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Standard Definition
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 support ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refresh Rate
The refresh rate, also known as vertical refresh rate, vertical scan rate or vertical frequency in reference to terminology originating with the cathode-ray tubes (CRTs), is the number of times per second that a raster-based display device displays a new image. This is independent from frame rate, which describes how many images are stored or generated every second by the device driving the display. On CRT displays, higher refresh rates produce less flickering, thereby reducing eye strain. In other technologies such as liquid-crystal displays, the refresh rate affects only how often the image can potentially be updated. Non-raster displays may not have a characteristic refresh rate. Vector displays, for instance, do not trace the entire screen, only the actual lines comprising the displayed image, so refresh speed may differ by the size and complexity of the image data. For computer programs or telemetry, the term is sometimes applied to how frequently a datum is updated with a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pixel Aspect Ratio
A pixel aspect ratio (PAR) is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel. Most digital imaging systems display an image as a grid of tiny, square pixels. However, some imaging systems, especially those that must be compatible with standard-definition television motion pictures, display an image as a grid of rectangular pixels, in which the pixel width and height are different. Pixel aspect ratio describes this difference. Use of pixel aspect ratio mostly involves pictures pertaining to standard-definition television and some other exceptional cases. Most other imaging systems, including those that comply with SMPTE standards and practices, use square pixels. PAR is also known as ''sample aspect ratio'' and abbreviated ''SAR'', though it can be confused with storage aspect ratio. Introduction The ratio of the width to the height of an image is known as the aspect ratio, or more precisely the di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMPTE 259M-C
SMPTE 259M is a standard published by SMPTE which "describes a 10-bit serial digital interface operating at 143/270/360 Mb/s." The goal of SMPTE 259M is to define a serial digital interface (based on a coaxial cable), called SDI or SD-SDI. There are 4 bit rate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...s defined, which are normally used to transfer the following standard video formats: References Film and video technology SMPTE standards {{Measurement-stub ... [...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] |
Horizontal Blanking
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nominal Analog 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raster Interrupt
A raster interrupt (also called a horizontal blank interrupt) is an interrupt signal in a legacy computer system which is used for display timing. It is usually, though not always, generated by a system's graphics chip as the scan lines of a frame are being readied to send to the monitor for display. The most basic implementation of a raster interrupt is the vertical blank interrupt. Such an interrupt provides a mechanism for graphics registers to be changed mid-frame, so they have different values above and below the interrupt point. This allows a single-color object such as the background or the screen border to have multiple horizontal color bands, for example. Or, for a hardware sprite to be repositioned to give the illusion that there are more sprites than a system supports. The limitation is that changes only affect the portion of the display below the interrupt. They don't allow more colors or more sprites on a single scan line. Modern protected mode operating systems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pixel Aspect Ratio
A pixel aspect ratio (PAR) is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel. Most digital imaging systems display an image as a grid of tiny, square pixels. However, some imaging systems, especially those that must be compatible with standard-definition television motion pictures, display an image as a grid of rectangular pixels, in which the pixel width and height are different. Pixel aspect ratio describes this difference. Use of pixel aspect ratio mostly involves pictures pertaining to standard-definition television and some other exceptional cases. Most other imaging systems, including those that comply with SMPTE standards and practices, use square pixels. PAR is also known as ''sample aspect ratio'' and abbreviated ''SAR'', though it can be confused with storage aspect ratio. Introduction The ratio of the width to the height of an image is known as the aspect ratio, or more precisely the di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pillarbox
The pillarbox effect occurs in widescreen video displays when black bars ( mattes or masking) are placed on the sides of the image. It becomes necessary when film or video that was not originally designed for widescreen is shown on a widescreen display, or a narrower widescreen image is displayed within a wider aspect ratio, such as a 16:9 image in a 2.39:1 frame (common in cinemas). The original material is shrunk and placed in the middle of the widescreen frame. Some older arcade games that had a tall vertical and short horizontal are displayed in pillarbox even on 4:3 televisions. Some early sound films made between 1928 and 1931, such as '' Sunrise: A Song of Two Humans'', were released in even narrower formats such as 1.20:1 to make room for the sound-on-film track on then-standard film stock. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Format Description
In television technology, Active Format Description (AFD) is a standard set of codes that can be sent in the MPEG video stream or in the baseband Serial digital interface, SDI video signal that carries information about their aspect ratio and other active picture characteristics. It has been used by television broadcasters to enable both 4:3 and 16:9 television sets to optimally present pictures transmitted in either format. It has also been used by broadcasters to dynamically control how down-conversion equipment formats widescreen 16:9 pictures for 4:3 displays. Standard AFD codes provide information to video devices about where in the coded picture the active video is and also the "Shoot and protect, protected area" which is the area that needs to be shown. Outside the protected area, edges at the sides or the top can be removed without the viewer missing anything significant. Video decoders and display devices can then use this information, together with knowledge of the displ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Center Cut
Pan and scan is a film editing technique used to modify widescreen images for display on a fullscreen screen. It involves cropping the sides of the original widescreen image and panning across it when the shot's focus changes. This cropping can result in the loss of key visual elements but may draw the viewers' attention towards a particular portion of the scene. "Pan and scan" was often used with VHS tapes before widescreen home media formats such as LaserDisc, DVD, and Blu-ray became common. The vertical equivalent, known as "tilt and scan" or "reverse pan and scan," was used to adapt older films such as ''Cinderella'' (1950) for widescreen formats. These techniques have been widely criticized since their inception, with critics often disapproving of pan and scan cropping because it can remove substantial portions of the original image: up to 43% for films with a 2.35:1 aspect ratio, up to 48% for earlier 2.55:1 films, and up to 52% for 2.76:1 films. Creating new shots or c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
