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When we transfer VHS to DVD, our decks use
the same basic operation of any VCR throughout history. No matter
what brand a VCR is, it will have four common
sections: an input section, a recorder section,
a reader section, and an output section. These are tied together
by the storage medium: the video tape itself.
The input section
is controlled by whatever is sending A/V information
into the VCR. For example, this could be a TV, cable
signal, camcorder, or another VCR.
The recorder section handles VHS conversion,
transferring all the input signals into a form that can be saved
to tape. It writes or records the information onto the storage
medium (on D-VHS, it writes VHS to digital). Conversely, the
reader section interprets information that is stored on the video
tape. For example, this might include television programs or
sound signals.
The reader converts the information into signals that are appropriate
for the output unit.
The output section is the direct opposite of the input area.
It is usually connected to a TV or another VCR. When we convert
tapes to DVD, we output to a DVD recorder; when we convert
video to AVI, the output it to a capture card.
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Let’s look at how the recorder section
works with the actual video tape (for example, when you copy
VHS to
VHS). A VCR video cassette holds
brown tape that is similar to an audio tape. The tape is constructed
from a long strip of plastic or mylar that is wound between two
reels inside the plastic cassette shell. On one side of the tape,
a material that can be magnetized is glued, usually an iron
oxide mixed with an adhesive binder.
The
tape is pulled around a cylinder in the VCR called a "head
drum." The drum has tiny electromagnets called "heads" mounted
on its surface. Electric signals from the audio and video of the
recorder section are passed through coils of wire in these heads,
which produce a tiny magnetic field that changes in respect
to the audio and video signals.
When the tape passes around the
drum in the recording section, the heads make contact with the
oxide on the tape, thereby causing the tape to feel the
magnetic field. The oxide becomes magnetized
in direct proportion to the signal in the head. Since several
heads are on the drum, multiple electric signals are converted
to magnetic fields applied to the tape, thereby writing the audio
or video information onto the tape, where it's stored for
playback. |
When you insert a tape to play it, gears,
arms and other mechanisms pull the tape into the machine. The
plastic tape is placed against read heads located in
the drum cylinder. Subtle variations in this mechanism is
why a time-base corrector is often useful when you record VHS
to DVD.
The heads sense the energy fields located
in the magnetic layer of tape. They then convert the magnetic
fields into small electrical signals. The signals are amplified
and sent to the output section, where a TV or similar device
is responsible for converting the audio and video signals into
light and sound.
It's that easy! When we copy
video to DVD,
our VHS VCRs, and that of any VHS to DVD service, use this same digital
transfers process every time. |
