Page 40 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

Section 2.5. Video Coding Basics 17

Table 2.1: The CIF family
Luma Chromas
pels=line lines=frame pels=line lines=frame

SQCIF 128 96 64 48
QCIF 176 144 88 72
CIF 352 288 176 144
4CIF 704 576 352 288
16CIF 1408 1152 704 576

4:2:0 mid-sited chroma subsampling and a frame rate of 30 frames=s. There
are a number of lower- and higher-resolution members in the CIF family.
Those are de ned in Table 2.1.

2.4.4.4 Other Formats
13
There are a number of other formats. For example, some HDTV systems use
a 1440 × 1050 luma at 30 frames=s with progressive scanning and no chroma
subsampling (i.e., 4:4:4).

2.5 Video Coding Basics

2.5.1 The Need for Video Coding
Table 2.2 shows the raw data rates of a number of typical video formats,
whereas Table 2.3 shows a number of typical video applications and the
bandwidths available to them. It is immediately evident that video coding
(or compression) is a key enabling technology for such applications. Consider
a 2-hour CCIR-601 color movie. Without compression, a 5-Gbit compact disc
(CD) can hold only 30 seconds of this movie. To store the entire movie on
the same CD requires a compression ratio of about 240:1. Without compres-
sion, the same movie will take about 36 days to arrive at the other end of a
384 kbits=s Integrated Services Digital Network (ISDN) channel. To achieve
real-time transmission of the movie over the same channel, a compression ratio
of about 432:1 is required.

13 A range of HDTV formats exist.