• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11C
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• pp.1098-1107
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• 2005

The emerging H.264/AVC video coding standard improves coding performance significantly by adopting many advanced techniques. This is achieved at the expense of great increasing encoder complexity. Specifically the intra prediction using RDO examines all possible combinations of coding modes, which depend on spatial directional correlation with adjacent blocks. For 4${\times}$4 luma blocks, there are 9 modes, and for 16${\times}$16 luma and 8${\times}$8 chroma blocks, there are 4 modes, respectively. Therefore the number of mode combinations for each macroblock is 592. This paper presents a method to reduce the RDO complexity using simple directional masks and neighboring modes. According to the proposed method, we reduce the number of mode combinations to 132 at the most. Experimental results show the proposed method reduces the encoding time up to $70\%$ with negligible loss of PSNR and bitrate increase compared to the H.264/AVC exhaustive search.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8C
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• pp.591-597
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• 2008

In this paper, we present a improved rate distortion optimization (RDO) for H.264 intra coding. By using new mode decision criteria pass for $I4{\times}4$ in company with the original RDO, the proposed method can achieve the better coding efficiency comparing with the original RDO. Our experimental results show that the proposed algorithm can archive about $0.64{\sim}1.6578%$ bit rate decrease at the same PSNR and $0.049{\sim}0.101dB$ PSNR increase at the same bit rate.

• Journal of Broadcast Engineering
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• v.13 no.3
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• pp.310-318
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• 2008

The H.264/AVC standard achieves higher coding efficiency than previous video coding standards with the rate-distortion optimization (RDO) technique which selects the best coding mode and reference frame for each macroblock. As a result, the complexity of the encoder have been significantly increased. In this paper, a fast intra-mode decision algorithm is proposed to reduce the computational load of intra-mode search, which is based on the inverse tree-structure edge prediction algorithm. First, we obtained the dominant edge for each $4{\times}4$ block from local edge information, then the RDO process is only performed by the mode which corresponds to dominant edge direction. Then, for the $8{\times}8$ (or $16{\times}16$) block stage, the dominant edge is calculated from its four $4{\times}4$ (or $16{\times}16$) blocks' dominant edges without additional calculation and the RDO process is also performed by the mode which is related to dominant edge direction. Experimental results show that proposed scheme can significantly improve the speed of the intra prediction with a negligible loss in the peak signal to noise ratio (PSNR) and a little increase of bits.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.34-44
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• 2008

In this paper, a new rate-distortion estimation method is proposed for fast rate-distortion optimized(RDO) mode decision in H.264 encoder. A bit-rate and distortion should be calculated by encoding and reconstruction of each macroblock mode in order to select the optimal RDO mode. To reduce the computations for getting them, a bit-rate and distortion is efficiently estimated in DCT domain. Simulation results show that the proposed method achieves computational saving about 81% of RDO mode decision and saves about 26% of total encoding time without noticeable degradation in coding performance.

• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.446-451
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• 2010

This paper addressed an another scheme of distortion estimation method based on simplified inverse quantization in H.264/AVC. The distortion is calculated by the difference of coefficient between quantized transform coefficients and that of inverse. In general, these process included such transforms as discrete cosine transform(DCT), quantization, inverse quantization(IQ), and Inverse DCT(IDCT). In proposed approach, IQ as well as IDCT process are skipped because of replacing a couple of approximated formulas. Some simulation have been conducted and it showed that the PSNR was almost the same, and reduced the rate-distortion optimization(RDO) mode decision time of 8~15% in comparison with conventional method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.81-82
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• 2017

본 논문에서는 PSNR 을 높이도록 최적화된 HEVC 의 율-왜곡 최적화(RDO)를 MS-SSIM 를 높이도록 하여 RDO 를 수행 하도록 한다. 구현 방법으로는 MS-SSIM 도출 방법과 비슷하도록 원본과 4 단계의 저역 통과 필터(LPF)를 통과한 결과에 대한 DCT(Discrete Cosine Transform) 를 수행하고 그 AC 계수의 비율로 lagrange multiplier(${\lambda}$)를 수정하는 방식이다. AC 계수 비율과 MS-SSIM 에서 도출 된 가중치, LPF 특성 등에 따라 새롭게 각 스케일의 가중치를 결정하여 최종적으로 ${\lambda}$ 가중치를 결정하여 그 결과를 바탕으로 RDO 를 수행한다. 시뮬레이션을 통해 제안의 방법과 HEVC reference software 의 BD-rate 계산 결과 7%의 PNSR, -13.2%의 MS-SSIM 를 얻을 수 있었고 이에 따라 주관적 화질을 개선했다고 할 수 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.81-84
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• 2021

In this paper, a rate-distortion optimization (RDO) model is proposed to find the joint bit allocation of geometry data and color data based on geometry-based point cloud compression (G-PCC) of Moving Picture Experts Group (MPEG). The mechanism of the method is to construct the RD models for geometry and color data through the training process. Afterward, two rate-distortion (RD) models are integrated as well as the decision of the parameter λ to obtain the final RDO model. The experimental results show that the proposed method can decrease 20% of the geometry Bjøntegaard delta bit rate and increase 37% of the color Bjøntegaard delta bit rate compared to the MPEG G-PCC TMC13v12.0 software.

• Journal of Broadcast Engineering
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• v.21 no.3
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• pp.341-348
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• 2016

HEVC is the next compression standard and is expected to be used widely replacing the conventional H.264/AVC standard. The compression ratio of the HEVC is twice times than H.264/AVC, whereas its computational complexity is increased by up to 40%. Many research efforts have been made to reduce the computational complexity and to speed up encoding. For intra coding, the rough mode decision (RMD) is commonly applied. The rate-distortion optimization (RDO) process to decide the best mode is too complex so that RMD chooses the candidate modes with a simple process and sends the candidates to RDO process. However, for large-size blocks, the RMD also requires considerable computations. In this paper, a down-sampling scheme is proposed for the RMD process. The reference pixel loading, predicted pixel generation are performed using the down-sampled pixel data. When the proposed scheme is applied to the RMD, the computational complexity is reduced by 70% with a marginal bitrate increase of 0.04%. In terms of area of hardware-based RMD, the gate count and the buffer size is reduced 33% and 66%, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.2
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• pp.435-449
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• 2023

The state-of-the-art video-based point cloud compression(V-PCC) has a high efficiency of compressing 3D point cloud by projecting points onto 2D images. These images are then padded and compressed by High-Efficiency Video Coding(HEVC). Pixels in padded 2D images are classified into three groups including origin pixels, padded pixels and unoccupied pixels. Origin pixels are generated from projection of 3D point cloud. Padded pixels and unoccupied pixels are generated by copying values from origin pixels during image padding. For padded pixels, they are reconstructed to 3D space during geometry reconstruction as well as origin pixels. For unoccupied pixels, they are not reconstructed. The rate distortion optimization(RDO) used in HEVC is mainly aimed at keeping the balance between video distortion and video bitrates. However, traditional RDO is unreliable for padded pixels and unoccupied pixels, which leads to significant waste of bits in geometry reconstruction. In this paper, we propose a new RDO scheme which takes 3D-Distortion into account instead of traditional video distortion for padded pixels and unoccupied pixels. Firstly, these pixels are classified based on the occupancy map. Secondly, different strategies are applied to these pixels to calculate their 3D-Distortions. Finally, the obtained 3D-Distortions replace the sum square error(SSE) during the full RDO process in intra prediction and inter prediction. The proposed method is applied to geometry frames. Experimental results show that the proposed algorithm achieves an average of 31.41% and 6.14% bitrate saving for D1 metric in Random Access setting and All Intra setting on geometry videos compared with V-PCC anchor.