However, the shield is often absent in low-end cables, which can result in picture degradation. Standard analog television signals go through several processing steps on their way to being broadcast, each of din patch port discards information and lowers the quality of the resulting images.
The first of these signals is called Y, which is created from all three original signals based on a formula that produces an overall brightness of the image, or luma. A signal with three components is no easier to broadcast than the original three-signal RGB, so additional processing is required. The first step is to combine the Pb and Pr to form the C signal, for chrominance. The phase and amplitude of the signal represent the two original signals. Each of these steps is subject to deliberate or unavoidable loss of quality. S-Video is an approach to this problem. It eliminates the final mixing of C with Y and subsequent separation at playback time.
The S-video cable carries video using two synchronized signal and ground pairs, termed Y and C. This signal contains both the saturation and the hue of the video. The luminance signal carries horizontal and vertical sync pulses in the same way as a composite video signal. Luma is a signal carrying luminance after gamma correction, and is therefore termed “Y” because of the similarity to the lower-case Greek letter gamma. In composite video, the signals co-exist on different frequencies. To achieve this, the luminance signal must be low-pass filtered, dulling the image. As S-Video maintains the two as separate signals, such detrimental low-pass filtering for luminance is unnecessary, although the chrominance signal still has limited bandwidth relative to component video.
Pr, the color resolution of S-Video is limited by the modulation on a subcarrier frequency of 3. 43 megahertz, depending on the standard. Carrying the color information as one signal means that the color has to be encoded in some way, typically in accord with NTSC, PAL, or SECAM, depending on the applicable local standard. Also, S-Video suffers from low color resolution. 250 lines horizontal for the Rec. 601-encoded signal of a DVD, or 30 lines horizontal for standard VCRs.
This section needs additional citations for verification. In many European Union countries, S-Video was less common because of the dominance of SCART connectors, which are present on most existing televisions. It is possible for a player to output S-Video over SCART, but televisions’ SCART connectors are not necessarily wired to accept it, and if not the display would show only a monochrome image. Game consoles sold in PAL territories usually do not output S-Video. The Nintendo 64 was a special case: Both NTSC and PAL models could output S-Video. In the US and some other NTSC countries, S-Video was provided on some video equipment, including most televisions and game consoles.