This paper presents an improved sequential MAP estimator to be used as a joint source-channel decoding technique for CABAC encoded data. The decoding process is compatible with realistic implementations of CABAC in standards like H.264, i.e, handling adaptive probabilities, context modeling and integer arithmetic coding. Soft-input decoding is obtained using an improved sequential decoding technique, which allows to obtain a tradeoff between complexity and efficiency. The algorithms are simulated in a context reminiscent of H264. Error detection is realized by exploiting on one side the properties of the binarization scheme and on the other side the redundancy left in the code string. As a result, the CABAC compression efficiency is preserved and no additional redundancy is introduced in the bit stream. Simulation results outline the efficiency of the proposed techniques for encoded data sent over AWGN and UMTS-OFDM channels.

This paper presents a MAP estimator for CABAC encoded data transmitted through a noisy channel. The decoding process has two characteristics (i) it provides an exact result, without approximation (ii) it is compatible with realistic implementations of CABAC in standards like H.264, i.e. taking into account finite precision problems and handling adaptive probabilities and context modeling. Simulation results outline the efficiency of the proposed method when applied in AWGN and UMTS-OFDM frameworks

In this paper, we present a joint source-channel decoding technique based on exact MAP estimation for data encoded by CABAC (context-based adaptive binary arithmetic coding) in standards like H.264/AVC. Soft decoding is put at work using an improved sequential decoding technique, achieving a trade-off between complexity and efficiency of the proposed algorithms. Error detection is realized by exploiting the binarization scheme and redundancy left in the code string, so that CABAC compression efficiency is preserved and no additional redundancy is compulsory

In joint source-channel (JSC) schemes based on arithmetic coding (AC), additional redundancy may be introduced in order to reduce transmission errors. The purpose of this work is to provide analytical tools to predict and evaluate the effectiveness of that redundancy. Integer binary AC is modeled by a reduced-state automaton in order to obtain a bit-clock trellis of the AC. Considering AC as a trellis code, distance spectra are then derived. In particular, an algorithm to compute the free distance of an arithmetic code is proposed. The obtained code properties allow to compute upper bounds on both bit error and symbol error probabilities and thus provide an objective criterion to analyze the behavior of JSCAC schemes when used on noisy channels

Due to its high compression efficiency, the H.264 video coder is very sensitive to impairments due to transmission over noisy channels. Most error resilience/concealment techniques provided in the H.264 standard were dealing with packet losses. In wireless environments, the proportion of corrupted packets (and thus considered as lost) may become very high. This paper shows that the H.264 decoder may be seen as a parity check decoder able to detect erroneous packets. Combined with soft estimation techniques, it allows to correct transmission errors and to reduce significantly the number of packets deemed lost. The proposed solution is compatible with the error-resilience features of H.264