Date: Sat, 30 Jul 1994 12:24:25 EDT From: Gary Bourgois Subject: Re: New Receiver (BUD Only) Semi s-video faq S-video is transmitted on two wires. The signal names are luminance or Y, and chrominance or C. The luminance (Y) carries the video information without the color. For example, a black and white tv could display a complete picture with just the luminance (Y) alone. The chrominance carries the color information of the s-video signals. The phase of the chrominance signal determines the actual hue, while the amplitude determines the the saturation of color. The chrominance signal is 3.58mhz and the luminance is 4.2mhz. Also these signals are not really Y and C when they come out of the s-video connector, they must be mixed and amplified in the reciever to drive the RGB guns, then they become Y and C. These two terms are treated interchangeably for simplicity by most texts on the subject, although they are not really the same once they are inside the reciever. Newer recievers and vcr's incorporate a new circuit called a comb filter. A comb filter filters out all frequencies that are multiples of 15.734khz chrominance signal transmission. This filtering results in nearly 25% increase in horizonal resolution of the pictures, as well as reduction of unwanted patterns and cross-color effects (noise) in the pictures. S-video is a standard, so s-video will always deliver a better picture than composite/baseband signals. The American video transmission standard NTSC is 525 lines of resolution, with an aspect ratio of 4:3. Any number of lines may be employed by the transmitting station usually between 482 and 495. 495. RokNroB >From xerox.com!BFisher.El_Segundo Thu Mar 31 15:01:17 1994 Received: by lopez.marquette.MI.US (smail2.5) id AA12549; Thu, 31 Mar 1994 15:01:15 EST Received: from alpha.Xerox.COM by destroyer.rs.itd.umich.edu (5.65/2.2) id AA10683; Thu, 31 Mar 94 14:40:14 -0500 Received: from AE_Mail_Service_7.ES_AE.Xerox.xns by alpha.xerox.com via XNS id < 14527(5)>; Thu, 31 Mar 1994 11:37:47 PST X-Ns-Transport-Id: 0000AA00BC93DE28312C Date: Thu, 31 Mar 1994 11:37:40 PST Sender: xerox.com!BFisher.El_Segundo From: xerox.com!bf.El_Segundo Subject: Making the S Connection In-Reply-To: " " To: tvro@lopez.marquette.mi.us Reply-To: xerox.com!bf.el_segundo Message-Id: <"31-Mar-94 11:37:40 PST".*.BFisher.El_Segundo@Xerox.com> If you will tell me who the keeper of the "(Already too big) FAQ" is, I will pass this along. -This was researched from a recent Stereo Review. "The introduction of Super VHS brought with it a new type of multipin video connector, called S-video or Y/C. Although the connector itself was a good idea that has since spread to Hi8 decks and camcorders, its debut in tandem with S-VHS may not have been, since it has led to some great misconceptions. Most important among these is the completely erroneous notion that VCR's equipped with S connectors cannot be used except with similarly equipped monitors. In fact, all VCR's with S connectors also have the usual complement of composite-video and RF inputs and outputs and will perform very nearly as well with those as they will with the S-video inputs and outputs. The other important misunderstanding is in the idea that the performance improvements associated with S-VHS are somehow tied to the S-video connectors. In truth, S-VHS's single benefit-higher resolution-has to do only with the bandwidth of the signal recorded on the tape, which the S connector doesn't affect at all. The single benefit of the S connector, on the other hand, is equally applicable to all consumer VCR formats, "super" or otherwise. To understand what this is all about, we have to know a little about how a VCR works. When color was added to television, it was done by putting the necessary information on a subcarrier plopped into the high-frequency end of the luminance (black-and-white) signal. Black-and-white receivers ignore this color (C) subchannel, but color sets extract the information it carries and use it together with the luminance (Y) information in the baseband signal to control the intensities of the beams from the three electron guns (for the red, green , and blue primary colors) in the picture tube. Performing this separation is not easy, however, and it almost inevitably results in either a loss of resolution or the creation of small, distracting artifacts, such as as the "hanging dots" that you may notice from time to time crawling along sharp horizontal transitions between areas of color. Professional videotape recorders and laserdiscs record the composite video signal (Y+C, or luminance plus color) directly, but when home VCR's were developed, bandwidth and other limitations forced a different approach, known as "color-under" recording. The color information is separated from the luminance signal and transposed down to a range of frequencies below those used for recording the luminance. This degrades the resolution somewhat, but it's better than going without color. When a videocassette is played back, the VCR normally recombines the color and luminance information into a composite-video signal that then goes to the monitor via a direct-video connection or gets modulated onto an RF carrier with the audio and sent to the monitor via its antenna terminals. Either way, the monitor has to reseparate the color and luminance portions of the video signal. All an S-video connector does is to short-circuit this process, keeping the luminance and color protions of the signal separate so that they don't have to be combined and pulled apart again. In most cases, this will yield a slightly cleaner picture, but the benefit is likely to be marginal, at best, unless the recorded color and luminance signals have always been separate, never tangled together in a composite-video signal. Camcorder recordings fall into this category, but that's about all. So why do some laserdisc players, which start with a composite-video signal, have S-video outputs? To prevent consumers from thinking that they lack a performance feature available on S-VHS and Hi8 VCR's. The only way a Y/C output can do any good on a laserdisc player is if its color-separation circuitry happens to be better than that in your monitor, which is possible but not likely." Cheers, Bill -- / Gary Bourgois, WB8EOH, The Birdwatcher: Marquette Michigan USA \ ([-o Radio Omega G3/17 5.8 - FRIDAY NIGHT LIVE Weekly 9PM Eastern o-]) \ Now a snazzy new DOMAIN address! flash@lopez.marquette.MI.US / GEnie: BIRDWATCHER FAX: (906) 228-7477 GWN BBS: (906) 228-4399