CCIR Rec. 601 (last version is 601-2) specifies the the image format, acquisition semantic, and parts of the coding for digital "standard" television signals. ("Standard" television is in the resolution of PAL, NTSC, and SECAM)
CCIR-601 gives the specification for encoding of 4:2:2 signals and a tentative specification of 4:4:4 encoding. 4:2:2 means, that the color-difference signals Cr and Cb are sampled with half of the sampling frequency of the luminance signal Y, that is 13.5MHz to 6.75MHz.
It also specifies the number of samples per line for 525/60(59,94) systems and 625/50 systems. The samples per total line are different, but the samples per active line are the same for both systems: 720 samples per active line. It does not specify the number of lines for both systems; this can be found in CCIR Rep. 624-4, which gives a detailed description of all parameters of the analog television systems, as NTSC, PAL, SECAM and all of the derivates.
The correspondence between the video signal levels and the quantization levels is also specified. The scale is between 0 and 255, for the luminance signal you have 220 quantization levels, for the color- difference signals 225 quantization levels. The signals are only coded with 8-bit per signal! - A official Recommendation for 10-bit coding is in progress.
One of the most important parts is the specification, in which way you can generate the digital signals Y,Cr,Cb from the analogue, gamma corrected signals E'r,E'g, and E'b. This part in the recommendation is very detailed and easy to understand.
The last part (Annex III) of the Recommendation - Filtering Characteristics - is may be one of the most important, but also the most ignored from the CG community! It describes in which way you have to filter the analogue signal to get the digital signals.
For us it means we have to look in which way we have to filter our RGB signals if we convert to YCrCb - which are the right filters, I don't know! - May be someone else can give us a brief description for this.
Very important to remember is, that the formulas given for the color conversion are for gamma corrected RGB signals! The gamma for the different television systems are specified in CCIR Report 624-4.
The encoding of the digital signal is described in detail in CCIR Rec. 656.
There are also national Standards for CCIR 601, e.g. you can find them from SMPTE (mostly in the US) or from the EBU (mostly in Europe).
Some detailed information concerning CCIR Rec. 601:
Title: CCIR Rec. 601-2 ENCODING PARAMETERS OF DIGITAL TELEVISION FOR STUDIOS (1990) Published: Recommendations of the CCIR, 1990 (Also Resolutions and Options) Volume XI - Part 1 Broadcasting Service (Television) pp 95-104 Source of Supply: International Telecommunication Union General Secretariat - Sales Section Place des Nations, CH-1211 Geneva 20 (Switzerland)