由于MPEG24AVC/H-264采用了可变块尺寸（variable block size） 和率失真最优化（rate distortion opti-mization）两项技术，视频编码流程中复杂度最高的运动估计（motion estimation）模块变得更加复杂。另一显著的变化就是，所获取的运动信息与目标码率紧密相关。这给传统的快速转码技术带来了很大困难。该文首先提出了一种分层模型，按由粗到细的方式描述每个宏块（macroblock）的运动信息。基于这个分层模型，文中提出了一种通过预编码获取运动信息的算法，从而生成视频序列运动特性的完整描述。有了这种运动信息描述，在编码或是转码的过程中，编码器可以跳过运动估计过程，编码复杂度因此大大减少。为进一步加快编码速度，还提出了从运动信息描述中抽取最优运动信息的快速算法。实验结果验证了所提算法的有效性，在大大降低编码复杂度的同时，编码性能与最优的MPEG24 AVC/H-264 非常接近。

We propose in this paper a novel error resilient transcoding scheme that can be placed at the boundary between wired and wireless networks via heterogeneous network links. This error resilient transcoder shall seamlessly complement the standard Scalable Video Coding (SVC) bitstream to offer additional error resilient adaptation capability for receiving devices. The novel error resilient transcoding scheme consists of three different modules; each is designed to meet various levels of complexity need. The three modules are all based on the Loss-Aware Rate-Distortion Optimization (LA-RDO) mode decision algorithm we have previously developed for SVC. However, each individual module can be tailored to different complexity requirements depending on whether and how the LA-RDO mode decision is implemented. Another innovation of this approach is the design of a fast rate control algorithm in order to maintain consistent bitrates between input and output of the transcoder. This rate control algorithm only needs picture-level bit information for training target quantization parameters. Simulation results demonstrate that, comparing with standard SVC, the proposed approach is able to achieve up to 4 dB gain for the enhancement layer video and up to 1 dB gain for the base layer video.

We present several efficient adaptive redundant picture coding methods for error resilient video coding. In our previous work, redundant picture coding in combining with reference picture selection, reference picture list reordering and hierarchical redundant picture allocation was proposed. This paper investigates how to allocate redundant pictures more efficiently according to the content characteristics of the primary pictures. Simulation results show that the adaptive redundant picture coding methods can achieve average PSNR improvements around 2 to 4 dB compared to the loss-aware rate distortion optimized (LA-RDO) intra macroblock refresh implemented in H.264/AVC Joint Model (JM). This paper also asserts that the methods do not introduce any additional end-to-end delay, therefore suit for low-delay applications such as video telephony and video conferencing, which demand better error resilience than other applications.

Temporal scalable video coding is a useful feature supported in all existing video coding standards. Though coding efficiency is still the predominant performance metric, buffer requirement is another important factor for assessment of temporal scalable video coding methods. This paper presents analyses of minimum buffer requirement for temporal scalable coding based on the most typical temporal scalable video coding structure, i.e., the so-called hierarchical B picture coding structure. Minimum buffer sizes required for decoding of both the full bitstreams and thinned bitstreams are derived. After that, some reference picture management methods are proposed in order to enable both minimum buffer consumption and maximum coding efficiency. Comparative experiment results showing how different reference picture marking methods affect coding efficiency are also provided.

Error resilient macroblock mode decision has been extensively investigated in the literature for single-layer video coding, for which error resilient mode decision is also called as intra refresh. In this paper, we present a loss-aware rate-distortion optimized macroblock mode decision algorithm for scalable video coding, wherein more macroblock coding modes than intra and inter are involved. Thanks to the good performance, the proposed method has been adopted into the Joint Scalable Video Model by the Joint Video Team.