Commonly used noun explains video
Video of ・Digital Video number
Digital video takes facility with the video of camera and so on first namely, the outside video color and brightness information change are telegraphic date, record again store medium (like the video tape) . When broadcasting, video signal is transformed to be frame information, make an appointment with 3 0 with every second speed is umbriferous go up to monitor, make human eye thinks it is moving uninterruptedly continuously. The frame rate that the film broadcasts is every second about 24 frame. If use oscilloscope (tool of a kind of test) will watch, not umbriferous imitate report signal resembles the scanning image of brain wave it seems that, by a few successive dentate mountain peak and valley composition. For memory vision message, the mountain peak of imitate video signal and valley must pass digital £¯ imitate (D /A) converter comes to those who be a number to transform " 0 " or " £± " . This transition process is the video that we say is caught (or collect a process) . If want to watch digital video on the television, need to become binary information decipher imitate signal to simulative converter from the number, ability undertakes broadcasting.
・Codec encode decoder
Encode decoder main effect is to video signal undertakes compression reconciliatory compression. Computer industry defines the true color that surveys a system through 24, this defined nearly 1 million kinds of color, approach the limit of human vision. Now, the basiccest V GA monitor has 640*480 to resemble element. If video needs,this is meant with every second the speed of 30 frame is broadcasted, criterion every second should transmit the information that is as high as 27MB, the hard disk of 1GB capacity can store only the video information of about 37 seconds. Must undertake compression handling to information consequently. Through abandoning information of a few numbers or be mixed by our eye easily the method of the picture news of cerebrum oversight, make the information content of video is reduced. This software that compresses solution pressing to video or hardware are encode decoder. The compressibility of encode decoder from general 2: 1-100: 1 differ, make handle much video data to become a possibility.
・ moves static image to compress
Static image compresses a technology basically is right spatial information undertakes compression, and to dynamic image, outside dividing pair of spatial information to undertake compression, undertake compression to time information even. Already formed 3 kinds to reduce a level at present:
1. JPEG (Joint Photographic Experts Group) standard:
Use at image of static state of monochromatic of £¯ of gray scale of successive color wither, multistage, color to compress. The graphical file that has higher compression ratio (the likelihood after the BMP file of a piece of 1000KB compresses JPEG format has 2 0 only - 30KB) , the lack fidelity degree in reducing a process is very small. Scope of application is at present wide (it is Internet webpage extremely in) . This kind has caustic to compress in sacrifice the circumstance of less detail falls 4 what use a model: 1 to 10: The compression ratio of 1 will file static image. Dynamic JPEG (M-JPEG) can is opposite orderly the each frame spurt of video is compressed all right, the picture that resembling each frame is independence is same. Dynamic J PEG can produce the video of high quality, Quan Bing, whole exercise, but, its need support is additional hardware.
2. H.261 standard: Basically apply to video phone and video TV conference.
3. MPEG (Motion Picture Experts Group, system of £¯ of sound of global image £¯ reduces a level) standard: Include frequency of MPEG video, MPEG and MPEG system (inspect frequency synchronism) 3 parts. MPEG reduces a level is in the light of athletic picture design, basic method is -- be collected inside unit time and save information of the first frame, store the others frame produces metabolic part relative to the first frame only next, with achieving compression goal. MPEG compresses a standard to be able to realize the compression between frame, its are average compression ratio can amount to 50: 1, compressibility is taller, and have unified pattern again, compatibility is good.
The level is reduced in multimedia data in, more use MPEG series level, include MPEG-1, 2, 4 etc.
MPEG-1 is used at transmitting 1. 5Mbps number stores according to transmitting the number of rate media campaign picture reachs the encode of its audio, after be being compressed through MPEG-1 standard, video data compressibility is 1/100-1 £¯ 2 00, frequency compressibility is 1 £¯ 6.5. MPEG-1 offers every second the image of resolution of 30 frame 352*240, should use appropriate compression when the technology, have be close to family expenses video to make type (VHS) the quality of the video tape. The video of the high quality that MPEG-1 promises to exceed 70 minutes and frequency memory are in a piece of CD-ROM dish on. What VCD uses is the standard of MPEG-1, this standard is one faces the video of class of domestic TV quality, frequency to reduce a level.
MPEG-2 basically spends TV in the light of high-definition Hunan (HDTV) need, transmission rate is 10Mbps, as compatible as MPEG-1, apply to the encode limits with taller even 1.5-60Mbps. MPEG-2 has every second the resolution of 30 frame 704*480, it is MPEG-1 those who broadcast speed is fourfold. It applies to the broadcast of high demand and recreational application process, be like: DSS satellite broadcast and DVD, MPEG-2 is family expenses video makes type (VHS) double of video tape resolution.
MPEG-4 standard is to exceed what small yard leads athletic picture and language to compress a standard to be used at transmitting rate under the real time image of 64Mbps, it can enclothe small frequency band not only, also develop to high frequency belt. Than before two standards character, m PEG one 4 compress for multimedia data offerred ? more capacious platform. What its more defines is a kind of a kind of format, framework, is not specific algorithm. It can use various multimedia technologies adequately, include to compress a few tools of itself, algorithm, also incorporate the technology such as image synthesis, speech synthesis.
・DAC
Count £¯ model to turn namely outfit change implement, one kind changes digital signal into the device of imitate signal. The digit of DAC is taller, signal is lack fidelity smaller. Picture is clearer also stable.
・AVI
AVI is the file format that is together speech and video and synchronous combination. It used a kind to caustic reduces kind to video file, but compression ratio is higher, accordingly although area area quality is not too good, but its application range is very wide still. A VI supports color and 256 RLE to compress. AVI information basically applies on multimedia CD, with will save all sorts of video information such as TV, film.
・RGB
The methodological be called by a joint name that has code to a kind of color is " color space " or " colour gamut " . Say with the simplest word, of a kind of any color on the world " color space " the number that can define to secure or variable. RGB (red, green, blue) a kind be numerous color space only. Use method of this kind of encode, every kinds of color can show the strength of ? red green and blue with 3 variable. When record and indication color image, r GB is a kind of the commonnest plan. But, it lacks the good compatibility with system of inchoate B/W display. Accordingly, many the method that manufacturer of electronic electric equipment uses generally is, RGB changeover becomes YUV color sky to be the same as, in order to maintain compatible, return RGB form according to needing to change again, so that be on computer monitor,show chromatic figure.
・YUV
YUV (also weigh YCrCb) it is the method of a kind of colour coding that is used by place of European TV system (belong to PAL) . YUV basically is used at optimizing the transmission of chromatic video signal, make its backward compatible and vintage monochrome television. Transmit photograph comparing with signal of R GB video, its biggest advantage depends on needing to take up only few bandwidth (the video signal that RGB asks to become independent 3 times is transmitted at the same time) . Among them " Y " express to be spent brightly (Lumina Nce or Luma) , namely ash rank value; And " U " and " V " denotive it is chroma (Chrominance or Chroma) , action is to describe video colour and degree of saturation, use at appointing the color like element. "Brightness " be to pass R GB to input signal to found, the method is the specific part overlay RGB signal arrives one case. "Chroma " the two respects ? that defined color is tonal with degree of saturation, express respectively with Cr and CB. Among them, c R mirrorred GB to input signal red part and RGB signal brightness to be worth the difference between. And the be the same as difference that what CB mirrors is value of brightness of part of blue of RGB input signal and RGB signal.
・ compound video and S-Video
Such forming of NTSC and signal of PAL color video- - have a signal of basic black and white video above all, it is next after pulse of every level synchronism, add pulse of a color and a luminance signal. Because chromatic signal is by a variety of data " overlay " rise, friend says for " compound video " . S -Video is the video interface with higher quality of a kind of signal, it cancelled the method of signal overlay, can avoid a few meaningless quality losses effectively. Its function is RGB3 primary colors and brightness undertake departing handling.
・NTSC, PAL and SECAM
Base band video is a kind of simple imitate signal, by video imitate data and video synchronism data is formed, use at sink shows picture correctly. The detail of signal depends on video standard of application or " make type "- - NTSC (Committee on Standard of TV of American whole nation, national Television Standards Committee) , PAL (fall line by line, phase Alternate Line) and SECAM (convey orderly with system of memory colour television, a kind of television system that France uses, SEquential Couleur Avec Memoire) . In PC domain, make type differ as a result of what use, put in incompatible circumstance. Take resolution for, some makes type every frame has 625 lines (50Hz) , every frame has some criterion only 525 lines (60 Hz) . Latter is the level that North America and Japan use, a general designation is NTSC. Normally, signal of a video is generated by source of a video, for instance camera, VCR or TV tuner. To transmit image, video source should generate ? above all perpendicular and synchronous signal (V SYNC) . This signal can establish sink facility again (PC monitor) , protect ask for new image to begin to show from the coping of screen. After issueing VSYNC signal, video source catchs the group of scanning image. After finishing, video source generates signal of synchronism of a level again, set sink again, so that from screen left begin to show next party. Each when be aimed at image, want to give out a scanning beam, and signal of pulse of synchronism of a level.
Additional, NTSC standard still stipulates video source per sec. needs to send 30 whole picture (frame) . If do not make other processing, twinkle the phenomenon will be very serious. To solve this problem, every frame by equational for two parts, every part 2 62.5 goes. One part is odd travel completely, another part is even travel completely. When showing, scan first odd travel, scan again even travel, improve the stability that image shows effectively, decrease twinkle. At present the colour television on the world basically has 3 kinds to make type, namely N TSC, PAL and SECAM make type, 3 kinds make type still cannot be united at present. What our country uses is PAL-D makes type.
・Ultrascale
Ultra6cale is Rockwell (Luokeweier) a kind of used scanning change a technology. Can be opposite perpendicular with horizontal way show undertake shrinking arbitrarily putting. In TV show on such interlaced scanning equipment line by line when video, whole process itself oneself is very troublesome. And use UltraScale ability wood, still can resemble be on computer monitor even Na Xiang, the freely direction freedom with spurt similar travel is adjustable.
