• Journal of Broadcast Engineering
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• v.21 no.6
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• pp.929-943
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• 2016

This paper proposes the rate control algorithm based on the S-JND (Saliency-Just Noticeable Difference) model for considering perceptual visual quality. The proposed rate control algorithm employs the S-JND model to simultaneously reflect human visual sensitivity and human visual attention for considering characteristics of human visual system. During allocating bits for CTU (Coding Tree Unit) level in a rate control, the bit allocation model calculates the S-JND threshold of each CTU in a picture. The threshold of each CTU is used for adaptively allocating a proper number of bits; thus, the proposed bit allocation model can improve perceptual visual quality. For performance evaluation of the proposed algorithm, the proposed algorithm was implemented on HM 16.9 and tested for sequences in Class B and Class C under the CTC (Common Test Condition) RA (Random Access), Low-delay B and Low-delay P case. Experimental results show that the proposed method reduces the bit-rate of 2.3%, and improves BD-PSNR of 0.07dB and bit-rate accuracy of 0.06% on average. We achieved MOS improvement of 0.03 with the proposed method, compared with the conventional method based on DSCQS (Double Stimulus Continuous Quality Scale).

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.147-154
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• 2015

In this paper, we employed a model which defines the sensitivity according to the background luminance, so called JND (Just Noticeable Difference), and applied to the video coding. The proposed method finds out the maximum possible quantization parameter for the current unit based on the threshold of JND model and reduce the bitrate with similar perceptual quality. It selects the higher quantization parameter and reduce the bitrate when the reconstructed signal which is coded with higher quantization parameter is in a range of allowance based on the JND threshold, i.e. the signal has the similar perceptual quality compared to that is coded with the initial quantization parameter. The proposed algorithm was implemented on HM16.0, which is a reference software of the latest video coding standard HEVC (High Efficiency Video Coding) and the coding performance was evaluated. Compared to HM16.0, the proposed algorithm achieved maximum 20.21% and 6.18% of average bitrate reduction with the similar perceptual quality.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.135-140
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• 2008

최근 관련 기술의 발전과 디지털 컨버전스의 가속화로 모바일 제품이 소형화, 다기능화 되어 가고 있다. 이러한 경향에 따라, 다양한 기능을 지원하기 위한 높은 사양의 디스플레이가 요구되고 있으며, 많은 업체들이 고화질, 고해상도 디스플레이의 개발에 경쟁적으로 매진하고 있다. 그러나 사용자의 인지적 특성을 고려하지 않은 고해상도 경쟁은 생산비용만 높이는 결과를 초래할 수 있다. 본 연구는 디스플레이의 설계 요소별 선호도를 분석하고, 사람이 탐지할 수 있는 두 자극 간의 최소한의 차이역(difference threshold)인 JND(Just Noticeable Difference)을 활용하여, 설계 요소의 인지적 특성을 파악하는 것을 목적으로 한다. 이를 위하여 모바일 제품에 주로 사용되는 TFT-LCD 를 평가 대상으로, 30 명의 피실험자를 대상으로 JND 측정실험을 수행하였으며, 실험결과를 바탕으로 디스플레이에 대한 주요 설계변수들의 특성을 파악하였다. 이 연구결과는 사용자의 선호도를 고려한 모바일 제품의 디스플레이 설계지침으로 활용될 수 있을 것이다.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.1
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• pp.27-35
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• 2004

A study was conducted to investigate an optimal vibration frequency for mobile phones with just noticeable difference(JND). The just noticeable difference, Weber's law, is the minimum amount by which stimulus intensity must be changed in order to produce a noticeable variation in sensory experience. In order to find the optimal vibration frequency, sixteen frequencies ranged from 24Hz to 603Hz were selected. Subjects then wereasked to differentiate a pair of vibration frequencies. For the analysis, the psychometric function to determine the optimal vibration frequency and the logistic regression to validate the determined frequency were used. The results show that the 2nd order polynomial equations were best fitted for the JND psychometric function and the optimal mobile phone vibrations were determined at 140Hz, 151 Hz, and 160Hz. With the ogive-shaped psychometric function developed by the logistic regression, the results of this study was validated that the determined vibration frequencies (140Hz, 151 Hz, and 160Hz) were optimal mobile phone vibration frequencies.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2741-2761
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• 2017

With the purpose of copyright protection for digital video, a novel H.264/AVC watermarking algorithm based on JND model is proposed. Firstly, according to the characteristics of human visual system, a new and more accurate JND model is proposed to determine watermark embedding strength by considering the luminance masking, contrast masking and spatial frequency sensitivity function. Secondly, a new embedding strategy for H.264/AVC watermarking is proposed based on an analysis on the drift error of energy distribution. We argue that more robustness can be achieved if watermarks are embedded in middle and high components of $4{\times}4$ integer DCT since these components are more stable than dc and low components when drift error occurs. Finally, according to different characteristics of middle and high components, the watermarks are embedded using different algorithms, respectively. Experimental results demonstrate that the proposed watermarking algorithm not only meets the imperceptibility and robustness requirements, but also has a high embedding capacity.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.16-22
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• 2009

In this paper, we propose an auto gain/offset which considers the visibility of human visual system (HVS) and the histogram of a target image jointly. In the proposed method, the lower and upper clipping thresholds are determined to maximize the averaged visibility of the contrast-stretched image. The target image is then contrast-stitched by the gain and offset derived from the clipping thresholds. We define the visibility as a quantity related to the spatial JND, which means the threshold below which any change of a pixel from its textured neighbors is not recognized by the HVS. Experimental results show that the contrast-stretched images by the proposed method have better global and local contrasts compared to the results by some conventional methods.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05d
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• pp.855-860
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• 2002

본 논문에서는 화질의 열화를 최소화함과 동시에 강인한 워터마크의 은닉을 위하여 멀티 웨이브릿 변환영역에서 인간 시각 특성(human visual system: HVS)을 고려한 적응 워터마크 은닉 기술을 제안한다. 멀티웨이브릿은 영상을 완전 복원시키는데 탁월한 효과가 있으며 경계영역에서 우수한 성능을 갖는다. 본 논문에서 사용한 멀티웨이브릿 함수는 근사화 차수가 2인 DHGM 멀티웨이브릿을 사용한다. 워터마크는 멀티웨이브릿 분해된 부대역들 중 저주파 영역을 제외한 중간 및 고주파 영역의 웨이브릿 계수 중에 HVS를 이용하여 얻은 문턱값에 의해 선택된 웨이브릿 계수들에만 은닉한다. 워터마크를 은닉하기 위한 지각모델은 영상 압축시 지각적 양자화기에 사용되는 정적 JND(just noticeable difference) 모델을 이용한다. 제안한 은닉모델은 영상의 특성에 따라 은닉하는 워터마크의 수가 각각 달라졌다. 또한, 여러 실험결과 우수한 비가시성과 강인성을 확인하였다.

• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.646-651
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• 1995

The correlation between the bitter taste and the surface tension was found for bitter tasting, aqueous solutions. By the Szyszkowski's equation, the surface tension (STR) and taste curves (JND) were derived more clearly using the Techplot program. The specific capillary activity (log b values) for bitter tasting solutions are negatively correlated to the recognition threshold. It was shown that a more bitter substances has greater capillary activity. The correlation between the recognition threshold $(log\;C_{1})$ and the substance specific constant (a and b values) of sensory (JND) and surface tension values indicates good agreement. This means that the model of surface area adsorption in the solution/air system can apply also for the sensory model microvillus membrane in the mouth.

• Journal of Broadcast Engineering
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• v.22 no.3
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• pp.381-396
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• 2017

In this paper, the perceptual rate control algorithm is studied for HEVC (High Efficiency Video Coding) encoder with bit allocation based on perceived visual quality. This paper proposes perceptual rate control algorithm which could consider perceived quality for HEVC encoding method. The proposed rate control algorithm employs adaptive bit allocation for frame and CTU level using the perceived visual importance of each CTU. For performance evaluation of the proposed algorithm, the proposed algorithm was implemented on HM 16.9 and tested for sequences in Class B under the CTC (Common Test Condition) RA (Random Access) case. Experimental results show that the proposed method reduces the bitrate of 3.12%, and improves BD-PSNR of 0.08dB and bitrate accuracy of 0.07% on average. And also, we achieved MOS improvement of 0.16 with the proposed method, compared with the conventional method based on DSCQS (Double Stimulus Continuous Quality Scale).

• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.649-659
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• 2021

Wall absorption treatment effectively reduces reverberation, but requires a large area for a live room and each wall absorption affects speech intelligibility differently. In this study, we try to find the most effective wall for the absorption treatment using the beamforming array microphone in terms of speech intelligibility. The absorption importance factor is defined by using the collision number of reflected sounds on each wall. It allows estimating how much the speech signal will be enhanced by the absorption treatment. A cuboid room with a size of 107 m³ and a reverberation time of 1.1 s is selected for the simulation. When a Helmholtz-type absorption is treated on the wall with the most significant importance factor, the modified clarity for 500 and 1k Hz is improved by 5.1 dB and 4.8 dB respectively, and the speech transmission index is enhanced by 0.06. The difference in results between the proposed method and commercial simulation code is less than a Just-Noticeable Difference (JND). The absorption treatment on the wall with the most significant importance factor shows improvement greater than the wall with the largest area, and its difference is larger than a JND value.