H.264/avc Technology And Development Strategy Of Thinking
0 Introduction As NGN, 3G and 3G evolution and NGBW such as video
, multimedia and the rapid development of network applications demand video services and storage applications as the core technology of high-efficiency video digital compression coding (decoding ) technology, more and more cause for concern, as the current broadcasting, video and multimedia communications in the field of bright spots and hot spots.
Video coding standard developed two organizations ITU-T Video Coding Experts Group (VCEG) and ISO / IEC of the Moving Picture Experts Group (MPEG).
ITU-T in 1993 developed the first video coding standard H.261, the output rate is p 64kbit / s, mainly used for ISDN and ATM and other prospective broadband and broadband video channel, is not appropriate PSTN and mobile communications and limited bandwidth narrowband channel and network applications. To meet the needs of low-rate video communication, ITU-T in 1996 and launched in less than suitable for 64kbit / s channel rate transmission of video coding standard H.263. 1998 years and introduced the second version of H.263 H.263 +, offers 12 kinds of alternative modes and other features to further improve the compression performance; also begun to develop and further improve performance short-term and long-term goals. The short-term objective shall be the third edition of 2000, enacted H.263 H.263 + +, its long-term goal of the so-called standard H.26x, the development of standards established for the H.264 basis.
Introduced in ITU-T standards while H.26x series, ISO / IEC led the corresponding video coding standard, including its business, including management, are also actively promoted the formation of a well-known MPEG-x series of standards (MPEG-1, MPEG-2, MPEG-4, MPEG-7 and MPEG-21, etc.), and received a more extensive use.
2001 , MPEG recognized the potential advantages and H.26L VCEG joint work with the need to establish a joint collaboration between the video group (JVT). 2001 9 months, in a JVT first meeting set for H.26L-based H.264 draft standard and test model TML-9. 2003 3 months, held in Pattaya, Thailand's seventh JVT meeting, JVT formation of the final draft standard were submitted to ITU-T and ISO / IEC approval, thus forming the second quarter of 2003, a unified standard H.264/AVC. The standard known as ITU-T H.264; in ISO / IEC claimed the MPEG4-Part10 AVC (Advanced VideoCoding, Part 10, Advanced Video Coding). This is the basic origin of H.264/AVC.
H.264/AVC coding efficiency in compression, self-adaptive video processing capabilities and network level, especially for IP networks and mobile networks, adaptive capacity, interference ability and stubborn health and other aspects, were greatly improved compared to H.263/MPEG-4, which has not been since 2003, the video industry and some vendors are beginning H.264/AVC of great hope, even reached almost fanatical pursuit of the situation like. not to say that high expectations right, H.264/AVC indeed a wide range of applications, including fixed or mobile video phone, mobile phones, real-time video conference, video monitoring, streaming, multimedia (hypermedia) video, Internet video and multimedia (hypermedia), IPTV, mobile TV and broadband telephone and video information storage, but their maturation process, the complexity and specified the exact period of market position, must have a calm, rational estimation, in order to ensure a positive, safe , scientific, pragmatic, and healthy development. Based on this mind, I planned to NGN and 3G evolution of the fixed, the actual demand situation of mobile video services, on the importance of H.264/AVC technology and its pragmatic development strategy on a number of personal views, information for analysis.
1 H.264/AVC important technical advances
NGN and 3G, 3G evolution and NGBW development shall be a major goal of multimedia applications including video. This, H.264/AVC defines three kinds of video service type, that session-based service (such as video telephony, video conferencing, etc.), live or pre-recorded video stream based services and multimedia messaging services by MMS.
NGNIP network and bandwidth to adapt to limited resources, time variant mobile / wireless channels of transmission needs, H.264/AVC in terms of adaptive capacity to match the network layer, to improve compression efficiency and Yuan channel resistance interference, and so have been more carefully designed, have a more significant performance enhancements and improvements.
1.1 layered video codec design
Video encoding and decoding structures and algorithms from the functional design is divided into two layers, namely, the video coding layer (VCL) and Network Adaptation Layer (NAL). VCL for efficient video coding; NAL for network adapter, which provides network performance of different matching adaptive processing capacity, it addresses the underlying network characteristics of the data package, including framing, send the appropriate signals to the logical channel, synchronize information using processing. NAL access to data from the VCL information, including header information, structural information and the actual payload section of the information, and then maps them to the lower of the transfer agreement. These agreements, such as H.320 & # 65380; H.323, H.324, MPEG-2 and so on. NAL units transmitted by RTP sequence number order, serial number set can be found which lost a VCL unit, even if the basic code image missing , with redundant code image can have more "rough" image restoration. At the same time, with images of film (Slice), slice group, macroblocks (MB) structure and the black and white macro block non-scan sequential order of the flexible macro block (FMO), P frames and switch arrangement (SP), switch I frame (SI) of the stream switching, stream splicing, random access and error recovery serve to improve the error concealment and anti-jamming capability, and contribute to the improvement of compression efficiency. NAL layer of the introduction of greatly increased complexity of H.264/AVC different channel network and the adaptability of & # 65377;
1.2 design efficient video coding
1.2.1 unified variable-length coding (UVLC) code table
Previous standard entropy coding usually variable-length Huffman coding, the code table is not uniform, can not adapt to changing
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