Video CD (abbreviated as VCD, also known as Compact Disc Digital Video, abbreviated as CDDV) is a home video format and the first format for distributing films on standard 120 mm (4.7 in) optical discs. The format was widely adopted in nearly all of Asia (except for Japan and South Korea), superseding the VHS and Betamax systems in those regions until DVD-Video became more affordable in the 2000s. The format is a standard digital data format for storing video on a compact disc. VCD discs/disc images are playable in dedicated VCD players and widely playable in most DVD players, personal computers and some video game consoles with an optical disc drive that is programmed to understand VCD discs. The Video CD standard was created in 1993 by Sony, Philips, Matsushita and JVC; it is referred to as the White Book standard. The MPEG-1 video compression format was also released that same year.
History
Predecessors
LaserDisc was first available on the market, in Atlanta, Georgia, on December 15, 1978. This 30 cm (12 in) disc could hold an hour of analog audio and video (digital audio was added a few years later) on each side. The LaserDisc provided picture quality nearly double the resolution of VHS tape and analog audio quality far superior to cheap mono VHS recorders (although the difference to the more expensive VHS HiFi stereo recorders was minuscule). Philips later teamed up with Sony to develop a new type of disc, called the compact disc or CD. Introduced in 1982 in Japan (1983 in the U.S. and Europe), the CD is about 120 mm (4.7 in) in diameter, and is single-sided. The format was initially designed to store digitized sound and proved to be a success in the music industry. In 1987, Philips released CD Video (CD-V), effectively a hybrid format combining analog LaserDisc-compatible video alongside separate audio-only CD-compatible tracks on a 12cm CD-sized disc. However, the disc's small size meant it could only hold six minutes of analog video, restricting it primarily to song-length music videos. CD Video had been discontinued by the early 1990s as Philips concentrated on more promising MPEG-based digital video compression.
Development By the early 1990s engineers were able to digitize and compress video signals, greatly improving storage efficiency. Because this new format could hold 74/80 minutes of audio and video on a 650/700MB disc, releasing movies on compact discs finally became a reality. Extra capacity was obtained by sacrificing the error correction, as it was believed that minor errors in the datastream would go unnoticed by the viewer. This format was named Video CD or VCD. Despite the similar name it differed fundamentally from—and was incompatible with—the earlier CD Video format.
VCD enjoyed a brief period of success, with a few major feature films being released in the format (usually as a 2 disc set). However the introduction of the CD-R disc and associated recorders stopped the release of feature films in their tracks because the VCD format had no means of preventing unauthorized (and perfect) copies from being made. Despite this, as of 2013, VCDs were still being produced and released in several countries in Asia with additional copy-protection. The development of more sophisticated, higher capacity optical disc formats yielded the DVD format, released only a few years later with a copy protection mechanism. DVD players use lasers that are of shorter wavelength than those used on CDs, allowing the recorded pits to be smaller, so that more information can be stored. The DVD was so successful that it eventually pushed VHS out of the video market once suitable recorders became widely available. Nevertheless, VCDs made considerable inroads into developing nations such as in Asia where low-cost VCD players as well as pirated copies of films were widespread.
Technical specifications
Structure Video CDs comply with the CD-i Bridge format, and are authored using tracks in CD-ROM XA mode. The first track of a VCD is in CD-ROM XA Mode 2 Form 1, and stores metadata and menu information inside an ISO 9660 filesystem. This track may also contain other non-essential files, and is shown by operating systems when loading the disc. This track can be absent from a VCD, which would still work but would not allow it to be properly displayed in computers. The rest of the tracks are usually in CD-ROM XA Mode 2 Form 2 and contain video and audio multiplexed in an MPEG program stream (MPEG-PS) container, but CD audio tracks are also allowed. Using Mode 2 Form 2 allows roughly 800 megabytes of VCD data to be stored on one 80 minute CD (versus 700 megabytes when using CD-ROM Mode 1). This is achieved by sacrificing the error correction redundancy present in Mode 1. It was considered that small errors in the video and audio stream pass largely unnoticed. This, combined with the net bitrate of VCD video and audio, means that almost exactly 80 minutes of VCD content can be stored on an 80-minute CD, 74 minutes of VCD content on a 74-minute CD, and so on. This was done in part to ensure compatibility with existing CD drive technology, specifically the earliest "1x" speed CD drives.
Video
Video specifications
Compression: MPEG-1 Aspect Ratio: 4:3 Resolution: analog NTSC compatible: 352×240 (240p) analog PAL/SECAM compatible: 352×288 (288p) Framerate: analog NTSC compatible : 29.97 or 23.976 frames per second analog PAL/SECAM compatible : 25 frames per second Bitrate: 1,150 kilobits per second (constant bitrate) Although many DVD video players support playback of VCDs, VCD video is only compatible with the DVD-Video standard if encoded at 29.97 frames per second or 25 frames per second. The 352×240 and 352×288 (or SIF) resolutions, when compared to the CCIR 601 specifications (defining the appropriate parameters for digital encoding of NTSC and PAL/SECAM TV signals), are reduced by half in all aspects: height, width, frame-rate, and chrominance.
Audio Audio specifications
Compression: MPEG-1 Audio Layer II (MP2) Sample Frequency: 44,100 hertz (44.1 kHz) Output: Dual channel, stereo, or Dolby Surround Bitrate: 224 kilobits per second (constant bitrate) As with most CD-based formats, VCD audio is incompatible with the DVD-Video standard due to a difference in sampling frequency; DVDs require 48 kHz, whereas VCDs use 44.1 kHz.
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