Fourth generation of video game consoles
In the history of computer and video games, the fourth generation of game consoles began on October 30, 1987 with the Japanese release of NEC Home Electronics' PC Engine. Although NEC released the first console of this era, sales were dominated by the rivalry between Nintendo's and Sega's consoles in North America: the Super Nintendo Entertainment System and the Sega Genesis. Handheld systems released during this time include the Nintendo Game Boy, released in 1989, the Sega Game Gear, first released in 1990. Nintendo was able to capitalize on its success in the previous, third generation, managed to win the largest worldwide market share in the fourth generation as well. Sega, was successful in this generation and began a new franchise, Sonic the Hedgehog, to compete with Nintendo's Super Mario series of games. Several other companies released consoles in this generation, but none of them were successful. There were other companies that started to take notice of the maturing video game industry and begin making plans to release consoles of their own in the future.
The emergence of fifth generation video game consoles, circa 1994, did not diminish the popularity of fourth generation consoles for a few years. In 1996, there was a major drop in sales of hardware from this generation and a dwindling number of software publishers supporting fourth generation systems, which together led to a drop in software sales in subsequent years; this generation ended with the discontinuation of the Neo Geo in 2004. Some features that distinguish fourth generation consoles from third generation consoles include: 16-bit microprocessors Multi-button game controllers with many buttons Parallax scrolling of multi-layer tilemap backgrounds Large sprites, 80–380 sprites on screen, though limited to a smaller number per scan line Elaborate colour, 64 to 4096 colours on screen, from palettes of 512 to 65,536 colours Stereo audio, with multiple channels and digital audio playback Advanced music synthesis Additionally, in specific cases, fourth generation hardware featured: Backgrounds with pseudo-3D scaling and rotation Sprites that can individually be scaled and rotated Flat-shaded 3D polygon graphics CD-ROM support via add-ons, allowing larger storage space and full motion video playback The PC Engine was the result of a collaboration between Hudson Soft and NEC and launched in Japan on October 30, 1987, under the name PC Engine.
It launched in North America on August 29, 1989. The PC Engine was quite successful in Japan due to titles available on the then-new CD-ROM format. NEC released a CD add-on in 1990 and by 1992 had released a combination TurboGrafx and CD-ROM system known as the TurboDuo. In the United States, NEC used Bonk, a head-banging caveman, as their mascot and featured him in most of the TurboGrafx advertising from 1990 to 1994; the platform was well received especially in larger markets, but failed to make inroads into the smaller metropolitan areas where NEC did not have as many store representatives or as focused in-store promotion. The TurboGrafx-16 failed to make a strong impact in North America; the TurboGrafx-16 and its CD combination system, the Turbo Duo, ceased manufacturing in North America by 1994, though a small amount of software continued to trickle out for the platform. The Mega Drive was released in Japan on October 29, 1988; the console was released in New York City and Los Angeles on August 14, 1989 under the name Sega Genesis, in the rest of North America that year.
It was launched in Australia on November 30, 1990 under its original name. Sega built their marketing campaign around their new mascot Sonic the Hedgehog, pushing the Genesis as the "cooler" alternative to Nintendo's console and inventing the term "Blast Processing" to suggest that the Genesis was capable of handling games with faster motion than the SNES, their advertising was directly adversarial, leading to commercials such as "Genesis does what Nintendon't" and the "'SEGA!' Scream". When the arcade game Mortal Kombat was ported for home release on the Genesis and Super Nintendo Entertainment System, Nintendo decided to censor the game's gore, but Sega kept the content in the game, via a code entered at the start screen. Sega's version of Mortal Kombat received more favorable reviews in the gaming press and outsold the SNES version three to one; this led to Congressional hearings to investigate the marketing of violent video games to children, to the creation of the Interactive Digital Software Association and the Entertainment Software Rating Board.
Sega concluded that the superior sales of their version of Mortal Kombat were outweighed by the resulting loss in consumer trust, cancelled the game's release in Spain to avoid further controversy. With the new ESRB rating system in place, Nintendo reconsidered its position for the release of Mortal Kombat II, this time became the preferred version among reviewers; the Toy Retail Sales Tracking Service reported that during the key shopping month of November 1994, 63% of all 16-bit video game consoles sold were Sega systems. The console still managed to sell 40 million units worldwide. By late 1995, Sega was supporting five different consoles and two add-ons, Sega Enterprises chose to discontinue the Mega Drive in Japan to concentrate on the new Sega Saturn. While this made perfect se
Closed captioning and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information. Both are used as a transcription of the audio portion of a program as it occurs, sometimes including descriptions of non-speech elements. Other uses have been to provide a textual alternative language translation of a presentation's primary audio language, burned-in to the video and unselectable. HTML5 defines subtitles as a "transcription or translation of the dialogue... when sound is available but not understood" by the viewer and captions as a "transcription or translation of the dialogue, sound effects, relevant musical cues, other relevant audio information... when sound is unavailable or not audible". The term "closed" indicates that the captions are not visible until activated by the viewer via the remote control or menu option. On the other hand, "open", "burned-in", "baked on", "hard-coded", or "hard" captions are visible to all viewers.
Most of the world does not distinguish captions from subtitles. In the United States and Canada, these terms do have different meanings. "Subtitles" assume the viewer can hear but cannot understand the language or accent, or the speech is not clear, so they transcribe only dialogue and some on-screen text. "Captions" aim to describe to the deaf and hard of hearing all significant audio content - spoken dialogue and non-speech information such as the identity of speakers and their manner of speaking - along with any significant music or sound effects using words or symbols. The term closed caption has come to be used to refer to the North American EIA-608 encoding, used with NTSC-compatible video; the United Kingdom and most other countries do not distinguish between subtitles and closed captions and use "subtitles" as the general term. The equivalent of "captioning" is referred to as "subtitles for the hard of hearing", their presence is referenced on screen by notation which says "Subtitles", or "Subtitles 888" or just "888", why the term subtitle is used to refer to the Ceefax-based Teletext encoding, used with PAL-compatible video.
The term subtitle has been replaced with caption in a number of markets - such as Australia and New Zealand - that purchase large amounts of imported US material, with much of that video having had the US CC logo superimposed over the start of it. In New Zealand, broadcasters superimpose an ear logo with a line through it that represents subtitles for the hard of hearing though they are referred to as captions. In the UK, modern digital television services have subtitles for the majority of programs, so it is no longer necessary to highlight which have captioning and which do not. Remote control handsets for TVs, DVDs, similar devices in most European markets use "SUB" or "SUBTITLE" on the button used to control the display of subtitles/captions. Regular open-captioned broadcasts began on PBS's The French Chef in 1972. WGBH began open captioning of the programs Zoom, ABC World News Tonight, Once Upon a Classic shortly thereafter. Closed captioning was first demonstrated at the First National Conference on Television for the Hearing Impaired in Nashville, Tennessee in 1971.
A second demonstration of closed captioning was held at Gallaudet College on February 15, 1972, where ABC and the National Bureau of Standards demonstrated closed captions embedded within a normal broadcast of The Mod Squad. The closed captioning system was encoded and broadcast in 1973 with the cooperation of PBS station WETA; as a result of these tests, the FCC in 1976 set aside line 21 for the transmission of closed captions. PBS engineers developed the caption editing consoles that would be used to caption prerecorded programs. Real-time captioning, a process for captioning live broadcasts, was developed by the National Captioning Institute in 1982. In real-time captioning, court reporters trained to write at speeds of over 225 words per minute give viewers instantaneous access to live news and entertainment; as a result, the viewer sees the captions within two to three seconds of the words being spoken. Major US producers of captions are VITAC, CaptionMax and the National Captioning Institute.
In the UK and Australasia, Red Bee Media and Independent Media Support are the major vendors. Improvements in speech recognition technology means that live captioning may be or automated. BBC Sport broadcasts use a "respeaker": a trained human who repeats the running commentary for input to the automated text generation system; this is reliable, though errors are not unknown. The National Captioning Institute was created in 1979 in order to get the cooperation of the commercial television networks; the first use of scheduled closed captioning on American television occurred on March 16, 1980. Sears had developed and sold the Telecaption adapter, a decoding unit that could be connected to a standard television set; the first programs seen with captioning were a Disney's Wonderful World presentation of the film Son of Flubber on NBC, an ABC Sunday Night Movie airing of Semi-Tough, Masterpiece Theatre on PBS. Until the passage of the Television Decoder Circuitry Act of 1990, television captioning was performed by a set-top box manufactured by Sanyo Electric a
CCIR System G
CCIR System G is an analog broadcast television system used in many countries. There are several systems in use and letter G is assigned for the European UHF system, used in the majority of Asian and African countries; some of the important specs are listed below. A frame is the total picture; the frame rate is the number of pictures displayed in one second. But each frame is scanned twice interleaving odd and lines; each scan is known as a field So field rate is twice the frame rate. In each frame there are 625 lines So line rate 625 • 25 = 15625 Hz; the RF parameters of the transmitted signal are the same as those for System B, used on the 7.0 MHz wide channels of the VHF bands. The only difference is the width of the guard band between the channels, which on System G is 1.0 MHz wider than for System B: in other words 1.15 MHz. A few countries use a variant of system G, known as System H. System H is similar to system G but the lower side band is 500 kHz wider; this makes much better use of the 8.0 MHz channels of the UHF bands by reducing the width of the guard-band by 500 kHz to the still generous value of 650 kHz.
Broadcast television systems Television transmitter Transposer World Analogue Television Standards and Waveforms Fernsehnormen aller Staaten und Gebiete der Welt
CCIR System I
CCIR System I is an analog broadcast television system. It was first used in the Republic of Ireland starting in 1962 as the 625-line broadcasting standard to be used on VHF Band I and Band III, sharing Band III with 405-line System A signals radiated in the north of the country; the UK started its own 625-line television service in 1964 using System I, but on UHF only - the UK has never used VHF for 625-line television except for some cable relay distribution systems. Since System I has been adopted for use by Hong Kong, the Falkland Islands and South Africa; the Republic of Ireland has extended its use of System I onto the UHF bands. As of late 2012, analog television is no longer transmitted in either the UK or the Republic of Ireland. South Africa expects to discontinue System I in 2013, Hong Kong by 2020; some of the important specs are listed below. A frame is the total picture; the frame rate is the number of pictures displayed in one second. But each frame is scanned twice interleaving odd and lines.
Each scan is known as a field So field rate is twice the frame rate. In each frame there are 625 lines So line rate 625 • 25 = 15625 Hz; the total RF bandwidth of System I was about 7.4 MHz, allowing System I signals to be transmitted in 8.0 MHz wide channels with an ample 600 kHz guard zone between channels. In specs, other parameters such as vestigial sideband characteristics and gamma of display device are given. System I has only been used with the PAL colour systems, but it would have been technically possible to use SECAM or a 625-line variant of the NTSC color system. However, apart from possible technical tests in the 1960s, this has never been done officially; when used with PAL, the colour subcarrier is 4.43361875 MHz and the sidebands of the PAL signal have to be truncated on the high-frequency side at +1.066 MHz. On the low-frequency side, the full 1.3 MHz sideband width is radiated. Additionally, in order to minimise beat-patterns between the chrominance subcarrier and the sound subcarrier, when PAL is used with System I, the sound subcarrier is moved off the originally-specified 6.0 MHz to 5.9996 MHz.
This is such a slight frequency shift that no alterations needed to be made to existing System I television sets when the change was made. No colour encoding system has any effect on the bandwidth of system I as a whole. Enhancements have been made to the specification of System I's audio capabilities over the years. Starting in the late 1980s and early 1990s it became possible to add a digital signal carrying NICAM sound; this extension to audio capability has eaten the guard band between channels, indeed there would be a small amount of analogue-digital crosstalk between the NICAM signal of a transmitter on channel N and the vestigial sideband of a transmission on channel N+1. Good channel planning means that under normal situations no ill effects are heard; the NICAM system used with System I adds a 700 kHz wide digital signal, needs to be placed at least 552 kHz from the audio subcarrier. VHF Band 1 was discontinued for TV broadcasting well before Ireland's digital switchover. ♥ No longer used for TV broadcasting.
UHF takeup in Ireland was slower than in the UK. A written answer in the Dáil Éireann shows that by mid 1988 Ireland was only transmitting on UHF from four main transmitters and 11 relays. † Officially these channels "don't exist", being between UHF Band IV and Band V and were supposed to be reserved for radio astronomy. However, from 1997 until the finish of analog TV in the UK in 2012, the UK used channels 35 through 37 for analog broadcasts of Channel 5. § Allocated, but never used in the UK. Broadcast television systems Television transmitter Transposer World Analogue Television Standards and Waveforms Fernsehnormen aller Staaten und Gebiete der Welt
A contour line of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional graph of the function f parallel to the y plane. In cartography, a contour line joins points of equal elevation above a given level, such as mean sea level. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, the steepness or gentleness of slopes; the contour interval of a contour map is the difference in elevation between successive contour lines. More a contour line for a function of two variables is a curve connecting points where the function has the same particular value; the gradient of the function is always perpendicular to the contour lines. When the lines are close together the magnitude of the gradient is large: the variation is steep. A level set is a generalization of a contour line for functions of any number of variables.
Contour lines are curved, straight or a mixture of both lines on a map describing the intersection of a real or hypothetical surface with one or more horizontal planes. The configuration of these contours allows map readers to infer relative gradient of a parameter and estimate that parameter at specific places. Contour lines may be either traced on a visible three-dimensional model of the surface, as when a photogrammetrist viewing a stereo-model plots elevation contours, or interpolated from estimated surface elevations, as when a computer program threads contours through a network of observation points of area centroids. In the latter case, the method of interpolation affects the reliability of individual isolines and their portrayal of slope and peaks. Contour lines are given specific names beginning "iso-" according to the nature of the variable being mapped, although in many usages the phrase "contour line" is most used. Specific names are most common in meteorology, where multiple maps with different variables may be viewed simultaneously.
The prefix "iso-" can be replaced with "isallo-" to specify a contour line connecting points where a variable changes at the same rate during a given time period. The words isoline and isarithm are general terms covering all types of contour line; the word isogram was proposed by Francis Galton in 1889 as a convenient generic designation for lines indicating equality of some physical condition or quantity. An isogon is a contour line for a variable. In meteorology and in geomagnetics, the term isogon has specific meanings. An isocline is a line joining points with equal slope. In population dynamics and in geomagnetics, the terms isocline and isoclinic line have specific meanings which are described below. A curve of equidistant points is a set of points all at the same distance from a given point, line, or polyline. In this case the function whose value is being held constant along a contour line is a distance function. In geography, the word isopleth is used for contour lines that depict a variable which cannot be measured at a point, but which instead must be calculated from data collected over an area.
An example is population density, which can be calculated by dividing the population of a census district by the surface area of that district. Each calculated value is presumed to be the value of the variable at the centre of the area, isopleths can be drawn by a process of interpolation; the idea of an isopleth map can be compared with that of a choropleth map. In meteorology, the word isopleth is used for any type of contour line. Meteorological contour lines are based on interpolation of the point data received from weather stations and weather satellites. Weather stations are exactly positioned at a contour line. Instead, lines are drawn to best approximate the locations of exact values, based on the scattered information points available. Meteorological contour maps may present collected data such as actual air pressure at a given time, or generalized data such as average pressure over a period of time, or forecast data such as predicted air pressure at some point in the future Thermodynamic diagrams use multiple overlapping contour sets to present a picture of the major thermodynamic factors in a weather system.
An isobar is a line of constant pressure on a graph, plot, or map. More isobars are lines drawn on a map joining places of equal average atmospheric pressure reduced to sea level for a specified period of time. In meteorology, the barometric pressures shown are reduced to sea level, not the surface pressures at the map locations; the distribution of isobars is related to the magnitude and direction of the wind field, can be used to predict future weather patterns. Isobars are used in television weather reporting. Isallobars are lines joining points of equal pressure change during a specific time interval; these can be divided into anallobars, lines joining points of equal pressure increase during a specific time interval, katallobars, lines joining points of equal pressure decrease. In general, weather systems move along an axis joining low isallobaric centers. Isallobaric gradi
Digital Visual Interface
Digital Visual Interface is a video display interface developed by the Digital Display Working Group. The digital interface is used to connect a video source, such as a video display controller, to a display device, such as a computer monitor, it was developed with the intention of creating an industry standard for the transfer of digital video content. This interface is designed to transmit uncompressed digital video and can be configured to support multiple modes such as DVI-A, DVI-D or DVI-I. Featuring support for analog connections, the DVI specification is compatible with the VGA interface; this compatibility, along with other advantages, led to its widespread acceptance over competing digital display standards Plug and Display and Digital Flat Panel. Although DVI is predominantly associated with computers, it is sometimes used in other consumer electronics such as television sets and DVD players. DVI's digital video transmission format is based on panelLink, a serial format developed by Silicon Image that utilizes a high-speed serial link called transition minimized differential signaling.
Like modern analog VGA connectors, the DVI connector includes pins for the display data channel. A newer version of DDC called DDC2 allows the graphics adapter to read the monitor's extended display identification data. If a display supports both analog and digital signals in one DVI-I input, each input method can host a distinct EDID. Since the DDC can only support one EDID, this can be a problem if both the digital and analog inputs in the DVI-I port detect activity, it is up to the display to choose. When a source and display are connected, the source first queries the display's capabilities by reading the monitor EDID block over an I²C link; the EDID block contains the display's identification, color characteristics, table of supported video modes. The table can designate a preferred native resolution; each mode is a set of CRT timing values that define the duration and frequency of the horizontal/vertical sync, the positioning of the active display area, the horizontal resolution, vertical resolution, refresh rate.
For backward compatibility with displays using analog VGA signals, some of the contacts in the DVI connector carry the analog VGA signals. To ensure a basic level of interoperability, DVI compliant devices are required to support one baseline video mode, "low pixel format". Digitally encoded video pixel data is transported using multiple TMDS links. At the electrical level, these links are resistant to electrical noise and other forms of analog distortion. Green text A single link DVI connection consists of four TMDS links. Three of the links represent the RGB components of the video signal for a total of 24 bits per pixel; the fourth link carries the pixel clock. The binary data is encoded using 8b10b encoding. DVI does not use packetization, but rather transmits the pixel data as if it were a rasterized analog video signal; as such, the complete frame is drawn during each vertical refresh period. The full active area of each frame is always transmitted without compression. Video modes use horizontal and vertical refresh timings that are compatible with CRT displays, though this is not a requirement.
In single-link mode, the maximum pixel clock frequency is 165 MHz that supports a maximum resolution of 2.75 megapixels at 60 Hz refresh. For practical purposes, this allows a maximum 16:10 screen resolution of 1920 × 1200 at 60 Hz. To support higher-resolution display devices, the DVI specification contains a provision for dual link. Dual-link DVI doubles the number of TMDS pairs doubling the video bandwidth; as a result, higher resolutions up to 2560 × 1600 are supported at 60 Hz. The maximum length recommended for DVI cables is not included in the specification, since it is dependent on the pixel clock frequency. In general, cable lengths up to 4.5 metres will work for display resolutions up to 1920 × 1200. Longer cables up to 15 metres in length can be used with display resolutions lower. For greater distances, the use of a DVI booster—a signal repeater which may use an external power supply—is recommended to help mitigate signal degradation; the DVI connector on a device is given one of three names, depending on which signals it implements: DVI-I DVI-D DVI-A Most DVI connector types—the exception is DVI-A—have pins that pass digital video signals.
These come in two varieties: single link and dual link. Single link DVI employs a single 165 MHz transmitter that supports resolutions up to 1920 × 1200 at 60 Hz. Dual link DVI adds six pins, at the center of the connector, for a second transmitter increasing the bandwidth and supporting resolutions up to 2560 × 1600 at 60 Hz. A connector with these additional pins is sometimes referred to as DVI-DL. Dual link should not be confused with dual display, a configuration consisting of a single computer connected to two monitors, sometimes using a DMS-59 connector for two single link DVI connections. In addition to digital, some DVI connectors have pins that pass an analog signal, which can be used to connect an analog monitor; the analog pins are the four that surround the flat blade on a DVI-A connector. A VGA monitor, for example, can be connected to a video source with DVI-I through the use of a passive adapter. Since the analog pins are directly compatible
A raster scan, or raster scanning, is the rectangular pattern of image capture and reconstruction in television. By analogy, the term is used for raster graphics, the pattern of image storage and transmission used in most computer bitmap image systems; the word raster comes from the Latin word rastrum, derived from radere. The pattern left by the lines of a rake, when drawn straight, resembles the parallel lines of a raster: this line-by-line scanning is what creates a raster, it is a systematic process of covering the area progressively, one line at a time. Although a great deal faster, it is similar in the most-general sense to how one's gaze travels when one reads lines of text. In a raster scan, an image is subdivided into a sequence of strips known as "scan lines"; each scan line can be transmitted in the form of an analog signal as it is read from the video source, as in television systems, or can be further divided into discrete pixels for processing in a computer system. This ordering of pixels by rows is known as raster scan order.
Analog television has discrete scan lines, but does not have discrete pixels – it instead varies the signal continuously over the scan line. Thus, while the number of scan lines is unambiguously defined, the horizontal resolution is more approximate, according to how the signal can change over the course of the scan line. In raster scanning, the beam sweeps horizontally left-to-right at a steady rate blanks and moves back to the left, where it turns back on and sweeps out the next line. During this time, the vertical position is steadily increasing, but much more – there is one vertical sweep per image frame, but one horizontal sweep per line of resolution, thus each scan line is sloped "downhill", with a slope of –1/horizontal resolution, while the sweep back to the left is faster than the forward scan, horizontal. The resulting tilt in the scan lines is small, is dwarfed in effect by screen convexity and other modest geometrical imperfections. There is a misconception that once a scan line is complete, a CRT display in effect jumps internally, by analogy with a typewriter or printer's paper advance or line feed, before creating the next scan line.
As discussed above, this does not happen: the vertical sweep continues at a steady rate over a scan line, creating a small tilt. Steady-rate sweep is done, instead of a stairstep of advancing every row, because steps are hard to implement technically, while steady-rate is much easier; the resulting tilt is compensated in most CRTs by the tilt and parallelogram adjustments, which impose a small vertical deflection as the beam sweeps across the screen. When properly adjusted, this deflection cancels the downward slope of the scanlines; the horizontal retrace, in turn, slants smoothly downward. In detail, scanning of CRTs is performed by magnetic deflection, by changing the current in the coils of the deflection yoke. Changing the deflection requires a voltage spike to be applied to the yoke, the deflection can only react as fast as the inductance and spike magnitude permit. Electronically, the inductance of the deflection yoke's vertical windings is high, thus the current in the yoke, therefore the vertical part of the magnetic deflection field, can change only slowly.
In fact, spikes do occur, both horizontally and vertically, the corresponding horizontal blanking interval and vertical blanking interval give the deflection currents settle time to retrace and settle to their new value. This happens during the blanking interval. In electronics, these movements of the beam are called "sweeps", the circuits that create the currents for the deflection yoke are called the sweep circuits; these create a sawtooth wave: steady movement across the screen a rapid move back to the other side, for the vertical sweep. Furthermore, wide-deflection-angle CRTs need horizontal sweeps with current that changes proportionally faster toward the center, because the center of the screen is closer to the deflection yoke than the edges. A linear change in current would swing the beams at a constant rate angularly. Computer printers create their images by raster scanning. Laser printers use a spinning polygonal mirror to scan across the photosensitive drum, paper movement provides the other scan axis.
Considering typical printer resolution, the "downhill" effect is minuscule. Inkjet printers have multiple nozzles in their printheads, so many of "scan lines" are written together, paper advance prepares for the next batch of scan lines. Transforming vector-based data into the form required by a display, or printer, requires a Raster Image Processor. Computer text is created from font files that describe the outlines of each printable character or symbol; these outlines have to be converted into what are little rasters, one per character, before being rendered as text, in effect merging their little rasters into that for the page. In detail, each line consists of: scanline, when beam is unblanked, moving to the right front porch, when beam is blanked, moving