An entropy decoding engine plays an important role in modern multimedia decoders. Previous researches that focused on the decoding performance paid a considerable attention to only one parameter such as the data parsing speed, but they did not consider the performance caused by a table configuration time and memory size. In this paper, we developed a novel method of entropy decoding based on the two step group matching scheme. Our approach achieves the high performance on both data parsing speed and configuration time with small memory needed. We also deployed our decoding scheme to implement an entropy decoding processor, which performs operations based on normal processor instructions and VLD instructions for decoding variable length codes. Several extended VLD instructions are prepared to increase the bitstream parsing process in modern multimedia applications. This processor provides a solution with software flexibility and hardware high speed for stand-alone entropy decoding engines. The VLSI hardware is designed by the Language for Instruction Set Architecture (LISA) with 23 Kgates and 110 MHz maximum clock frequency under TSMC 0.18 µm technology. The experimental simulations revealed that proposed processor achieves the higher performance and suitable for many practical applications such as MPEG-2, MPEG-4, H.264/AVC and AAC.

A novel variable-length code (VLC), called alternate VLC (AVLC), is proposed, which employs two types of VLC to encode source symbols alternately. Its advantage is that it can not only stop the symbol error propagation effect, but also correct symbol insertion errors and symbol deletion errors, which is very important in video communication.

Reversible variable length codes (RVLCs), which make instantaneous decoding possible in both forward and backward directions, are exploited to code data stream in noisy enviroments. Because there is no redundancy in code words of RVLCs, RVLCs are suitable for very low bit-rate video coding. Golomb-Rice code, one of variable length code for infinite number of symbols, is widely used to encode exponentially distributed non-negative integers. We propose a reversible variable length code by modifying Golomb-Rice code, which is called parity check reversible Golomb-Rice code and abbreviated to P-RGR code. P-RGR code has the same code length distribution as GR code but can detect one-bit error in any arbitrary position of the code stream. The sets of P-RGR code words in both directions are identical so that they can be constructed by nearly the same algorithm. Furthermore, this paper also gives a general construction method for all instantaneously decodable RGR codes.

Recently portable computers and mobile communications have been developed rapidly. Along with the developments of mobile computing environment, the demands of transmitting images over wireless channels are growing. However, high efficiency image coding techniques are not designed for the wireless communication channels. The use of variable length codes (VLCs) in those coding techniques makes a receiver hard to synchronize with the codewords on the noisy channel. On the other hand, a variable length code transmission technique utilizing multicode CDM (Code Division Multiplex) has been proposed. In this paper, the multicode CDM technique is applied to wireless transmission of images compressed by the H. 263 algorithm. Especially, the proposed technique is employed for motion vector transmission. In consequence, the proposed transmission technique reduces the required Eb/N0 as compared with the conventional transmission technique.

We consider the optimal average cost of variable length source code averaged with a given probability distribution over source messages. The problem was argued in Csiszar and Korner's book. In a special case of binary alphabet, we find an upper bound to the optimal cost minus an ideal cost, where the ideal cost is the entropy of the source divided by a unique scalar that makes negative costs logarithmic probabilities. Our bound is better than the one given in the book.

In this paper, a new variable length code transmission technique utilizing multicode DS/SS is proposed. A common problem associated with the use of variable length codes over wireless channels is loss of synchronization due to bit inversion caused by channel noise. The loss of synchronization produces burst errors in the received source symbols. The proposed system assigns multiple spreading codes to a single user to transmit variable length codes. The number of the spreading codes is equal to the maximum bit length of the codewords. All the bits of the codeword are spread and transmitted at one time by utilizing the assigned multiple spreading codes. Therefore no synchronization of the codeword is required. This paper evaluates the performance of the proposed technique over an AWGN channel and a Rayleigh fading channel. Our results show that the proposed technique improves the symbol error rate (SER) performance by 2-3 dB on the AWGN channel and 10-20 dB on the Rayleigh fading channel as compared with a conventional transmission technique. The source-channel coding suitable for the proposed technique improves the performance by another 15 dB on the Rayleigh fading channel. The proposed transmission technique works even in a low Es/No region.