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HOW MANY LINES OF RESOLUTION
DOES AN S-VIDEO SIGNAL PUT OUT
Most direct satellite receivers (DSS receivers) have "composite," "S-Video," and "RF" outputs. New DSS Products These are the jacks found on the back for the connection to the television, VCR, or modulator.
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 In case you are wondering about these connectors, this graphic is the back of a typical DSS receiver. It resembles the back side of other video devices like DVD players, VCRs, and cable boxes. It has three output connectors for connecting to your equipment. In terms of quality of the picture, starting with the best to use:
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- S-Video
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- Composite (the yellow jack labeled "Video")
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- Coax RF Output (labeled "To TV/VCR")
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When you have a choice, use the connectors that give you the best picture, starting with S-Video. However, we are getting ahead of ourselves.
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 | | | Coax RF Jack | |
  | The most familiar connector to most folks is the coax RF output connector. Most video devices have this jack, although it has been rare to find this plug on DVD players and other high-end devices. This one output carries the audio and video on a modulated frequency. Just like a roof top antenna or cable TV signal, this one line can carry multiple signals on different frequencies or television channels. For a video device, like our sample DSS receiver, the video and audio signals from this connector have been converted to channel 3 or 4 by means of a "modulator" inside the DSS receiver. At your TV, the tuner "de-modulates" this signal back into audio (for the speakers) and video (for the picture tube). This modulating and demodulating will degrade the picture quality. Additionally, the audio signal sent via this line is monaural, not stereo sound (bet you didn't know that!)
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| | | RCA Jack | |
  | The "Composite" audio and video outputs are the most versatile ones to use since most TVs have these inputs. The jacks are commonly called RCA jacks (probably since they invented them decades ago.) For this DSS receiver, three cables are needed to carry the signals between the receiver and the television. I could write an entire column about cables and quality, but I won't. I will be happy if you use these connections for your video device over the RF coax lines mentioned above. The video line carries all the video information on one cable. It is what we call a "baseband signal," meaning that the signal is not modulated to a channel. It's pure video signals. The two audio lines maintain the stereo sound for your system, so you'll enjoy better quality sound. Because the signal is not converted or modulated as much as the RF coax lines, you'll end up with a better picture.
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| | | S-Video Jack | |
  | The best picture output we can get from this unit will be achieved by using the "S-Video" plug. S-Video, which is sometimes confused with "S-VHS," is similar to the video composite output. This single jack only sends the video information, so you will still need to use the RCA audio outputs for sound. The S-Video jack sends out two video signals, the luminance (brightness factor) and chrominance (color factor). It's a more precise way of displaying the output picture. The improved luminance and chrominance may in some cases produce about 50% better picture quality. The improvement is noticeable in very sharp edges, bright vivid colors, and an overall crisp look. When the latest generation of video game consoles are connected to a television with the S-video connector, the quality will rival that of arcade games.
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An S-video connection between the video device and the TV keeps the chrominance (C) and luminance (Y) information completely separate. When your television receives a signal via the RF Coax antenna jack or the RCA composite lines, the Y and C information must be separated. This is done by using a comb filter inside the TV, or in the cheaper models, a notch filter. If you connect your DSS to your television with the RF or composite video connectors (both of which pass a combined video signal), the separate C and Y information inside the DSS receiver must be recombined in the DSS, sent to the television, and then separated again. Each time the signals are combined and separated, the C and Y information in the picture is degraded. By using an S-video connector, the Y and C information are kept separate and the picture quality is maximized.
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| | | SVGA and Component | |
All we have discussed here is the quality of the picture's quality components, the chrominance (C) and luminance (Y) information. The differences between all three types of connectors here only deal with the separation or lack of separation of those two signals. They don't involve the number of lines or video resolution on a screen.
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 | There are two additional video connections beginning to appear on video gear; SVGA and Component. Both are further attempts to keep parts of the video signal apart and give the viewer a better picture. In the photo on the right is a shot of the back side of our newest DSS HDTV Tuner from RCA. It includes all three video jacks mentioned earlier plus a jack labeled "HD Monitor Out". While looking like the video jack found on the back of your computer, it's made for High Definition-ready televisions. This jack does indeed provide more lines of resolution.
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 The last type of video output making its appearance these day is the "Component" output jacks. The signals here are further separated into the three primary colors televisions work with. The quality levels between component and SVGA are pretty close and there is still much debate about which is better. If you have the opportunity to invest in a new TV with one of these connectors, don't be too concerned about which one it has as long as it has at least one of them. Smarthome has been selling a converter to change SVGA signals into component signals for some time now as #777060 VGA to Component Video Converter.
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Getting back to the lines of resolution issue, we have learned that for the most part, the output connection doesn't have too much impact on the lines we see on the screen. Below is a table that estimates the line of resolution one can expect from some different sources.
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| Video Source | Lines of resolution | | Over the air Broadcast | 330 lines | | Regular cable | Highly variant, probably not more than 400 lines on even the best system | | DBS (digital satellite) | Around 420 lines. Practically less due to them trying to squeeze more channels in. Pay-per-view movie channels may be over 500. | | VHS | 240 lines | | S-VHS videotape | 425 lines | | DVD | 480 lines |
The "source" used by cable or satellite from a broadcast station is usually not the ~330 line signal coming out of the broadcast antenna; rather, it's from some point in the chain prior to that where the resolution is theoretically higher.
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PPV movies look so good because they are not compressed as much as other channels. Additionally, the movies are digitized ahead of time and basically played back from a hard drive instead of a tape or DVD and compressed on-the-fly.
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Off-air TV has about 380 lines of resolution, and this arrives at the TV with an average of 330 lines. The problem is that the average TV set using North American NTSC can achieve only about 220 lines.
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updated 6/28/05
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