神马文学网colorspace
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BT.709或者601，是YUV变换到RGB的两种算法601是标清的标准，CCIR-601可规定的图像清晰度即是标准清晰度的参数，每一行扫描行有720个有效像素，而每一帧的有效扫描行数对于525/60及625/50两种制式分别为480行及576行。
709高清标准，ITU-R BT.709 用于制作及国际节目交换的高清晰度电视标准参数值 YUV Color Space
The YUV color space is used by the PAL(Phase Alternation Line), NTSC (NationalTelevision System Committee), and SECAM(Sequentiel Couleur Avec Mémoire or Sequential Color with Memory) composite color video standards. The black-and-white system used only luma (Y) information; color information(U and V) was added in such a way that a black-and-white receiver would still display a normal black-and-white picture. Color receivers decoded the additional color information to display a color picture.
The basic equations to convert between gamma-corrected RGB (notated as R´G´B´ and discussed later in this chapter) and YUV are:
Y = 0.299R´ + 0.587G´ + 0.114B´
U = – 0.147R´ – 0.289G´ + 0.436B´ = 0.492 (B´ – Y)
V = 0.615R´ – 0.515G´ – 0.100B´= 0.877(R´ – Y)
R´ = Y + 1.140V
G´ = Y – 0.395U – 0.581V
B´ = Y + 2.032U
For digital R´G´B´ values with a range of 0–255, Y has a range of 0–255, U a range of 0 to±112, and V a range of 0 to ±157. These equations are usually scaled to simplify the implementation in an actual NTSC or PAL digital encoder or decoder.
Note that for digital data, 8-bit YUV and R´G´B´ data should be saturated at the 0 and 255 levels to avoid underflow and overflow wrap-around problems.
If the full range of (B´ – Y) and (R´ – Y) had been used, the composite NTSC and PAL levels would have exceeded what the (then current) black-and-white television transmitters
and receivers were capable of supporting. Experimentation determined that modulated subcarrier excursions of 20% of the luma (Y) signal excursion could be permitted above white and below black. The scaling factors were then selected so that the maximum level of 75% amplitude, 100% saturation yellow and cyan color bars would be at the white level (100 IRE).-------------------YCbCr Color Space
The YCbCr color space was developed as part of ITU-R BT.601 during the development of a world-wide digital component video standard (discussed in Chapter 4). YCbCr is a
scaled and offset version of the YUV color space. Y is defined to have a nominal 8-bit range of 16–235; Cb and Cr are defined to have a nominal range of 16–240. There are several
YCbCr sampling formats, such as 4:4:4, 4:2:2, 4:1:1, and 4:2:0 that are also described.
709高清标准，ITU-R BT.709 用于制作及国际节目交换的高清晰度电视标准参数值 YUV Color Space
The YUV color space is used by the PAL(Phase Alternation Line), NTSC (NationalTelevision System Committee), and SECAM(Sequentiel Couleur Avec Mémoire or Sequential Color with Memory) composite color video standards. The black-and-white system used only luma (Y) information; color information(U and V) was added in such a way that a black-and-white receiver would still display a normal black-and-white picture. Color receivers decoded the additional color information to display a color picture.
The basic equations to convert between gamma-corrected RGB (notated as R´G´B´ and discussed later in this chapter) and YUV are:
Y = 0.299R´ + 0.587G´ + 0.114B´
U = – 0.147R´ – 0.289G´ + 0.436B´ = 0.492 (B´ – Y)
V = 0.615R´ – 0.515G´ – 0.100B´= 0.877(R´ – Y)
R´ = Y + 1.140V
G´ = Y – 0.395U – 0.581V
B´ = Y + 2.032U
For digital R´G´B´ values with a range of 0–255, Y has a range of 0–255, U a range of 0 to±112, and V a range of 0 to ±157. These equations are usually scaled to simplify the implementation in an actual NTSC or PAL digital encoder or decoder.
Note that for digital data, 8-bit YUV and R´G´B´ data should be saturated at the 0 and 255 levels to avoid underflow and overflow wrap-around problems.
If the full range of (B´ – Y) and (R´ – Y) had been used, the composite NTSC and PAL levels would have exceeded what the (then current) black-and-white television transmitters
and receivers were capable of supporting. Experimentation determined that modulated subcarrier excursions of 20% of the luma (Y) signal excursion could be permitted above white and below black. The scaling factors were then selected so that the maximum level of 75% amplitude, 100% saturation yellow and cyan color bars would be at the white level (100 IRE).-------------------YCbCr Color Space
The YCbCr color space was developed as part of ITU-R BT.601 during the development of a world-wide digital component video standard (discussed in Chapter 4). YCbCr is a
scaled and offset version of the YUV color space. Y is defined to have a nominal 8-bit range of 16–235; Cb and Cr are defined to have a nominal range of 16–240. There are several
YCbCr sampling formats, such as 4:4:4, 4:2:2, 4:1:1, and 4:2:0 that are also described.