• Title/Summary/Keyword: Intra-picture coding

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Reduction Method of Added Information Generated by Increasing the Number of Quantizer Reconstruction Levels (양자화 복원 레벨 개수 증대로 발생되는 부가정보 감소방법)

  • Wu, Ya-Lin;Kwon, Soon-Kak;Kwon, Oh-Jun
    • Journal of Korea Multimedia Society
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    • v.13 no.8
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    • pp.1154-1162
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    • 2010
  • Because it is easy to implement the scalar quantizer, it is used in various video coding systems. Although the scalar quantizer with a large quantization stepsize can reduce the amount of data, it has disadvantage that the reconstructed picture quality is poor. In this paper, we propose an efficient method which improves the coding performance by maintaining original quantization stepsize and increasing the number of quantization reconstruction levels. Simultaneously, for the purpose of solving the problem of transmitting the added symbol informations which is used to indicate the region of quantizer reconstruction level as the number of quantizer reconstruction level is increased, we also suggest the method to reduce the added informations. Therefore, for the intra-coded picture of H.264 video coding system, we generate the huffman codes for the symbol informations of quantization reconstruction regions by 4${\times}$4(horizontal 4 pixels, vertical pixels) block unit. Furthermore, for the inter-coded picture, we also generate the huffman codes for the symbol informations of quantization reconstruction regions by 8${\times}$8 blocks and 4${\times}$4 blocks within a macroblock. Adopting this method of reducing the added information by increasing the number of quantization reconstruction region, It is shown that the coding performance can be improved at the same bitrate.

A New Data Partitioning of DCT Coefficients for Error-resilient Transmission of Video (비디오의 에러내성 전송을 위한 DCT 계수의 새로운 분할 기법)

  • Roh, Kyu-Chan;Kim, Jae-Kyoon
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.39 no.6
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    • pp.585-590
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    • 2002
  • In the typical data partitioning for error-resilient video coding, motion and macroblock header information is separated from the texture information. It can be an effective tool for the transmission of video over the error prone environment. For Intra-coded frames, however, the loss of DCT (discrete cosine transform) coefficients is fatal because there is no ther information to reconstruct the corrupted macroblocks by errors. For Inter-coded frames, when error occurs in DCT coefficients, the picture quality is degraded because all DCT coefficients are discarded in those packets. In this paper, we propose an efficient data partitioning and coding method for DCT-based error-resilient video. The quantized DCT coefficients are partitioned into the even-value approximation and the remainder parts. It is shown that the proposed algorithm provides a better quality of the high priority part than the conventional methods.

Error Concealment Method Based on POCS for Multi-layered Video Coding (다계층 비디오 코딩에 적용 가능한 POCS 기반 에러 은닉 기법)

  • Yun, Byoung-Ju
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.46 no.4
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    • pp.67-75
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    • 2009
  • Multi-layered video coding that provides scalability across the visual content has emerged for easily adaptive service over current heterogeneous network. However, the network is still error prone environment so that video service may suffer packet loss or erroneous decoding of the video. Especially distortion caused by the burst error may propagate to several pictures until intra refreshing, which will raise a terrific degradation of picture quality. To overcome the problem at terminal independently, we propose a new error concealment algorithm for the multi-layered video coding. The proposed method uses the similarity of between layers in the multi-layered video coding and POCS (Projections Onto Convex Sets) which is a powerful error concealment tool, but heavily dependent on initial values. To find adequate initial value which can reduce iteration times as well as achieve high performance, we took consideration into both features of layered approach coding and the correlation in neighbor blocks. The simulation results show that the proposed concealment method works well.

Adaptive Reference Structure Decision Method for HEVC Encoder (HEVC 부호화기의 적응적 참조 구조 변경 방법)

  • Mok, Jung-Soo;Kim, JaeRyun;Ahn, Yong-Jo;Sim, Donggyu
    • Journal of Broadcast Engineering
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    • v.22 no.1
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    • pp.1-14
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    • 2017
  • This paper proposes adaptive reference structure decision method to improve the performance of HEVC (High Efficiency Video Coding) encoder. When an event occurs in the input sequence, such as scene change, scene rotation, fade in/out, or light on/off, the proposed algorithm changes the reference structure to improve the inter prediction performance. The proposed algorithm divides GOP (Group Of Pictures) into two sub-groups based on the picture that has such event and decides the reference pictures in the divided sub-groups. Also, this paper proposes fast encoding method which changes the picture type of first encoded picture in the GOP that has such event to CRA (Clean Random Access). With the statistical feature that intra prediction is selected by high probability for the first encoded picture in the GOP carrying such event, the proposed fast encoding method does not operate inter prediction. The experimental result shows that the proposed adaptive reference structure decision method improves the BD-rate 0.3% and reduces encoding time 4.9% on average under the CTC (Common Test Condition) for standardization. In addition, the proposed reference structure decision method with the picture type change reduces the average encoding time 12.2% with 0.11% BD-rate loss.

A Rate Control Algorithm of MPEG-2 Video Encoding Based Target Bit Matching at Scene Changes (장면전환 발생시 예상 비트 조정을 통한 MPEG-2 비디오 부호화 비트율 제어 알고리즘)

  • Moon Ho-seok;Park Sang-sung;Sohn Myung-ho;Jang Dong-sik
    • Journal of KIISE:Software and Applications
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    • v.31 no.12
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    • pp.1621-1627
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    • 2004
  • The decrease of visual quality at scene change occurs when the difference between the amount of target bits and actual coding is high. Especially, scene change at the P-Picture can lead to severely degrade visual qualities at itself and the pictures referencing it. In this paper, under the occurrence of scene change, we propose a new method, based on the analysis of existing inaccurate bits allocation, to improve the visual qualities of scene-changed and following pictures. The method allocates extra bits to scene-changed Picture and changes them upto the level of the complexity of intra picture. Also, the method changes target bits of following pictures upto the complexity of picture prior to the scene change. Computer simulation shows that the proposed method has improved 0.5-1.2dB higher than TM5 method in terms of PSNR.

Temporal Directmode for B Picture in H.264 / MPEG-4 AVC (H.264 / MPEG-4 AVC에서의 B 픽쳐를 위한 시간적 다이렉트 모드)

  • 전병문
    • Journal of Broadcast Engineering
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    • v.7 no.4
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    • pp.300-309
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    • 2002
  • The object of this paper is to make temporal direct mode clear by providing a solution to the following problem : if the co-located block in the list 1 reference picture for direct mode has only the 1ist 1 motion vector or both the 1ist 0 and list 1 motion vectors, then which motion vector will be used for the direct mode motion vector calculation\ulcorner This paper also shows how to derive reference picture index and direct mode motion vector for each list in order to guarantee the high coding efficiency. when the co-located macroblock is in intra mode. Furthermore, the reasonable calculation methods for the direct mode motion vectors in the various cases are presented. Finally, experimental results show that the proposed temporal direct mode provides the comparable performance against the spatial direct mode. Therefore, the simulation proves that the proposed temporal direct mode is acceptable.

Enhanced intra prediction mode decision method for VVC (VVC 부호화기의 화면내 부호화 모드 결정 개선 방법)

  • Yun, ByungJin;Gwon, Daehyeok;Choe, JaeRyun;Choi, Haechul
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2019.11a
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    • pp.191-193
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    • 2019
  • ISO/IEC JTC1 WG11 Moving Picture Expers Group 과 ITU-T SC16 은 Joint Video Experts Team 을 구성하여 차세대 비디오 부호화 표준으로서 Versatile Video Coding(VVC)를 표준화 중이다. VVC 는 현재 블록의 화면내 예측 모드일 가능성이 높은 모드의 집합인 Most Probable Mode(MPM) 리스트를 유도하고, MPM 을 이용하여 효율적으로 화면내 예측 모드를 부호화한다. VVC 참조 소프트웨어는 주변 블록의 화면내 예측 모드가 일치하는지 여부에 따라 1 개 또는 2 개의 모드를 최종 후보 선택을 위한 과정인 Rate-Distortion Optimization(RDO) 과정에 추가한다. 하지만 현재 MPM 은 항상 첫 번째 후보로 Planar 모드가 위치하며 이로 인하여, 주변 블록의 화면내 예측 모드가 RDO 에 추가되지 않는 경우가 존재한다. 따라서 본 논문은 VVC 의 부호화기에서 주변 블록의 화면내 예측 모드가 고려되지 않는 경우가 존재하는 문제를 해결하기 위한 방법을 제안한다. 제안 방법은 MPM 유도 과정에서 RDO 에 포함할 후보의 개수를 수정하여 RDO 과정에 항상 주변 블록의 화면내 예측 모드가 추가되도록 한다. 본 논문은 실험을 통해 제안 방법이 약 0.04%의 부호화 효율을 향상시켰음을 보인다.

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Effective segmentation of non-rigid object in a still picture and video sequences (정지영상/동영상에서 non-rigid object의 효율적인 영역 분할 방식에 관한 연구)

  • Lee, In-Jae;Kim, Yong-Ho;Kim, Jung-Gyu;Lee, Myeong-Ho;An, Chi-Deuk
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.39 no.1
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    • pp.17-31
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    • 2002
  • The new MPEG-4 video coding standard enables content-based functionalities. Image segmentation is an indispensable process for it. This paper addresses an effective segmentation of non-rigid objects. Non-rigid objects are deformable objects with fuzzy, blurred and indefinite boundaries. So it is difficult to segment deformable objects precisely. In order to solve this problem, we propose an effective segmentation of non-rigid objects using watershed algorithms in still pictures. And we propose an automatic segmentation through intra-frame and inter-frame segmentation process in video sequences. Automatic segmentation preforms boundary-based and region-based segmentation to extract precise object boundaries.

Study on Image Distortions and Bit-rate Changes Induced by Watermark based-on $4{\times}4$ DCT of H.264/AVC (H.264/AVC의 $4{\times}4$ DCT기반 워터마크에 따른 영상왜곡과 비트율 변화에 대한 연구)

  • Kim, Sung-Min;Won, Chee-Sun
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.42 no.5 s.305
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    • pp.115-122
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    • 2005
  • There are some problems in directly applying the conventional MPEG bit-stream based watermarking schemes to the bit-stream of a new compression standard, H.264/AVC. In this paper we analyze the effects of the conventional DCT-based watermarking scheme to H.264/AVC, especially in terms of image distortions and bit-rate changes. It turns out that the intra-frame prediction md CAVLC of H.264/AVC with the watermarking worsen the image distortions and bit-rate changes. The experiment results show on average 28.17dB decrease in PSNR and 56.71% increase in bit-rate over all QPs.