ITU-RBT.709 and BT.601 are ITU-R recommendations for digitizingcomponent video. BT.601 is aimed at Standard Definition Television( SDTV) and DVDs, whereas BT.709 is specified for high definition televisionHDTV, HD-DVDs and Blu-Ray discs.
BT.709 or Rec. 709 was specified in 1990 for HDTV with 1,250 lines. In 2000, BT.709-4 was added, which supports HDTV with 1,080 lines. The sampling rate for the luminance signal is 74.25 MHz, its quantization is 10 bits, the sampling frequency for the chrominance signals is 37.125 MHz, and the color subsampling is 4:2:2. The frame rates are 24 Hz, 25 Hz, 30 Hz, 50 Hz, and 60 Hz, and playback is interlaced, 1,080i, and progressive scan, 1,080p.
BT.709 also specifies the color space within the CIE color space by defining the color coordinates for red, green, and blue. The xy coordinate points for red are 0.640/0.330, for green 0.300/0.600 and for blue 0.150/0.060. The color space corresponds to that of sRGB and covers about 36% of the visible colors. It is much smaller than that of UHDTV, which is specified in BT.2020, and corresponds very closely with luminance. The digitized HDTV component signal is transmitted as an HD-SDI(High Definition Serial Digital Interface) signal.