視頻信號分類及介紹

1、視頻信號分類及介紹XXXColor Spaces RGB - most basic of the color spaces YCbCr - digital representation of the video signal developed as part of ITU-R BT.601 Nominal ranges of: Y = 16-235 Cb, Cr = 16-240 YPbPr - analog representation of the video signal RGB to YCbCr - HDTVassumes 8-bit data with a 16235 nomina

2、l range YPbPr Generation - HDTV assumes 10-bit DAC with an output range of 01.305VVideo Signals Composite video: = y + u * sin wsct +v * cos wsct S video: luma = y chroma = u * sin wsct +v * cos wsct Component video: luma = y Pb = 1.146 * u Pr = 0.813 * v RGB Composite Video Standards NTSC, PAL, SEC

3、AM NTSC: Color is 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

4、.5 304 -0.41 0 0 -1.0 160 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 a

5、nd frame (refresh) rates Always 3 color components: Red, Green, Blue Synchronization is carried via TTL-style dedicated HSYNC,VSYNC signals HSYNC: 1 pulse per line VSYNC: 1 pulse per frame (field)Popular PC Graphics FormatsA total of 18 formats exists, defined by ATSC (Advanced Television Systems Co

6、mmittee) 1080I (1080 active 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 FormatsFormat Calc

7、ulationSampling speed1080I1125 x 2200 x 60/2 74.25 MHz720P1650 x 750 x 6074.25 MHzVertical lines Pixels Aspect ratio Picture rate1080192016:0960I, 30P, 24P720128016:0960P, 30P, 24P48070416:9 & 4:360P, 60I, 30P, 24P4806404:0360P, 60I, 30P, 24PHDTV SDTV RGB Component VideoNOTE: Trilevel sync shown is for HDTV;bilevel (negative sync) for SDTVYPbPr