• 한국데이타베이스학회:학술대회논문집
• /
• 한국데이타베이스학회 2000년도 추계학술대회 E-Business와 정보보안
• /
• pp.358-363
• /
• 2000

본 논문에서는 디지털오디오 원시 데이터의 양에 따라 적당한 양의 오디오워터마크를 생성, 삽입하여 일정한 수준의 오디오데이터의 품질을 유지하도록 하는 적응적 워터마킹을 제안한다. 제안하는 알고리즘은 심리음향모델인 frequency masking과 Wavelet 변환의 개념을 적용한다. 저작권자 혹은 소유자의 데이터는 PN-sequence를 이용하여 생성된다. 워터마크 생성량의 조절은 특정한 모듈이 담당하게 되는데 이 모듈은 원시 데이터의 크기에 따라 워터마크의 적당한 양을 산출하여 오디오데이터의 품질을 유지하도록 한다.

• 대한의용생체공학회:의공학회지
• /
• 제30권6호
• /
• pp.529-534
• /
• 2009

One of the characteristics of the hearing impaired is that their frequency selectivity is poorer than that of the normal hearing. To compensate this, formant enhancement algorithms and spectral contrast enhancement algorithms have been developed. However in some cases, these algorithms fail to improve the frequency selectivity of the hearing impaired. One of the reasons is the acoustic masking among enhanced formants. In this study, we tried to enhance the formants based on the individual masking characteristic of each subject. The masking characteristic used in this study was minimum level difference (MLD) between the first formant to the second formant while acoustic masking was occurred. If the level difference between the two formants in each frame is larger than the MLD, the gain of the first formant was decreased to reduce the acoustic masking that occurred among formants. As a result of the speech discrimination test, using formant enhanced speeches, speech discrimination score (SDS) of the speeches having differently enhanced formants was significantly superior to SDS of the speeches having equally enhanced formants. It means that suppression of the acoustic masking among formants improve frequency selectivity of the hearing impaired.

• 한국멀티미디어학회논문지
• /
• 제21권2호
• /
• pp.108-116
• /
• 2018

In this paper, we propose an image enhancement method based on Multi-Scale Retinex theory that designs Unsharp Masking Filter (UMF) and emphasizes the contrast ratio adaptively. Unsharp Masking (UM) technique emphasizes image sharpness and improves contrast ratio by adding high frequency component to the original image. The high frequency component is obtained by differentiating between original image and low frequency image. In this paper, we present how to design an UMF kernel and to adaptively apply it to increase the contrast ratio according to multi-scale retinex theory which resembles human visual system. Experimental results show that the proposed method has better quantitative performance indexes such as PSNR, ambe & SSIM and better qualitative feature like halo artifact suppression.

• 방송공학회논문지
• /
• 제8권3호
• /
• pp.268-277
• /
• 2003

본 논문에서는 비가시성을 유지하면서 강인함을 최대로 높이기 위해 워터마크를 삽입할 때 인간시각 시스템(human visual system, HVS)을 이용한다. 우선 HVS를 세가지 관점에서 고려한 후 각각의 특성을 결합한 최적화된 HVS 가중치 맵(HVS optimized weighting map)을 제안한다. 즉, 주파수 마스킹(frequency masking), 공간 마스킹(spatial masking), 그리고 움직임 마스킹(motion masking)을 결합한 전역 마스킹 맵(global masking map)을 제안한다. 본 논문에서는 키(key) 값에 의해 발생된 랜덤 시퀀스와 로고의 배타적 논리합에 의해 결합된 워터마크를 전역 마스킹 결과에 따라 비디오 프레임에 삽입하고, 그 양은 제어 변수에 의해 조절된다. 이때 워터마크를 압축되지 않은 비디오 프레임에 삽입함으로써, 다양한 부호화 방법에 적용할 수 있는 일반적 워터마킹 방법을 제안한다. 컴퓨터 모의실험을 통해 제안한 방법으로 삽입된 워터마크의 비가시성을 확인했으며, 제안된 방법은 워터마크 삽입 용량(capacity) 면에서도 우수함을 알 수 있다. 또한 MPEG 부호화 및 재부호화 공격, 그리고 여러 프레임 공격 등에 대해서 제안한 방법이 강인함을 확인하였다.

• 전기학회논문지
• /
• 제56권3호
• /
• pp.629-631
• /
• 2007

In hands-free full-duplex communication systems, acoustic signals picked up by the microphones can be mixed with echo signals as well as noises, which may result in poor performance of the corresponding communication system. Also, the system performance may decrease further if the reverberation occurs since it is harder to estimate the impulse response of the demixing system. For blind source separation (BSS) in such cases, a time-frequency masking approach can be employed to separate undesired echo signals and noises, but, permutation ambiguities also should be solved for the echo cancellation. In this paper, we propose a new acoustic echo cancellation (AEC) approach utilizing the time-frequency masking and higher-order statistics, whereby a desired signal selection, based on coherence and third-order statistics (i.e., kurtosis), is introduced along with output signal normalization. Simulation results demonstrate that the proposed approach yields better echo and noise cancellation performances than the conventional AEC approaches.

• Journal of Multimedia Information System
• /
• 제4권2호
• /
• pp.65-73
• /
• 2017

This paper proposes a method to improve the image quality by designing Unsharp Mask Filter (UMF) based on Retinex theory which controls the frequency pass characteristics adaptively. Conventional unsharp masking technique uses blurring image to emphasize sharpness of image. Unsharp Masking(UM) adjusts the original image and sigma to obtain a high frequency component to be emphasized by the difference between the blurred image and the high frequency component to the original image, thereby improving the contrast ratio of the image. In this paper, we design a Unsharp Mask Filter(UMF) that can process the contrast ratio improvement method of Unsharp Masking(UM) technique with one filtering. We adaptively process the contrast ratio improvement using Unsharp Mask Filter(UMF). We propose a method based on Retinex theory for adaptive processing. For adaptive filtering, we control the weights of Unsharp Mask Filter(UMF) based on the human visual system and output more effective results.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 2002년도 정기총회 및 학술대회
• /
• pp.163-168
• /
• 2002

본 논문에서는 워터마크의 기본적인 요구사항인 비가시성(invisibility)을 유지하면서 강인함(robustness)을 최대로 하기 위해 워터마크를 삽입할 때 인간시각 특성(Human Visual System, HVS)을 이용한다. 특히, 주파수 마스킹(frequency masking), 공간 마스킹(spatial masking), 그리고 움직임 마스킹(motion masking)을 결합한 전역마스킹(global masking) 기법을 제안한다. 주파수 마스킹은 프레임을 DCT 변환한 후 주파수 민감도 표(frequency sensitivity table)를 이용해 위치 정보를 구한다. 공간 마스킹은 밝기(luminance) 및 윤곽선(edge) 정보를 이용해서 구하며. 움직임 마스킹은 이웃하는 프레임간의 움직임 변화를 이용하여 프레임간의 상관성을 고려한다. 본 논문에서는 키(key) 값에 의해 발생된 랜덤시퀀스와 로고의 배타적 논리합(exclusive OR)에 의해 결합된 워터마크를 전역 마스킹 결과에 따라 압축되지 않은 비디오 프레임에 직접 적용했으며, 실험을 통해 MPEG 부호화 및 재부호화 공격에 대해서 제안한 방법이 강인함을 확인했다.

• Journal of Audiology & Otology
• /
• 제23권1호
• /
• pp.27-32
• /
• 2019

Background and Objectives: Detection of auditory signals may be improved when maskers far from the frequency of the target signal are coherently amplitude-modulated. This improvement of signal detection is called comodulation masking release (CMR). In the CMR experiments, flankers have been usually arranged symmetrically. In practice, we will be confronted with a problem by using symmetric flankers due to the limited output of clinical audiometers, especially at high-frequency. We aimed to check whether flanker arrangement has any effect on the amount of CMR, especially when there is no flankers with a frequency higher than the signal. Subjects and Methods: Eighteen normal hearing listeners ranging in age from 20 to 46 years old participated. Symmetric (2-2) and asymmetric (3-1 and 4-0) flankers were used and then the amount of CMR compared among them. Results: Our results showed in the same numbers of flankers, there were no statistically CMR differences between symmetric and asymmetric arrangement. Also when we did not have a flanker at a frequency higher than the signal and all flankers were placed below the signal, there was no statistically difference with the symmetric arrangement. Conclusions: The asymmetry of the flankers and also omitting the flankers with a frequency higher than the signal, have no effect on CMR results. We concluded that CMR can be considered by using clinical audiometer.

• 대한청각학회지
• /
• 제23권1호
• /
• pp.27-32
• /
• 2019

Background and Objectives: Detection of auditory signals may be improved when maskers far from the frequency of the target signal are coherently amplitude-modulated. This improvement of signal detection is called comodulation masking release (CMR). In the CMR experiments, flankers have been usually arranged symmetrically. In practice, we will be confronted with a problem by using symmetric flankers due to the limited output of clinical audiometers, especially at high-frequency. We aimed to check whether flanker arrangement has any effect on the amount of CMR, especially when there is no flankers with a frequency higher than the signal. Subjects and Methods: Eighteen normal hearing listeners ranging in age from 20 to 46 years old participated. Symmetric (2-2) and asymmetric (3-1 and 4-0) flankers were used and then the amount of CMR compared among them. Results: Our results showed in the same numbers of flankers, there were no statistically CMR differences between symmetric and asymmetric arrangement. Also when we did not have a flanker at a frequency higher than the signal and all flankers were placed below the signal, there was no statistically difference with the symmetric arrangement. Conclusions: The asymmetry of the flankers and also omitting the flankers with a frequency higher than the signal, have no effect on CMR results. We concluded that CMR can be considered by using clinical audiometer.

• 한국음향학회지
• /
• 제31권6호
• /
• pp.367-372
• /
• 2012

본 논문은 64채널 디지털 보청기를 위한 소음 차폐 알고리즘을 소개한다. 125 Hz에서 8000 Hz 주파수 대역 사이에서 64채널을 위해, 125 Hz의 주파수 분해도를 유지하였다. 사람의 달팽이관과 유사한 스펙트럼 차폐 처리 효과를 보청기 소음 감쇠 처리 알고리즘에 적용하였다. 이론적 알고리즘은 어셈블러 언어의 프로그램 소프트웨어로 변환하여 디지털 보청기용 DSP IC 칩으로 이식하였다. 일부 소음 차폐 프로그램 코드를 보여주며 설명하였고, 실시간으로 소음 처리 되는 결과를 전기음향 실험에 의해 증명하였다.