set up.

    Figure 136. Capturing analog video signals into your computer often ends in an indescribable tangle of cables.

    Digitizing VHS recordings

    The video format VHS has been very widespread for more than twenty years. So a lot of people have old analog video recordings stored on videotapes, either in large videocassettes or in the form of VHS home video recordings.

    These videotapes have a magnetic coating, which preserves the video signals. The tapes lose their signal power as time goes by. The recordings just disappear quietly and calmly. Which is why it is obviously a good idea to try and “re-record” these videos in a digital format. And it can easily be done – as long as you are patient (more than this writer) and have the right equipment (a fast computer, for example).

    When you have re-recorded your old videos on, for instance, video CDs, then you don’t have to worry about them anymore. It is just a question of looking after the CD disks, but they will probably last longer than the VHS tapes.

    Analog connection with video

    The analog video signals have to be captured into the computer. This is done in several ways. In practice the video images are captured either via an S video plug or via a so-called composite connection, which uses a current RCA phono plug. The third possibility, component video, isn’t used in this connection.

     

    Connection

    Description

    Composite

    The most primitive form for signal. Found in almost all equipment. A signal.

    S-Video

    Better images, as the signal is divided into two components:  luminance and chrominance.

    Component

    The best quality: The signal is divided into three components  (Y/Pb/Pr), and this gives the highest resolution and the best colour reproduction. Is used for, among other things, projectors and plasma screens.

    Figure 137.The three types of cable connections that are used for the transmission of analog video signals.

    It might also be possible for you to capture video and audio signals via a SCART plug (see Figure 145 on page 3).

    Audio and images separately

    When we work with a normal VHS video, either from a video camera or from a video player, then the audio and the image are captured separately. In practice, the only ways of doing this are:

     

    Connection

    Function

    Type of plug

    S-Video

    Video image

    4 pin miniDIN.

    Video OUT

    Video image

    RCA (yellow plug).

    Audio OUT

    Audio

    RCA, right (red).
    RCA, left (white).

    Headphones

    Audio

    Mini-jack, stereo

    Figure 138. In connection with a VHS video, it is these plugs that are used for the analog video and audio signals.

    The four plugs, S-video and three times RCA phono, reoccur in many video devices, television and various computer boxes and cards. In some video cameras the audio is captured in a headphone port.

    In Figure 139, you can see the port for S-Video on the left and the three RCA plugs (also called AV plugs) on the right. See too Figure 140.

    Figure 139. Plugs, which can capture analog video in a computer.

    Grabber capturing

    Let us assume that you have a VHS recording you would like to have digitized. To be able to do this you have to have a video grabber. This is a device, which can receive analog video signals and convert them into digital data. This means that the video recording has to be played, and that the analog signal is conducted into the computer to the grabber.

    If you want the easiest set up, then get a grabber box, which can be connected to the computer’s USB port. The box has the necessary ports for video signals and the digital signals are transmitted from the box to the computer via a USB connection with a simple little cable.

    Figure 140. A USB based video grabber. USB version 2.0 ensures large bandwidth.

    The problem with this type of box is that the most widespread version of USB (1.1) can only transmit rather small amounts of data. Which means that the video recordings have a limited resolution and not the best quality. The box in Figure 140 is one such grabber. If your computer has a USB 2.0. plug then the transmission speed can be multiplied many times. But generally, these small (and otherwise smart) boxes have a bad reputation. They are attempting to make a cheap and easy video capture; but the final product is often a recording of a miserable quality.


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