Motivated by recent results in Joint Source/Channel coding and decoding, we consider the decoding problem of Arithmetic Codes (AC). In fact, in this article we provide different approaches which allow one to unify the arithmetic decoding and error correction tasks. A novel length-constrained arithmetic decoding algorithm based on Maximum A Posteriori sequence estimation is proposed. The latter is based on soft-input decoding using a priori knowledge of the source-symbol sequence and the compressed bit-stream lengths. Performance in the case of transmission over an Additive White Gaussian Noise channel is evaluated in terms of Packet Error Rate. Simulation results show that the proposed decoding algorithm leads to significant performance gain while exhibiting very low complexity. The proposed soft input arithmetic decoder can also generate additional information regarding the reliability of the compressed bit-stream components. We consider the serial concatenation of the AC with a Recursive Systematic Convolutional Code, and perform iterative decoding. We show that, compared to tandem and to trellis-based Soft-Input Soft-Output decoding schemes, the proposed decoder exhibits the best performance/ complexity tradeoff. Finally, the practical relevance of the presented iterative decoding system is validated under an image transmission scheme based on the JPEG 2000 standard and excellent results in terms of decoded image quality are obtained.

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International audienceMost source coding standards (voice, audio, image and video) use Variable-Length Codes (VLCs) for compression. However, the VLC decoder is very sensitive to transmission errors in the compressed bit-stream. Previous contributions, using a trellis description of the VLC codewords to perform soft decoding, have been proposed. Significant improvements are achieved bythis approach when compared with prefix decoding. Nevertheless,for realistic VLCs, the complexity of the trellis technique becomesintractable. In this paper, we propose a soft-input VLC decodingmethod using an a priori knowledge of the lengths of the sourcesymbolsequence and the compressed bit-stream with Maximum A Posteriori (MAP) sequence estimation. Performance in the case of transmission over an Additive White Gaussian Noise (AWGN)channel is evaluated. Simulation results show that the proposed decoding algorithm leads to significant performance gain incomparison with the prefix VLC decoding besides exhibiting very low complexity. A new VLC decoding method generating additional information regarding the reliability of the bits of the compressed bit-stream is also proposed. We consider the serial concatenation of a VLC with two types of channel code and perform iterative decoding. Results show that, when concatenated with a recursive systematic convolutional code (RSCC), iterativedecoding provides remarkable error correction performance.In fact, a gain of about 2.3 dB is achieved, in the case of transmission over an AWGN channel, with respect to tandem decoding. Second, we consider a concatenation with a low-density parity-check (LDPC) code and it is shown that iterative joint source/channel decoding outperforms tandem decoding and an additional coding gain of 0.25 dB is achieved

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Most multimedia source encoders produce scalable bit streams that are vulnerable to noisy channel effects. Unequal error protection (UEP) designs are attractive solutions for such scalable bit streams. In the other hand, the structure of multiple concatenated codes, which consist of the combination of two or more elementary encoders and interleavers, offers a flexible implementation of unequal data protection. To provide an efficient protection for embedded source bit streams, an adaptive concatenated coding/decoding design is proposed in this paper inspired by serially concatenated turbo codes. This scheme involves iterative decoding of concatenated codes for JPEG 2000 image transmission. In the case of time varying channels, the concatenated coding rates are adaptively chosen to maximize the visual quality. The simulation results show that the proposed scheme achieves better image quality improvements at the receiver side compared with a conventional multiple turbo codes-based design, with significant peak-signal-to-noise ratio gains. INDEX TERMS Scalable bit streams, unequal error protection (UEP), multiple concatenated codes, iterative decoding, JPEG 2000. Recently, [5] proposed a turbo code that provides descending protection capabilities for the data according to their locations

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