• 인터넷정보학회논문지
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• 제8권5호
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• pp.141-150
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• 2007

본 논문에서는 VoIP(Voice over IP) 통신에서 효율적으로 사용할 수 있는 Low bit Encoding에 의한 새로운 스테가노그라피 모델을 제안한다. Low bit Encoding 방법을 사용하는 대부분의 스테가노그라피 모델은 비밀 메시지 삽입 용량에 제한이 있다는 것과 비밀 메시지 위치를 쉽게 인지할 수 있다는 문제점을 가지고 있다. 이러한 문제점을 개선하였고 사람의 가청구간을 벗어나는 영역에 1 비트 이상의 비밀 메시지를 삽입하여 커버 데이터에 숨길 수 있는 메시지의 삽입 용량을 향상시켰다. 은닉 위치는 삽입 메시지 길이를 시드로 가지는 의사난수를 이용하여 선택하여, 공격자가 은닉된 비밀 메시지를 쉽게 공격할 수 없도록 하였다. 제안된 모델은 VoIP환경 하에서 적합하도록 구현하였으며, 웨이브파일에 정보은닉을 하여 전송할 수 있을 뿐만 아니라 사용자에 대한 기본정보 및 인증 시스템에서 다양한 정보를 은닉 하는데 활용할 수 있다.

• 한국통신학회논문지
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• 제25권5A호
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• pp.726-742
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• 2000

A novel rte control algorithm consisting of two major components, i.e. a variable encoding frame rate method and a hybrid DCT/wavelet I-frame coding scheme, is proposed in this work for low bit rate video coding. Most existing rate control algorithms for low bit rate video focus on bit allocation at the macroblock level under a constant frame rate assumption. The proposed rate control algorithm is able to adjust the encoding frame rate at the expense of tolerable time-delay. Furthermore, an R-D optimized hybrid DCT/wavelet scheme is used for effective I-frame coding. The new rate-control algorithm attempts to achieve a good balance between spatial quality and temporal quality to enhance the overall human perceptual quality at low bit rates. It is demonstrated that the rate control algorithm achieves higher coding efficiency at low bit rates with a low additional computational cost. The variable frame rate method and hybrid I-frame coding scheme are compatible with the bi stream structure of H.263+.

• 한국통신학회논문지
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• 제21권7호
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• pp.1654-1667
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• 1996

The conventional fractal image compression methods have high computational complexity at encoding reduce PSNR at low bit rate and havehighly visible blocking effects in a reconstructed image. In this paper we propose a fractal image compression method based on disctete wavelet transform domain, which takes the absolute value of discrete wavelet transform coefficient, and assembles the discrete wavelet tranform coefficients of different highpass subbands corresponding to the same spatial block and then applies "0" encoding according to the energy of each range blocks. The proposed method improved PSNR at low bit rate and reduced computational complexity at encoding distinctly. Also, this method can achieve a blockless reconstructed image and perform hierarchical decoding without recursive constractive transformation. Computer simulations with several test images show that the proposed method shows better performance than convnetional fractal coding methods for encoding still pictures. pictures.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.54-58
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• 2007

A real-time frame-layer rate control algorithm with a token bucket traffic shaper is proposed for distortion variation minimization. The proposed rate control method uses a non-iterative optimization method for low computational complexity, and performs bit allocation at the frame level to minimize the average distortion over an entire sequence as well as variations in distortion between frames. The proposed algorithm does not produce time delay from encoding, and is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better visual and PSNR performances than the existing rate control method.

• The Journal of the Acoustical Society of Korea
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• 제16권3E호
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• pp.44-49
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• 1997

In this paper, we propose an adaptive encoding method of fixed codebook in CELP coders and implement an adaptive fixed code exited linear prediction(AF-CELP) speech coder. AF-CELP exploits the fact that the fixed codebook contribution to speech signal is also periodic like the adaptive codebook (or pitch filter) contribution. By modeling the fixed code book with the pitch lag and the gain from the adaptive codebook, AF-CELP can be implemented at low bit rates as well as low complexity. Listening tests show that a 6.4 kbit/s AF-CELP has a comparable quality to the 8 kbit/s CS-ACELP in background noise conditions.

• 한국컴퓨터산업학회논문지
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• 제7권5호
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• pp.513-520
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• 2006

In this paper, we propose a novel real-time frame-layer rate control algorithm using sliding window method for low bit rate video coding. The proposed rate control method performs bit allocation at the frame level to minimize the average distortion over an entire sequence as well as variations in distortion between frames. A new frame-layer rate-distortion model is derived, and a non-iterative optimization method is used for low computational complexity. In order to reduce the quality fluctuation, we use a sliding window scheme which does not require the pre-analysis process. Therefore, the proposed algorithm does not produce time delay from encoding, and is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better visual and PSNR performance than the existing TMN8 rate control method.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권5호
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• pp.443-450
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• 2013

This paper propose a new ROM data encoding method that takes into account of a sequential access pattern to reduce the power consumption in ROMs used in applications such as FIR filters that access the ROM sequentially. In the proposed encoding method, the number of 1's, of which the increment leads to the increase of the power consumption, is reduced by applying an exclusive-or (XOR) operation to a bit pair composed of two consecutive bits in a bit line. The encoded data can be decoded by using XOR gates and D flip-flops, which are usually used in digital systems for synchronization and glitch suppression. By applying the proposed encoding method to coefficient ROMs of FIR filters designed by using various design methods, we can achieve average reduction of 43.7% over the unencoded original data in the power consumption, which is larger reduction than those achieved by previous methods.

• ETRI Journal
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• 제45권3호
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• pp.404-417
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• 2023

This paper proposed a novel method for constructing quasi-cyclic low-density parity-check (QC-LDPC) codes of medium to high code rates that can be applied in cloud data storage systems, requiring better error correction capabilities. The novelty of this method lies in the construction of sparse base matrices, using a girth greater than 4 that can then be expanded with a lift factor to produce high code rate QC-LDPC codes. Investigations revealed that the proposed large-sized QC-LDPC codes with high code rates displayed low encoding complexities and provided a low bit error rate (BER) of 10^-10 at 3.5 dB E_b/N₀ than conventional LDPC codes, which showed a BER of 10^-7 at 3 dB E_b/N₀. Subsequently, implementation of the proposed QC-LDPC code in a softwaredefined radio, using the NI USRP 2920 hardware platform, was conducted. As a result, a BER of 10^-6 at 4.2 dB E_b/N₀ was achieved. Then, the performance of the proposed codes based on their encoding-decoding speeds and storage overhead was investigated when applied to a cloud data storage (GCP). Our results revealed that the proposed codes required much less time for encoding and decoding (of data files having a 10 MB size) and produced less storage overhead than the conventional LDPC and Reed-Solomon codes.

• 방송공학회논문지
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• 제18권2호
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• pp.297-310
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• 2013

본 연구에서는 디지털 방송 TV, VOD 등 제한된 네트워크 대역폭에서 서비스를 제공하기 위해 비디오 콘텐츠를 부호화하는 과정에서 고정된 비트율을 이용한 화질과 비교하여 주관적 화질을 유지하면서 적절한 비트율을 찾는 방법을 제시한다. 제안하는 예측 구조는 먼저 프레임에서 비트와 연관성이 있는 파라미터를 추출하여 프레임의 복잡도를 계산한 후, 비트가 많이 할당될 것으로 예상되는 프레임을 찾아 후보 프레임으로 추출하며, 추출된 후보 프레임들에 대해 실제 부호화하는 과정으로써 목표 화질을 기준으로 수학적 모델링을 통해 최종적으로 전송될 비트율을 예측하는 구조를 설계하였다. 실험 결과, 고정 비트율에 비해 저복잡도 영상에서 평균 43%의 비트 감소율을 보였으며, 이러한 영상의 비트 감소율이 있음에도 주관적 화질을 유지함을 알 수 있었다. 비디오 콘텐츠별 적절한 비트율을 찾기 위해 기존 구조에서는 다수의 부호화를 통해 결과물들의 주관적 화질 검증을 반복적으로 거치는 반면, 제안하는 구조는 사람이 관여하여 주관적 화질 검증을 반복적으로 수행하지 않아도 되며 일부 프레임만을 부호화하여 비트율 예측이 가능하다. 따라서 전체 프레임 중 평균 4% 프레임을 부호화하여 자동적으로 비트율을 찾을 수 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.75-76
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• 2008

A low complexity encoding scheme for coarse grain scalability is proposed. The proposed method exploits the statistics of residuals between current and reference blocks using the macroblock mode predicted from the previous quality layer. To test how the mode is optimal in the current layer, the statistical hypothesis testing for the variances of the residual sub-blocks is performed. The proposed method reduces the total encoding time up to 51% when three CGS scalability layers are encoded. However, the quality degradation and bit-rate increment of the each layer are negligible.