Super Video CD
Super Video CD (Super Video Compact Disc or SVCD) is a digital format for storing video on standard compact discs. SVCD was intended as a successor to Video CD and an alternative to DVD-Video, and falls somewhere between both in terms of technical capability and picture quality. Although SVCDs proved more sophisticated than VCDs, the format remains in the latter's shadow.
Technical specifications
Structure
Similar to VCDs, SVCDs comply with the CD-i Bridge format, and are authored (or "burned") using the CD-ROM XA format. The first track is in CD-ROM XA Mode 2, Form 1, and contains metadata about the disc. The other tracks are in Mode 2, Form 2, and contain audio and video multiplexed in a MPEG program stream (MPEG-PS) container. This allows roughly 800 megabytes of data to be stored on one 80 minute CD (versus 700 megabytes when using Mode 1). One CD can hold up to 35 minutes of full quality SVCD-format video and audio.
Video
S-Video
Separate Video, commonly termed S-Video, Super-Video and Y/C, is a signaling standard for standard definition video, typically 480i or 576i. By separating the black-and-white and coloring signals, it achieves better image quality than composite video, but has lower color resolution than component video.
Signal
The S-video cable carries video using two synchronized signal and ground pairs, termed Y and C.
Y is the luma signal, which carries the luminance – or black-and-white – of the picture, including synchronization pulses.
C is the chroma signal, which carries the chrominance – or coloring-in – of the picture. 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.
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