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Super Video CD

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File:SVCDlogo.svg
Compact Disc Super Video (SVCD) logo/trademark

Super Video CD (Super Video Compact Disc or SVCD) is a format used 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.

Technical specifications

SVCD has two-thirds the resolution of DVD, and over 2.7 times the resolution of VCD. One CD-R disc can hold up to 60 minutes of standard quality SVCD-format video. While no specific limit on SVCD video length is mandated by the specification, one must lower the video bitrate, and therefore quality, in order to accommodate very long videos. It is usually difficult to fit much more than 100 minutes of video onto one SVCD without incurring significant quality loss, and many hardware players are unable to play video with an instantaneous bitrate lower than 300 to 600 kilobits per second.

Video

The combined audio and video bitrates should not exceed 2756 kilobits.

Interlaced video is supported (though not required) for SVCD video, except for any video at 23.976 frames per second, as it must use 3:2 pulldown.

Unlike other CD-based video formats such as China Video Disc and Video CD, Super Video CD video is incompatible with the DVD-Video standard due to a conflict in resolution. However, the 480x480/576 resolution is supported by the HD DVD standard.

Audio

As with most Compact Disc-based video formats, SVCD audio is incompatible with the DVD-Video standard due to the difference in frequency; DVDs require 48 kHz, whereas SVCDs use 44.1 kHz.

Additional features

The SVCD standard supports several other features, including menus, hyperlinks, karaoke lyric highlighting, four selectable overlay subtitle streams, and DVD-quality slide shows with resolution up to 704x480 (NTSC) or 704x576 (PAL). SVCDs may have two separate stereo or four mono audio tracks (for commentary or additional languages); audio may have up to 6 channels (in a 5.1 arrangement) using the MPEG-2 Multichannel surround sound format, though space constraints and poor hardware support make it somewhat impractical.

Playback issues

Presentation of SVCD titles on most players is marred by an unfortunate violation of sampling theory almost built into the spec. The "2/3" choice for resolution is rarely consistently implemented end to end through the full player electronics. Because a DVD player might include provisions for various VCD, SVCD, and DVD horizontal resolutions (360, 480, 540 or 720) and only one analog low pass filter is provided, 2 out of the 3 formats will suffer aliasing when presented on the screen. Usually, the best resolution, DVD 720 dictates filter design, with SVCD display suffering from "foldover". While displays should follow correct theory, the objectionable aliasing artifacts that result are usually buried in noise from other sources, such as camera, quantization, and MPEG artifacts.

History of development

Super Video CD was originally developed by the government-backed China Recording Standards Committee, under direction from the Chinese Ministry of Information Industry, as an enhancement to the Video CD format. One of the motivating factors in its development was the need for an alternative to the DVD format that would not be restricted by technology royalties. The Chinese government was concerned that the DVD format was too tightly controlled by foreign companies, and that a significant opportunity existed for the development of a domestic format that could deliver comparable quality without the restrictions of DVD. It was also hoped that SVCD's development would help to drive down the cost of consumer DVD players and DVD licensing fees in China.

SVCD started as one of three independent efforts to solve these problems. The other two were China Video Disc (CVD), developed by C-Cube Microsystems, and High-Quality Video CD (HQ-VCD), developed by the Video CD Consortium, consisting of Philips, Sony, Matsushita and JVC, that created the original Video CD specification. CVD was first out of the gate, and had completed its specification before the other two had even reached a draft stage. The Ministry of Information and Video CD Consortium agreed to join forces, incorporating the features of HQ-VCD under a unified SVCD format, but by the time their specification was ready in July 1998, CVD had already been adopted by major manufacturers of VCD players. In order to maintain compatibility, CVD was also brought under the unified SVCD format, resulting in the Chaoji Video CD specification in November 1998. Chaoji Video CD, or Chaoji VCD, is roughly synonymous with Super VCD. A Super VCD player must be able to play a variety of formats, including SVCD, CVD, VCD 2.0, VCD 1.1 and CD-DA discs.

SVCD is under consideration for IEC standardization, so SVCD will likely become recognized internationally as a standard CD format, just as the Compact Disc and Video CD formats already are. Philips has already added an SVCD logo to its canon of official Compact Disc logos. SVCD titles are available commercially in China, Hong Kong, Taiwan, and several other Asian countries; whether the SVCD standard will enjoy commercial success outside of Asia remains to be seen, however. In the Western world, the format is more commonly used to store home videos or movies copied from DVD and Laserdisc.

See also

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