Xingang Liu

A Temporal Error Concealment Method for H.264/AVC Using Motion Vector Recovery

Recently H.264/AVC is rapidly deployed in the mobile multimedia market, such as terrestrial and satellite DMB (digital multimedia broadcasting), and Internet multimedia streaming systems. To provide the better quality under the unreliable communication environments, we propose a motion vector (MV) recovery method for the temporal error concealment. The H.264/AVC adopts the various block sizes for the motion estimation and compensation, ranging from 16times16 to 4times4 block sizes. To increase the accuracy in the temporal error concealment, the 4times4 block size is used as the MV recovery unit. Flexible MB ordering (FMO) option, by which the neighboring MBs can be transmitted in the different packets, is used. The MVs of the lost MBs are recovered based on the MV tendency which is derived from the neighboring MVs. The simulation results show that the proposed method improves video quality up to 2.95dB and 2.45dB, compared with the H.264/AVC test model and Lagrange interpolation method, respectively.

Energy Efficiency Routing with Node Compromised Resistance in Wireless Sensor Networks

For the energy limited wireless sensor networks, the critical problem is how to achieve the energy efficiency. Many attackers can consume the limited network energy, by the method of capturing some legal nodes then control them to start DoS and flooding attack, which is difficult to be detected by only the classic cryptography based techniques with common routing protocols in wireless sensor networks (WSNs). We argue that under the condition of attacking, existing routing schemes are low energy-efficient and vulnerable to inside attack due to their deterministic nature. To avoid the energy consumption caused by the inside attack initiated by the malicious nodes, this paper proposes a novel energy efficiency routing with node compromised resistance (EENC) based on Ant Colony Optimization. Under our design, each node computes the trust value of its 1-hop neighbors based on their multiple behavior attributes evaluation and builds a trust management by the trust value. By this way, sensor nodes act as router to achieve dynamic and adaptive routing, where the node can select much energy efficiency and faithful forwarding node from its neighbors according to their remaining energy and trust values in the next process of data collection. Simulation results indicate that the established routing can bypass most compromised nodes in the transmission path and EENC has high performance in energy efficiency, which can prolong the network lifetime.

An Objective Video Quality Metric for Compressed Stereoscopic Video

Stereoscopic video create the impression of depth by using two slightly different viewpoints. Conventional video quality assessment methods for 2D video are not suitable for stereoscopic video, so a new video quality assessment model for stereoscopic video is needed. In this paper, we propose a new objective video quality metric for compressed stereoscopic video. The proposed algorithm uses blocking artifacts, blurring in edge regions and video quality difference between two views. Blocking artifacts and blurring in edge regions are distortion appeared in the compressed video, and they are widely used in conventional video quality model. Difference in video quality between two views considers 3D effect of stereoscopic video. To verify the performance of the proposed algorithm, we performed subjective evaluation of stereoscopic video, and we confirmed that the proposed algorithm is superior to the conventional algorithms in respect to correlation with the subjective evaluation.

Low complexity intra prediction algorithm for MPEG-2 to H.264/AVC transcoder

Transcoding MPEG-2 video into H.264/AVC format is highly necessary for the broad distribution of digital video contents to mobile terminals. Since H.264/AVC achieves great coding efficiency by employing computationally demanding algorithms, the computational complexity of the transcoder is one of technically challenging issues. The empirical results show that DCT energy trend in the decoded MB of MPEG-2 bitstream has strong correlation with the Intra prediction modes of H.264/AVC. Based on the relationship, the mode skipping rule of intra prediction mode decision in the H.264/AVC encoder part of the transcoder is proposed in this paper. The simulation results show that the proposed algorithm can achieve on average 72.36% reduction in computational complexity, compared with that of the conventional transcoder.

Fast Interframe mode decision algorithm based on mode mapping and MB activity for MPEG-2 to H.264/AVC transcoding

Recently the latest video coding standard H.264/AVC is widely used for the mobile and low bitrate video codec in the various multimedia terminals. On the other hand, the MPEG-2 MP@HL codec has become the center of digital video contents since it is the standard codec for the Digital TV (DTV). To provide the bridge between the contents in MPEG-2 and mobile terminals, the transcoding of MPEG-2 contents into H.264/AVC format is an inevitable technology in the digital video market. The main bottleneck in the process lies in the computational complexity. In H.264/AVC, the variable block size (VBS) mode decision (MD) is used in the Interframe for the improved performance in the motion compensated prediction. For the macroblock (MB) which cannot be accurately predicted with one motion vector (MV), it is partitioned into smaller blocks and predicted with different MVs. In addition, SKIP and Intra modes are also permitted in the Interframe MD of H.264/AVC to further ameliorate the encoding performance. With the VBS MD technology, the Inter prediction accuracy can be improved significantly. However, the incidental side-effect is the high computational complexity. In this paper, we propose a fast Interframe MD algorithm for MPEG-2 to H.264/AVC transcoding. The relationships between SKIP and Intra modes are detected at first to map these two kinds of modes directly from MPEG-2 to H.264/AVC. And then the MB activity will be scaled by the residual DCT energy obtained from the MPEG-2 decoding process to estimate the block sizes of the MB mode for H.264/AVC Interframe MD. In our proposed method, the original redundant candidate modes can be eliminated effectively, resulting in the reduction of the computational complexity. It can reduce about 85% Rate-to-Distortion Cost (RDCost) computing and 45% entire processing time compared with the well-known cascaded transcoder while maintaining the video quality.

Hybrid No-Reference Video Quality Assessment Focusing on Codec Effects

Currently, the development of multimedia communication has progressed so rapidly that the video program service has become a requirement for ordinary customers. The quality of experience (QoE) for the visual signal is of the fundamental importance for numerous image and video processing applications, where the goal of video quality assessment (VQA) is to automatically measure the quality of the visual signal in agreement with the human judgment of the video quality. Considering the codec effect to the video quality, in this paper an efficient non-reference (NR) VQA algorithm is proposed which estimates the video quality (VQ) only by utilizing the distorted video signal at the destination. The VQA feature vectors (FVs) which have high relationships with the subjective quality of the distorted video are investigated, and a hybrid NR VQA (HNRVQA) function is established by considering the multiple FVs. The simulation results, testing on the SDTV programming provided by VCEG Phase I, show that the proposed algorithm can represent the VQ accurately, and it can be used to replace the subjective VQA to measure the quality of the video signal automatically at the destinations.

An Adaptive Mode Decision Algorithm Based on Video Texture Characteristics for HEVC Intra Prediction

The latest High Efficiency Video Coding (HEVC) standard could achieve the highest coding efficiency compared with the existing video coding standards. To improve the coding efficiency of the intra frame, a quad-tree-based variable block size coding structure that is flexible to adapt to various texture characteristics of images and up to 35 intra-prediction modes for each prediction unit (PU) is adopted in HEVC. However, the computational complexity is increased dramatically because all the possible combinations of the mode candidates are calculated in order to find the optimal rate distortion cost using the Lagrange multiplier. To alleviate the encoder computational load, this paper proposes an adaptive mode decision algorithm based on texture complexity and direction for HEVC intra prediction. First, an adaptive coding unit selection algorithm according to each depth levels’ texture complexity is presented to filter out unnecessary coding block. Then, the original redundant mode candidates for each PU are reduced according to its texture direction. The simulation results show that the proposed algorithm could reduce around 56% encoding time on average while maintaining the encoding performance efficiently with only a 1.0% increase in BD-rate compared with the test model HM16 of HEVC.

High-speed inter-view frame mode decision procedure for multi-view video coding

With the amazing development of visual identification systems, multi-view video which is one of the main types of three-dimensional (3D) video signals, captured by a set of video cameras from various viewpoints, has attracted much interest recently. The multi-view video coding (MVC) uses the joint multi-view video model (JMVM) established on H.264/AVC as the core codec to achieve excellent coding efficiency. However, the concomitant problem is the huge encoding complexity especially due to the heavy Rate-to-Distortion Cost (RDCost) computational load of the mode decision (MD) process, which limits the applications of MVC for mobile terminals and embedded systems. In this paper, a high-speed MD (HSMD) algorithm is proposed for the inter-view frames of multi-view video signal. The redundant candidate modes of each macroblock (MB) in the inter-view frames are eliminated to reduce the original RDCost computational load by utilizing multiple efficiency parameters. The quantitative analysis verifies our proposal in theory and the simulation results show that the proposed HSMD algorithm can reduce the encoding time by over 90% for the inter-view video frames with negligible quality loss compared with the original JMVM codec. The proposed algorithm can be widely employed for real-time multi-view signal encoding especially under the mobile and embedded environments to realize the real-time encoding process.

Analysis of Motion Vector Predictor in Multiview Video Coding System

In this paper, various motion vector predictors are analyzed and their selection method is proposed for 3D video coding. In a ubiquitous multimedia system, video compression has been expected to be an important element since an available bandwidth is very limited. In the proposed method, several motion vector predictors are competed each other with the slightly modified rate-distortion criterion. Spatial, temporal, and inter-view predictors are considered as motion vector predictors to reduce spatial, temporal, and interview redundancies, respectively. The proposed method increases the motion vector coding efficiency by selecting the best motion vector predictor among them. Accordingly, overall bit rates are reduced by 5.2 % in average, up to 6.1 %compared to reference software JMVC 6.0 in terms of the Bjontegaard Metric.

A Fast Intra MB Mode Decision Method for the MPEG-2 to H.264 Transcoder

In this paper we propose an Intra mode decision method for the MPEG-2 to H.264/AVC transcoders to reduce the huge computational complexity. The DCT coefficients from the MPEG-2 decoder are used for the intra mode decision of H.264/AVC encoder. Based on the spatial activity analysis with the coefficients, early mode decision method between Intra16x16 and Intra4x4 modes and the Intra prediction direction are proposed. The empirical results show that the proposed method reduces about 70% computational complexity reduction compared with conventional method at the slight reduction in PSNR.