Browsing by Author "Correa, Guilherme"
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- Classification-based early termination for coding tree structure decision in HEVCPublication . Correa, Guilherme; Assunção, Pedro; Cruz, Luis A. da Silva; Agostini, LucianoThe High Efficiency Video Coding (HEVC) standard provides improved compression rates in comparison to its predecessors at the cost of large increases in computational complexity. An important share of such increases is due to the introduction of flexible Coding Tree structures, which best configuration is decided through exhaustive tests in a Rate-Distortion Optimization (RDO) scheme. In this work, an early termination method for the decision of such structures was designed using classification trees obtained through Data Mining techniques. The classification trees were trained using intermediate encoding results from a training set of video sequences and implemented in the encoder to skip the full RDO-based decision. An average reduction of 37% in the HEVC encoder computational complexity was achieved when using the designed classification trees, with a negligible cost of only 0.28% in terms of Bjontegaard Delta-rate increase.
- Computational Resource Management for Video Coding in Mobile EnvironmentsPublication . Correa, Guilherme; Assunção, Pedro; Agostini, Luciano; Cruz, Luis A. da SilvaThe increase of computational resources in mobile devices and the availability of reliable communication infrastructures provide support for acquisition, display, coding/decoding and transmission of high-resolution video in a broad set of equipment such as tablets and smartphones. Nevertheless, real-time video encoding and decoding is still a challenge in such computing environments, especially when considering the amount of computational resources required by state-of-the-art video coding standards. Moreover, battery technologies did not evolve as much as desired, which makes power consumption minimization an important issue for the mobile devices industry and users. Therefore, in current mobile systems, the available computational resources along with battery-life are responsible for imposing significant limitations on mobile real-time multimedia communications. This chapter presents an overview of the state-of-the-art research on management of computational resources for video encoding systems in mobile communications equipment. A review on computational complexity analysis of both H.264/AVC and HEVC video coding standards is presented, followed by a description of current methods for modelling, reducing and controlling the expenditure of computational resources on these video codecs. Finally, future trends on computational complexity management for video codecs implemented on power-constrained devices are lined out.
- Fast coding tree structure decision for HEVC based on classification treesPublication . Correa, Guilherme; Assunção, Pedro; Agostini, Luciano; Cruz, Luis A. da SilvaThe High Efficiency Video Coding (HEVC) standard provides improved compression rates in comparison to its predecessors at the cost of large increases in computational complexity. An important share of such increases is due to the introduction of flexible Coding Tree structures, which best configuration is decided through exhaustive tests in a rate-distortion optimization (RDO) scheme. In this work, an early termination method for the decision of such structures was designed using classification trees obtained through Data Mining techniques. The classification trees were trained using intermediate encoding results from a set of video sequences and implemented in the encoder to avoid the full RDO-based decision. An average reduction of 37 % in the HEVC encoder computational complexity was achieved when using the designed classification trees, with a negligible cost of only 0.28 % in terms of Bjontegaard Delta-rate increase.
- Fast HEVC Encoding Decisions Using Data MiningPublication . Correa, Guilherme; Assunção, Pedro; Agostini, Luciano Volcan; Cruz, Luis A. da SilvaThe High Efficiency Video Coding standard provides improved compression ratio in comparison with its predecessors at the cost of large increases in the encoding computational complexity. An important share of this increase is due to the new flexible partitioning structures, namely the coding trees, the prediction units, and the residual quadtrees, with the best configurations decided through an exhaustive rate-distortion optimization (RDO) process. In this paper, we propose a set of procedures for deciding whether the partition structure optimization algorithm should be terminated early or run to the end of an exhaustive search for the best configuration. The proposed schemes are based on decision trees obtained through data mining techniques. By extracting intermediate data, such as encoding variables from a training set of video sequences, three sets of decision trees are built and implemented to avoid running the RDO algorithm to its full extent. When separately implemented, these schemes achieve average computational complexity reductions (CCRs) of up to 50% at a negligible cost of 0.56% in terms of Bjontegaard Delta (BD) rate increase. When the schemes are jointly implemented, an average CCR of up to 65% is achieved, with a small BD-rate increase of 1.36%. Extensive experiments and comparisons with similar works demonstrate that the proposed early termination schemes achieve the best rate-distortion-complexity tradeoffs among all the compared works.
- Four-step algorithm for early termination in HEVC inter-frame prediction based on decision treesPublication . Correa, Guilherme; Assunção, Pedro; Agostini, Luciano; Cruz, Luis A. da SilvaThe flexible encoding structures of High Efficiency Video Coding (HEVC) are the main responsible for the improvements of the standard in terms of compression efficiency in comparison to its predecessors. However, the flexibility provided by these structures is accompanied by high levels of computational complexity, since more options are considered in a Rate-Distortion (R-D) optimization scheme. In this paper, we propose a four-step early-termination method, which decides whether the inter mode decision should be halted without testing all possibilities. The method employs a set of decision trees, which are trained offline once, using information from unconstrained HEVC encoding runs. The resulting trees present a mode decision accuracy ranging from 97.6% to 99.4% with a negligible computational overhead. The method is capable of achieving an average computational complexity decrease of 49% at the cost of a very small Bjontegaard Delta (BD)-rate increase (0.58%).
- Pareto-Based Method for High Efficiency Video Coding With Limited Encoding TimePublication . Correa, Guilherme; Assunção, Pedro; Agostini, Luciano Volcan; Cruz, Luis A. da SilvaSeveral different methods have been investigated in recent years, aiming at computational complexity reduction and scaling of High Efficiency Video Coding (HEVC) software implementations. However, maintaining the encoding time per frame or group of pictures (GOPs) below an adjustable upper bound is still an open research issue. A solution for this problem is devised in this paper based on a set of Pareto-efficient encoding configurations, identified through rate-distortion-complexity analysis. The proposed method combines a medium-granularity encoding time control with a fine-granularity encoding time control to accurately limit the HEVC encoding time below a predefined target for each GOP. It is shown that the encoding time can be kept below a desired target for a wide range of encoding time reductions, e.g., up to 90% in comparison with the original encoder. The results also show that compression efficiency loss (Bjøntegaard delta-rate) varies from negligible (0.16%) to moderate (9.83%) in the extreme case of 90% computational complexity reduction.