The Words of Video
Video has a language of its own, in several different ways.
It has often struck me as odd, for instance, that audio equipment carries English panel
markings practically everywhere in the world. Even in Japan, where most of the components
come from, hi-fi companies use English on their domestic models. It was once explained to
me that early buyers preferred foreign audio to homegrown stuff, and it almost always came
from Britain or the U.S., labeled in English. To add a foreign "feel" to their
own products, Japanese companies used English as well.
But video has always been different. Televisions were
traditionally marketed more like appliances than sophisticated electronic gear, so
Japanese TV sets have always had Japanese markings. If nothing else, that served to
illustrate the low-tech image television had from its birth until the video boom of the
past years. While audiophiles reveled in technical minutiae and arcane jargon, TV buyers
concerned themselves mostly with furniture finish.
Eventually consumers began to demand better TV sets, better
VCRs, and better audio from both, and the video industry made great technical strides in a
very short time. Tape was joined by laserdiscs and then DVDs, but in a field that had
mostly ignored the details of performance for years, there was no common vocabulary that
buyers could use to quantify the various improvements. The newfound emphasis on video
performance, and the lack of a standard nomenclature to describe it, has led to a good
deal of consumer confusion.
Take the term "resolution," for instance.
Virtually everyone agrees that this has something to do with sharpness or picture detail
-- and so it does -- but relatively few buyers know precisely what it means. For one
thing, what we usually refer to simply as "resolution" is actually
"horizontal luminance resolution". It's horizontal because that's the only thing
that matters; vertical resolution is determined by the fixed number of scanning lines that
make up the picture.
Resolution is measured in lines: the number of alternating
black and white vertical lines that can be distinguished using a test signal. One common
misconception is that the total number of such lines across the screen is what's being
measured; instead, it is the number of lines in a horizontal width equal to the screen's
height. Thus, with a conventional TV set, if you could count 400 lines across the whole
screen, the resolution would be only 300 lines because the height is only three-quarters
of the width.
Even so, that only refers to one sort of horizontal
resolution. A video signal is made up of two parts: luminance (brightness) and chrominance
(color). The conventional resolution figure is usually stated only for the first of these;
chroma resolution is generally far worse (like, 50 lines or so), and is rarely quoted.
Even more confusing, perhaps, are the terms used to denote
the various enhancements to the audio portion of video hardware and software. For a lot of
consumers, for example, the terms "hi-fi" and "stereo" are more or
less synonymous, but the two phrases applied to a VCR mean radically different things. The
linear audio track in first-generation VCRs was split in two at an early stage to create a
sound system that was definitely stereo, but sounded even worse than the original --
terrible -- mono track. This practice ultimately disappeared, but if your ancient recorder
simply says "stereo," that's probably what you've got. If the machine carries
the "Hi-Fi" label, however, it contains AFM (audio frequency modulation) sound,
which is both true high fidelity and stereo.
"Dolby" is also confusing when applied to video
equipment. When the original linear sound track was split in two, the noise level jumped
dramatically. To counteract this, some VCRs added Dolby B noise reduction -- the same
system included in virtually all ordinary audio cassette recorders. But if you rent a tape
that says it has Dolby, this has nothing to do with noise reduction; instead, it indicates
that the tape is encoded in Dolby Surround sound (which it may or may not spell out).
Dolby in a DVD is usually Dolby Digital, but if it's an older movie (even on a newly
released disc) it may have only two channels of audio, which can be decoded by a Dolby Pro
Logic decoder, just like a tape.
Gradually the terminology is settling down and acquiring
something like fixed meanings. For many, however, it’s still about as comprehensible
as Japanese. And that doesn't even address the whole new vocabulary of digital TV. We'll
talk about that in an upcoming month.
...Ian G. Masters
ian@mastersonaudio.com
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