1.1 Introduction
Significant progress in digital audio/video processing and communication technology has enabled the dream of many applications such as High-Definition Television (HDTV) broadcasting, digital versatile disk (DVD) storage, high-quality real-time audio/video streaming over various networks, and recent 3DTV. Among these technologies, digital audio/video coding or compression technique has assumed an important role to bridge the gap between huge amount of video data required for the transmission/storage and limited bandwidth of communication channels or limited size of storages. For most applications, a huge number of receivers are used. Therefore, the multimedia standards including audio/video/image coding standards are needed and they are very important for the multimedia industry.
Since the early 1990s, several multimedia standards including digital audio/video/image coding standards have been successfully developed. For developing these standards, especially for video coding standards, two international organizations have taken important roles and led the actions. These two organizations are the Moving Pictures Expert Group (MPEG) which belongs to International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC), and the Video Coding Expert Group (VCEG) of the International Telecommunication Union (ITU). The video coding standards developed by ISO/IEC include MPEG-1 [1], MPEG-2 [2], and MPEG-4 [3], the still image coding, JPEG [4] and JPEG-2000 [5], as well as multimedia interface standard MPEG-7 [6] and Multimedia Framework standard MPEG-21 [7]. The standards developed by ITU include H.261 [8], H.263 [9], and H.264/AVC [10]. The H.262 is the same as MPEG-2, which is a joint standard of MPEG and ITU. The H.264/AVC video coding standard is developed by the joint video team (JVT) of MPEG and VCEG which is also referred to as the MPEG-4 Part 10 [10]. These standards have found many successful applications. The applications can be mainly classified into two aspects: digital television (DTV) and digital telephony. With the advances of computer technologies, personal computers (PCs) have become the most flexible and most inexpensive platform for digital video communication and players. Currently, a joint collaborative team on video coding (JCT-VC) of MPEG and VCEG is making efforts to develop a next-generation video coding which is referred to as high-efficiency video coding (HEVC).
From the history of multimedia standards development, it can be summarized that a successful multimedia standard, which is widely accepted by the industry and extensively used in many applications, should have several important features. The first important feature is that the standard should adopt the most advanced techniques developed at that time. These techniques are able to solve the most difficult problems to meet the immediate needs from the industry. For example, during the development of Advanced Television Systems Committee (ATSC) HDTV standard, the industry was required to provide full-quality HDTV service in a single 6 MHz channel. The function of compression layer has to compress the raw data from about 1 Gbps to the data rate of ∼19 Mbps to satisfy the 6 MHz spectrum bandwidth requirement. This goal has been achieved by using the main profile and high level of MPEG-2 video coding standard and advanced digital modulation technique. The MPEG-2 video standard uses hybrid coding techniques, which mainly combine the discrete cosine transform (DCT) with motion-compensated predictive coding and other techniques to provide 50:1 compression ratio at the broadcast quality. Therefore, the MPEG-2 becomes the basis of the standard for DTV. Also the techniques adopted by the standard should consider both facts, that is, good coding performance and less computational complexity. Specially, the industry has to consider the implementation issues before accepting a standard. Sometimes, the techniques adopted by standards may be a trade-off between performance and computational complexity. Some techniques have significant technical innovation but may not be adopted by the previous standard due to the implementation difficulty at that time. But it may be adopted by the later standard or extension of standard with advances of computer and VLSI technology. Many examples about this can be found in the standard of H.264/AVC [10,11].
The second important feature is that the audio/video coding standards should be independent of transmission and storage media. The compressed video and audio bitstreams can be used for different applications. The bitstreams can be transmitted through broadcasting, computer network, wireless network, and other media. They can also be stored in different kinds of storage. In order to achieve this goal, a system layer standard has been developed. System standards specify the packetization, multiplexing, and packet header syntax for delivering or storing the audio- and video-compressed bitstreams in different media.
Another feature the standards should have is compatibility. Compatibility is important for manufacturers. If a new standard can decode the bitstrea...
