OK, you’ve decided to step up to better picture quality. You are the proud owner of a new high-quality camcorder or VCR, perhaps Hi8 or S-VHS. You’ve opened the box and inside are a number of little plastic bags holding all kinds of cables and accessories. Sure, you had to pay a little more than you would for ordinary equipment, but it’s really going to be worth it to you for the better picture quality.
You may have decided on your new purchase for any of a number of reasons. You might want to view your video on a larger monitor or high-resolution TV set where picture quality makes more of a difference. Or perhaps you’d like to edit your video and you know that using one of the standard formats would result in video that just wouldn’t measure up.
Surprisingly, in spite of what you spent on all this new equipment, understanding how to use a simple ten dollar cable can make the difference between enjoying the extra quality and having most of it go to waste. Even more surprising is the fact that such a cable probably came with your new equipment, free of charge.
So what is this magical connection? Its the S-video or Y/C cable. It’s such an unobtrusive item that you may have missed it while unpacking your new equipment. But understanding what it is and how to use it–the subjects of this article–can help you discover why you spent the extra money on a high-band video format.
What It Is (and Where It Came From)
The Y/C cable is a way of sending video signals from one piece of equipment to another while maintaining a high degree of picture quality. Theoretically, you could use Y/C cables to improve the picture quality for any video equipment that has the proper circuitry, but there’s a catch: manufacturers only include the necessary connectors on their higher-priced equipment. Some large-screen or high-resolution monitors and TV sets also have S-video connectors, but other more common equipment doesn’t.
The inventors of S-VHS developed the S-video connection system over a decade ago. The S-VHS system improved how video signals recorded onto the tape itself. However, when it was time to play the tape back, the results didn’t look so great if you had to use a standard composite video cable to hook up to your monitor. Even less impressive results were obtained using RF cables to connect the VCR to a TV. These RF cables used a method of carrying signals very similar to over-the-air television broadcasts, and presented certain problems that have been with us since the development of color television in the early 1950s.
The problems stem from the need to make color television signals watchable on black and white TVs. By the time color came on the scene, there were already millions of black and white sets in use. Technicians tried one color system that threatened to make all the existing black and white sets obsolete overnight. It was a colossal failure, and was taken off the market in just a few months. They had to devise a new color system that would allow viewers to watch the video in black and white on black and white sets, and in color on color sets. Designing a system to do this was one of the most challenging engineering projects ever undertaken in the world of television.
The solution was to mix a separate color signal into the existing black and white information in a way that wouldnt interfere with the picture on black and white sets. Color sets can detect this signal and use it to make a color picture. Since color sets are more expensive to make, black and white sets are still popular today, so this compatibility is still very important.
Now that the engineers have done their work, it’s not too hard to understand what they did and why Y/C cables can make such a dramatic difference. An example from the world of music can help show how they work.
All Together Now
Let’s say youre listening to a piece of classical music. If you listen carefully, you can probably pick out a single instrument–the French Horn, for instance. If you play the piece over again and listen for the flutes this time, you could pick out most of what theyre playing as well.
What you’re doing with your ears (and your brain) when you do this is very similar to what’s known as "filtering" in the world of electronics. An electronic filter tries to pick out just certain frequencies from a complete signal. Examples of filters that you already use in daily life are the tuner controls of radios and TV sets that can pick out just the station you want from all the signals coming in from the antenna or from cable. The bass and treble controls on your stereo, which are sloppy or "broadband" filters that partially filter out or boost a whole range of frequencies in the signal, are another example.
Just as the music an orchestra plays consists of the notes coming from a number of instruments, a complete or "composite" video signal is a kind of music where different instruments (frequencies) represent different characteristics of the picture. Of course, most of this music is at much higher frequencies than you can hear, but the principle is pretty much the same.
Paint By Numbers
In the video signal, a very low frequency tone (called the vertical sync pulse) indicates the start of each picture or "frame" of video. A higher frequency signal (called the horizontal sync pulse) indicates the start of each single horizontal line in the picture. A still higher frequency represents the lighter and darker areas along each of these lines. It is these lighter and darker areas that, when all the lines come together, make a complete black and white picture. Finally, at a frequency that’s right in the middle of these, theres yet another signal that represents the colors to show along each line. This signal causes the TV set or video monitor to sort of "paint in" the colors in the black and white picture already represented by the other frequencies.
Do You Hear What I Hear?
Lets go back to the example of the orchestra for a moment. The color signal is kind of like the sound of a single flute, mixed in with the whole orchestra of the black and white signal. Let’s say you were trying to learn the flute part, but you didn’t have any sheet music, so you had to play it by ear. You might play a recording of the full orchestra over and over again, listening carefully for the flute. Though you might be able to do it with some practice, it would be especially difficult during the parts where many other instruments were playing at the same time. The flute part would be harder to pick out during these passages because the sounds of the other instruments would blend in, or "interfere," with the sound of the flute.
Likewise, the combination of frequencies in a composite video signal presents quite a challenge to the filters inside the TV set or video monitor that are listening for just the color signal. They must do this as accurately as possible or the picture wont look right; it wont have the right colors, or it will suffer from various kinds of interference where the color and black and white signals get mixed in with each other. People wearing dresses or suits with very fine stripes or plaids provide one example of this problem. Suddenly, they may appear to have rainbows of color shimmering on them. Another case is where two very bright colors are right next to each other in the picture. Often, the line separating the two will be fuzzy or have a neat row of tiny notches that move along the edge. Sometimes, there may even be a fine line of a completely different color separating the two. Most people ignore these "artifacts" in the picture most of the time, but as you make successive copies of a videotape in the editing process, these "color errors" build up, making the end result look that much worse.
Staying In Tune
Obviously, one way to help the situation is to design better filter circuits. (Perhaps you’ve heard of comb filters, a popular selling point a few years ago). But using a Y/C cable offers us another solution. Back to our flute music example: let’s say you’d still like to learn the part, but now youre able to buy a special multi-track recording of the piece, prepared just for flute players. One track has just the flute part; the other track has all the other instruments. Now, you can play back just the flute part and hear it clearly. You could also play the whole thing together and hear how it fits into the full orchestra.
By now, you’ve probably figured out that Y/C video signals are kind of like having one part of the music on a separate audio track. The "Y" commonly represents luminance, which is the black and white content of the picture together with the sync pulses (the part of the signal that tells the frames and lines of the picture when to start). The "C" commonly refers to chroma, or the color portion of the signal. In a Y/C cable, the luminance and chrominance portions of the signal each travel on a separate pair of wires. If you look closely at the end of an S-video connector, you can see the four pins or four holes, one for each wire.
Inside the monitor or TV set, the Y signal feeds directly to the various circuits that control the scanning lines and monochrome characteristics of the picture. The C signal goes directly to the color circuits, which use it to control the colors. This scheme eliminates the filtering, allowing both circuits (monochrome and color) to do a better job by giving them a clearer signal to work with in the first place. The edges between light and dark can be sharper and the areas of rich color won’t bleed as much into neighboring parts of the picture. The unwanted rainbows, false colors and blurred edges are cleaned up as well.
Inside a VCR, the Y and C signals travel on separate circuits and then record on the tape at widely separated frequencies. Upon playback, it’s easy to filter them out from each other. The problem has always been how to keep them that way when it’s time to send them on to another piece of equipment.
Getting the best picture quality means that you have to use Y/C cables for every video connection in the entire chain of equipment through which your video travels, including your monitor or TV. This means from camcorder to VCR, to edit VCR, to copy VCR, to viewing monitor. If you use an ordinary video cable at any stage, you’ll miss out on much of the extra picture quality you paid for.
The good news is that by using Y/C cables, your own videos may actually end up looking better than anything you can get over the air or on cable. That’s because the broadcasters and cable companies don’t have the advantage of sending you the color signals separately; they have to send them mixed together in a single composite signal.
Now that you know how to make sure your new equipment gives you all of the extra quality you paid for, its time to take it out and start using it. And when youve shot some footage that you can be proud of, youll have the Y/C connections to do your project justice.
Identifying and Attaching a Y/C Cable
Usually, a Y/C cable isn’t marked as such. Look for a cable with round connectors containing 4 metal pins and one plastic pin. If you carefully examine your new equipment, you should find a connector on it somewhere (perhaps under a rubber cover if it’s a camcorder or behind a hinged door on some VCRs) that this cable will fit snugly into. Usually, this connector is labeled as S-video or just Y/C. Avoid any similar connector that says Control-L, LANC or remote; these connections serve other purposes.
To attach a Y/C cable, be careful to line up the pins so they’ll go in correctly. Use caution; the pins are small and therefore easy to bend. Almost all Y/C cables have a tubular metal shell surrounding the pins which has a groove near the top to guide you. There may also be an arrow or dot molded into the plastic on the cable that lines up with a similar arrow or dot on the connector panel of the equipment.
Dont confuse the Y/C cable with the more common composite video connectors that resemble the cables used for audio. The composite video cable uses an RCA-type connector, with only one pin in the center and a metal shell around the outside. These attach to connectors labeled simply "video," with a yellow colored ring around the hole for the pin. These days, composite video cables usually come bound to a pair of audio cables (red for right; white, gray or black for left; yellow for video).
Some Practical Advice
Of course, there are other factors that can limit the advantage of using Y/C connections. To get the most out of your Y/C connection, here are some suggestions:
- Make sure you carry the video signal via Y/C cables from beginning to end (see figures 1 and 2).
- If you’re editing by copying portions onto a tape in a second VCR, connect the Y/C output from the playback VCR to the Y/C input connector on the recording VCR. Note that the way you connect monitors to your editing system usually won’t affect the picture quality on the final tape, only what you see during editing (see figure 3). However, if you pass your video signals through a piece of equipment that has composite signals only, such as a waveform monitor, this will affect your final video quality.
- Some VCRs have a switch to determine which kind of video connection you’re using (composite or Y/C), so make sure it’s set to the correct position.
- When playing back a tape, use a monitor or TV set that has a Y/C connector, and be sure to connect the VCRs Y/C output connector to the Y/C connector on the monitor.
- Don’t connect a composite video cable in tandem with a Y/C cable for any individual connection. Otherwise, the VCR may use the composite signal instead of the Y/C signal and you won’t get the better picture quality.