Athar Ali Moinuddin

Wavelet Based Embedded Image Coding Using Unified Zero-Block-Zero-Tree Approach

In this paper, we propose a unified approach of exploiting both inter- and intra-band correlations among the wavelet coefficients in a single algorithm. Most of the existing wavelet based image coding techniques are either based on zero-tree approach or zero-block (quad-tree) approach. The zero-tree based coders exploit only inter-band correlations whereas zero-block based coders exploit only intra-band correlations among the wavelet coefficients. Thus this work is an attempt to fuse the features of both block- and tree-based coding algorithms into a single algorithm. The proposed algorithm generates fully embedded bit stream. Simulation results show that the proposed algorithm outperforms existing wavelet based image coders. Additionally, the memory requirements due to the auxiliary lists is also reduced as compared to the zero-tree based coders

Physical layer unequal error protection of wavelet coded video using Hierarchical QAM

Unequal Error protection (UEP) of wavelet coded video is investigated using Hierarchical Quadrature Amplitude Modulation (HQAM). Based on the unequal sensitivity of coded bit stream against transmission errors, this paper investigates the properties of HQAM constellation to provide different degree of error protection to the coded bits having different degree of importance. This paper proposes an UEP scheme, performed at the physical layer using HQAM to protect higher priority (more sensitive) bits strongly without any additional bandwidth, but at the cost of increased errors in the lower priority (less sensitive) bits. The performance of the transmission system is evaluated under the Additive White Gaussian Noise (AWGN). Simulation results verify the improvements in the performance.

Optimized cross-layer unequal error protection for wireless video communication

Error control strategies to video bitstream are usually provided at different layers of the communication network. Optimizing the error control strategies at different layers independently leads to inefficient utilization of the resources. In this paper, a cross-layer strategy to optimally utilize the application and physical layer resources for unequal error protection (UEP) of wavelet coded scalable video is investigated. We propose a cross-layer optimized UEP scheme, combining optimal forward error correction (FEC) at application layer and hierarchical QAM (HQAM) at physical layer. A look-up table-based approach, to select optimal parameter values at both layers that maximizes the overall video quality for a given channel condition, is suggested. A wide range of video sequences of different degree of motion and texture are considered to design the look-up table. The major advantage of the look-up table based approach is the low computation complexity of the transmission system, which is one of the major issue in portable video communication devices. Simulation results show the proposed scheme outperforms other techniques comprehensively over a wide range of channel conditions.

Reliable transmission of wavelet-based scalable video over wireless networks using cross-layer approach

The conventional network layers are mainly designed for fixed networks and are not suitable to cope the challenges offered by the modern wireless networks. Moreover, certain functionalities can be implemented simultaneously in more than one layer. For example, unequal error protection (UEP) can be performed at the application layer, using forward error correction (FEC), but it is bandwidth inefficient. On the other hand, UEP can also be performed at the physical layer using hierarchical modulation to protect higher priority bits more strongly without any additional bandwidth, but at the cost of increased errors in the lower priority bits. The authors propose a cross-layer UEP approach to enhance reliability of scalable video by combining adaptive FEC at the application layer and hierarchical quadrature amplitude modulation (HQAM) at the physical layer. The idea is to slightly reduce the FEC protection of higher priority bits and increase the FEC protection of low-priority bits in such a fashion that the overall data rate at the application layer remains unchanged. The higher priority bits are additionally protected using HQAM at the physical layer. Simulation results show significant improvements in performance when the proposed scheme is used.

An Efficient Wavelet Based Embedded Color Image Coding Technique using Block-Tree Approach

In this paper, we propose a simple and efficient technique for embedded color image coding. The proposed algorithm exploits inter- and intra-subband correlations of the wavelet transformed luminance (Y) and chrominance (U and V) planes as well as the interdependency among the coefficients of the three-color planes. The coefficients of the three-color planes are linked through the composite spatial orientation trees (CSOT) having root nodes in the Y-plane only. The CSOT is defined for blocks of coefficients rather than a single coefficient. Thus, the proposed algorithm combines the features of both zero-tree and zero-block based algorithm into a single algorithm due to the use of block-tree hierarchical structure. Simulation results show the improved performance of the proposed algorithm over other sate-of-the-art coders such as MPEG-4, color SPIHT (CSPIHT), color SPECK (CPECK), and JPEG-2000.

Unequal error protection (UEP) of wavelet coded video using multi-layered Hierarchical QAM

In this paper, the performance of unequal error protection (UEP) scheme for wavelet coded video using multi-layered 64-Hierarchical QAM (64-HQAM) is presented. Depending on the error sensitivity of coded video bitstream against channel errors, the bitstream is partitioned into multiple sub-streams. The most sensitive sub-stream is assigned highest protection while least sensitive are assigned lowest protection by adjusting the distance between points in the constellation diagram of HQAM. The performance of the communication system is evaluated for Additive White Gaussian Noise (AWGN) channel. The simulation results demonstrate that three-layer UEP provides increased Quality-of-Service (QoS) compared to level two-layer UEP.

Efficiently-mapped adaptive hierarchical QAM for reliable scalable video communication

This paper proposes an efficiently-mapped adaptive hierarchical QAM (AHQAM) scheme for unequal error protection (UEP) of embedded video bitstream. The coded bits of each frame are hierarchically partitioned into high priority (HP) and low priority (LP) substream, using two-staged partitioning strategy. Then pairs of stream blocks, one from each substream are selected judiciously to form symbols, which are modulated using HQAM with varying modulation parameter. The proposed scheme is generic in nature and can be applied to any scalable video bitstream. Simulations are performed with 16-AHQAM for AWGN channel and it is observed that the proposed scheme offers up to 7.2 dB improvement in quality of received video as compared to 16-HQAM.

Optimized unequal error protection of embedded video bitstream using adaptive-hierarchical QAM

In this paper, a reliable video communication system using adaptive Hierarchical QAM (HQAM) is designed to provide optimized unequal error protection (UEP) to embedded video bitstreams. Based on the relative importance of bits, video bitstream is partitioned into two priorities, namely High Priority (HP) and Low Priority (LP) substreams. Then, the optimal value of modulation (or hierarchical) parameter (α) of HQAM, which controls the relative error protection of these substreams, is selected from a pre-designed look-up table. The proposed system adapts itself by adapting the optimal α according to the varying channel condition, without changing the modulation level. This is in contrast to conventional WiMAX and LTE systems, in which dynamic switching among multiple modulations is used to adapt the varying channel conditions. This paper proposes HQAM with adaptive α as an alternative to the multiple modulation schemes. Moreover, for fixed average transmission power, receiver demodulates symbols without the knowledge of α. In order to further improve the video quality and to reduce the effects of erroneously received LP bits, the proposed system uses another level of adaptation, in which received LP bits are adaptively considered or discarded, before decoding the video, depending on the channel conditions (or optimized α). Simulation results show that proposed system can achieve significant improvement in the video quality compared to QAM based EEP scheme and non-adaptive HQAM.

Unequal error protection of embedded video bitstream with optimized FEC

In this paper, an optimized unequal error protection scheme using Forward Error Correction (FEC) for transmission of embedded video bitstream over AWGN channel is investigated. The scheme exploits the non-uniform importance and error sensitivity of the bits generated by the a wavelet video coder. Depending upon their importance in the reconstruction of the video, the bitstream is first divided into High Priority (HP) and Low Priority (LP) substreams. Then appropriate FEC is applied to these substreams to protect them against the channel errors. The optimal FEC parameters are searched using an offline optimization technique subject to constraint that end-to-end transmission distortion is minimized. A look-up table with optimal FEC parameters for wide range of channel conditions, is designed. Furthermore, this paper also argues that whether optimized UEP has any advantage over EEP for protection of embedded bitstream. This scheme is suitable for real-time video communication using portable devices which possess low processing capabilities and small battery power.

No-reference image quality assessment of wavelet coded images

In the modern era of Internet, many user-end applications require the estimation of quality of images directly from the bitstreams, as the original image may not be available. This is a challenging issue. In this paper, we propose a novel approach of no-reference (NR) objective quality assessment of wavelet coded images. The proposed method is based on estimation of the contribution of each received bit in an embedded bitstream in the reduction of mean-square error (MSE), assuming initial image with all zero pixel values. Mathematical analysis is carried out to estimate the quantization errors in terms of MSE reduction, in wavelet-based SPIHT coding algorithm. The simulation results demonstrate the effectiveness of the proposed method.