Edge Feature Based Fast Mode Decision Algorithm for H. 264 Intra Prediction

The emerging video coding standard H.264[1],provides the state-of-the-art video coding techniquesto meet a wide range of applications. Among thosetechniques, intra prediction is regarded as one of themain factors that contribute to the success ofH.264[2]. The rate distortion optimization (RDO)technology has been employed in H.264 for intra pre-diction mode selection to achieve good codingefficien-cy, which makes encoder extremely complex. Efforts have been made in developing fast H.264intra…     

APPENDIX A： ALTERNATIVE WAY OF OBTAINING THE LEAST-SQUARES PROBLEM

It is worth to mention that Eq.（19） can be found alternatively first by describing the boundary conditions at each of the sampling points to obtain a set of linear equations with respect to the modal coefficients Then, determining the number of sampling points in order that the number of linear equations be twice the number of unknowns     

基于H.264/AVC帧间宏块预测模式的快速判决方法

1 Introduction The emerging H.264/AVC video coding standard hasbeen developed and standardized collaboratively byboth ITU-T VCEG and ISO/IEC MPEG organizations .As the newest international video coding standard ,H.264/AVC represents a number of advances i…     

Fast mode decision for inter macroblocks in H. 264/AVC

In this paper, a fast mode decision algorithm for inter macroblocks in H.264/AVC is proposed, The algorithm is able to classify all modes by both gradient operator and comparison of space-time correlation. Because only part of modes is used to compare with each other the computational complexity can be reduced greatly. The simulation results show that it takes about 75 % of encoding time for other algorithm with similar visual quality.     

Improved fast intra prediction algorithm of H.264/AVC

With advanced prediction modes of intra prediction, intra coding of H.264/AVC offers significant coding gains compared with previous video coding standards. It uses an important tool called Lagrangian rate-distortion optimization (RDO) technique to decide the best coding mode for a block, but the computational burden is extremely high. In this paper, we proposed an improved fast intra prediction algorithm including block type selection and mode decision algorithm based on analysis of edge feature of a block. Our algorithm filters out unlikely block type and candidate modes to reduce the RDO calculations. Experimental results showed that the proposed algorithm can reduce the computation complexity of intra prediction from 52.90% to 56.31%, with 0.04 dB PSNR degradation and 2% increase of bit rate.     

基于相邻帧相关性的帧间宏块模式选择算法

H．264／AVC在帧间运动估计／补偿编码过程中定义了7种帧间编码模式，并采用率失真优化全遍历策略来选择最优模式，这使计算复杂度急剧增加．针对这一问题，阐明了需对如何准确、快速地对块预测模式做出选择进行相关的研究．并就利用自然图像序列中相邻帧所表现出的强相关性提出了一种快速的帧间编码模式选择算法，通过计算部分编码模式来减少计算的复杂性．实验结果表明，该方法平均节省时间约18％，比特率平均下降约0．02％，而PSNR平均仅仅降低0．02dB．     

Resynchronization and remultiplexing for transcoding to H.264/AVC

H.264/MPEG-4 AVC standard appears highly competitive due to its high efficiency, flexibility and error resilience. In order to maintain universal multimedia access, statistical multiplexing, or adaptive video content delivery, etc., it induces an immense demand for converting a large volume of existing multimedia content from other formats into the H.264/AVC format and vice versa. In this work, we study the remultiplexing and resynchronization issue within system coding after transcoding, aiming to sustain the management and time information destroyed in transcoding and enable synchronized decoding of decoder buffers over a wide range of retrieval or receipt conditions. Given the common intention of multiplexing and synchronization mechanism in system coding of different standards, this paper takes the most widely used MPEG-2 transport stream (TS) as an example, and presents a software system and the key technologies to solve the time stamp mapping and relevant buffer management. The solution reuses previous information contained in the input streams to remultiplex and resynchronize the output information with the regulatory coding and composition structure. Experimental results showed that our solutions efficiently preserve the performance in multimedia presentation.     

Dominant edge direction based fast intra mode decision in the H.264/AVC encoder

The H.264/AVC video coding standard uses an intra prediction mode with 4×4 and 16×16 blocks for luma and 8×8 blocks for chroma. This standard uses the rate distortion optimization （RDO） method to determine the best coding mode based on the compression performance and video quality. This method offers a large improvement in coding efficiency compared to other compression standards, but the computational complexity is greater due to the various intra prediction modes. This paper proposes a fast intra mode decision algorithm for real-time encoding of H.264/AVC based on the dominant edge direction （DED）. The DED is extracted using pixel value summation and subtraction in the horizontal and vertical directions. By using the DED, three modes instead of nine are chosen for RDO calculation to decide on the best mode in the 4×4 luma block. For the 16×16 luma and the 8 × 8 chroma, only two modes are chosen instead of four. Experimental results show that the entire encoding time saving of the proposed algorithm is about 67% compared to the full intra search method with negligible loss of quality.     

基于各向同性Sobel算子的H.264/AVC帧内预测模式选择算法

H.264/MPEG-4 AVC定义了9种4×4亮度块的预测模式,在参考模型JM中所采用的RDO计算复杂度较高。本文提出了一种基于各向同性Sobel算子的H.264的快速帧内编码模式选择算法,降低预测的复杂度,提高编码速度。测试表明,此算法能够使编码速度提高将近75%。     

一种具有可分级转码能力的空时OFDM视频传输方法

结合空时OFDM和转换编码技术,提出了一种无线衰落信道下具有可分级转码能力的鲁棒视频传输方法.采用可分级转码器将高质量的MPEG-2压缩视频转换为低码率、低分辨率MPEG-4可分级码流来满足网络带宽和终端设备显示的要求.在接收端采用一种层干扰抑制算法,使得分层空时OFDM系统不同层的传输性能存在差异,从而使系统具有不对等保护能力.根据分级码流的重要程度不同,将转码输出的可分级码流分别由分层空时编码OFDM系统的不同层来实现视频的鲁棒传输.实验结果表明:在典型的随机突发错误的无线环境下,提出的具有可分级转码能力的系统的视频传输性能优于传统的非分级转码的视频传输系统.     

A fast motion estimation algorithm for mobile communications

The limitation of processing power, battery life and memory capacity of portable terminals requires reducing encoding complexity in mobile communications. Motion estimation (ME) is the most computationally intensive module in a typical video codec, which determines not only the encoder’s performance but also the reconstructed video quality. In this paper, a fast ME algorithm for H.264/AVC baseline profile coding is proposed based on the analysis of motion vector field and error surface, and the statistical distributions of different type macroblocks (MBs). Simulation results showed that: in comparison with MVFAST, the proposed algorithm can decrease the computational load over 7.2% with no requirement of expanding memory capacity while maintaining the same video quality as MVFAST. Furthermore, its simplicity makes it easy to be implemented on hardware.     

A fast motion estimation algorithm for mobile communications

The limitation of processing power, battery life and memory capacity of portable terminals requires reducing encoding complexity in mobile communications. Motion estimation (ME) is the most computationally intensive module in a typical video codec, which determines not only the encoder's performance but also the reconstructed video quality. In this paper, a fast ME algorithm for H.264/AVC baseline profile coding is proposed based on the analysis of motion vector field and error surface, and the statistical distributions of different type macroblocks (MBs). Simulation results showed that: in comparison with MVFAST, the proposed algorithm can decrease the computational load over 7.2% with no requirement of expanding memory capacity while maintaining the same video quality as MVFAST. Furthermore, its simplicity makes it easy to be implemented on hardware.     

H.264帧内预测算法改进

帧内预测是H.264视频编解码标准中重要的组成部分,它能够显著提高压缩比率,但是大大提高了计算复杂度,很难运用到实时传输中,因此,如何提高运算速率是改进算法的核心问题。提出了一种快速模式选择算法,在保证图像质量的情况下较大地提高了帧内编码速度。     

H.264编码器中基于最匹配块的快速帧间模式选择方法

In H.264 encoder, all possible coding modes should be checked to choose the most appropriate mode for every macroblock, which adds a heavy computation burden to the encoder. In this paper, a fast inter-mode decision method is presented to reduce computation complexity of an H.264 encoder. By detecting the best matching block （BMB） before transform and quantization, some coding modes can be skipped and the corresponding encoding steps can be omitted for these BMBs. Meanwhile this method can also be used to detect all-zero blocks. The experimental results show that this method achieves consistently significant reduction of encoding time while keeping almost the same rate-distortion performance.     

Temporal Error Concealment Technique for MPEG-4 Video Streams

Concerning inter4v mode employed widely in MPEG-4 video, a new temporal error concealment scheme for MPEG-4 video sequences is proposed, which can selectively interpolate one or four motion vectors (MVs) for the missing macroblock (MB) according to the estimated MB coding mode. Performance of the proposed scheme is compared with the existing schemes with multiple testing sequences at different bit error rates. Experimental results show that the proposed algorithm can mask the impairments caused by transmission errors more efficiently than 0 MV and average MV methods by consuming more time for different bit error rates. It has an acceptable image quality close to that obtained by the selective motion vector matching (SMVM) algorithm, while taking less than half of cycles of operations. The proposed concealment scheme is suitable for low complexity video real-time implementations.     

An error resilient scheme for H.264 video coding based on distortion estimated mode decision and nearest neighbor error concealment

Although H.264 video coding standard provides several error resilience tools, the damage caused by error propagation may still be tremendous. This work is aimed at developing a robust and standard-compliant error resilient coding scheme for H.264 and uses techniques of mode decision, data hiding, and error concealment to reduce the damage from error propagation. This paper proposes a system with two error resilience techniques that can improve the robustness of H.264 in noisy channels. The first technique is Nearest Neighbor motion compensated Error Concealment (NNEC) that chooses the nearest neighbors in the reference frames for error concealment. The second technique is Distortion Estimated Mode Decision (DEMD) that selects an optimal mode based on stochastically distorted frames. Observed simulation results showed that the rate-distortion performances of the proposed algorithms are better than those of the compared algorithms.     

An Improvement of MPEG-4 Rate Control Algorithm

Frame skipping in low bit video coding could significantly reduce the visual quality of reconstructed video. At the same time, if the complexity of the video sequence remains high for a long period, then driving up the long term average bit rate, the only resort of MPEG-4 Q2 rate control algorithm results in using a high quantization scale, which shows a poor visual quality of the reconstructed video. This paper analyzes the main causes of frame skipping in current MPEG-4 frame rate control scheme, and presents a new rate control algorithm based on the quadratic R-D model over a CBR channel. Key features of the present work are. 1) the bits allocated to each P-frame or B-frame are in proportion to its distance from the end of this GOP, i.e. more bits are allocated to the frames that are nearer to their reference Ⅰ -frame: 2) the target buffer level is changeable in the GOP, at the end of each GOP( five P-frames or B-frames), the target buffer level is linearly reduced from 1/2 to 1/4 of buffer size, to other frames, the target buffer level is set to 1/2 of buffer size: 3 ) a selective and judicious use of the reduced resolution mode, in addition to a modulation of the quantization scale parameter, is to control the average long term bit rate. Experimental results with different video sequences of varied complexity, encoded at low bit rates show better efficacy of the proposed algorithm than MPEG-4 Q2 rate control scheme, and the experimental results also show that the improved algorithm has significantly reduced the number of frame skipping, increased the overall PSNR, and improved the perceptual quality.     

A fast block-matching algorithm based on variable shape search

INTRODUCTION Block-matching motion estimation is a key video coding technology that reduces the temporal redundancy between adjacent frames. The 3GPP/ 3GPP2 mandatory video codecs (MPEG-4 Simple Profile or H.263 Baseline) have adopted this tech- nology extensively. However, block-matching motion estimation is quite computationally intensive if the Full Search (FS) algorithm is used which exhaus- tively checks all possible candidate motion vectors within the search window. Therefore…     

基于H.264多参考帧的运动估计快速算法

在H.264编码算法的基础上,提出了多参考帧的运动估计快速算法--三维菱形搜索法(TDDS).实验结果表明,与未使用快速算法相比,使用本文提出的快速算法,在平均码率增加不到0.1%,恢复图像平均PSNR(峰值信噪比)下降不到0.1dB的情况下,编码速度提高2.5倍,满足实时视频通信的要求.算法与H.264标准兼容,可用于实际产品.     

Fast Non-Local Means Algorithm Based on Krawtchouk Moments

Non-local means(NLM)method is a state-of-the-art denoising algorithm, which replaces each pixel with a weighted average of all the pixels in the image. However, the huge computational complexity makes it impractical for real applications. Thus, a fast non-local means algorithm based on Krawtchouk moments is proposed to improve the denoising performance and reduce the computing time. Krawtchouk moments of each image patch are calculated and used in the subsequent similarity measure in order to perform a weighted averaging. Instead of computing the Euclidean distance of two image patches, the similarity measure is obtained by low-order Krawtchouk moments, which can reduce a lot of computational complexity. Since Krawtchouk moments can extract local features and have a good antinoise ability, they can classify the useful information out of noise and provide an accurate similarity measure. Detailed experiments demonstrate that the proposed method outperforms the original NLM method and other moment-based methods according to a comprehensive consideration on subjective visual quality, method noise, peak signal to noise ratio(PSNR), structural similarity(SSIM) index and computing time. Most importantly, the proposed method is around 35 times faster than the original NLM method.