Page 38 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

Section 2.4. Digital Video 15

(a) 4:2:2 (b) 4:1:1 (c) 4:2:0 co-sited (d) 4:2:0 mid-sited
luma sample chroma sample
Figure 2.2: Chroma subsampling patterns

can be either midway between luma samples (Figure 2.2(d)) or co-sited with
odd-numbered luma samples (Figure 2.2(c)). 10

2.4.4 Digital Video Formats

Exchange of digital video between di6erent industries, applications, networks,
and hardware platforms requires standard digital video formats. Following are
the most commonly used formats.

2.4.4.1 CCIR-601
The International Consultative Committee for Radio (CCIR) 11 Recommen-
dation 601 [14] de nes a digital video format for the international exchange
and broadcast of production-quality TV programs. As with analog standards,
CCIR-601 de nes two interlaced systems: 525=60 and 625=50. The main fam-
ily within the standard uses a chroma subsampling of 4:2:2. The luma sam-
pling frequency is 13:5MHz, the chroma sampling frequency is 13:5 × 0:5=
6:75MHz, and the components are quantized to 8 bits. In the 525=60 system,
the luma component of the frame has active dimensions of 720 pels × 480 lines
and the chroma components have 360 pels × 480 lines. In the 625=50 system,
the corresponding values are 720 × 576 for luma and 360 × 576 for chroma.
Note that despite the di6erences between the two systems, they generate the
same raw bit rate 12 of 165:89 Mbits=s. The standard is based on component

10 In view of this lack of consistency, the authors adopt the terms mid-sited and co-sited to
describe the two cases.
11 The CCIR is currently known as ITU-R (International Telecommunications Union—Radio
Sector).
12 Bit rate=[(720 × 480) + 2(360 × 480)] × 30 × 8=[(720 × 576) + 2(360 × 576)] × 25 × 8=
165888000 bits=s, where the 2 refers to the two chroma components, the 30 and the 25are
the frame rates of the two systems, and the 8 is the number of bits per sample.