An efficient biprediction decision scheme of high efficiency video coding (HEVC) is proposed for fast-encoding applications. For low-delay video applications, bidirectional prediction can be used to increase compression performance efficiently with previous reference frames. However, at the same time, the computational complexity of the HEVC encoder is significantly increased due to the additional biprediction search. Although a some research has attempted to reduce this complexity, whether the prediction is strongly related to both motion complexity and prediction modes in a coding unit has not yet been investigated. A method that avoids most compression-inefficient search points is proposed so that the computational complexity of the motion estimation process can be dramatically decreased. To determine if biprediction is critical, the proposed method exploits the stochastic correlation of the context of prediction units (PUs): the direction of a PU and the accuracy of a motion vector. Through experimental results, the proposed method showed that the time complexity of biprediction can be reduced to 30% on average, outperforming existing methods in view of encoding time, number of function calls, and memory access.
MPEG has produced standards that have provided the industry with the best video compression technologies. In order to address the diversified needs of the Internet, MPEG issued the Call for Proposals (CfP) for internet video coding in July, 2011. It is anticipated that any patent declaration associated with the Baseline Profile of this standard will indicate that the patent owner is prepared to grant a free of charge license to an unrestricted number of applicants on a worldwide, non-discriminatory basis and under other reasonable terms and conditions to make, use, and sell implementations of the Baseline Profile of this standard in accordance with the ITU-T/ITU-R/ISO/IEC Common Patent Policy. Three different codecs had responded to the CfP, which are WVC, VCB and IVC. WVC was proposed jointly by Apple, Cisco, Fraunhofer HHI, Magnum Semiconductor, Polycom and RIM etc. it’s in fact AVC baseline. VCB was proposed by Google, and it’s in fact VP8. IVC was proposed by several Universities (Peking University, Tsinghua University, Zhejiang University, Hanyang University and Korea Aerospace University etc.) and its coding tools was developed from Zero. In this paper, we give an overview of the coding tools in IVC, and evaluate its performance by comparing it with WVC, VCB and AVC High Profile.
A data reuse-based fast subpixel motion estimation (SME) method for high efficiency video coding (HEVC) is proposed. Since SME is one of the most computation-intensive tools in the encoder process, conventional research on SME focused on the reduction of the computational complexity. The applied data-reuse architecture for the design of fast SME substantially reduces computational complexity at the cost of a reasonable increase in memory bandwidth. The core of the proposed data-reuse method is the replacement of redundant computations in SME with the memory access operations of previously computed values. The proposed method was tested in the latest video coding standard, HEVC, with experimental results showing a reduction in operational complexity of ∼64.14%, and a reduction in encoding time of ∼56.13%, compared to the SME in the HEVC reference encoder.
A fast coding unit (CU) decision method is proposed for high efficiency video coding (HEVC) by determining early the CU sizes based on coding tree pruning. One of the most effective, a newly introduced concept in HEVC, is variable CU size. In determining the best CU size, the reference encoder of the HEVC tests every possible CU size in order to estimate the coding performance of each CU defined by the CU size. This causes major computational complexity within the encoding process, which should be overcome for the implementation of a fast encoder. A simple tree-pruning algorithm is proposed that exploits the observation where the subtree computations can be skipped if the coding mode of the current node is sufficient (e.g., SKIP mode). The experimental results show that the proposed method was able to achieve a 40% reduction in encoding time compared to the HEVC test model 3.0 encoder with only a negligible loss in coding performance. The proposed method was adopted in HEVC test model 4.0 encoder at JCT-VC 6th meeting.
In this paper, we propose a fast intramode decision method in MPEG-4 AVC/H.264 based on the intraprediction cost. The rate-distortion function in MPEG-4 AVC/H.264 exhaustively computes the distortion and bit rate of every mode type, which results in high computational complexity. The target of a good, fast mode decision method is to reduce computational complexity with minimal loss of rate-distortion performance. The proposed algorithm is based on prediction cost estimation using the variances of input pixels and those of residual values to determine the minimal number of mode types for a given macroblock. The test results show that the total encoding time is reduced by 77.4%, on average, compared to that of the JM 13.2 reference encoder.
AVC/H.264 supports the use of multiple reference frames (e.g., 5 frames in AVC/H.264) for motion estimation (ME), which demands a huge computational complexity in ME. We propose an adaptive search range adjustment scheme to reduce the computational complexity of ME by reducing the search range of each reference frame-from the (t-1)'th frame to the (t-5)'th frame-for each macroblock. Based on the statistical analysis that the 16×16 mode type is dominantly selected rather than the other block partition mode types, the proposed method reduces the search range of the remaining ME process in the given reference frame according to the motion vector (MV) position of the 16×16 block ME. In the case of the (t-1)'th frame, the MV position of the 8×8 block ME-in addition to that of 16×16 block ME-is also used for the search range reduction to sub-block partition mode types of the 8×8 block. The experimental results show that the proposed method reduces about 50% and 65% of the total encoding time over CIF/SIF and full HD test sequences, respectively, without any noticeable visual degradation, compared to the full search method of the AVC/H.264 encoder.
The best performance in compression efficiency is provided by MPEG-4 AVC/H.264 but at the cost of high computational complexity to select the best mode during the mode decision process. To reduce this complexity, we propose a fast mode decision algorithm that exploits the spatiotemporal correlation of the macroblock (MB) modes and the rate-distortion (RD) costs from the previous and current frames. The proposed method determines the candidate modes for the current MB based on the modes of the four spatially neighboring and temporally collocated MBs. It also incorporates the RD costs of the four reference MBs and the current MB. The experimental results show that the AVC/H.264 encoder using our proposed method achieves about 73% speedup (up to 86.5%) compared to the AVC/H.264 JM 11.0 encoder while preserving a 0.25% increment in total encoding bits with a loss of only 0.09 dB in peak SNR.
KEYWORDS: Computer programming, 3D modeling, Solid modeling, Visualization, Computer simulations, Iterated function systems, Surgery, Visual compression, Digital electronics, Data communications
In MPEG-4, 3D mesh coding (3DMC) achieves 40:1 to 50:1 compression ratio over 3-D meshes (in VRML IndexedFaceSet representation) without noticeable visual degradation. This substantial gain comes not for free: it changes the vertex and face permutation order of the original 3-D mesh model. This vertex and face permutation order change may cause a serious problem for animation, editing operation, and special effects, where the original permutation order information is critical not only to the mesh representation, but also to the related tools. To fix this problem, we need to transmit the vertex and face permutation order information additionally. This additional transmission causes the unexpected increase of the bitstream size. In this paper, we proposed a novel vertex and face permutation order compression algorithm to address the vertex and face permutation order change by the 3DMC encoding with the minimal increase of side information. Our proposed vertex and face permutation order coding method is based on the adaptive probability model, which makes allocating one fewer bits codeword to each vertex and face permutation order in every distinguishable unit as encoding proceeds. Additionally to the adaptive probability model, we further increased the coding efficiency of the proposed method by representing and encoding each vertex and face permutation order per connected component (CC). Simulation results demonstrated that the proposed algorithm can encode the vertex and face permutation order losslessly while making up to 12% bit-saving compared with the logarithmic representation based on the fixed probability model.
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