Combined CELP Speech Coding and Quadrature Amplitude Modulation

. In this paper, a method for optimizing the index map between the output indices of a wideband (7 kHz) CELP speech coder and the channel symbols for a power constrained channel and multilevel signaling is presented. The method is based on simulated annealing and makes use of dynamic scaling of a QAM signal constellation during the optimization procedure in order to optimize for a fixed transmitted power. The resulting system is shown to give a significant gain in terms of channel signal-to-noise ratio when compared to a reference system based on arbitrary index maps. 1. Introduction Recently, there has been a lot of work in the area of combined source and channel coding. Most of this work has focused on the transmission of samples from a discrete source over a binary symmetric channel (BSC) without power constraints [1-4]. In [1] simulated annealing (SA) was used to find a good index map between the output indices from a vector quantizer (VQ) and the binary codewords of a BSC. In thi..

Robust and Efficient Video Communication Based on Combined Source- and Channel Coding

A video communication system based on combined source- and channel coding is proposed. The proposed system uses a subband video coder structure in combination with powerconstrained channel-optimized vector quantization (PCCOVQ) to achieve efficient and robust transmission of the video signal over a channel with multidimensional PAM signaling. The side information is protected by using a sufficiently large minimum distance of the PAM signal constellation. This ensures error free transmission for the channel-optimized case, and graceful degradation for channel mismatch situations. For the main information, however, PCCOVQ with direct mapping from the source parameter space to the channel (modulation) space is used. A video communication system based on the H.263 video coder is used as a reference. The proposed system compares favorably to the reference system, and offers graceful degradation for channel mismatch situations. 1. INTRODUCTION Combined source and channel coding systems have..

Robust Subband Video Coding with Leaky Prediction

The use of leaky prediction in a video transmission system designed for noisy channels is investigated. For the proposed system, graceful degradation is achieved by finding good index maps between the quantized source coder parameters and the amplitude levels of a QAM signal constellation. The contribution of this paper, however, is to investigate the use of leaky prediction to further increase the robustness to channel noise. It is shown that by using a temporal prediction coefficient slightly less than one, large improvements can be achieved with only a small degradation for the noiseless case. The performance of the proposed system is comparable to a reference system based on the H.263 video coder for high CSNR values, and degrades far more gracefully for low CSNR values. 1. INTRODUCTION Recently, there has been much interest in combined source coding and channel coding /modulation for transmission over noisy channels. In [1], the index assignment problem was addressed by using si..

Combined Video Coding And Multilevel Modulation

A video transmission system based on combined source coding and multilevel modulation is proposed. For the proposed system, graceful degradation for noisy channels is obtained by finding good index maps between the quantized source coder parameters and the amplitude levels of a multilevel QAM signal constellation. The index maps are designed both for good neighbor properties and for power efficient transmission by using simulated annealing. The performance of the proposed system is comparable to a reference system based on the H.263 coder for high CSNR values, and degrades far more gracefully for low CSNR values. 1. INTRODUCTION Recently, there has been much interest in combined source coding and channel coding/modulation for transmission over noisy channels. Some of the work has been focused on binary symmetric channels (BSCs) [1, 2], while other studies have considered amplitude continuous channels [3, 4, 5, 6, 7]. In [1], the index assignment problem was addressed by using simulate..

Bandwidth Compression For Continuous Amplitude Channels Based On Vector Approximation To A Continuous Subset Of The Source Signal Space

Two methods for transmission of a continuous amplitude source signal over a continuous amplitude channel with a power constraint are proposed. For both methods, bandwidth reduction is achieved by mapping from a higher dimensional source space to a lower dimensional channel space. In the first system, a source vector is quantized and mapped to a discrete set of points in a multidimensional PAM signal constellation. In the second system the source vector is approximated with a point in a continuous subset of the source space. This operation is followed by mapping the resulting vector to the channel space by a one-to-one continuous mapping resulting in continuous amplitude channel symbols. The proposed methods are evaluated for a memoryless Gaussian source with an additive white Gaussian noise channel, and offer significant gains over previously reported methods. Specifically, in the case of two-dimensional source vectors, and one-dimensional channel vectors, the gap to the optimum perfor..

Channel-Optimized Subband Video Coding For Channels With A Power Constraint

A video communication system based on combined sourcechannel coding is proposed. The proposed system uses a hybrid subband video coder structure in combination with power-constrained channel-optimized vector quantization (PCCOVQ) to achieve efficient and robust transmission of the video signal over a channel with multidimensional PAM signaling. The error-sensitive side information parameters are protected by using traditional channel coding and a sufficiently large minimum distance of the PAM signal constellation. This ensures error free transmission for the channeloptimized case, and graceful degradation for channel mismatch situations. For the main information, PCCOVQ with a direct mapping from the source parameter space to the channel (modulation) space is used. A traditional video communication system based on the H.263 video coder is used as a reference. The proposed system compares favorably to the reference system for high rate applications, and offers graceful degradation for c..

Block Based Motion Compensation Based on the Spectral Flatness Measure

Traditionally, the mean squared error between the current and the previous frames has been considered as an appropriate criterion for selecting the displacement vectors in hybrid video coders. However, with a spatial coding method utilizing the correlation between samples, the error criterion should take both the mean squared error as well as the shape of the spectrum into account. In particular, it can be shown that when the spatial domain coder is based on a DCT and dynamic bit allocation, improved performance can be achieved by using the geometric mean of the DCT coefficient variances as error criterion. Furhermore, it is shown that with the new error criterion, the probability distribution of the motion vectors is changed drastically, allowing for further coding gains as well as reductions in complexity. 1. INTRODUCTION During recent years, the most popular method for video sequence coding has been a hybrid coding scheme utilizing both spatial and temporal redundancies. Usually, t..

On Optimal Tiling Of The Spectrum In Subband Image Compression

The performance of subband image coders depends on the proper choice of frequency partitioning in the subband domain. It is therefore desirable to have an adaptive nonuniform filter bank to cope with the frequency characteristics of the image at hand. However, a good choice, if a nonadaptive structure is to be used, is combinations of uniform parallel and octave-band treestructured filter banks. In this paper, uniform parallel (8-channel, 32-tap), and 3-stage and 6-stage octaveband tree-structured systems are compared using a fixed rate coder for image coding purposes. Favorable results are obtained using the combination of a parallel filter bank and a tree-structured system. The coding results are comparable to the "best" results reported in the literature. 1. INTRODUCTION Filter banks (FBs) find applications in communications, filtering, restoration, compression, etc.. In compression applications, the popularity is due to the fact that most signal sources, e.g. speech and image dat..

Lossless Subband Image Compression Using Integer Coefficient Filter Banks

A new class of two-channel filter banks having integer filter coefficients is proposed. The integer filter coefficients are obtained by maximizing for subband coding gain. The number of bits required to represent the subband samples are kept low through efficient nonlinear implementation techniques. Several integer coefficient filter banks are tested for lossless image compression. An octave-band (dyadic) frequency partitioning with 6-stages is preferred. In this way, we achieve a progressive image transmission based on multiresolution image representation in a lossless mode. Two different coding strategies are investigated. Firstly, enumeration techniques from pyramid vector quantization (PVQ) scheme are adopted. Secondly, a classwise entropy coding scheme is employed. Both coding schemes tend to perform fairly well, however, the classwise entropy coding scheme performs better than the PVQ based scheme. The compression ratios are encouraging compared to the best results reported so fa..

Efficient Coding Of The Classification Table In Low Bit Rate Subband Image Coding By Use Of Hierarchical Enumeration

A new method for lossless coding of the classification table in low bit rate subband image coders with block-wise classification is proposed. The method is referred to as hierarchical enumeration and uses an algorithmic enumeration technique to associate a fixed-length unique binary codeword with each possible combination of integers defining the classification table. The resulting bit rate is less than the first order entropy of the classification table. When using hierarchical enumeration in combination with pyramid vector quantization of the subband samples, a high performance image coder using only fixed-length codewords is obtained. The proposed coder compares favorably with state-of-the art image coders using variable-length coding. 1. INTRODUCTION During recent years, the efficiency of still image coding algorithms has improved significantly. Typically, state-of-theart algorithms can achieve compression ratios which are 2-3 times higher than the existing JPEG standard [1]. In o..