SVCD
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Super Video Compact Disc (SVCD) is a format used for storing video on standard compact discs or CD-Rs. Picture and audio quality is less than that of the DVD format, but higher than its predecessor Video CD (VCD).
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Technical specifications
SVCDs store digital video in MPEG-2 format at a resolution of 480x480 pixels (for NTSC) or 480x576 pixels (for PAL). There is no standard for a SECAM-format SVCD.
Video may be encoded at a variable bit rate, up to 2.6 megabits per second. Audio is stored in MPEG Audio Layer 2 format, with a bit rate varying from 128 to 384 kilobits per second. With ordinary recordable CD-R media, approximately 35 to 60 minutes of video and audio can be stored.
The SVCD format has a number of advantages over VCD in addition to increased picture quality. SVCD discs can theoretically have up to 8 channels of audio (in a 7.1 arrangement) via the MPEG Multichannel surround sound format. However, most discs have only standard MPEG stereo (2.0), bilingual (1+1) or mono (1.0) channel audio, probably because of the lack of MPEG Multichannel-compliant hardware (especially in NTSC countries) and the space-constraints of CD-ROM media.
(Note that Dolby Digital, DTS and other surround sound formats are not used or supported with SVCD - only MPEG Multichannel. This may be because MPEG Multichannel was developed by Philips, who also co-developed the SVCD format, and is a competitor of other digital audio formats.)
Additionally, it has support for overlay subtitles and karaoke lyric highlighting, hyperlinks, and still-image slide shows with resolution up to 704x480 (NTSC) or 704x576 (PAL), very similar to DVD.
SVCD resolution is slightly lower than Laserdisc's horizontal resolution of approximately 550 lines, though Laserdisc uses an analog signal which is measured and behaves differently than digital video. Regardless, as a digital medium, SVCD is less prone to signal degredation and other weaknesses of ageing analog recordings. Most casual users cannot tell the difference between a good SVCD and a DVD, primarily due to the typical composite-signal television often used for playback being the quality bottleneck.
Due its rather rare video resolution, SVCD movies can't be easily converted into DVD-Video format without re-encoding, although various ways are available that allow hacking the MPEG video headers in order to fool the DVD players to think that the video's resolution is one of DVD-Video standard's resolutions. Additional difficulties are posed by the fact that NTSC DVD-Video standard doesn't officially support MPEG Audio Layer 2 as its audio format.
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.
External links
- Technical Explanation of SVCD (http://www.xp-media.com/svcd.pdf)
- AfterDawn's SVCD guides (http://www.afterdawn.com/guides/)
- VideoHelp (http://www.videohelp.com/)
See also
- miniDVD - DVD video on a CDde:Super Video Compact Disc