The definition of the television basically is decided by two respects, resolution and bandwidth. Resolution expresses normally with the form of multiplication, be like 640*480, among them 640 express what screen standard way shows to resemble element, namely horizontal definition, namely the how many line that we often say; 480 it is screen on perpendicular direction resemble element. Resolution is the parameter that describes picture resolution.
Bandwidth is the video bandwidth that points to indication equipment, it is equal to *135% of frequency of resolution * field. For example: Cheek live abroad sticks S Mei natrium to bilge DTV of ↙ of cherry of Li of magpie of of Li of D cook and stir) resolution is 340*255, field frequency is 50HZ, so its inspect frequency bandwidth =340*255*50*135%=5.84MHZ.
Additional, the aspect ratio of present indication screen has two kinds, one kind is 4: 3, one kind is 16: 9. Among them 4: 3 use on television of common picture tube commonly, and 16: 9 multi-purpose go up in high-definition clear television.
The definition cent of digital TV is 3 grade: Common definition TV (PDTV) , its level definition is 200- - 300 lines; Standard definition TV (SDTV) , its level definition is 500- - 600 lines; High definition TV (HDTV) , its level definition is 1000 lines above, according to relevant standard definition, its resolution is 1920*1080, use 16: The screen scale of 9.
The 1MHZ video bandwidth of general picture tube is corresponding the horizontal definition of 52 lines, so, the video bandwidth of common definition TV is 300/52=5.76MHZ; The video bandwidth of standard definition TV is 600/52=11.52MHZ; The bandwidth of high definition TV is 1920/52=37MHZ. However, according to relevant specification regulation, the bandwidth of high definition TV is 30MHZ, visible, picture tube television is what cannot show HDTV is all resemble element, also can show only at most resemble element entirely 81% (30/37) .
The different cent of present mark Qing Dynasty and means of scanning of field of high-definition TV basis is the following kinds of formats: SDTV-480I (perpendicular resolution is 480 lines, interlaced scanning) ; SDTV-480P (perpendicular resolution is 480 lines, progressive scanning) ; The aspect ratio of screen all is 4: 3. HDTV-1080I (perpendicular resolution is 1080 lines, interlaced scanning) ; HDTV-1080P (perpendicular resolution is 1080 lines, progressive scanning) ; HDTV-720P (perpendicular resolution is 720 lines, progressive scanning) ; The aspect ratio of screen all is 16: 9.
32 what supportive HDTV calls on market now- - its level definition also won't exceed 36 inches picture tube television 600 lines, it is highest grade picture tube television, its level definition also achieves 800 strings nevertheless, for this, the television of alleged HDTV picture tube on market is not real HDTV television.
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