• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.3 s.309
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• pp.9-16
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• 2006

Many image and video compression algorithms work by splitting the image into blocks and producing variable-length code bits for each block data. If variable-length code data are transmitted consecutively over error-prone channel without any error protection technique, the receiving decoder cannot decode the stream properly. So the standard image and video compression algorithms insert some redundant information into the stream to provide some protection against channel errors. One of redundancies is resynchronization marker, which enables the decoder to restart the decoding process from a known state in the event of transmission errors, but its usage should be restricted not to consume bandwidth too much. The Error Resilient Entropy Code(EREC) is well blown method which can regain synchronization without any redundant information. It can work with the overall prefix codes, which many image compression methods use. This paper proposes EREREC method to improve FEREC(Fast Error-Resilient Entropy Coding). It first calculates initial searching position according to bit lengths of consecutive blocks. Second, initial offset is decided using statistical distribution of long and short blocks, and initial offset can be adjusted to insure all offset sequence values can be used. The proposed EREREC algorithm can speed up the construction of FEREC slots, and can improve the compressed image quality in the event of transmission errors. The simulation result shows that the quality of transmitted image is enhanced about $0.3{\sim}3.5dB$ compared with the existing FEREC when random channel error happens.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.281-285
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• 2000

This paper proposes context-based coding methods for variable length coding of inter-frame DCT coefficients. The proposed methods classify run-level symbols depending on the preceding coefficients. No extra overhead needs to be transmitted, since the information of the previously transmitted coefficients is used for classification. Two entropy coding methods, arithmetic coding and Huffman coding, are used for the proposed context-based coding. For Huffman coding, there is no complexity increase from the current standards by using the existing inter/intra VLC tables. Experimental results show that the proposed methods give ～ 19% bits gain and ～ 0.8 dB PSNR improvement for adaptive inter/intra VLC table selection, and ～ 37% bits gain and ～ 2.7dB PSNR improvement for arithmetic coding over the current standards, MPEG-4 and H.263. Also, the proposed methods obtain larger gain for small quantizaton parameters and the sequences with fast and complex motion. Therefore, for high quality video coding, the proposed methods have more advantage.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.2
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• pp.121-128
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• 2008

Accurate voice activity detection have a great impact on performance of speech applications including speech recognition, speech coding, and speech communication. In this paper, we propose methods for voice activity detection that can adapt to various car noise situations during driving. Existing voice activity detection used various method such as time energy, frequency energy, zero crossing rate, and spectral entropy that have a weak point of rapid. decline performance in noisy environments. In this paper, the approach is based on existing spectral entropy for VAD that we propose voice activity detection method using MFB(Met-frequency filter banks) spectral entropy, gradient FFT(Fast Fourier Transform) spectral entropy. and gradient MFB spectral entropy. FFT multiplied by Mel-scale is MFB and Mel-scale is non linear scale when human sound perception reflects characteristic of speech. Proposed MFB spectral entropy method clearly improve the ability to discriminate between speech and non-speech for various in noisy car environments that achieves 93.21% accuracy as a result of experiments. Compared to the spectral entropy method, the proposed voice activity detection gives an average improvement in the correct detection rate of more than 3.2%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.371-381
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• 2005

In this paper, we propose an advanced hardware architecture for the CAVLC entropy encoder/decoder engine for real time video compression. The CAVLC (Context-based Adaptive Variable Length Coding) is a lossless compression method in H.264/AVC and it has high compression efficiency but has computational complexity. The reference memory size is optimized using partitioned storing method and memory reuse method which are based on partiality of memory referencing. We choose the hardware architecture which has the most suitable one in several encoder/decoder architectures for the mobile devices and improve its performance using parallel processing. The proposed architecture has been verified by ARM-interfaced emulation board using Altera Excalibur and also synthesized on Samsung 0.18 um CMOS technology. The synthesis result shows that the encoder can process about 300 CIF frames/s at 150MHz and the decoder can process about 250 CIF frames/s at 140Mhz. The hardware architectures are being used as core modules when implementing a complete H.264/AVC video encoder/decoder chip for real-time multimedia application.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.743-746
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• 2001

An improved zerotree-structure based wavelet coding algorithm is proposed. When the descendants of a significant coefficient are all zerotree, its four-childs are coded respectively in conventional EZW. But in the proposed algorithm, a new symbol is assigned for the significant coefficient. Entropy for both methods are analyzed and new coding scheme is proposed. The experimental results show that the Proposed algorithm has a better performance than the original EZW algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1141-1154
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• 1996

The para-unitary (PU) M band filter bank, which can beused for M band decomposition, has many useful properties. In this ppaer, attempts have been made to design and and analyze the linear phase para-unitary (LPPU) M band filter bank, which is appropriate to the image coding application. First, we derive a unified coding gain in terms of the correlation in the band, as well as the energy compaction. And M band filter bank has been designed, maximizing the new coding gain. Then, we analyze the image coding performance of the LPPU M band filter bank, such as the energy compaction, the correlation in the band and the entropy. From the analysis, it is shown that the coding gain for LPPU M band filter bank improves, and the coding gain for the LPPU 4 band filter bank approaches very closely to that for LPPU 8 band filter bank, as the length of the filter increases. This fact is also verified by the coding results on the real images.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.1
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• pp.64-74
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• 2008

It is well-known that the coding efficiency of CABAC which is one of the entropy coding methods in H.264/AVC is lower than that of CAVLC at high bitrate in intra coding, even if CABAC shows higher coding efficiency than CAVLC. Therefore, for high quality video application, this paper proposes new binarization methods about the quantized DCT coefficients that are partitioned into four regions such that CABAC shows similar coding efficiency to CAVLC at high bitrate. The proposed binarization methods consist of separate binarization tables about the four partitioned DCT coefficients considering the statistical characteristics of the quantized DCT coefficients. The proposed binarizaton method for the quantized DCT coefficients shows higher coding efficiency than CABAC in H.264/AVC and shows very similar result to CAVLC at high bitrate.

• The Journal of the Acoustical Society of Korea
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• v.28 no.7
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• pp.618-629
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• 2009

The MPEG-4 Audio Lossless Coding (ALS) standard belongs to the family MPEG-4 audio coding standards. In contrast to lossy codecs such as AAC, which merely strive to preserve the subjective audio quality, lossless coding preserves every single bit of the original audio data. The ALS core codec is based on forward-adaptive linear prediction, which combines remarkable compression with low complexity. Additional features include long-term prediction, multichannel coding, and compression of floating-point audio material. This paper describes the basic elements of the ALS codec with a focus on prediction, entropy coding, and related tools and points out the most important applications of this standardized lossless audio format.

• Journal of Electrical Engineering and information Science
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• v.1 no.1
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• pp.91-97
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• 1996

This paper proves by straightforward computation an interesting property of a recursive indexing: it preserves the entropy of a geometrically-distributes stationary memoryless source. This result is a pleasant surprise because the recursive indexing though one-to-one, is a symbol-to-string mapping and the entropy is measured in terms of the source symbols. This preservation of the entropy implies that the minimum average number of bits needed to represent a geometric memoryless source by the recursive indexing followed by a good binary encoder of a finite imput alphabet remains the same as that by a good encoder of an infinite input alphabet. Therefore, the recursive indexing theoretically keeps coding optimality intact. For this reason recursive indexing can provide an interface for a binary code with a finite code book that performs reasonably well for a source with an infinite alphabet.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.9 no.3
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• pp.103-107
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• 1984

According to rapid developments in data communication, we have being used every infromation with ease. In receiving and transmitting the infromation acquired, it is being needed to transmit it with minimizing bits if possible. Therefore this paper suggests the efficient coding system, that is, OCM(Octal-Compact Mapping) technique. In case of average-case, it has 3.5bytes in entropy with 8 symbols. This means it is compressed more than at least 1 byte as compared with another coding techniques. It decreases the redundancy of data and is superior to another data compression techniques.