Most video coding standards, including MPEG-4, use variable length codes to encode the discrete cosine transform (DCT) coefficients of intra. frames and inter frames, and the motion vector information. Although variab...
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ISBN:
(纸本)0819448222
Most video coding standards, including MPEG-4, use variable length codes to encode the discrete cosine transform (DCT) coefficients of intra. frames and inter frames, and the motion vector information. Although variable length codes can achieve good compression, they are very sensitive to channel errors, especially in Wireless channels, which are characterized by bursty errors. jointsource-channel decoding (JSCD) is emerging as a potential alternative to traditional error resilience methods. for dealing with this sensitivity to channel errors. This paper describes one such JSCD for the reliable transmission of MPEG-4 video over wireless channels. We apply the maximum a posteriori probability based JSCD developed for first order Markov sources' to both inter and intra coded macroblocks. Experiments indicate that the proposed decoder gives significant improvements (9 dB in some cases) for MPEG-4 video with error resilience at various channel error rates.
An optimised construction of variable-length error-correcting codes (VLEC) is proposed in this paper. Compared to the state-of-the-art, the three main improvements consist first in improving the codewords search algor...
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ISBN:
(纸本)0780377990
An optimised construction of variable-length error-correcting codes (VLEC) is proposed in this paper. Compared to the state-of-the-art, the three main improvements consist first in improving the codewords search algorithm complexity/efficiency trade-off, second in loosening the codewords deletion rule, and third in taking advantage of eventual previous searches. It is shown that the optimised algorithm can find good VLEC codes for alphabets up to 200 symbols, and outperforms existing algorithms.
We investigate multicast/broadcast of digital video over spread-spectrum CDMA cellular networks, a platform targeted at various kinds of multimedia services. In particular, we propose an end-to-end embedded transmissi...
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ISBN:
(纸本)0819450235
We investigate multicast/broadcast of digital video over spread-spectrum CDMA cellular networks, a platform targeted at various kinds of multimedia services. In particular, we propose an end-to-end embedded transmission scheme which combines a scalable video source coder, adaptive power allocation, adaptive channelcoding and an embedded multiresolution modulation strategy to simultaneously deliver a basic quality-of-service (QoS) to less capable receivers and an enhanced QoS for more capable receivers. We demonstrate the efficacy of this approach using the ITU-T H.263+ video source coder, although the approach is generally applicable to other scalable sourcecoding schemes as well.
In this paper, we first develop a rate-distortion (R-D) model for DCT-based video coding incorporating the macroblock (MB) intra refreshing rate. For any given bit rate and intra refreshing rate, this model is capable...
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In this paper, we first develop a rate-distortion (R-D) model for DCT-based video coding incorporating the macroblock (MB) intra refreshing rate. For any given bit rate and intra refreshing rate, this model is capable of estimating the corresponding coding distortion even before a video frame is coded. We then present a theoretical analysis of the picture distortion caused by channel errors and the subsequent inter-frame propagation. Based on this analysis, we develop a statistical model to estimate such channel errors induced distortion for different channel conditions and encoder settings. The proposed analytic model mathematically describes the complex behavior of channel errors,in a video coding and transmission system. Unlike other experimental approaches for distortion estimation reported in the literature, this analytic model has very low computational complexity and implementation cost, which are highly desirable in wireless video applications. Simulation results show that this model is able to accurately estimate the channel errors induced distortion with a minimum delay in processing. Based on the proposed sourcecoding R-D model and the analytic channel-distortion estimation, we derive an analytic solution for adaptive intra mode selection and jointsource-channel rate control under time-varying wireless channel conditions. Extensive experimental results demonstrate that this scheme significantly improves the end-to-end video quality in wireless video coding and transmission.
We propose a joint source-channel coding system for fractal image compression. We allocate the available total bit rate between the source code and the channel code using a Lagrange multiplier optimization technique. ...
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We propose a joint source-channel coding system for fractal image compression. We allocate the available total bit rate between the source code and the channel code using a Lagrange multiplier optimization technique. The principle of the proposed unequal error protection strategy is to partition the information bits into sensitivity classes and to assign one code from a range of error-correcting codes to each sensitivity class in a nearly optimal way. Experimental results show that joint source-channel coding with fractal image compression is feasible, leads to efficient protection strategies, and outperforms previous works in this field that covered only channelcoding with a fixed source rate. (C) 2002 Society of Photo-Optical Instrumentation Engineers.
We propose a multiresolution algorithm to jointly optimize a source coder and channel coder. The variable-rate source coder combines an optimal bit-allocation strategy and efficient stack-run coding. This compression ...
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We propose a multiresolution algorithm to jointly optimize a source coder and channel coder. The variable-rate source coder combines an optimal bit-allocation strategy and efficient stack-run coding. This compression scheme, concatenated with appropriate rate-compatible punctured convolutional codes, provides a competitive approach to recent state-of-the-art extensions of zerotree methods to noisy channels. Results show that under the assumption of almost zero probability of decoding error, the proposed scheme provides good performance for a lower complexity.
The main purpose of this paper is to show that once the video sourcecoding is dependent on the channel characteristics, better performance can be achieved in terms of reconstructed video quality. Our study considers ...
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ISBN:
(纸本)0780375890
The main purpose of this paper is to show that once the video sourcecoding is dependent on the channel characteristics, better performance can be achieved in terms of reconstructed video quality. Our study considers a fixed overall bit rate transmission of 64 kbit/s over error prone memoryless binary channels and the source coder is the ITU-T H.263 video standard. The variable H.263 sourcecoding rate adapts to a particular channel Bit Error Rate (BER) at any instant of time. Firstly, we investigated the error sensitivities of H.263 syntactical elements and grouped them into several classes of different significance. By identifying the most sensitive elements, we developed a data grouping (DG) technique which by itself, exhibits improved error resilience. Secondly, we design an Unequal Error Protection (UEP) scheme and compare its performance with an equivalent (same sourcecoding bit rate) Equal Error Protection (EEP) scheme, using Rate Compatible Punctured Convolutional (RCPC) codes of different rates for forward error protection. Both forward error correction schemes adopted have resulted in PSNR improvements, over 20 dB for BERs higher than of 4x10(-3). Finally, if during the real time encoding process, the encoder is aware of the channel BER and there is an unlimited number of code rates, this paper shows that UEP and EEP strategies provide quite similar performances.
We consider the problem of transmitting a band-limited Gaussian source on an additive band-limited Gaussian noise channel. The well-known "threshold effect"dictates that the more powerful a code is, the more...
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We consider the problem of transmitting a band-limited Gaussian source on an additive band-limited Gaussian noise channel. The well-known "threshold effect"dictates that the more powerful a code is, the more sensitive it is to the exact knowledge of the channel noise. A code is said to be robust if it is asymptotically optimal for a wide range of channel noise. Thus, robust codes have a "graceful degradation" characteristic and are free of the threshold effect. It is demonstrated that robust codes exist whenever the source and channel bandwidths are equal. In the unequal-bandwidth case, a collection of nearly robust jointsource-channel codes Is constructed using a hybrid digital-analog (HEIA) coding technique. For designing nearly robust codes, a matched tandem code whose channel encoder's output is partially/fully matched to its input is proposed and the existence of an asymptotically optimal matched tandem code is shown. The nearly robust codes achieve the Shannon limit (theoretically optimum distortion) and have a less severe threshold effect. Finally, for the case of two different noise conditions, the distortion regions of these codes are determined.
A jointsource-channel hybrid digital-analog (HDA) vector quantization (VQ) system is presented. The main advantage of the new VQ-based HDA system is that it achieves excellent rate-distortion-capacity performance at ...
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A jointsource-channel hybrid digital-analog (HDA) vector quantization (VQ) system is presented. The main advantage of the new VQ-based HDA system is that it achieves excellent rate-distortion-capacity performance at the design signal-to-noise ratio (SNR) while maintaining a "graceful improvement" characteristic at higher SNRs. It is demonstrated that, within the HDA framework, the parameters of the system can be optimized using an iterative procedure similar to that of channel-optimized vector quantizer design. Comparisons are made with three purely digital systems and one purely analog system. It is found that, at high SNRs, the VQ-based HDA system is superior to the other investigated systems. At low SNRs, the performance of the new scheme can be improved using the optimization procedure and using soft decoding in the digital part of the system. These results demonstrate that the introduced scheme provides an attractive method for terrestrial broadcasting applications.
In this paper, we investigate the performances of Gaussian modeling and linear prediction tools for error detection and concealment in the transmission of still images. We consider the transmission of subband encoded ...
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In this paper, we investigate the performances of Gaussian modeling and linear prediction tools for error detection and concealment in the transmission of still images. We consider the transmission of subband encoded images through two types of channels. We model the residual correlation between subband coefficients by considering them as jointly Gaussian variables. The first transmission medium considered is a packet-oriented channel, where some packets are lost during transmission. The problem is to estimate the values of missing coefficients. In this case, particular care must be taken while evaluating correlation matrices from incomplete data. The other system considered is based on a discrete memoryless noisy channel affecting the data being transmitted. The challenge is here first to determine the locations of the errors-which is done through hypotheses tests-and then to replace them by estimates based on their neighbors. The reconstruction via linear prediction is shown to give better results than median filtering based reconstruction. Error detection through this Gaussian model also shows promising results, in particular when channel statistics are taken into account in a jointsource-channel decoding framework.
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