The BT.709 YCbCr signal has unused code space, a limitation imposed for broadcasting purposes. In particular only 16-240 is used for the color Cb/Cr channels out of the 0-255 digital values available for 8 bit data encoding. xvYCC makes use of this portion of the signal to store extended gamut color data by using code values 1-15 and 241-254 in the Cb/Cr channels for gamut-extension.
