Source Symbol Purging-Based Distributed Conditional Arithmetic Coding

Abstract

A distributed arithmetic coding algorithm based on source symbol purging and using the context model is proposed to solve the asymmetric Slepian–Wolf problem. The proposed scheme is to make better use of both the correlation between adjacent symbols in the source sequence and the correlation between the corresponding symbols of the source and the side information sequences to improve the coding performance of the source. Since the encoder purges a part of symbols from the source sequence, a shorter codeword length can be obtained. Those purged symbols are still used as the context of the subsequent symbols to be encoded. An improved calculation method for the posterior probability is also proposed based on the purging feature, such that the decoder can utilize the correlation within the source sequence to improve the decoding performance. In addition, this scheme achieves better error performance at the decoder by adding a forbidden symbol in the encoding process. The simulation results show that the encoding complexity and the minimum code rate required for lossless decoding are lower than that of the traditional distributed arithmetic coding. When the internal correlation strength of the source is strong, compared with other DSC schemes, the proposed scheme exhibits a better decoding performance under the same code rate.

Distributed conditional arithmetic coding based on adaptive source-symbol purging

“…For lossless decoding, the required minimum code rate (RMCR) of a DSC scheme can be used to present the coding efficiency of that DSC scheme [9]. Table 2 shows the RMCR of DCASACP, SPDCAC, and DAC coding different sources when ( | ) = 0.1.…”

“…The initial probability distribution of all methods is set to 0.5. The purging rate of SPDCAC is set to the maximum value (1/2), and the maximum coding interval expand factor of DAC is set according to [9]. We can find it from the table.…”

“…Another idea of using arithmetic coding to implement DSC is to puncture the codeword of the arithmetic encoder to reduce the number of bits that need to be transmitted [8]. Recently, a very easy to be implemented scheme named Source Symbol Purging-Based Distributed Conditional Arithmetic Coding (SPDCAC) was proposed in [9] which uses a very simple way to increase the compression rate: based on a fixed purging rate, only a part of the symbols in the source sequence is encoding by the arithmetic encoder. This scheme shows better performance than DAC.…”