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Nominal Analogue Blanking
Nominal analogue blanking is the outermost part of the overscan of a standard definition digital television image. It consists of a gap of black (or nearly black) pixels at the left and right sides, which correspond to the end and start of the horizontal blanking interval: the front porch at the right side (the end of a line, before the sync pulse), and the back porch at the left side (the start of a line, after the sync pulse and before drawing the next line). Digital television ordinarily contains 720 pixels per line, but only 702 (PAL) to 704 (NTSC) of them contain picture content. The location is variable, since analogue equipment may shift the picture sideways in an unexpected amount or direction. The exact width is determined by taking the definition of the time required for an active line in PAL or NTSC, and multiplying it by the pixel clock of 13.5 MHz of Digital SDTV. PAL is exactly 52 μs, so it will equate to exactly 702 pixels. Notably, screen shapes a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overscan
Overscan is a behaviour in certain television sets in which part of the input picture is cut off by the visible bounds of the screen. It exists because cathode-ray tube (CRT) television sets from the 1930s to the early 2000s were highly variable in how the video image was positioned within the borders of the screen. It then became common practice to have video signals with black edges around the picture, which the television was meant to discard in this way. Origins Early analog televisions varied in the displayed image because of manufacturing tolerance problems. There were also effects from the early design limitations of power supplies, whose DC voltage was not regulated as well as in later power supplies. This could cause the image size to change with normal variations in the AC line voltage, as well as a process called blooming, where the image size increased slightly when a brighter overall picture was displayed due to the increased electron beam current causing the CRT anod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard-definition Television
Standard-definition television (SDTV; also standard definition or SD) is a television system that uses a resolution that is not considered to be either high or enhanced definition. ''Standard'' refers to offering a similar resolution to the analog broadcast systems used when it was introduced. History and characteristics SDTV originated from the need for a standard to digitize analog TV (defined in BT.601) and is now used for digital TV broadcasts and home appliances such as game consoles and DVD disc players. Digital SDTV broadcast eliminates the ghosting and noisy images associated with analog systems. However, if the reception has interference or is poor, where the error correction cannot compensate one will encounter various other artifacts such as image freezing, stuttering, or dropouts from missing intra-frames or blockiness from missing macroblocks. The audio encoding is the last to suffer a loss due to the lower bandwidth requirements. Standards that suppor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Television
Digital television (DTV) is the transmission of television signals using Digital signal, digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio (commonly 16:9) in contrast to the narrower format (4:3) of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same Bandwidth (signal processing), bandwidth as a single analog channel, and provides many new features that analog television cannot. A digital television transition, transition from analog to digital broadcasting began around 2000. Different digital television broadcasting st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horizontal Blank
Horizontal blanking interval refers to a part of the process of displaying images on a computer monitor or television screen via raster scanning. CRT screens display images by moving beams of electrons very quickly across the screen. Once the beam of the monitor has reached the edge of the screen, it is switched off, and the deflection circuit voltages (or currents) are returned to the values they had for the other edge of the screen; this would have the effect of retracing the screen in the opposite direction, so the beam is turned off during this time. This part of the line display process is the Horizontal Blank. In detail, the Horizontal blanking interval consists of: * front porch – blank while still moving right, past the end of the scanline, * sync pulse – blank while rapidly moving left; in terms of amplitude, "blacker than black". * back porch – blank while moving right again, before the start of the next scanline. Colorburst occurs during the back porch, and un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analog Television
Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, instantaneous phase and frequency, phase and frequency of an analog signal. Analog signals vary over a continuous range of possible values which means that electronic noise and interference may be introduced. Thus with analog, a moderately weak signal becomes Noise (video), snowy and subject to interference. In contrast, picture quality from a digital television (DTV) signal remains good until the signal level drops below digital cliff, a threshold where reception is no longer possible or becomes intermittent. Analog television may be wireless (terrestrial television and satellite television) or can be distributed over a cable network as cable television. All broadcast television systems used analog signals before the arrival of DTV. Motivated by the lower bandwidth requ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DivX
DIVX (Digital Video Express) is a discontinued digital video format. Created in part by Circuit City, it was an unsuccessful attempt to create an alternative to video rental in the United States. The format's poor reception from consumers resulted in major financial losses for Circuit City and is credited with being part of the company's downfall. Format DIVX was a rental format variation on the DVD player in which a customer would buy a DIVX disc (similar to a DVD) for approximately US$4.50, which was watchable for up to 48 hours from its initial viewing. After this period, the disc could be viewed by paying a continuation fee to play it for two more days. Viewers who wanted to watch a disc an unlimited number of times could convert the disc to a "DIVX silver" disc for an additional fee. "DIVX gold" discs that could be played an unlimited number of times on any DIVX player were announced at the time of DIVX's introduction, but no DIVX gold titles were ever released. Eac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overscan
Overscan is a behaviour in certain television sets in which part of the input picture is cut off by the visible bounds of the screen. It exists because cathode-ray tube (CRT) television sets from the 1930s to the early 2000s were highly variable in how the video image was positioned within the borders of the screen. It then became common practice to have video signals with black edges around the picture, which the television was meant to discard in this way. Origins Early analog televisions varied in the displayed image because of manufacturing tolerance problems. There were also effects from the early design limitations of power supplies, whose DC voltage was not regulated as well as in later power supplies. This could cause the image size to change with normal variations in the AC line voltage, as well as a process called blooming, where the image size increased slightly when a brighter overall picture was displayed due to the increased electron beam current causing the CRT anod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Safe Area (television)
Safe area is a term used in television production to describe the areas of the television picture that can be seen on television screens. Older televisions can display less of the space outside of the safe area than ones made more recently. Flat panel screens, plasma displays and liquid crystal display (LCD) screens generally can show most of the picture outside the safe areas. The use of safe areas in television production ensures that the most important parts of the picture are seen by the majority of viewers. The size of the title-safe area is typically specified in pixels or percent. The NTSC and PAL analog television standards do not specify official overscan amounts, and producers of television programming use their own guidelines. Some video editing software packages for non-linear editing systems (NLE) solutions have a setting which shows the safe areas while editing. Title-safe area The title-safe area or graphics-safe area is, in television broadcasting, a re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertical Blanking Interval
In a raster scan display, the vertical blanking interval (VBI), also known as the vertical interval or VBLANK, is the time between the end of the final visible line of a frame or field and the beginning of the first visible line of the next frame or field. It is present in analog television, VGA, DVI and other signals. Here the term field is used in interlaced video, and the term frame is used in progressive video and there can be a VBI after each frame or field. In interlaced video a frame is made up of 2 fields. Sometimes in interlaced video a field is called a frame which can lead to confusion. In raster cathode-ray tube (CRT) displays, the blank level is usually supplied during this period to avoid painting the retrace line—see raster scan for details; signal sources such as television broadcasts do not supply image information during the blanking period. Digital displays usually will not display incoming data stream during the blanking interval even if present. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
