CCIR-601 Video Standard
CCIR (the International Radio Consultative Committee) recommendation 601 specifies the image format, and coding for digital television signals.
Sony states that the PDX10p satisfies the CCIR-601 standard at 4:2:0, but this does not mean that the PDX10 does not record values outside the 16- 235 area! This picture information can be utilised by the editor under extreme light situtations as a kind of spare room.

The main parameters of CCIR 601 are listed below:


YUV encoding 4:2:2
Sampling frequency for Y (MHz) 13.5
Sampling frequency for U and V (MHz) 6.75
No of samples per line 720
No of levels for Y component 220
No of levels for U,V components 225

The number of levels is less than 256 because black is defined as 16 and white as 235
to allow for overshoot in the analogue signal to be digitally coded.

Most digital video recording systems comply with CCIR 601 or a subset of it.  

The 625-line (PAL) DVC compression standard (not DVCPRO) specifies this 4:2:0 sampling pattern:

DVC is field-aware, and this diagram is meant to show an interleaved frame. In the 625-line DVC sampling pattern, Cr and Cb samples are not co-sited. Instead, we get a whole line of Cr samples from each field, then we get a whole line of Cb samples from each field. The top two lines of the standard DVC frame contain Cr samples.

A (German) overview of the DV compression formats:
pm:   4.2.0 comression is used by PAL
  4.1.1 comression is used by NTSC