Editing S-Video (section)

==Background==
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Standard [[analog television]] signals go through several processing steps on their way to being broadcast, each of which discards information and lowers the quality of the resulting images.

The image is originally captured in [[RGB]] form and then processed into three signals known as [[YPbPr]]. 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 (video)|luma]]''. This signal closely matches a traditional [[black and white television]] signal and the Y/C method of encoding was key to offering [[backward compatibility]]. Once the Y signal is produced, it is subtracted from the blue signal to produce '''Pb''' and from the red signal to produce '''Pr'''. To recover the original RGB information for display, the signals are mixed with the Y to produce the original blue and red, and then the sum of those is mixed with the Y to recover the green.

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. This signal is then [[Bandwidth (signal processing)|bandwidth]]-limited to comply with requirements for broadcasting. The resulting Y and C signals are mixed together to produce [[composite video]]. To play back composite video, the Y and C signals must be separated, and this is difficult to do without adding artifacts.

Each of these steps is subject to deliberate or unavoidable loss of quality. To retain that quality in the final image, it is desirable to eliminate as many of the encoding/decoding steps as possible. S-Video is an approach to this problem. It eliminates the final mixing of C with Y and subsequent separation at playback time.