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The scope of the terms Y′UV, YUV, YCbCr, YPbPr, etc., is sometimes ambiguous and overlapping. Y′UV is the separation used in PAL.; YDbDr is the format used in SECAM and PAL-N, unusually based on non-gamma-corrected (linear) RGB, making the Y component true luminance.
YCbCr is sometimes abbreviated to YCC.Typically the terms Y′CbCr, YCbCr, YPbPr and YUV are used interchangeably, leading to some confusion. The main difference is that YPbPr is used with analog images and YCbCr with digital images, leading to different scaling values for U max and V max (in YCbCr both are ) when converting to/from YUV.
The three values of the YCoCg color model are calculated as follows from the three color values of the RGB color model: [2] [] = [] [] The values of Y are in the range from 0 to 1, while Co and Cg are in the range of −0.5 to 0.5, as is typical with "YCC" color models such as YCbCr.
For example, applying a histogram equalization directly to the channels in an RGB image would alter the color balance of the image. Instead, the histogram equalization is applied to the Y channel of the YIQ or YUV representation of the image, which only normalizes the brightness levels of the image.
The analogue YUV and digital YCbCr refer to a variety of linear methods to try to separate lightness from chroma signals in an RGB input using linear combination. As the input RGB values are gamma-corrected, such a separation does not truly produce lightness and two chroma signals, but a "luma" signal and two "chrominance" signals instead.
However, the term YUV is often used erroneously to refer to Y'CbCr encoding. Hence, expressions like "4:2:2 YUV" always refer to 4:2:2 Y'CbCr, since there simply is no such thing as 4:x:x in analog encoding (such as YUV). Pixel formats used in Y'CbCr can be referred to as YUV too, for example yuv420p, yuvj420p and many others.
For example, when an ordinary RGB digital image is compressed via the JPEG standard, the RGB color space is first converted (by a rotation matrix) to a YCbCr color space, because the three components in that space have less correlation redundancy and because the chrominance components can then be subsampled by a factor of 2 or 4 to further ...
Like YC B C R, it is based on gamma corrected RGB primaries; the two are numerically equivalent but YP B P R is designed for use in analog systems while YC B C R is intended for digital video. [1] The EOTF (gamma correction) may be different from common sRGB EOTF and BT.1886 EOTF.