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1、视频信号分类及介绍XXXColor SpacesRGB - most basic of the color spacesYCbCr - digital representation of the video signaldeveloped as part of ITU-R BT.601Nominal ranges of:Y = 16-235Cb, Cr = 16-240YPbPr - analog representation of the video signalRGB to YCbCr - HDTVassumes 8-bit data with a 16235 nominal rangeY
2、PbPr Generation - HDTVassumes 10-bit DAC with an output range of 01.305VVideo SignalsComposite video:= y + u * sin wsct +v * cos wsctS video: luma = ychroma = u * sin wsct +v * cos wsctComponent video:luma = yPb = 1.146 * u Pr = 0.813 * v RGB Composite Video Standards NTSC, PAL, SECAMNTSC: Color is
3、quadrature-modulated by subcarrier. Short burst of subcarrier at the beginning of each line used as reference for amplitude (saturation) and phase (hue).PAL: Similar to NTSC. Burst phase alternates from line to line.SECAM: Color is frequency modulated. 140 896 0.75 40 256 -0.5 47.5 304 -0.41 0 0 -1.
4、0 160 1023 1.0sync tipblankblackwhitemaxIRE pixel float 40 IREpixel = sync_height/40 * IREfloat = (pixel - 512) / 512 Composite Video Signal(Example: NTSC)U,VU,VYYY(n+2)fh(n+1)fhnfhfh/2fh/2Composite Frequency Spectrum(Example: NTSC)Many formats exist with different resolutions and frame (refresh) ra
5、tesAlways 3 color components: Red, Green, BlueSynchronization is carried via TTL-style dedicated HSYNC,VSYNC signalsHSYNC: 1 pulse per lineVSYNC: 1 pulse per frame (field)Popular PC Graphics FormatsA total of 18 formats exists, defined by ATSC (Advanced Television Systems Committee) 1080I (1080 acti
6、ve lines, interlaced) and 720P (720 lines, progressive) are two of the most popular formats Both result in same same pixel (sampling) clock frequency of 74.25MSPS (calculation below) Based on this an 80MSPS DAC is sufficient for HDTVPopular Component Video FormatsHDTV SDTV RGB Component VideoNOTE: Trilevel sync shown is for HDTV;bilevel (negative sync) for SDTVYPbPr Component Video (HDTV)NOTE: Trilevel sync shown is for HDTV;bilevel (negative sync) for SDTV视频信号分类及介绍XXXSEP 2007
