Rec. 601

CCIR 601 is the old name of a standard published by the CCIR (now ITU-R) for encoding interlaced analogue video signals in digital form. It includes methods of encoding 525-line 60 Hz and 625-line 50 Hz signals, both with 720 luminance samples and 360 chrominance samples per line. Regardless of the frame rate, the luminance sampling frequency is 13.5 MHz. The colour encoding system is known as 4:2:2, that being the ratio of Y:Cb:Cr samples (luminance data:blue chroma data:red chroma data).

The CCIR 601 signal is effectively a digitally encoded analog component video signal, and thus includes data for the horizontal and vertical sync and blanking intervals. Each sample encodes two 8-bit pixel values, optionally encoded using an 8-bit to 10-bit channel code: the resulting data rate is thus 216 Mbit/s for the 8-bit version (as used in D1 digital tape recording) or 270 Mbits/s for the 10-bit version (as used in D5 digital tape recording).

In each 8-bit luminance sample, the value 16 is used for black and 235 for white, to allow for overshoot and undershoot. The values 0 and 255 are used for sync encoding. The Cb and Cr samples use the value 128 to encode a zero value.

References

• ITU-R Recommendation BT.601-5 (10/95) Studio encoding parameters of digital television for standard 4:3 and wide-screen 16:9 aspect ratios