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92-500: The format is a standard digital data format for storing video on a compact disc . VCDs are playable in dedicated VCD players and widely playable in most DVD players , personal computers and some video game consoles . However, they are less playable in most Blu-ray Disc players, vehicle audio with DVD/Blu-ray support and video game consoles such as the Sony PlayStation and Xbox due to lack of backward compatibility for

184-465: A signal , thus which keys are pressed. When the keyboard processor detects that a key has changed state, it sends a signal to the CPU indicating the scan code of the key and its new state. The symbol is then encoded or converted into a number based on the status of modifier keys and the desired character encoding . A custom encoding can be used for a specific application with no loss of data. However, using

276-403: A 12×/10×/32× CD drive can write to CD-R discs at 12× speed (1.76 MB/s), write to CD-RW discs at 10× speed (1.46 MB/s), and read from CDs at 32× speed (4.69 MB/s), if the CPU and media player software permit speeds that high. Software distributors, and in particular distributors of computer games, often make use of various copy protection schemes to prevent software running from any media besides

368-416: A CD-ROM, each track can have its sectors in a different mode from the rest of the tracks. They can also coexist with audio CD tracks, which is the case of mixed mode CDs . Both Mode 1 and 2 sectors use the first 16 bytes for header information, but differ in the remaining 2,336 bytes due to the use of error correction bytes. Unlike an audio CD, a CD-ROM cannot rely on error concealment by interpolation ;

460-749: 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

552-414: A block). Disc image formats that store raw CD-ROM sectors include CCD/IMG , CUE/BIN , and MDS/MDF . The size of a disc image created from the data in the sectors will depend on the type of sectors it is using. For example, if a CD-ROM mode 1 image is created by extracting only each sector's data, its size will be a multiple of 2,048; this is usually the case for ISO disc images . On a 74-minute CD-R, it

644-458: A group of switches that are polled at regular intervals to see which switches are switched. Data will be lost if, within a single polling interval, two switches are pressed, or a switch is pressed, released, and pressed again. This polling can be done by a specialized processor in the device to prevent burdening the main CPU . When a new symbol has been entered, the device typically sends an interrupt , in

736-466: A higher reliability of the retrieved data is required. To achieve improved error correction and detection, Mode 1, used mostly for digital data, adds a 32-bit cyclic redundancy check (CRC) code for error detection, and a third layer of Reed–Solomon error correction using a Reed-Solomon Product-like Code (RSPC). Mode 1 therefore contains 288 bytes per sector for error detection and correction, leaving 2,048 bytes per sector available for data. Mode 2, which

828-509: 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 of lower quality than VHS video, for example exhibiting VCD block artifacts (rather than the analog noise seen in VHS sources), but does not deteriorate further with each use. Producing video CDs involves stripping out high- and low-frequency sounds from

920-477: A proprietary interface, such as the Panasonic CD interface , LMSI/Philips, Sony and Mitsumi standards. Virtually all modern CD-ROM drives can also play audio CDs (as well as Video CDs and other data standards) when used with the right software. CD-ROM drives employ a near- infrared 780 nm laser diode . The laser beam is directed onto the disc via an opto-electronic tracking module, which then detects whether

1012-485: A pure instrumental version for karaoke singing. Prior to this, karaoke music was carried on LaserDiscs . VCD's growth had slowed in areas that could afford DVD-Video , which offered 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 had simultaneously seen significant growth in emerging economies like India , Indonesia , South America , and Africa as

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1104-448: A specialized format, so that the CPU can read it. For devices with only a few switches (such as the buttons on a joystick ), the status of each can be encoded as bits (usually 0 for released and 1 for pressed) in a single word. This is useful when combinations of key presses are meaningful, and is sometimes used for passing the status of modifier keys on a keyboard (such as shift and control). But it does not scale to support more keys than

1196-424: A standard encoding such as ASCII is problematic if a symbol such as 'ß' needs to be converted but is not in the standard. It is estimated that in the year 1986, less than 1% of the world's technological capacity to store information was digital and in 2007 it was already 94%. The year 2002 is assumed to be the year when humankind was able to store more information in digital than in analog format (the "beginning of

1288-489: A very similar manner (only differing from audio CDs in the standards used to store the data). Discs are made from a 1.2 mm thick disc of polycarbonate plastic , with a thin layer of aluminium to make a reflective surface. The most common size of CD-ROM is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as shaped compact discs in numerous non-standard sizes and molds (e.g., business card-sized media ), also exist. Data

1380-450: Is binary data , which is represented by a string of binary digits (bits) each of which can have one of two values, either 0 or 1. Digital data can be contrasted with analog data , which is represented by a value from a continuous range of real numbers . Analog data is transmitted by an analog signal , which not only takes on continuous values but can vary continuously with time, a continuous real-valued function of time. An example

1472-467: 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. DVI ( Digital Video Interactive ) is a compression technique that stored 72 minutes of video on a CD-ROM . In 1998, Intel acquired the technology from RCA 's Sarnoff Research Labs. DVI never caught on. Super Video CD

1564-504: Is a free, open-source media player software which supports VCD on Windows , MacOS , Linux and BSD . Windows Media Player prior to version 9 does not support playing VCD directly. 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 natively by Media Player Classic , VLC Media Player and MPlayer . QuickTime Player also does not support playing VCD directly, though it can play

1656-589: Is a format intended to be the successor of VCD, offering better quality of image and sound. The format uses MPEG-2 video at 480x480 or 480x576 and supports multiple bitrate and channel options for encoding audio. Video CDs were unable to gain acceptance as a mainstream format in North America , chiefly because the established VHS format was less expensive, offered comparable video quality, and could be recorded over. The advent of recordable CDs , inexpensive recorders, and compatible DVD players spurred VCD acceptance in

1748-463: Is a maximum. 20× was thought to be the maximum speed due to mechanical constraints until Samsung Electronics introduced the SCR-3230, a 32× CD-ROM drive which uses a ball bearing system to balance the spinning disc in the drive to reduce vibration and noise. As of 2004, the fastest transfer rate commonly available is about 52× or 10,400 rpm and 7.62 MB/s. Higher spin speeds are limited by the strength of

1840-511: 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

1932-417: Is an XVCD variant that requires the use of a proprietary quantization matrix , created by Karl Wagner and made available for non-commercial use. In addition to standard VCD resolutions, KVCD allows for non-standard resolutions like 528×480/576, though hardware support for KVCDs authored with these resolutions is limited. DVCD or Double VCD is a method to accommodate longer videos on a CD. A non-standard CD

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2024-578: Is defined as "1× speed". Therefore, for Mode 1 CD-ROMs, a 1× CD-ROM drive reads 150/2 = 75 consecutive sectors per second. The playing time of a standard CD is 74 minutes, or 4,440 seconds, contained in 333,000 blocks or sectors . Therefore, the net capacity of a Mode-1 CD-ROM is 650 MB (650 × 2 ). For 80 minute CDs, the capacity is 703 MB. CD-ROM XA is an extension of the Yellow Book standard for CD-ROMs that combines compressed audio, video and computer data, allowing all to be accessed simultaneously. It

2116-517: Is incompatible with the DVD-Video standard due to a difference in sampling 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, the same duration as a standard 74 minute audio CD. The MPEG-1 compression used records mostly the differences between successive video frames, rather than write out each frame individually. Similarly,

2208-523: Is limited to Dolby Surround matrixed within the stereo tracks, while DVDs are capable of six channels of discrete surround sound via Dolby Digital AC-3. Early devices supporting Video CD playback include the Philips CD-i systems and the Amiga CD-32 (albeit via an optional decoder card). Disc playback is also available both natively and as an option on some CD- and DVD-based video game consoles, including

2300-418: Is more appropriate for image or video data (where perfect reliability may be a little bit less important), contains no additional error detection or correction bytes, having therefore 2,336 available data bytes per sector. Both modes, like audio CDs, still benefit from the lower layers of error correction at the frame level. Before being stored on a disc with the techniques described above, each CD-ROM sector

2392-551: Is most commonly used in computing and electronics , especially where real-world information is converted to binary numeric form as in digital audio and digital photography . Since symbols (for example, alphanumeric characters ) are not continuous, representing symbols digitally is rather simpler than conversion of continuous or analog information to digital. Instead of sampling and quantization as in analog-to-digital conversion , such techniques as polling and encoding are used. A symbol input device usually consists of

2484-428: Is possible to fit larger disc images using raw mode, up to 333,000 × 2,352 = 783,216,000 bytes (~747 MB). This is the upper limit for raw images created on a 74 min or ≈650 MB Red Book CD. The 14.8% increase is due to the discarding of error correction data. CD-ROM capacities are normally expressed with binary prefixes , subtracting the space used for error correction data. The capacity of a CD-ROM depends on how close

2576-534: Is present in the computer's CD-ROM drive. Manufacturers of CD writers ( CD-R or CD-RW ) are encouraged by the music industry to ensure that every drive they produce has a unique identifier, which will be encoded by the drive on every disc that it records: the RID or Recorder Identification Code. This is a counterpart to the Source Identification Code (SID), an eight character code beginning with " IFPI " that

2668-576: Is referred to as the White Book standard. The MPEG-1 format was also released that same year. 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 that of VHS tape and analog audio quality far superior to cheap mono VHS recorders (although

2760-593: Is scrambled to prevent some problematic patterns from showing up. These scrambled sectors then follow the same encoding process described in the Red Book in order to be finally stored on a CD. The following table shows a comparison of the structure of sectors in CD-DA and CD-ROMs: The net byte rate of a Mode-1 CD-ROM, based on comparison to CD-DA audio standards, is 44,100 Hz × 16 bits/sample × 2 channels × 2,048 / 2,352 / 8 = 150 KB/s (150 × 2 ) . This value, 150 Kbyte/s,

2852-421: Is stored on the disc as a series of microscopic indentations called "pits", with the non-indented spaces between them called "lands". A laser is shone onto the reflective surface of the disc to read the pattern of pits and lands. Because the depth of the pits is approximately one-quarter to one-sixth of the wavelength of the laser light used to read the disc, the reflected beam 's phase is shifted in relation to

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2944-464: Is the air pressure variation in a sound wave . The word digital comes from the same source as the words digit and digitus (the Latin word for finger ), as fingers are often used for counting. Mathematician George Stibitz of Bell Telephone Laboratories used the word digital in reference to the fast electric pulses emitted by a device designed to aim and fire anti-aircraft guns in 1942. The term

3036-402: Is used for data. XA Mode 2 Form 2 has 2,324 bytes of user data, and is similar to the standard Mode 2 but with error detection bytes added (though no error correction). It can interleave with XA Mode 2 Form 1 sectors, and it is used for audio/video data. Video CDs , Super Video CDs , Photo CDs , Enhanced Music CDs and CD-i use these sector modes. The following table shows a comparison of

3128-689: The ISO 9660 standard in 1988. One of the first products to be made available to the public on CD-ROM was the Grolier Academic Encyclopedia , presented at the Microsoft CD-ROM Conference in March 1986. CD-ROMs began being used in home video game consoles starting with the PC Engine CD-ROM (TurboGrafx-CD) in 1988, while CD-ROM drives had also become available for home computers by

3220-446: The digital age "). Digital data come in these three states: data at rest , data in transit , and data in use . The confidentiality, integrity, and availability have to be managed during the entire lifecycle from 'birth' to the destruction of the data. All digital information possesses common properties that distinguish it from analog data with respect to communications: Even though digital signals are generally associated with

3312-464: The original PlayStation (only on the SCPH-5903 model). Early software supporting Video CD playback include XingMPEG . Early PC hardware supporting Video CD playback include proprietary VCD decoder card . Later, because the introduction of Pentium II processor which supports MMX extension, and later graphics cards had included video decoding function, the use of VCD decoder card declined. VLC

3404-729: The .DAT files (stored under \MPEGAV for video and audio data) reliably, and plugins were available. Direct access playback support is available within Windows XP MCE , Windows Vista and newer (including Windows 10 ), classic Mac OS , BSD , macOS , and Linux among others, either directly or with updates and compatible software. Most DVD players are compatible with VCDs, and VCD-only players are available throughout Asia, and online through many shopping sites. Some older Blu-ray and HD-DVD players also retained support, as do CBHD players as well. However, most Blu-ray players, most vehicle audio with DVD/Blu-ray support, Xbox family, and

3496-432: The 1990s were called " multimedia " computers because they incorporated a CD-ROM drive, which allowed for the delivery of several hundred megabytes of video, picture, and audio data. The first laptop to have an integrated CD-ROM drive as an option was 1993's CF-V21P by Panasonic ; however, the drive only supported mini CDs up to 3.5 inches in diameter. The first notebook to support standard 4.7-inch-diameter discs

3588-538: 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. On some films, they feature English on the left audio channel and Cantonese on the right; more commonly Hong Kong VCDs will feature Mandarin on one channel and Cantonese on

3680-539: 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 , differentiated by the VCD logo. 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

3772-492: The Sony PlayStation ( 2 / 3 / 4 / 5 ) cannot play VCDs; this is because while they have backwards playback compatibility with the DVD standard, these player can not read VCD data because the player software does not have support for MPEG-1 video and audio, the player software lacks ability to read MPEG-1 stream in DAT files alongside MPEG-1 stream in standard MPEG, AVI , and Matroska files, or

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3864-488: 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. The VCD format

3956-553: The VCD format had no means of preventing unauthorized (and perfect) copies from being made. However, as of 2013 VCDs are still being released in several countries in Asia, but now with 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

4048-734: The VCDs, such as Intercontinental Video Ltd. of Hong Kong, Sunny Video in Malaysia, Vision Interprima Pictures in Indonesia, CVD International and Pacific Marketing and Entertainment Group in Thailand, Excel Home Entertainment in India, Berjaya-HVN and InnoForm Media in both Malaysia and Singapore, Scorpio East Entertainment in Singapore, as well as Viva Video , Magnavision Home Video, and C-Interactive Digital Entertainment in

4140-565: The advent of White Book VCD, Philips started releasing movies in the Green Book CD-i format, calling the subformat CD-i Digital Video (CD-i DV). 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. Approximately 30 CD-i DV titles were released before

4232-401: The audio frequency range is limited to those sounds most clearly heard by the human ear. The VCD standard also features the option of DVD-quality still images/slide shows with audio, at resolutions of 704×480 ( 480i , analog NTSC compatible) or 704×576 ( 576i , analog PAL/SECAM compatible). Version 2.0 also adds the playback control (PBC), featuring a simple menu like DVD-Video. Shortly before

4324-415: The audio was digital). Therefore, CD-V distribution was limited to featuring music videos , and it was soon discontinued by 1991. 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

4416-406: The beam has been reflected or scattered. CD-ROM drives are rated with a speed factor relative to music CDs. If a CD-ROM is read at the same rotational speed as an audio CD , the data transfer rate is 150 Kbyte/s, commonly called "1×" (with constant linear velocity, short "CLV" ). At this data rate, the track moves along under the laser spot at about 1.2 m/s. To maintain this linear velocity as

4508-497: The binary electronic digital systems used in modern electronics and computing, digital systems are actually ancient, and need not be binary or electronic. CD-ROM#CD-ROM XA extension A CD-ROM ( / ˌ s iː d iː ˈ r ɒ m / , compact disc read-only memory ) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data computers can read, but not write or erase. Some CDs, called enhanced CDs , hold both computer data and audio with

4600-513: The company he founded, Gauss Electrophysics. The LaserDisc was the immediate precursor to the CD, with the primary difference being that the LaserDisc encoded information through an analog process whereas the CD used digital encoding. Key work to digitize the optical disc was performed by Toshi Doi and Kees Schouhamer Immink during 1979–1980, who worked on a taskforce for Sony and Philips . The result

4692-421: The company switched to the current VCD format for publishing movies in 1994. XVCD (eXtended Video CD) is the name generally given to any format that stores MPEG-1 video on a compact disc in CD-ROM XA Mode 2 Form 2, but does not strictly follow the VCD standard in terms of the encoding of the video or audio. A normal VCD is encoded to MPEG-1 at a constant bit rate (CBR), so all scenes are required to use exactly

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4784-423: The data are recorded on them by a laser changing the properties of a dye or phase transition material in a process that is often referred to as " burning ". Data stored on CD-ROMs follows the standard CD data encoding techniques described in the Red Book specification (originally defined for audio CD only). This includes cross-interleaved Reed–Solomon coding (CIRC), eight-to-fourteen modulation (EFM), and

4876-522: 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 be swapped out completely for MP3 audio. These changes can be advantageous for those who want to either maximize video quality, or use fewer discs. KVCD (K Video Compression Dynamics)

4968-500: The data stored in these sectors corresponds to any type of digital data, not audio samples encoded according to the audio CD specification. To structure, address and protect this data, the CD-ROM standard further defines two sector modes, Mode 1 and Mode 2, which describe two different layouts for the data inside a sector. A track (a group of sectors) inside a CD-ROM only contains sectors in the same mode, but if multiple tracks are present in

5060-450: 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, 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

5152-401: The disc at 1600 to 4000 rpm, giving a linear velocity of 9.6 m/s and a transfer rate of 1200 Kbyte/s. Above 12× speed most drives read at Constant angular velocity (CAV, constant rpm) so that the motor is not made to change from one speed to another as the head seeks from place to place on the disc. In CAV mode the "×" number denotes the transfer rate at the outer edge of the disc, where it

5244-622: The earliest "1x" speed CD drives. Video specifications 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 specifications As with most CD-based formats, VCD audio

5336-553: The early 2000s, and the use of CD-ROMs for commercial software is now uncommon. The earliest theoretical work on optical disc storage was done by independent researchers in the United States including David Paul Gregg (1958) and James Russel (1965–1975). In particular, Gregg's patents were used as the basis of the LaserDisc specification that was co-developed between MCA and Philips after MCA purchased Gregg's patents, as well as

5428-449: The end of the 1980s. In 1990, Data East demonstrated an arcade system board that supported CD-ROMs, similar to 1980s LaserDisc video games but with digital data, allowing more flexibility than older LaserDisc games. By early 1990, about 300,000 CD-ROM drives were sold in Japan, while 125,000 CD-ROM discs were being produced monthly in the United States. Some computers that were marketed in

5520-516: The first Japanese COMDEX computer show in 1985. In November 1985, several computer industry participants, including Microsoft , Philips , Sony , Apple and Digital Equipment Corporation, met to create a specification to define a file system format for CD-ROMs. The resulting specification, called the High Sierra format, was published in May 1986. It was eventually standardized, with a few changes, as

5612-538: The incoming beam, causing destructive interference and reducing the reflected beam's intensity. This is converted into binary data. Several formats are used for data stored on compact discs, known as the Rainbow Books . The Yellow Book , created in 1983, defines the specifications for CD-ROMs, standardized in 1988 as the ISO / IEC 10149 standard and in 1989 as the ECMA -130 standard. The CD-ROM standard builds on top of

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5704-673: The late 1990s. Over 10 years later, commonly available drives vary between 24× (slimline and portable units, 10× spin speed) and 52× (typically CD- and read-only units, 21× spin speed), all using CAV to achieve their claimed "max" speeds, with 32× through 48× most common. Even so, these speeds can cause poor reading (drive error correction having become very sophisticated in response) and even shattering of poorly made or physically damaged media, with small cracks rapidly growing into catastrophic breakages when centripetally stressed at 10,000–13,000 rpm (i.e. 40–52× CAV). High rotational speeds also produce undesirable noise from disc vibration, rushing air and

5796-413: The latter capable of being played on a CD player , while data (such as software or digital video) is only usable on a computer (such as ISO 9660 format PC CD-ROMs). During the 1990s and early 2000s, CD-ROMs were popularly used to distribute software and data for computers and fifth generation video game consoles . DVDs as well as downloading started to replace CD-ROMs in these roles starting in

5888-524: The maximum video capacity of one disc, a viewer had to change the disc upon reaching halfway (unless the discs were played on a VCD changer that could hold multiple discs and play them automatically in succession), whereas a single VHS tape could hold 3.5 hours of continuous video. When playing a DVD , the viewer is taken 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

5980-399: The music industry. A few years later, Philips decided to give CDs the ability to produce video, utilizing the same technology as its LaserDisc 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

6072-431: The number of bits in a single byte or word. Devices with many switches (such as a computer keyboard ) usually arrange these switches in a scan matrix, with the individual switches on the intersections of x and y lines. When a switch is pressed, it connects the corresponding x and y lines together. Polling (often called scanning in this case) is done by activating each x line in sequence and detecting which y lines then have

6164-510: The older MPEG-1 format, inability to read MPEG-1 in .dat files alongside MPEG-1 in standard MPEG-1, AVI, and Matroska files, or inability to read CD-ROM XA discs. Some Laserdisc players that were released in the late 90s support VCD as well as the Sony PS1 model SCPH-5903 marketed in Southeast Asia. The Video CD standard was created in 1993 by Sony , Philips , Matsushita and JVC ; it

6256-412: The optical head moves to different positions, the angular velocity is varied from about 500 rpm at the inner edge to 200 rpm at the outer edge. The 1× speed rating for CD-ROM (150 Kbyte/s) is different from the 1× speed rating for DVDs (1.32 MB/s). When the speed at which the disc is spun is increased, data can be transferred at greater rates. For example, a CD-ROM drive that can read at 8× speed spins

6348-473: The original Red Book CD-DA standard for CD audio. Other standards, such as the White Book for Video CDs , further define formats based on the CD-ROM specifications. The Yellow Book itself is not freely available, but the standards with the corresponding content can be downloaded for free from ISO or ECMA. There are several standards that define how to structure data files on a CD-ROM. ISO 9660 defines

6440-432: The original CD-ROMs. This differs somewhat from audio CD protection in that it is usually implemented in both the media and the software itself. The CD-ROM itself may contain "weak" sectors to make copying the disc more difficult, and additional data that may be difficult or impossible to copy to a CD-R or disc image, but which the software checks for each time it is run to ensure an original disc and not an unauthorized copy

6532-468: The other. This is similar to selecting a language track on a DVD, except it is 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 to the compression method used. Additionally, VCD movie surround sound capability

6624-576: The outer edge of the disc with the same rotational speed as a standard ( constant linear velocity , CLV) 12×, or 32× with a slight increase. However, due to the nature of CAV (linear speed at the inner edge is still only 12×, increasing smoothly in-between) the actual throughput increase is less than 30/12; in fact, roughly 20× average for a completely full disc, and even less for a partially filled one. Problems with vibration, owing to limits on achievable symmetry and strength in mass-produced media, mean that CD-ROM drive speeds have not massively increased since

6716-463: The outward data track is extended to the disc's outer rim. A standard 120 mm, 700 MB CD-ROM can actually hold about 703 MB of data with error correction (or 847 MB total). In comparison, a single-layer DVD-ROM can hold 4.7 GB (4.7 × 10 bytes) of error-protected data, more than 6 CD-ROMs. CD-ROM discs are read using CD-ROM drives. A CD-ROM drive may be connected to the computer via an IDE ( ATA ), SCSI , SATA , FireWire , or USB interface or

6808-479: The player lacks ability to read CD-ROM XA discs. Digital data Digital data , in information theory and information systems , is information represented as a string of discrete symbols, each of which can take on one of only a finite number of values from some alphabet , such as letters or digits. An example is a text document , which consists of a string of alphanumeric characters . The most common form of digital data in modern information systems

6900-529: The polycarbonate plastic of which the discs are made. At 52×, the linear velocity of the outermost part of the disc is around 65 m/s. However, improvements can still be obtained using multiple laser pickups as demonstrated by the Kenwood TrueX 72× which uses seven laser beams and a rotation speed of approximately 10×. The first 12× drive was released in late 1996. Above 12× speed, there are problems with vibration and heat. CAV drives give speeds up to 30× at

6992-584: 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 due to their cheaper manufacturing and retail costs. Video CDs comply with the CD-i Bridge format, and are authored using tracks in CD-ROM XA mode. The first track of

7084-424: 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

7176-575: The spindle motor itself. Most 21st-century drives allow forced low speed modes (by use of small utility programs) for the sake of safety, accurate reading or silence, and will automatically fall back if numerous sequential read errors and retries are encountered. Other methods of improving read speed were trialled such as using multiple optical beams, increasing throughput up to 72× with a 10× spin speed, but along with other technologies like 90~99 minute recordable media, GigaRec and double-density compact disc ( Purple Book standard) recorders, their utility

7268-482: The standard file system for a CD-ROM. ISO 13490 is an improvement on this standard which adds support for non-sequential write-once and re-writeable discs such as CD-R and CD-RW , as well as multiple sessions . The ISO 13346 standard was designed to address most of the shortcomings of ISO 9660, and a subset of it evolved into the UDF format, which was adopted for DVDs . A bootable CD specification, called El Torito ,

7360-462: The structure of sectors in CD-ROM XA modes: When a disc image of a CD-ROM is created, this can be done in either "raw" mode (extracting 2,352 bytes per sector, independent of the internal structure), or obtaining only the sector's useful data (2,048/2,336/2,352/2,324 bytes depending on the CD-ROM mode). The file size of a disc image created in raw mode is always a multiple of 2,352 bytes (the size of

7452-407: The use of pits and lands for coding the bits into the physical surface of the CD. The structures used to group data on a CD-ROM are also derived from the Red Book . Like audio CDs (CD-DA), a CD-ROM sector contains 2,352 bytes of user data, composed of 98 frames, each consisting of 33 bytes (24 bytes for the user data, 8 bytes for error correction, and 1 byte for the sub code). Unlike audio CDs,

7544-451: The video with extras (mostly trailers and commercials) taking place before or after it, like on a VHS cassette. Subtitles are found on many Asian VCDs but cannot be removed, unlike on DVDs. The subtitles are embedded on the video during the encoding process (" hardsubbed "). It is 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

7636-424: The video, resulting in lower audio quality than VHS. While both formats need fast-forwarding to find certain scenes, rewinding to the beginning upon reaching the end is not required in VCD. The resolution is just half below that of common VHS resolution. Video CDs did not come with closed captioning (on-screen text to aid viewers with hearing problems). When watching a film that exceeds 74 minutes (nearly 1¼ hours),

7728-413: 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 to 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

7820-466: Was IBM 's ThinkPad 755CD in 1994. On early audio CD players that were released prior to the advent of the CD-ROM, the raw binary data of CD-ROM was played back as noise. To address this problem, the subcode channel Q has a "data" flag in areas of the disc that contain computer data rather than playable audio. The data flag instructs CD players to mute the audio. CD-ROMs are identical in appearance to audio CDs , and data are stored and retrieved in

7912-829: Was due, in part, to most households not already owning VCRs 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 unauthorized content as a principal incentive for VCD player ownership. VCDs are often produced and sold in Asian countries and regions, such as China (including Hong Kong ), Taiwan , Singapore , Malaysia , Thailand , Cambodia , Laos , Brunei , Myanmar , Indonesia , Philippines , Vietnam , Bangladesh , India , Turkey , Pakistan and Afghanistan . In many Asian countries, major Hollywood studios (and Asian home video distributors) have licensed companies to officially produce and distribute

8004-525: Was intended as a bridge between CD-ROM and CD-i ( Green Book ) and was published by Sony and Philips , and backed by Microsoft , in 1991, first announced in September 1988. "XA" stands for eXtended Architecture. CD-ROM XA defines two new sector layouts, called Mode 2 Form 1 and Mode 2 Form 2 (which are different from the original Mode 2). XA Mode 2 Form 1 is similar to the Mode 1 structure described above, and can interleave with XA Mode 2 Form 2 sectors; it

8096-463: Was issued in January 1995, to make a CD emulate a hard disk or floppy disk . Pre-pressed CD-ROMs are mass-produced by a process of stamping where a glass master disc is created and used to make "stampers", which are in turn used to manufacture multiple copies of the final disc with the pits already present. Recordable ( CD-R ) and rewritable ( CD-RW ) discs are manufactured by a different method, whereby

8188-1036: Was nullified by the introduction of consumer DVD-ROM drives capable of consistent 36× equivalent CD-ROM speeds (4× DVD) or higher. Additionally, with a 700 MB CD-ROM fully readable in under 2.5 minutes at 52× CAV, increases in actual data transfer rate are decreasingly influential on overall effective drive speed when taken into consideration with other factors such as loading/unloading, media recognition, spin up/down and random seek times, making for much decreased returns on development investment. A similar stratification effect has since been seen in DVD development where maximum speed has stabilised at 16× CAV (with exceptional cases between 18× and 22×) and capacity at 4.3 and 8.5 GB (single and dual layer), with higher speed and capacity needs instead being catered to by Blu-ray drives. CD-Recordable drives are often sold with three different speed ratings: one speed for write-once operations, one for re-write operations, and one for read-only operations. The speeds are typically listed in that order; i.e.

8280-482: 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

8372-510: Was the Compact Disc Digital Audio (CD-DA), defined in 1980. The CD-ROM was later designed as an extension of the CD-DA, and adapted this format to hold any form of digital data, with an initial storage capacity of 553 MB . Sony and Philips created the technical standard that defines the format of a CD-ROM in 1983, in what came to be called the Yellow Book . The CD-ROM was announced in 1984 and introduced by Denon and Sony at

8464-459: 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. However, popularity has declined over the years, as the number of Hong Kong factories that produced VCDs dropped from 98 in 1999 to 26 in 2012. This popularity

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