YCbCr and RGB
All video discs, including Blu-ray, DVD and Video CDs, are encoded as YCbCr. While many displays accept RGB as well as YCbCr, RGB is generally reserved for output to computer monitors. RGB has a data range of 0-255. The 0-255 essentially refers to the number of colors that are available and R, G, and B, refer to Red, Green, and Blue respectively. With this color setting, each of the colors is given equal weight (which translates into equal bandwidth). In a YCbCr system, the luminance information is transmitted separately and a color difference system is used to derive green. In practical application YCbCr is no different than RGB in terms of quality when done correctly.
Technical Note: YCbCr vs. YPbPr
There is often confusion regarding YCbCr and YPbPr, however it is very easy to understand the difference. YCbCr is simply the digital "component video" format that is used in DVDs, digital TV and Video CDs. Digital camcorders (MiniDV, DV, Digital Betacam, etc.) output YCbCr over interfaces such as FireWire or SDI. YPbPr is simply the analogue version which manifests itself in the form of the three (red, green and blue) RCA connections on most displays (referred to as "component video"). Where analogue YPbPr uses three cables for connectivity, digital YCbCr uses only one.
YCbCr has a native data range of 16-235 (though it technically can do 0-255, but more on that later). The difference? Well, while you would think that RGB and its 0-255 would have a greater amount of color, the discs we all watch are mastered at the YCbCr 16-235 levels. In keeping with our definition of accuracy, the best thing you can do is match the original - this avoids interpolation and possible distortion of the original color and image.
Full (Extended) Range vs. Limited (Normal) Range
What has this got to do with anything - don't worry I'm getting to that. When the HDMI people (Silicon Image) set up the HDMI spec, they put down some ground rules. According to Section 6.6 of the HDMI 1.3 Specification document:
Black and white levels for video components shall be either “Full Range” or “Limited Range.” YCbCr components shall
always be Limited Range while RGB components
may be either Full Range or Limited Range. While using RGB, Limited Range shall be used for all video formats defined in CEA-861-D, with the exception of VGA (640x480) format, which requires Full Range.
Basically, in YCbCr mode, full range signal (0-255, which it can do) is not allowed and limited range values are specified (16-235 for 8-bit color sources). Initially, analogue sources & displays had something called under- or overshoot which in essence took into account the 1-15 and 236 to 255 values so YCbCr was limited to 16-235
zdroj:
http://www.audioholics.com/home-thea...vels-xvycc-rgb
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