DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

ITU-R Rec. BT.601-5, Studio
encoding parameters of digital television
for standard 4:3 and widescreen
16:9 aspect ratios. Should
this standard be revised, it will be
denoted Rec. BT.601-6.
Recall from page 90 that in
Rec. 601, C B and C R are cosited –
each is centered on the same
location as Y’ j , where j is even.
Most 4:2:2 systems now accommodate
10-bit components.
Digital video interfaces 15
This chapter provides an overview of digital interfaces
for uncompressed and compressed SDTV and HDTV.
Component digital SDTV interface (Rec. 601, “4:2:2”)
The notation 4:2:2 originated as a reference to a
chroma subsampling scheme that I outlined on page 90.
During the 1980s, it came to denote a specific component
digital video interface standard incorporating 4:2:2
chroma subsampling. In the 1990s, the 4:2:2 chroma
subsampling format was adopted for HDTV. As a result,
the notation 4:2:2 is no longer clearly limited to SDTV,
and no longer clearly denotes a scanning or interface
standard. To denote the SDTV interface standard, I use
the term Rec. 601 interface instead of 4:2:2.
In Rec. 601, at 4:3 aspect ratio, luma is sampled at
13.5 MHz. C B and C R color difference components are
horizontally subsampled by a factor of 2:1 with respect
to luma – that is, sampled at 6.75 MHz each. Samples
are multiplexed in the sequence {C B , Y 0 ’, C R , Y 1 ’}.
Sampling at 13.5 MHz produces a whole number of
samples per total line (S TL) in 480i systems (with
858 S TL) and 576i systems (with 864 S TL). The word
rate at the interface is twice the luma sampling
frequency: For each luma sampling clock, a color difference
sample and a luma sample are transmitted. An
8-bit, 4:2:2 interface effectively carries 16 bits per pixel;
the total data rate is 27 MB/s. A 10-bit serial interface
effectively carries 20 bits per pixel, and has a total bit
rate of 270 Mb/s.
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