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Video is an electronic medium for the recording , copying and broadcasting of moving visual images . [ edit ] History Video technology was first [ citation needed ] developed for cathode ray tube (CRT) television systems, but several new technologies for video display devices have since been invented. Charles Ginsburg led an Ampex research team developing the first practical video tape recorder (VTR). In 1951 the first video tape recorder captured live images from television cameras by converting the camera's electrical impulses and saving the information onto magnetic video tape . Video recorders sold for $50,000 in 1956, and videotape cost $300 per one-hour reel. [ 1 ] However, prices steadily dropped over the years; in 1971, Sony began selling videocassette recorder (VCR) tapes to the public.
Video
Motion compensation is an algorithmic technique employed in the encoding of video data for video compression , for example in the generation of MPEG-2 files. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture may be previous in time or even from the future.
Motion compensation
Motion interpolation
Motion interpolation is a form of video processing in which intermediate animation frames are generated between existing ones, in an attempt to make animation more fluid, and to compensate for display motion blur . [ edit ] Applications [ edit ] Software Some video software suites and plugins offer motion-interpolation effects to enhance digitally-slowed video.
위키백과, 우리 모두의 백과사전. RGB 비트맵 그림의 맨 위 왼쪽 모퉁이에 웃는 얼굴 이 있다고 치자. 확대를 하면 커다란 웃는 얼굴은 오른쪽과 같이 보이게 된다.
Raster graphics
In computer science and telecommunication , interleaving is a way to arrange memory in a non- contiguous way to increase performance. It is typically used: In error-correction coding , particularly within data transmission , disk storage , and computer memory . For multiplexing of several input data over shared media.
Interleaving
Cutaway rendering of a color CRT: 1. Three Electron guns (for red, green, and blue phosphor dots) 2. Electron beams 3. Focusing coils 4. Deflection coils 5. Anode connection 6.
CRT
Overscan is extra image area around the four edges of a video image that may not be seen reliably by the viewer. It exists because television sets in the 1930s through 1970s were highly variable in how the video image was framed within the cathode ray tube (CRT). [ edit ] Origins of overscan Early televisions varied in their displayable area because of manufacturing tolerance problems. There were also effects from the early design limitations of linear power supplies, whose DC voltage was not regulated as well as in later switching-type power supplies.
Overscan
YUV pixel formats
YUV formats fall into two distinct groups, the packed formats where Y, U (Cb) and V (Cr) samples are packed together into macropixels which are stored in a single array, and the planar formats where each component is stored as a separate array, the final image being a fusing of the three separate planes. In the diagrams below, the numerical suffix attached to each Y, U or V sample indicates the sampling position across the image line, so, for example, V0 indicates the leftmost V sample and Yn indicates the Y sample at the (n+1)th pixel from the left. Subsampling intervals in the horizontal and vertical directions may merit some explanation.Chrominance
Chrominance ( chroma or C for short) is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal (or Y for short). Chrominance is usually represented as two color-difference components: U = B′ − Y′ (blue − luma) and V = R′ − Y′ (red − luma). Each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard. In composite video signals, the U and V signals modulate a color subcarrier signal, and the result is referred to as the chrominance signal; the phase and amplitude of this modulated chrominance signal correspond approximately to the hue and saturation of the color. In digital-video and still-image color spaces such as Y′CbCr , the luma and chrominance components are digital sample values. Separating RGB color signals into luma and chrominance allows the bandwidth of each to be determined separately.
MPEG logo MPEG Format is used on several media. This picture relates some of the most known media to the MPEG Format version and container format ( TS and PS ) used. The Moving Picture Experts Group ( MPEG ) is a working group of experts that was formed by ISO and IEC to set standards for audio and video compression and transmission. [ 1 ] It was established in 1988 by the initiative of Hiroshi Yasuda ( Nippon Telegraph and Telephone ) and Leonardo Chiariglione , [ 2 ] group Chair since its inception. The first MPEG meeting was in May 1988 in Ottawa, Canada. [ 3 ] [ 4 ] [ 5 ] As of late 2005, MPEG has grown to include approximately 350 members per meeting from various industries, universities, and research institutions.
MPEG
MPEG-2 system
MPEG-2 (aka H.222/H.262 as defined by the ITU ) is a standard for "the generic coding of moving pictures and associated audio information". [ 1 ] It describes a combination of lossy video compression and lossy audio data compression methods, which permit storage and transmission of movies using currently available storage media and transmission bandwidth. [ edit ] Main characteristics MPEG-2 is widely used as the format of digital television signals that are broadcast by terrestrial (over-the-air), cable , and direct broadcast satellite TV systems. It also specifies the format of movies and other programs that are distributed on DVD and similar discs. TV stations , TV receivers , DVD players, and other equipment are often designed to this standard. MPEG-2 was the second of several standards developed by the Moving Pictures Expert Group ( MPEG ) and is an international standard ( ISO / IEC 13818).Program-specific information (PSI) is metadata about a program (channel) and part of an MPEG transport stream . The PSI data contains five tables: PAT (program association table) CAT (conditional access table) PMT (program map table) NIT (network information table) TDT (time and date table) PSI is carried in the form of a table structure. Each table structure is broken into sections and can span multiple transport stream packets.
PSI
Digital storage media command and control ( DSM-CC ) is a toolkit for developing control channels associated with MPEG-1 and MPEG-2 streams. It is defined in part 6 of the MPEG-2 standard (Extensions for DSM-CC) and uses a client/server model connected via an underlying network (carried via the MPEG-2 multiplex or independently if needed). DSM-CC may be used for controlling the video reception, providing features normally found on Video Cassette Recorders ( VCR ) (fast-forward, rewind, pause, etc.). It may also be used for a wide variety of other purposes including packet data transport. It is defined by a series of weighty standards, principally MPEG-2 ISO / IEC 13818-6 (part 6 of the MPEG-2 standard).