This paper presents a scheme for video transmission over wireless LANs based on an effective QoS model and channel state estimation (CSE). The proposed QoS model is able to effectively characterize the performance of video transmission over error prone wireless channels. Unlike existing schemes that use complicated metrics based on the actual distortion computed from decoded video frames, the proposed model employs H.264 group of pictures (GOP) level estimator of decodable slice rate (GEDSR). This new GEDSR model can be obtained from simplified calculation of decodable I, P, and B slices without computing the actual distortions. With this model, it is possible for the estimation to include the dependence of error control such as forward error correction and redundant slices. In this research, we also develop an adaptive cross-layer feedback mechanism based on channel status, maximum retry limit value, and RTS/CTS function. Extensive simulations have been carried out to confirm the effectiveness of the proposed GEDSR model for the distortion analysis. The experimental results of the GEDSR model analysis have been applied to selecting forward error correction (FEC) coding parameters for video streams to respond to dynamic channel changes. Simulations on video transmission over wireless LAN show that the proposed scheme is able to achieve significant performance gains (7dB) over schemes without channel feedback.

This paper presents a new scheme for robust video transmission over packet erasure wireless channels based on Wyner-Ziv coding of motion regions. The multipath fading and shading of the wireless channels usually lead to loss or erroneous video packets which on occasions result in some spontaneous drop in video quality. Existing approaches with forward error correction (FEC) and error concealment have not been able to provide the desired robustness in video transmission. We develop a new scheme with a motion-based Wyner-Ziv coding (MWZC) by leveraging distributed source coding (DSC) ideas for error robustness. This new scheme is based on the fact that motion regions of a given video frame are particularly important in both objective and perceptual video quality and hence should be given preferential Wyner-Ziv coding based embedded protection. To achieve high coding efficiency, we determine the underlining motion regions based on a rate-distortion model. Within the framework of H.264/AVC specification, motion region determination can be efficiently implemented using flexible macroblock ordering (FMO) and data partitioning (DP). The bit stream generated by the proposed scheme consists two parts: the systematic portion generated from conventional H.264/AVC bit stream and the supplementary bit stream for error robust video transmission generated by the Wyner-Ziv coding of motion regions. Experimental results demonstrate that the proposed scheme significantly outperforms both decoder-based error concealment (DBEC) and conventional FEC with DBEC approaches.

In this paper, we propose a suite of efficient schemes for the representation of spatial and temporal correlations of video signals in distributed video coding (DVC). These schemes consist of zero motion skipping, Gray codes, and sign bits coding of DCT coefficients developed to improve the overall rate-distortion (R-D) performance of distributed video coding. Existing schemes have focused on exploiting the spatial and temporal correlation without sufficient investigation on the efficient representation of the correlation. We believe this is one of the reasons that there still exists substantial gap between current DVC and traditional hybrid video coding. In traditional hybrid coding, a suite of efficient representation schemes such as zig-zag scan, run length code, and skipped macroblock have contributed significantly to excellent R-D performance. The efficient representation schemes we developed for DVC in this research will also lead to improved rate-distortion performance comparing with existing DVC schemes. We present in this paper the overall framework for the proposed zero motion skip and the analysis for efficient representations of both DCT coefficients and their signs. The experiment results show that the distributed video coding based on these efficient representations is able to achieve considerably improved rate-distortion performance over existing schemes.

In this paper, we propose a new rate allocation algorithm for transform domain Wyner-Ziv video coding (WZVC) without feedback. In contrast to conventional video coding, Wyner-Ziv video coding aims to design simple intra-frame encoding and complex inter-frame decoding based on the Slepian-Wolf and Wyner-Ziv distributed source coding theorems. To allocate proper number of bits to each frame, most existing Wyner-Ziv video coding solutions need a feedback channel (FC) at the decoder. However, in many video coding applications, the FC is not allowed. Moreover, the FC will introduce latency and an increase of decoder complexity because several iterative decoding operations may be needed to decode the data to achieve target video quality. The proposed algorithm predicts the number of bits for each Wyner-Ziv frame at the encoder as a function of the coding mode and the quantization parameters. Such predictions will not significantly increase the complexity at the encoder. However, the prediction will be able to properly select the best mode and quantization parameter for encoding each Wyner-Ziv frame. Experimental results show that the proposed algorithms is able to achieve good encoder rate allocation while still maintains consistent coding efficiency. Comparing to the WZVC coder with FC, this new WZVC coder without FC induces only a small loss in Rate-Distortion performance.

Distributed source coding (DSC) has been attracting more and more research interests recently, particularly for mobile wireless applications. However, most existing DSC schemes assume that the coded information is transmitted error free to the decoder end. In this paper, we report our latest investigations on distributed source coding under noisy transmission environments. It is expected that these investigations provide useful guidelines for practical DSC system design when the transmission is actually not error free. Especially, many current schemes in DSC adopted the channel coding principles to accomplish the source coding tasks. We shall illustrate that the channel coding-based DSC schemes possess some inherent noise combating capability to recover possible channel errors under noisy transmission environments. Specifically, we shall report the investigations of Turbo DSC under various environments: error free, noisy transmission with additional forward error correction (FEC) and noisy transmission without FEC. Our experimental results show that, with the same number of bits transmitted through noise channel, the unprotected Turbo DSC outperforms the FEC protected Turbo DSC.

In this paper, we present a distributed video coding scheme based on zero motion identification at the decoder and constrained rate adaptive low density parity check (LDPC) codes. Zero-motion-block identification mechanism is introduced at the decoder, which takes the characters of video sequence into account. The constrained error control decoder can use the bits in the zero motion blocks as a constraint to achieve a better decoding performance and further improve the overall video compression efficiency. It is only at the decoder side that the proposed scheme exploits temporal and spatial redundancy without introducing any additional processing at the encoder side, which keeps the complexity of the encoding as low as possible with certain compression efficiency. As a powerful alternative to Turbo codes, LDPC codes have been applied to our scheme. Since video data are highly non-ergodic, we use rate-adaptive LDPC codes to fit this variation of the achievable compression rate in our scheme. We propose a constrained LDPC decoder not only to improve the decoder efficiency but also to speed the convergence of the iterative decoding. Simulation demonstrates that the scheme has significant improvement in the performances. In addition, the proposed constrained LDPC decoder may benefit other application.

In this paper, we present a distributed video coding scheme based on low punctured turbo codes and zero motion encoding strategy. Most recent distributed video coding schemes have a common structure: the encoded bit streams consist of both side information derived from previous frames and syndrome bits derived from channel coding such as Turbo codes. Turbo codes are often punctured to generate scalable compressed video bit streams. We demonstrate in this paper that the generation of side information and the design of the punctured Turbo codes can be integrated to improve the overall coding performance. In the encoding of the video frames, zero motion blocks can be identified and made known to decoder so that the reference frames at the decoder shall have some blocks remain unchanged. While constructing the frame at the decoder, the Turbo decoder may be able to use this information as a constraint to achieve an improved performance. However, we discover a better way of making use of zero motion blocks by skipping the encoding of these blocks. The skip at the encoder will result in the direct reduction of the video coding bit rate as well as lower punctured Turbo codes. Since low punctured Turbo codes perform better, the combined effects on the reduced rate side information and an improved Turbo coding performance leads to an overall performance improvement. Simulation results based on this approach show that integrated low punctured Turbo codes and zero motion skip encoding strategy indeed achieves better performance than the constrained punctured Turbo coding. Furthermore, this scheme can be extended to other channel coding schemes, such as Product Accumulate code, that have been adopted in distributed video coding.

In conventional video coding, the complexity of an encoder is generally much higher than that of a decoder because of operations such as motion estimation consume significant computational resources. Such codec architecture is suitable for downlink transmission model of broadcast. However, in the contemporary applications of mobile wireless video uplink transmission, it is desirable to have low complexity video encoder to meet the resource limitations on the mobile devices. Recent advances in distributed video source coding provide potential reverse in computational complexity for encoder and decoder. In the same spirit, we proposed in this paper a syndrome-based light-weight video encoding scheme for mobile wireless applications. This scheme is based on two innovations: (1) adoption of low resolution low quality reference frames for motion estimation at the decoder; (2) introduction of more powerful product accumulate code. Extensive experimental results have confirmed that this syndrome based encoding can reduce computational complexity at the encoder while maintaining good reconstruction quality at the decoder. Therefore, this light weight video coding scheme is suitable for mobile wireless applications

This paper offers a practical distributed data compression in wireless sensor networks based on convolutional code and turbo code. An improved Viterbi algorithm for distributed source coding (VA-DSC) is proposed to take the advantage of the known parity bits at the decoder. When the algorithm is applied to recursive systematic convolutional (RSC) and turbo codes, it can decrease both the decoding error probability and the computation complexity. Also a scheme of applying distributed source coding to wireless sensor networks is proposed to ensure receiving the data correctly as well as reducing the energy consumption in the networks.