i wonder why HSV and YUV are different formats, even though they both works similarly (based on the brightness), if not what is the difference and i have confusions with YPbPr and YCbCr , can anyone give directions to understand these color formats.
YUV is basically a member of the television broadcast industry video/image color encoding formats, and was created during the transition of black & white broadcast into color. A backwards (B&W) compatible color broadcast was needed that could still be received by the existing B&W receivers, yet could also enable color reception with (then) new color TV receivers. The European broadcast systems PAL (ENG-GRM), and the American NTSC (USA-JAPAN) were using color space encodings defined by YUV (PAL) and YIQ (NTSC).
The very successful installment of YUV into the existing commercial TV base has naturally led to its adoption into the digital multimedia too; MPEG-I, MPEG-II, and MPEG-IV are all based on digital variants of YUV color spaces. Moreover, the most wide spread image compression codec, JPEG, also uses (digital) YUV variant.
YUV is quite easily obtained from RGB by a simple matrix transform. Y represents the approximate black and white (or luminance) information, and U-V carry the chroma (color) information. The angle between (U,V) pair at a pixel, representing the hue and the magnitude representing the saturation. U and V components are AC signals, without a DC.
HSV (Hue, Saturation, Value) is not that easy to obtain via a simple linear (matrix) transform from RGB values. It is more suitable for color photography science and It's not a broadcast friendly format, and hence not used there.
YPbPr is a variant of analog YUV video color format, sutiable for high-definition. Where the Y component is similar to YUV, but Pb is the blue difference and Pr is the red difference channel. It's used in High-End monitor equipment for high resolution (high bandwidth) analog video input, which is worse than pure RGB but better than composite CVBS video.
YCbCr is a digital variant of YUV (probably YPbPr in essence). It's obtained by sampling the corresponsing analog format. There are so many variations that it's hard to refer to the specific one in a general statement.
You shall consult TV broadcast engineering books for more tabulated answers.
So the best discussion I can point to is in this PDF on Charles Poynton's site.
The PDF goes on to much more detailed explanations of each color space, and how to convert between them. It's a bit longer than I want to type out (or cut-and-paste images of). :-)
YUV, YPbPr and YCbCr are all basically same, but just with different scale factors for the signals. YUV signals are used when encoding/decoding analog composite video, YPbPr signals exists at analog component video interface and YCbCr signals are digital numbers. There is brightness (luma) channel Y and two color difference signals (U and V, Pb and Pr, Cb and Cr). If you only look at color, color is representend by U and V in cartesian X-Y coordinates on a plane. The HSV system represents color as hue and saturation, which corresponds to polar coordinates in the plane, hue being the angle and saturation being the distance from origin.
There are various ways to re-express rgb primaries (that themselves can be defined in different ways) in order to achieve something. That something could be «extending monochrome television to color». Or «expressing luminance in a way that mimics the human visual system». Or «relegating color differences in a way that conveniently lets you reduce their transmission/storage bandwidth with little loss of perceived quality».
A color scientist wanting to analyse human perception might choose different analysis tools from a video camera that must produce 8 million pixels 60 times a second day in and day out.