• 대한전자공학회논문지
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• 제25권4호
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• pp.447-452
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• 1988

This paper proposes a hybrid image coding in order to improve the coding performance by combining the BTC with the DPCM. And utilizing the human perceptual characteristics, a new objective image quality evaluation method has been proposed to obtain an excellent result in good agreement with the subjective quality evaluation. A hyb-1 method consisting of the DPCM and the AMBTC has retained a good picture quality at the bit rate of 1.5 bits/pel. A hyb-3 method combining the EBTC-3 with the DPCM has scarcely degraded the picture quality compared with the original image at the bit rate of 2.1 bits/pel. A newly proposed mehtod of picture quality evaluation accumulating a blocky noise at the edge block and an impulsive noise at the flat block selectively has been coincident with the subjective evaluation of quality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권1호
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• pp.379-394
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• 2012

The ever-increasing demand for H.264 scalable video coding (H.264/SVC) distribution motivates researchers to devise ways to enhance the quality of video delivered on the Internet. Furthermore, researchers and practitioners in general depend on computer simulators to analyze or evaluate their designed network architecture or proposed protocols. Therefore, a complete toolset, which is called myEvalSVC, for evaluating the delivered quality of H.264/SVC transmissions in a simulated environment is proposed to help the network and video coding research communities. The toolset is based on the H.264 Scalable Video coding streaming Evaluation Framework (SVEF) and extended to connect to the NS2 simulator. With this combination, people who work on video coding can simulate the effects of a more realistic network on video sequences resulting from their coding schemes, while people who work on network technology can evaluate the impact of real video streams on the proposed network architecture or protocols. To demonstrate the usefulness of the proposed new toolset, examples of H.264/SVC transmissions over 802.11 and 802.11e are provided.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권9호
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• pp.3672-3684
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• 2015

Recently, the standardization of backward compatible JPEG image coding for high dynamic range (HDR) image has been undertaken to establish an international standard called "JPEG XT." The JPEG XT consists of two layers: the base layer and the residual layer. The base layer contains tone mapped low dynamic range (LDR) image data and the residual layer contains the error signal used to reconstruct the HDR image. This paper gives the result of a study to evaluate the overall performance of tone mapping operators (TMOs) for this standard. The evaluation is performed using five HDR image datasets and six TMOs for profiles A, B, and C of the proposed JPEG XT standard. The Tone Mapped image Quality Index (TMQI) and no reference image quality assessment (NR IQA) are used for measuring the LDR image quality. The peak signal to noise ratio (PSNR) is used to evaluate the overall compression performance of JPEG XT profiles A, B, and C. In TMQI and NR IQA measurements, TMOs using display adaptive tone mapping and adaptive logarithmic mapping each gave good results. A TMO using adaptive logarithmic mapping gave good PSNRs.

• 전자공학회논문지B
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• 제29B권11호
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• pp.93-101
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• 1992

HVS based transform coding techniques for still images take the lowest spatial frequency and luminance contrast sensitivity as the most crucial factors in determining the image quality perceived by human eye. Only the frequency weighting has been main issue. The proposed Weighted Discrete Cosine Transform (WDCT) has the lowest frequency of about 4 [cyc/deg] in 8$\times$8 subblock with the contrast-weighted DC coefficient. The error criteria have been rederived to adapt the contrast weighting for performance evaluation. The proposed scheme has produced higher quality images compared to the unweighted and other schemes.

• 한국통신학회논문지
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• 제38C권8호
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• pp.651-662
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• 2013

본 연구에서는 적용대상체계에 적합한 시큐어 코딩룰을 선정 평가하기 위한 방안으로, 적용대상 체계의 특성에 따른 체계적용적합성(개발언어적합성, 플랫폼적합성), 위협평가(침해의 심각성, 침해의 가능성), 적용기대효과(신뢰성/품질향상, 수정 비용) 등을 종합적으로 고려한 시큐어 코딩룰의 선정 평가 방안을 제시하였다. 이를 활용하여, 전장관리정보체계의 체계 특성에 부합하는 197개의 시큐어 코딩룰을 선정하였다. 또한 선정된 각 코딩룰 별로 대상 체계에 대한 적용을 위한 우선 순위를 산정하였다.

• 대한음성학회지:말소리
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• 제61호
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• pp.75-86
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• 2007

In this paper, we propose a scalable audio coder, which has a variable bandwidth from the narrowband speech bandwidth to the audio bandwidth and also has a bit-rate from 8 to 320 kbits/s, in order to cope with the quality of service(QoS) according to the network load. First of all, the proposed scalable coder splits bandwidth of the input audio into narrowband up to around 4 kHz and above. Next, the narrowband signals are compressed by a speech coding method compatible to an existing standard speech coder such as G.729, and the other signals whose bandwidth is above the narrowband are compressed on the basis of a psychoacoustic model. It is shown from the objective quality tests using the signal-to-noise ratio(SNR) and the perceptual evaluation of audio quality(PEAQ) that the proposed scalable audio coder provides a comparable quality to the MPEG-1 Layer III (MP3) audio coder.

• 전자공학회논문지B
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• 제33B권4호
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• pp.156-163
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• 1996

In this paper, we described the implementation and the sound quality assessment of a real-time stereo audio codec using TMS320C40 DSP (digital signal processing) chip for low bitrte and high quality audio. We implemented hardware and software in order to overcome a real-time processing problem of audio compression algorithm that can be produced by largely recursive computing and complexity of the process. We have studied five types of distortion that can be produced by perceptual coding and the codec was evaluated by eight test musics that are selected in SQAM (sound quality assessment material) 422-2-4-2 produced by EBU (european broadcast union). The subjective listening tests were carried out on the codec quality and preformance by double blind method in a listening room with eleven listeners. As a result, 5 grade-impairment scale was scored under minus one and the codec quality was evaluated to be perceptible, but not annoying.

• 음성과학
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• 제10권4호
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• pp.137-147
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• 2003

Speech synthesis can classify by synthesis way, that is waveform coding, source coding and mixture coding. Specially, waveform coding is suitable for high quality synthesis. However, it is not desirable by synthesis techniques of syllable or phoneme unit because it do not separate and handles excitation and formant part. Therefore, there is a need for pitch alteration method applied in synthesis by the rule in waveform coding. This study propose about pitch alteration method that use spectrum scaling after do to flatten spectra by subband linear approximation to minimize spectrum distortion. This paper show evaluation whether show excellency of some measure compared with LPC, Cepstrum, lifter function and method that propose. estimation method seeks distribution of each flattened signal and measured degree of flattened spectra Signal flattened is normalized, So that highest point amounts to zero, and distribution of signal ,whose average is zero, is calculated. this show result that measure the spectrum distortion rate to estimate performance of method that propose. The average spectrum distortion rate was kept below the average 2.12%, so the method that propose is superiors than existent method.

• 한국컴퓨터정보학회논문지
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• 제11권4호
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• pp.197-206
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• 2006

정지 영상 압축 표준인 JPEG2000의 가장 큰 특징 중의 하나는 관심영역(ROI) 코딩이다. JPEG2000은 다양한 ROI 기법과 ROI 파리미터를 제공하는데, 이것을 특정 응용 프로그램에 적용하기 위해서는 적절한 값을 선택해야 한다. 본 논문에서는 JPEG2000 성능에 영향을 미치는 ROI 코딩 기법과 ROI 파라미터가 ROI 품질과 전체 영상 품질에 어떤 영향을 미치는지를 평가한다. 평가에 사용된 ROI 기법은 Maxshift 방법과 Implicit 방법이며 평가된 파라미터는 타일 크기와 ROI 크기, 코드블록의 크기, DWT 분해 레벨의 수, ROI 중요도가 사용된다. 타일 크기가 크면 품질은 좋아지며, ROI가 크면 품질은 떨어지며, 코드블록은 Maxshit와 Implicit 모두에서 $32{\times}32$가 최고의 품질을 보이며, ROI 중요도가 커지면 품질은 떨어지고, 분해 레벨의 수가 증가할수록 품질은 떨어진다.

• 한국IT서비스학회지
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• 제19권1호
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• pp.71-87
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• 2020

As diverse online information services are introduced and the use of them are increasing, the importance of the quality control over the online information services is also increasing. Therefore, studies are being attempted to derive quality evaluation models for online information services, but these showed many limitations. In order to overcome the limitations of the previous studies and create more appropriate quality evaluation model, this study analyzed 408 data collected through the interviews with the users of Korea national online information services (NDSL, NTIS) using content analysis and the coding method of ground theory. Through the analysis, we identified the quality evaluation model (13 elements, 6 dimensions) of online information services and the description and insights of each elements. And the priorities of the most significant element(amount of information) and other key elements(such as the usefulness of the information, the diversity of the field, etc.) were figured out through the frequency analysis. Through these inductive methods based on the responses of users, the quality control model could be derived, which is different from the previous researches. This study is the first study which derived the quality evaluation model of online information service through the inductive way based on 408 interview responses from users. Therefore, the results of this study will be helpful to the post researchers who conduct studies on the quality of online information service, etc. Moreover, the results of this study are expected to provide references of frame for decision-making of working-level officials who have to manage the quality of online information services.