definition of Wikipedia
||This article has multiple issues. Please help improve it or discuss these issues on the talk page.
|Media type||Optical disc|
|Encoding||MPEG-1 video + audio|
|Capacity||Up to 800 MB|
|Read mechanism||780 nm wavelength semiconductor laser|
|Developed by||Sony, Philips, Matsushita, JVC|
|Usage||audio and video storage|
Before the advent of DVD and Blu-ray, the Video CD (abbreviated as VCD, and also known as View CD, Compact Disc digital video) became the first format for distributing films on standard 120 mm optical discs. The format is a standard digital format for storing video on a Compact Disc. VCDs are playable in dedicated VCD players, most DVD-Video players, personal computers, and some video game consoles.
The VCD standard was created in 1993 by Sony, Philips, Matsushita, and JVC and is referred to as the White Book standard. Though supplanted by the two aforementioned formats, VCDs are still popular, particularly in the low cost market.
In the early 1970s, Philips and MCA developed the Laserdisc. That optical medium is 30 cm in diameter, and holds an hour of analog video (along with audio in either analog or digital) on both sides. Though they provide superior picture quality through countless playbacks, Laserdiscs were always overshadowed by VHS because of their high price and lack of recording abilities.
Near the end of the 1970s, Philips created a small-scale version of the Laserdisc. The disc is 120 mm in diameter, and is single-sided. Dubbed the compact disc or CD, the format was initially designed to store digitized sound and proved to be a success in the music industry.
A few years later, Philips decided to give CDs the ability to produce video just like its 12-inch counterpart. This led to the creation of CD Video (CD-V) in 1987. However, the disc's small size significantly impeded the ability to store analog video; thus only 5 minutes of picture information could fit on the disc's surface (despite the fact that the audio was digital). Therefore CD-V distribution was limited to featuring music videos.
By the early 1990s engineers were able to digitize video signals, greatly improving storage efficiency. Because this new format could hold 83 minutes of audio and video, releasing movies on compact discs finally became a reality. Extra capacity was obtained by sacrificing the error correction (it was believed that minor errors in the datastream would go unnoticed by the viewer). This format was named Video CD or VCD.
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.
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, where they are still in use today.
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.
As with most CD-based formats, VCD audio is incompatible with the DVD-Video standard due to a difference in frequency; DVDs require 48 kHz, whereas VCDs use 44.1 kHz.
By compressing both the video and audio streams, a VCD is able to hold 74 minutes of picture and sound information, nearly the same duration as a standard 79 minute audio CD. The MPEG-1 compression used records mostly the differences between successive video frames, rather than write out each frame individually. Similarly, the audio frequency range is limited to those sounds most clearly heard by the human ear.
Video CDs are authored using the Mode 2/XA format, allowing roughly 800 megabytes of VCD data to be stored on one 80 minute CD (versus 700 megabytes when using Mode 1). 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.
The VCD standard also features the option of DVD-quality still images/slide shows with audio, at resolutions of 704x480 (NTSC) or 704x576 (PAL/SECAM). Version 2.0 also adds the playback control (PBC), featuring a simple menu like DVD-video.
352x240 and 352x288 (or SIF) resolution was chosen because it is half the vertical, and half the horizontal resolution of NTSC and PAL video, respectively. This is approximately half the resolution of an analog VHS tape which is ~330 horizontal and 480 vertical (NTSC) or 330x576 (PAL).
An example of the software control chart [taken from Flower And Snake disc 1 of 3] including menu commands found in the configuration volume as "CDI_VCD.CFG"
CONTROLS=ALL CURCOL=YELLOW PSDCURCOL=RED PSDCURSHAPE=ARROW INITLANG=DAT SUBTTYPE=OVERLAYED SUBTTCOL=EBEBEB SUBSTCOL=101010 SUBTBCOL=0 SUBTACOL=999999 CENTRTRACK=2 AUTOPLAY=AUTO_ON DUALCHAN=DUAL_ON TIMECODE_X=64 TIMECODE_Y=100 LOTID_X=64 LOTID_Y=64 ALBUM=STANDARD
Shortly before the advent of White Book VCD, Philips started releasing movies in the Green Book CD-i format. While these used a similar format (MPEG-1), due to minor differences between the standards these discs are not compatible with VCD players. Philips' CD-i players with the Full Motion Video MPEG-1 decoder cartridge would play both formats. Only a few CD-i DV titles were released before the company switched to the current VCD format for publishing movies.
XVCD (eXtended Video CD) is the name generally given to any format that stores MPEG-1 video on a compact disc in Mode 2/XA, but does not strictly follow the VCD standard.
A normal VCD is encoded to MPEG-1 at a constant bit rate (CBR), so all scenes are required to use exactly the same data rate, regardless of complexity. However, video on an XVCD is typically encoded at a variable bit rate (VBR), so complex scenes can use a much higher data rate for a short time, while simpler scenes will use lower data rates. Some XVCDs use lower bitrates in order to fit longer videos onto the disc, while others use higher bitrates to improve quality. MPEG-2 may be used instead of MPEG-1.
To further reduce the data rate without significantly reducing quality, the size of the GOP can be increased, a different MPEG-1 quantization matrix can be used, the maximum data rate can be exceeded, and the bit rate of the MP2 audio can be reduced (or even the use of MP3 audio instead of MP2 audio). These changes can be advantageous for those who want to either maximize video quality, or use fewer discs.
KVCD (K Video Compression Dynamics) is an XVCD variant that requires the use of a proprietary-quantization matrix, available for non-commercial use. KVCD is notable because the specification recommends a non-standard resolution of 528x480 or 528x576. KVCDs encoded at this resolution are only playable by computers with CD-ROM drives, and a small number of DVD players.
DVCD or Double VCD is a method to accommodate longer videos on a CD. A non-standard CD is overburned to include up to 100 minutes of video. However, some CD-ROM drives and players have problems reading these CDs, mostly because the groove spacing is outside specifications and the player's laser servo is unable to track it.
The advent of recordable CDs, inexpensive recorders, and compatible DVD players spurred VCD acceptance in the US in the late 1990s and early 2000s. However, DVD burners and DVD-Video recorders were available by that time, and equipment and media costs for making DVD-Video fell rapidly. DVD-Video, with its longer run time and much higher quality, quickly overshadowed VCD in areas that could afford it. In addition many early DVD players could not read recordable (CD-R) media, and this limited the compatibility of home-made VCDs. Almost every modern stand-alone DVD-Video player can play VCDs burned on recordable media. However, some modern players cannot play VCDs; for instance, the Sony PlayStation 3.
The VCD format was very popular throughout Asia (except Japan and South Korea) in the late 1990s through the 2000s, with 8 million VCD players sold in China in 1997 alone, and more than half of all Chinese households owning at least one VCD player by 2005.
This popularity is, in part, because most households did not already own VHS players when VCDs were introduced, the low price of the players, their tolerance of high humidity (a notable problem for VCRs), easy storage and maintenance, and the lower-cost media. Western sources have cited counterfeiting as a principal concern of VCD users.
VCDs are often produced and sold in Asian countries and regions such as Mainland China, Taiwan, Hong Kong, Singapore, Malaysia, Thailand, Burma, Indonesia, Philippines, India, Pakistan and Bangladesh. In many Asian countries, major Hollywood studios (and Asian home video distributors) have licensed companies to officially produce and distribute the VCDs, such as MCA Home Video in Pakistan, ERA of Hong Kong, Sunny Video in Malaysia, Vision in Indonesia, CVD International and Pacific Marketing and Entertainment Group in Thailand, Excel Home Videos in India, Berjaya-HVN and InnoForm Media in both Malaysia and Singapore, Scorpio East Entertainment in Singapore, as well as VIVA Video, Magnavision, and The Video to C in the Philippines. Legal Video CDs can often be found in established video stores and major book outlets in most Asian countries. They are typically packaged in jewel cases like commercial CDs, though higher-profile films may be released in keep cases. The consumer should always check for the VCD or DVD logo so as to avoid purchasing the wrong format.
In Asia, the use of VCDs as carriers for karaoke music is very common. One channel would feature a mono track with music and singing, another channel a pure instrumental version for karaoke singing. Prior to this, karaoke music was carried on laserdiscs.A large number of CD Movies sell in Indian market.
In Burma, VCDs are the medium of an underground video network that largely stays beneath the sights of the military regime, although VCD trends are reported on by expatriate newspapers. Popular videos include Buddhist monks speaking out against the regime and comedy skits ruthlessly mocking military leaders. It is reported that even soldiers watch VCDs in their barracks.
VCD's growth has slowed in areas that can afford DVD-Video, which offers most of the same advantages, as well as better picture quality (higher resolution with fewer digital compression artifacts) due to its larger storage capacity. However, VCD has simultaneously seen significant new growth in emerging economies like India, Indonesia, South America and Africa as a low-cost alternative to DVD. As of 2004, the worldwide popularity of VCD was increasing.
Overall picture quality is intended to be comparable to VHS video. Poorly compressed VCD video can sometimes be lower quality than VHS video, but VCD exhibits block artifacts (rather than the analog noise seen in VHS sources) and does not deteriorate further with each use. While both formats need fast-forwarding to find certain scenes, rewinding to beginning upon reaching the end is not required in VCD.
Though technically superior when compared to tape-based mediums, VCDs have a few minor flaws. Videos in the format do not come with closed caption (written words appearing on-screen to aid viewers with hearing problems). When watching a film that exceeds 74 minutes, which is the maximum video capacity of one disc, a viewer would have to stand up and change the disc upon reaching half-way (unless the discs are played on a VCD changer that could hold multiple discs as well as playing them automatically in succession), whereas a single VHS can hold 3½ hours of continuous video.
When playing a DVD, the viewer is brought to a main menu which gives them options (watch the feature film, view deleted scenes, play some special applications, etc.). VCDs are usually straightforward, playing them often goes directly to the video with extras (mostly trailers and commercials) taking place before or after it.
Subtitles are found on many Asian VCDs but cannot be removed, unlike DVDs. The subtitles are embedded on the video during the encoding process. It's not uncommon to find a VCD with subtitles for two languages.
Though the VCD technology can support it, most films carried on VCDs do not contain chapters, requiring the viewer to fast-forward to resume the program after playback has been stopped. This is mostly because VCD technology is able to start playback at a chapter point but there is nothing to signal the player that the chapter has changed during a program. This can be confusing for the user as the player will indicate that it is still playing chapter 1 when it has played through to chapter 2 or later. Pressing the Next button would cause playback from the beginning of chapter 2. However, preview material is sometimes stored in a separate chapter, followed by a single chapter for the film.
VCDs are often bilingual. Because they feature stereo audio, disc players have an option to play only the left or right audio channel. For example, ERA of Hong Kong's release of the animated film The Iron Giant features English on the left audio channel and Cantonese on the right. This is similar to selecting a language track on a DVD, except it's limited to 2 languages, due to there being only two audio channels (left and right). The audio track effectively becomes monaural.
VCD's most noticeable disadvantage compared to DVD is image quality, due both to the more aggressive compression necessary to fit video into such a small capacity as well as the compression method used. Additionally, VCDs are available only in stereo, while DVDs are capable of six channels of discrete surround sound. The audio compression of VCDs also suffers from not being able to pull off the Haas effect for matrixed surround sound.
VCD does have a few advantages over DVD-Video:
Video CDs are not popular in the US, Canada and Europe, so its support is limited among mainstream software. Windows Media Player prior to version 9 and QuickTime Player do not support playing VCD directly, though they can play the .DAT files (stored under \MPEGAV for video and audio data) reliably, and plugins were available. Windows Vista added native support of VCD along with DVD-Video and can launch the preferred application upon insertion. The disc format is also supported using Windows Media Player Classic variations and VLC Media Player both support VCDs natively.
Most DVD players are compatible with VCDs and VCD-only Players are available throughout Asia, and online through many shopping sites. Some Blu-ray and HD-DVD players also retain support, as do CBHD players as well.
Dictionary and translator for handheld
New : sensagent is now available on your handheld
A windows (pop-into) of information (full-content of Sensagent) triggered by double-clicking any word on your webpage. Give contextual explanation and translation from your sites !
With a SensagentBox, visitors to your site can access reliable information on over 5 million pages provided by Sensagent.com. Choose the design that fits your site.
Improve your site content
Add new content to your site from Sensagent by XML.
Crawl products or adds
Get XML access to reach the best products.
Index images and define metadata
Get XML access to fix the meaning of your metadata.
Please, email us to describe your idea.
Lettris is a curious tetris-clone game where all the bricks have the same square shape but different content. Each square carries a letter. To make squares disappear and save space for other squares you have to assemble English words (left, right, up, down) from the falling squares.
Boggle gives you 3 minutes to find as many words (3 letters or more) as you can in a grid of 16 letters. You can also try the grid of 16 letters. Letters must be adjacent and longer words score better. See if you can get into the grid Hall of Fame !
Change the target language to find translations.
Tips: browse the semantic fields (see From ideas to words) in two languages to learn more.