M. Tun

Error-Resilient Scheme for Wavelet Video Codec Using Automatic ROI Detection and Wyner-Ziv Coding Over Packet Erasure Channel

The error-resilient for video transmission over the Internet in which regarded as the packet erasure channel is always a tough task and has gained lots of attentions. The main contradictory problem lies between error-resilient and bandwidth usage. Additional redundant data has to be added to achieve robust transmission which leads to huge bandwidth usage. In this paper, an error-resilient scheme called Wyner-Ziv Error-Resilient (WZER) based on a receiver driven layered Wyner-Ziv (WZ) coding framework is proposed. The WZER purposely emphasizes on the protection of the Region of Interest (ROI) area in the frame thus to achieve the better tradeoff between the bandwidth usage and error-resilience. WZER is designed to work for the scenario of wavelet based video coding over packet erasure channel, where several techniques including automatic ROI detection, ROI mask generation, Rate distortion optimization (RDO) quantization, WZ coding with layer design, and packet level Low Density Parity Check (LDPC) code are used. The performances of the proposed WZER are simulated based on average PSNR of luminance, perceptual reconstruction and bandwidth usage and compared with normal Forward Error Correction (FEC) full protection scheme and no protection scheme. The results show the advantages of the proposed WZER over traditional FEC protection, especially in the aspects of the recovery of the subject area and bandwidth efficiency.

Error-Resilient Performance of Dirac Video Codec Over Packet-Erasure Channel

Video transmission over the wireless or wired network requires error-resilient mechanism since compressed video bitstreams are sensitive to transmission errors because of the use of predictive coding and variable length coding. This paper investigates the performance of a simple and low complexity error-resilient coding scheme which combines source and channel coding to protect compressed bitstream of wavelet-based Dirac video codec in the packet-erasure channel. By partitioning the wavelet transform coefficients of the motion-compensated residual frame into groups and independently processing each group using arithmetic and forward error correction (FEC) coding, Dirac could achieves the robustness to transmission errors by giving the video quality which is gracefully decreasing over a range of packet loss rates up to 30% when compared with conventional FEC only methods. Simulation results also show that the proposed scheme using multiple partitions can achieve up to 10 dB PSNR gain over its existing un-partitioned format. This paper also investigates the error-resilient performance of the proposed scheme in comparison with H.264 over packet-erasure channel.

Rate control algorithm based on quality factor optimization for Dirac video codec

Rate control plays an essential role in video coding and transmission to provide the best video quality at the receiver end given the constraint of certain network conditions. This paper proposes a rate control algorithm for the wavelet-based open-source Dirac video codec. The existing Dirac architecture has a constant-quality control mechanism based on rate-distortion optimization (RDO), giving variable bitrate. The proposed algorithm exploits the existing constant-quality control, which is governed by a parameter called quality factor (QF) to give a constant bitrate. A mathematical model called the rate-quality factor (R-QF) is derived to generate optimum QF for the current coding frame using the bitrate resulting from the encoding of the previous frame in order to meet the target bitrate. The proposed algorithm is a complete one-pass process and does not require complex mathematical computation. The process of calculating the QF is simple and, further, calculation is not required for each coded frame. It also provides the rate control solution for both intra-frame-only and inter-frame coding modes. The experimental results show that the proposed algorithm can control the bitrate precisely (i.e. within 1% of target bitrate in average for inter-frame coding mode and near-perfect flat response in generated bits vs. frame number curve in intra-frame-only coding mode). Moreover, the variation of bitrate over each group of pictures (GOP) in inter-frame coding mode is lower than that of H.264 using JM11. This is an advantage in preventing the buffer overflow and underflow for real-time multimedia data streaming. More importantly, there is no PSNR performance loss because of application of the proposed rate control algorithm. It gives superior quality over relatively static motion sequences and fast motion sequences with average quality as shown in the analysis and evaluations presented in this paper.

An Error-Resilient Algorithm Based on Partitioning of the Wavelet Transform Coefficients for a DIRAC Video Codec

Video transmission over the wireless or wired network require protection from channel errors since compressed video streams are very sensitive to transmission errors because of the use of predictive coding and variable length coding. In this paper, we propose a method to achieve robustness to transmission errors to the compressed bit-stream of wavelet based open source video codec, Dirac. By partitioning the wavelet transform coefficients into groups and independently processing each group using arithmetic and turbo coding, we could achieve the robustness to transmission errors of the compressed video stream in the packet erasure wired network. Simulation results show that the proposed technique can achieve up to 5dB PSNR gain over the un-partitioning method

An efficient rate control algorithm for a wavelet video codec

Rate control plays an essential role in video coding and transmission to provide the best video quality at the receivers end given the constraint of certain network conditions. In this paper, a rate control algorithm using the Quality Factor (QF) optimization method is proposed for the wavelet-based video codec and implemented on an open source Dirac video encoder. A mathematical model which we call Rate-QF (R - QF) model is derived to generate the optimum QF for the current coding frame according to the target bitrate. The proposed algorithm is a complete one pass process and does not require complex mathematical calculation. The process of calculating the QF is quite simple and further calculation is not required for each coded frame. The experimental results show that the proposed algorithm can control the bitrate precisely (within 1% of target bitrate in average). Moreover, the variation of bitrate over each Group of Pictures (GOPs) is lower than that of H.264. This is an advantage in preventing the buffer overflow and underflow for real-time multimedia data streaming.

Semi-hierarchical motion estimation for the dirac video codec

In this paper, a semi-hierarchical way of motion estimation for the Dirac video encoder is proposed. The algorithm requires fewer numbers of SAD calculations per block while the compression efficiency and PSNR remain the same. There is huge saving in terms of SAD calculation per block especially in moderate level motion sequences. Moreover, the proposed algorithm has the ability to increase or decrease the search range depending upon the complexity of the motion in order to maintain the accuracy of the motion estimation to a certain level and can be use in any type of standard video encoders.

A Novel Rate Control Algorithm for the Dirac Video Codec Based upon the Quality Factor Optimization

In this paper, we propose a novel rate control algorithm for the wavelet-based open source Dirac video codec by using the quality factor (QF) optimization method. We derived a mathematical model which we call Rate-QF (R-QF) model to generate the optimum QF for the current coding frame according to the target bitrate. The proposed algorithm is completely one pass process and does not require complex mathematical calculation. The process of calculating the QF is quite simple and does not require calculating for each and every frames being coded. The experimental results show that the proposed algorithm can control the bitrate precisely (within 1% of the target bitrate in average). Moreover, the bitrate fluctuating which is the variation of bitrate over each and every group of pictures (GOPs) is lower than that of H.264, which is one of the desirable features to avoid buffer over flow and under flow in real time broadcasting.

Motion estimation using partial cost function calculation

Having fast and efficient motion estimation is crucial in todays advance video compression technique. In this paper, a method which we call partial cost function calculation is proposed for faster cost calculation in finding the exact match for any type of block matching algorithms. It is based upon the reduced number of operations which follows a certain pattern, instead of calculating the cost for all points within a block. The experimental results show that the proposed method gives two to eight times reduction (depending upon the block size used) in the computational load with the motion estimation accuracy loss which is negligible compared with full cost function calculation and can be used in conjunction with any type of fast block matching algorithms.

Enabling Error-Resilient Internet Broadcasting using Motion Compensated Spatial Partitioning and Packet FEC for the Dirac Video Codec

Video transmission over the wireless or wired network require protection from channel errors since compressed video bitstreams are very sensitive to transmission errors because of the use of predictive coding and variable length coding. In this paper, a simple, low complexity and patent free error-resilient coding is proposed. It is based upon the idea of using spatial partitioning on the motion compensated residual frame without employing the transform coefficient coding. The proposed scheme is intended for open source Dirac video codec in order to enable the codec to be used for Internet broadcasting. By partitioning the wavelet transform coefficients of the motion compensated residual frame into groups and independently processing each group using arithmetic coding and Forward Error Correction (FEC), robustness to transmission errors over the packet erasure wired network could be achieved. Using the Rate Compatibles Punctured Code (RCPC) and Turbo Code (TC) as the FEC, the proposed technique provides gracefully decreasing perceptual quality over packet loss rates up to 30%. The PSNR performance is much better when compared with the conventional data partitioning only methods. Simulation results show that the use of multiple partitioning of wavelet coefficient in Dirac can achieve up to 8 dB PSNR gain over its existing un-partitioned method.