Page 68 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

Section 3.3. Chronological Development 45

INTRA mode switching on a macroblock level, zigzag scanning, RLE, scalar
quantization, and VLC entropy coding have become key elements in most
video coding standards.

3.3.3 CCIR-721

In parallel to the standardization activities of CCITT, CCIR started standardiza-
tion of video coding for contribution-quality TV signals. Recommendation 721
[60] was issued in 1990. Its main target was the transmission of component
coded digital TV signals for contribution-quality applications at bit rates near
140 Mbits=s. The recommendation used a simple form of intra/eld DPCM to
achieve a low implementation complexity and a high degree of random access
(which is important for video postprocessing in studios).

3.3.4 CCIR-723

CCIR Recommendation 723 [61] was issued in 1992. Its main target was
the coding of component digital TV signals for contribution-quality appli-
cations in the range 34–45 Mbits=s. The recommendation employs a hybrid
MC-DPCM=DCT with one intra/eld mode and two inter/eld modes (with and
without MC). Both the CCIR-721 and the CCIR-723 recommendations are not
generic. In contrast to other standards, they fully specify both the encoder and
the decoder.

3.3.5 MPEG-1

In 1988, the Moving Picture Experts Group (MPEG) was created under Sub-
committee (SC) 2 of ISO (ISO=SC2). The group is now Working Group (WG)
11 of SC29 under the Joint Technical Committee (JTC) 1 of ISO=IEC. Thus,
its o,cial denotation is ISO=IEC JTC1=SC29=WG11. The main aim of the
group was to develop a video coding standard for digital media storage ap-
plications at up to 1:5 Mbits=s. In 1991 the group drafted its ISO=IEC 11172
(MPEG-1) standard [62], which became an international standard in 1992.
The MPEG-1 video algorithm is very similar to the H.261 algorithm but with
2
some advanced techniques, like bidirectional prediction and half-pel MC . The
standard also provides for some speci/c storage requirements, like random ac-
cess and fast forward=reverse searches. Although the standard was developed
mainly for storage applications, it was designed to be generic. Thus, it was

2 Half-pel MC was proposed during the development of the H.261 but was thought to be too
complex at that time.