• Title/Summary/Keyword: DC 영상

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DC Offset Adjusted Inter Prediction Algorithm for Improving H.264/AVC Video Coding Efficiency (H.264/AVC 동영상 압축율 향상을 위한 DC 오프셋 보정에 기반한 인터 예측 알고리즘)

  • Yoon, Dae-Il;Kim, Hae-Kwang
    • Journal of Broadcast Engineering
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    • v.16 no.5
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    • pp.793-796
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    • 2011
  • H.264/AVC compresses video data by applying DCT transform, quantization and entropy coding processes to the residual signal obtained by inter/intra prediction. This paper proposes a method enhancing an existing DC offset adjustment technology which uses information of neighboring blocks to reduce residual information for improving coding efficiency. DC offset information is not sent over bitstreams, but calculated in the same way both in the decoder and in the encoder. Experimental results show that the proposed method enhances coding efficiency by 0.25% in average BD-Rate compared to H.264/AVC and gives better or worse coding efficiency compared to the existing DC offset method depending on video sequences with coding efficiency degradation by 0.09% in average BD-Rate. This experimental results also show that further coding efficiency improvement is possible by applying the proposed method adaptively to slice or macroblock coding units.

Design of Multiple-symbol Lookup Table for Fast Thumbnail Generation in Compressed Domain (압축영역에서 빠른 축소 영상 추출을 위한 다중부호 룩업테이블 설계)

  • Yoon, Ja-Cheon;Sull, Sanghoon
    • Journal of Broadcast Engineering
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    • v.10 no.3
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    • pp.413-421
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    • 2005
  • As the population of HDTV is growing, among many useful features of modern set top boxes (STBs) or digital video recorders (DVRs), video browsing, visual bookmark, and picture-in-picture capabilities are very frequently required. These features typically employ reduced-size versions of video frames, or thumbnail images. Most thumbnail generation approaches generate DC images directly from a compressed video stream. A discrete cosine transform (DCT) coefficient for which the frequency is zero in both dimensions in a compressed block is called a DC coefficient and is simply used to construct a DC image. If a block has been encoded with field DCT, a few AC coefficients are needed to generate the DC image in addition to a DC coefficient. However, the bit length of a codeword coded with variable length coding (VLC) cannot be determined until the previous VLC codeword has been decoded, thus it is required that all codewords should be fully decoded regardless of their necessary for DC image generation. In this paper, we propose a method especially for fast DC image generation from an I-frame using multiple-symbol lookup table (mLUT). The experimental results show that the method using the mLUT improves the performance greatly by reducing LUT count by 50$\%$.

Multiresolution Watermarking Scheme on DC Image in DCT Compressed Domain (DCT 압축영역에서의 DC 영상 기반 다해상도 워터마킹 기법)

  • Kim, Jung-Youn;Nam, Je-Ho
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.45 no.4
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    • pp.1-9
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    • 2008
  • This paper presents a rapid watermarking algorithm based on DC image, which provides a resilience to geometric distortion. Our proposed scheme is based on $8{\times}8$ block DCT that is widely used in image/video compression techniques (e.g., JPEG and MPEG). In particular, a DC image is analyzed by DWT to embed a watermark. To overcome a quality degradation caused by a watermark insertion into DC components, we discern carefully the intensity and amount of watermark along the different subbands of DWT. Note that the proposed technique supports a high throughput for a real-time watermark insertion and extraction by relying on a partial decoding (i.e., DC components) on $8{\times}8$ block DCT domain. Experimental result shows that the proposed watermarking scheme significantly reduces computation time of 82% compared with existing DC component based algorithm and yet provides invariant properties against various attacks such as geometric distortion and JPEG compression, etc.

Face Detection and Recognition in MPEG Compressed Video (MPEG 압축 비디오 상에서의 얼굴 영역 추출 및 인식)

  • 여창욱;황본우;이성환
    • Proceedings of the Korean Information Science Society Conference
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    • 1998.10c
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    • pp.452-454
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    • 1998
  • 본 논문에서는 MPEG 압축 비디오 상에서 얼굴 영역을 추출하고 이를 인식하는 방법에 대하여 제안한다. 제안된 방법은 크게 MPEG 압축 비디오의 처리를 위한 축소된 DC 영상의 구성 단계, 축소된 DC 영상에서의 얼굴 영역 추출 단계, 그리고 얼굴 영역이 추출된 프레임에 대한 압축 복원 및 얼굴 인식의 3단계로 구성되어있다. DC 영상의 구성 단계에서는 압축 복원 없이 DCT 계수의 DC 값과 2개의 AC 값만을 사용하여 부분적인 2차원 역 DCT 변환을 이용한 방법을 사용하였으며, 얼굴 영역 추출 단계에서는 DC 영상에 대해 얼굴의 색상 및 형태 정보를 이용한 얼굴 후보 영역 추출 방법과 K-L 변환 및 역 변환의 오차에 의한 얼굴 영역 추출 방법을 사용하였다. 얼굴 인식 단계에서는 얼굴 영역이 추출된 프레임에 대하여 GOP 단위의 압축 복원을 수행한 후 고유 얼굴 영상을 이용한 방법으로 얼굴 인식을 수행하였다. 제안된 방법의 성능을 검증하기 위하여 뉴스와 드라마 MPEG 비디오를 대상으로 실험을 수행하였으며, 실험 결과 제안된 방법이 효율적임을 알 수 있었다.

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Face Detection and Recognition in MPEG Compressed Video (MPEG 압축 비디오 상에서의 얼굴 영역 추출 및 인식)

  • 여창욱;유명현
    • Korean Journal of Cognitive Science
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    • v.11 no.2
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    • pp.79-87
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    • 2000
  • In this paper we present a face recognition and face detection algorithm in MPEG compressed video. The proposed method consists three stage of processing steps. The first step is to produce a spatially reduced DC image form MPEG compressed video for processing. And the second step is face detection on reduced DC image. Finally, the last step is face recognition on partially extracted compressed frames which contain the detected faces. The spatially reduced DC image is produced from two dimensional inverse DCT of the DC coefficient and the first two AC coefficients. The face detection is performed on DC image and face recognition is performed on one extracted frame per GOP by using the K-L transform. In order to evaluate the proposed method, we carried out experiments on video database. The experiment results show the proposed method is very efficient and helpful for target tasks.

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Image Retrieval Using Edge-based Variable Block DC (에지 기반 가변 블록 DC를 이용한 영상 검색)

  • 김동우;서은주;장언동;안재형
    • Proceedings of the Korea Multimedia Society Conference
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    • 2002.05c
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    • pp.268-271
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    • 2002
  • 현재 우리가 접하는 영상은 모양, 색상, 질감 등의 성분을 이용한 검색 방법이 필요하다. 이중 질감 특성을 고려한 DC 영상 검색 기법은 구현이 간단하고 검색이 빠른 장점이 있다. 특히 블록을 가변으로 하였을 경우 검색 속도와 정확성을 효율적으로 높일 수 있다. 그러나 기존의 방법은 가변 블록을 하기 위하여 단순히 이진 영상을 가지고 객체 유무를 판단하므로 객체 영역 판단의 정확성이 낮아지고, 계산량이 많아지는 단점이 있다. 이러한 문제점을 해결하기 위해 객체 영역 판단에 에지를 이용하는 방법을 제안한다. 제안한 방법의 경우 객체 영역 판단의 정확성을 높이고 계산량을 줄일 수 있다.

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A Statistical Approache to Scene Change Detection using Motion Compensation in MPEG (움직임 보상을 이용한 MPEG 비디오의 통계적 장면전환검출)

  • Jang, Dong-Sik;Kwon, Do-Kyoung;Lee, Man-Hee
    • Journal of KIISE:Computing Practices and Letters
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    • v.7 no.5
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    • pp.440-450
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    • 2001
  • This paper discusses an effective algorithm which is proposed for abrupt scene change detection in MPEG bitstream. The proposed algorithm restores DC images by decoding only DC coefficients and estimates the new motion vectors between adjacent DC images and detects scene change by similarity measure between frames. The proposed algorithm calculates similarity measure between adjacent frames, i.e motion compensated inter-frame correlation, and detects scene change by comparing this similarity measure with threshold value independent of sequences. Experimental results show that the proposed algorithm has more than 90% \`recall\` and \`precision\` in almost sequences and these results can be considered better than other algorithms using threshold value dependent of sequences.

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Scene Change Detection and Key Frame Selection Using Fast Feature Extraction in the MPEG-Compressed Domain (MPEG 압축 영상에서의 고속 특징 요소 추출을 이용한 장면 전환 검출과 키 프레임 선택)

  • 송병철;김명준;나종범
    • Journal of Broadcast Engineering
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    • v.4 no.2
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    • pp.155-163
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    • 1999
  • In this paper, we propose novel scene change detection and key frame selection techniques, which use two feature images, i.e., DC and edge images, extracted directly from MPEG compressed video. For fast edge image extraction. we suggest to utilize 5 lower AC coefficients of each DCT. Based on this scheme, we present another edge image extraction technique using AC prediction. Although the former is superior to the latter in terms of visual quality, both methods all can extract important edge features well. Simulation results indicate that scene changes such as cut. fades, and dissolves can be correctly detected by using the edge energy diagram obtained from edge images and histograms from DC images. In addition. we find that our edge images are comparable to those obtained in the spatial domain while keeping much lower computational cost. And based on HVS, a key frame of each scene can also be selected. In comparison with an existing method using optical flow. our scheme can select semantic key frames because we only use the above edge and DC images.

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Improved Reconstruction Algorithm for Spiral Scan Fast MR Imaging with DC offset Correction (DC offset을 보정한 나선 주사 초고속 자기공명영상의 재구성 알고리즘)

  • 안창범;김휴정
    • Journal of Biomedical Engineering Research
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    • v.19 no.3
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    • pp.243-250
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    • 1998
  • Reconstruction aspects of spiral scan imaging for ultra fast magnetic resonance imagine(MRI) have been investigated with polar and rectangular coordinates-based reconstruction. For the reconstruction of the spiral scan imaging, acquired data in spiral trjectory should be converted to polar or rectangular grids, where interpolation techniques are used. Various reconstruction algorithms for spiral scan imaging are tested, and reconstructed image qualities are compared with computed phantom. An improved reconstruction algorithm with dc-offset correction in projection domain is proposed, which provides the best reconstructed image quality from the simulation. Image artifact with existing algorithms is completely removed with the proposed method.

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Neural Network을 이용한 동영상 장면전환 검출

  • 조승현;장동식
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 2000.04a
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    • pp.554-557
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    • 2000
  • 이 논문은 MPEG 비디오 스트림에서 급격하거나 점진적인 장면전환을 검출하는 효과적인 방법을 제안하고 있다. 이 방법에서는 MPEG 압축 영역에서 DC계수를 통해 DC 영상을 복원한 다음 이전 영상과의 그레이레벨 값과의 차이를 구하여 평균값을 가지고 있고 현재 프레임의 그레이 레벨값과 비교하여 임계값이상의 차이가 나면 장면전환이 이루어졌다는 것을 검출하는 알고리즘이다. 을 이용하여 임계값을 구하여 실시간으로 적용함으로 높은 적중률을 가질 수 있게 된다. DC계수는 MPEG에서 가장 많은 정보를 포함하고 있으므로 속도 상승을 위해 AC계수의 값을 계산하지 않는다. 실험결과 고정 임계값을 적용한 다른 방법보다 높은 적중률을 나타났다.

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