• 자연과학논문집
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• 제8권2호
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• pp.77-82
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• 1996

영상을 텍스처와 같은 성질의 영역으로 세그멘트 함으로써 새로운 very low bit rate 세그멘테이션 영상코딩 기술을 제안한다. 영역은 Human Visual System(HVS) 과 프락탈 특성을 이용하여 3 가지의 다른 텍스처 크래스(인간이 인지한 상 인텐셔티 (크라스 I), 부드러운 텍스처 (크라스 II) 및 거칠은 텍스처 (크리스 III) 중 1 가지로 구분한다. Very low bit rate 영상코더를 설계하기 위해 각각의 텍스처 크라스에 대해 nonoverlap과 overlap 세그멘테이션 방법을 결정하는 것이 중요하다. 좋은 화질을 갖는 재생영상은 여러 종류의 영상에 대해서 약 0.10에서 0.21비트/피셀에서 얻는다.

• The Journal of the Acoustical Society of Korea
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• 제15권2E호
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• pp.85-91
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• 1996

New very low bit rate segmentation video image coding technique is proposed by segmenting image into textually homogeneous regions. Regions are classified into one of three perceptually distinct texture classes(perceived constant intensity, smooth texture, and rough texture) using the Human Visual System(HVS) and the fractals. To design very low bit rate video image coder, it is very important to determine the best block size for estimation the fractal dimension and the thresholding of the fractal dimension for each texture class. Good quality reconstructed images are obtained with about 0.10 to 0.21 bit per pixel(bpp) for many different types of imagery.

• 정보와 통신
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• 제11권8호
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• pp.60-77
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• 1994

This paper presents a survey of video coding schemes which use wavelet transform for the videophone on very low bit rate commun ication chan nel( ego 10 Kbps Public Service Telephone Network). Firstly, we introduce the standardization efforts to make the low bit rate videophone architecture and the typical application of low bit rate video coding scheme. Secondly, we summarize the several requirements on videophone, delay, encoder/decoder complexity, low bitrate, and progressive transmission capability. Third, we review the basic theory of wavelet transform without much mathematics. We compare the wavelet transform with short-time fourier transform and subband filters. Fourth, we summarize the video coding schemes proposed so far, and evaluate them with Ule requirements. Lastly, we conclude with fu¬ture research directions.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.45-48
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• 2003

In general, speech coding methods are classified into the following three categories: the waveform coding, the source coding and the hybrid coding. Fast speaking is possible to encode with a few information compared with slow speaking rate. In case of speaking rate, low frequency band is more important than high frequency band while listening. Speech vocoding technique is developing to way with low bit rate and complexity and high sound quality. the CELP type of vocoder support very good sound quality with low bit rate but these vocoders don't consider about the speaking rate. When we consider speaking rate and encode the frame depending on the speaking rate, the bit rate is able to reduce the bit rate than the conventional vocoder. We propose the technique to estimate the speaking rate and applied PSOLA technique in case of the frame of slow speaking rate. As a result of simulation bit rate can be reduced about 300 bps.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1996년도 학술대회
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• pp.175-180
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• 1996

In this paper, a new image segmentation method based on merging of two low contrast neighbor regions iteratively is proposed. It is suitable for very low bit rate coding. The proposed method reduces efficiently contour information and preserves subjective and objective image quality. It consists of image segmentation using 4-level hierarchical structure based on mathematical morphology and 1-level region merging structure using the contrast difference of two adjacent neighbor regions. For each segmented region of the third level, two adjacent neighbor regions having low contrast difference value in fourth level based on contrast difference value is merged iteratively. It preserves image quality and shows the noticeable reduction of the contour information, so that it can improve the bottleneck problem of segmentation-based coding at very low bit rate.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.349-350
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• 2006

This paper presents very low bit rate speech coder, ZFE-CELP(ZINC Function Excitation-Code Excited Linear Prediction). The ZFE-CELP speech codec is based on a ZINC function and CELP modeling of the excitation signal respectively according to the frame characteristic such as a voiced speech and an unvoiced speech. And this paper suggest strategies to improve the speech quality of the very low bit rate speech coder.

• 한국정보처리학회논문지
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• 제4권10호
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• pp.2629-2639
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• 1997

최근 초저속 전송 매체용 비디오 코딩 기법에 대한 관심이 높아지고 있다. 그러나 기존의 블럭을 기반으로 하는 변환 코딩기법들은 비트율 제한으로 인해 블럭화 현상 등으로 화질 열화가 심하다. 본 논문에서는 초저속 전송 매체를 위하여 웨이브릿 변환과 다중해상도 움직임 추정 및 보상 기법을 이용하는 비디오 코딩 시스템을 제안한다. 제안된 시스템은 non-stationary 신호를 적응적으로 표현하며, 인간 시각 특성을 잘 반영하는 웨이브릿 변환을 사용한다. 웨이브릿 변환된 계수들은 움직임 추정 및 보상 후 예측 오차의 크기에 따라서 다양한 모드로 코딩된다. 이와 함께 일정한 화질을 유지하기 위하여 간단한 버퍼 제어 기법을 사용한다. 실험을 통하여 제안된 기법은 블럭화 현상이 줄어들며, 기존의 블럭을 기반으로 하는 변환 코딩 기법보다 복원 영상의 화질이 좋음을 보였다.

• 한국통신학회논문지
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• 제21권5호
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• pp.1132-1140
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• 1996

In video coding systems, an effective rate control method is one of the most improtant issues for the good video quality. This paper presents an adaptive rate control scheme based on the buffer fullness, quantization, and buffer utilization for very low bit rate communication lines, such as 16kbit/s, 24bit/s, and so on. The strategy is implemented on H.263, whichis a vide coding algorithm for narrow band telecommunication channels up to 64kbit/s recommended by ITU-T SG15, to show the effectiveness. The simulation result shows that the suggested rate control scheme has better SNR performance and buffer utilization of source coder than those of linear and non-linear[9] buffer control strategies.

• 한국통신학회논문지
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• 제21권4호
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• pp.822-833
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• 1996

The video coding for very low bit rate has recently received considerable attention, but conventional block based transform coding schemes suffer from the blocking effect for the constraints of bit rates. In this paper, we present a video coding sysem suing multi-resolution motion estimation/compensation with variable size block(VMRME/C) and multi-resolution vector quantization(MRVQ) in wavelet transform domain for very low bit rate coding. It is shown that the presented scheme has better performance in the peak signal-to-nose ratio(RSNR) by 0.2-0.6 dB as well as subjective quality than that of conventional block based transform video coding techniques(especially, H. 263 which is DCT based video coding).

• 한국통신학회논문지
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• 제25권3B호
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• pp.529-540
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• 2000

본 논문에서는 비트율이 매우 한정된 응용에 적용되는 초저속 동영상 부호화 표준인 H.236plus에 기반한 의미기반 율-제어 기법을 제안한다. 기존의 율-제어 기법들은 의미기반이 아닌 단순히 프레임에 대해 매크로 블록 단위로 최적의 양자화 파라미터를 설정해 정해진 비트율을 조정하나, 본 논문에서는 부호화 효율을 높이기 위해 의미 영역인식 및 우선권 부여를 통해 영역별로 최적의 양자화 파라미터를 설정함으로써 제약된 비트 내에서 주관적인 화질의 향상을 보이는 기법을 제안한다. 제안하고자하는 기법의 핵심은 부호화 시 배경에 해당하는 영역에 배정되는 비트량을 할당해 전경(얼굴) 영역에 비트 자원을 더 많이 배정함으로써 주관적인 화질을 보호, 개선하기 위한 것이다.