Digital Video - How Does It Work?
Digital video. In today's age we take this amazing piece of
technology so much for granted. The truth is, that we are able
to create digital video at all is simply amazing.
To understand digital video you first need a basic understanding
of analogue video or what is more commonly referred to as
videotape or even before that, video film.
Technically, motion pictures are simply the speeding up and
displaying of still photos. Early motion pictures were recorded
on film similar to photographic film. If you were to examine
motion picture film it would look very similar to the negatives
you'd see after taking your photos to the local photo-mart to be
developed. To oversimplify things, motion pictures is simply
taking those negatives, stringing them together and running them
through a high speed projector to produce the illusion of
movement. Of course the process today for film is much more
complex than that but you get the basic idea.
So then what is the difference between video film or tape and
digital video?
This is where we have to move into the area of computers. For
the purpose of not confusing anyone this will be described as
simply as possible. In order to create digital video you first
have to start with an analogue or film image. Let's take for
example a home camcorder which still uses video tape similar to
the tape used in VCR tapes. After filming the moving image the
camcorder would then be hooked up to a computer interface which
is an analogue to digital converter. The film is then run
through the converter where each image in the motion sequence is
converted to a sequence of bits. The higher the bit
concentration, whether it be 8 bit, 16 bit, 32 bit or higher,
the more of the film quality that's preserved. The reason for
this is because for each image to be salvaged the converter
translates the image density, color, shape and other attributes
into digital format. The more information there is to store the
more bits are required to store it accurately. For example. it
would not take as many bits to store the image of say a black
tie as it would a photo of the Mona Lisa because the Mona Lisa
has more detail to it. So some images you can get away with
storing less information whereas other images you would not even
be able to recognize what they were, even if you were storing
the same amount of information. Again, this is simplifying
things greatly.
Okay, so what's the benefit of digital video if any? Actually
the benefit is pretty great. With analogue film over time the
film gets old and goes bad. So many old movies have had to be
restored because of the terrible shape of the original prints.
Some were so bad they couldn't be restored. With digital, there
is nothing to get old. Bits don't age. So the digital video that
you see today will look exactly the same 1000 years from today.
With this technology you never have to worry about losing video
of historic significance. A movie made today will not have to be
restored 100 years from now.
Artistic people will claim that the quality of digital video is
cold, that you don't have the warmth of the look of film images.
There may be something to that and the argument will probably go
on for sometime about which is better. But one thing is for
sure. Digital video is here to stay, which means that our films
of our 25th anniversary celebration are also here to stay.