Fatma Belghith

TZSearch pattern search improvement for HEVC motion estimation modules

Motion estimation (ME) is a key operation for video compression. In fact, it contributes heavily to the compression efficiency by removing temporal redundancies. This process is the most critical part in a video encoder and can consume itself more than 50% of coding complexity or computational coding time. To reduce the computational time, many fast ME algorithms were proposed and implemented. The present paper proposes a fast ME algorithm that improves the basic Test Zone Search (TZS) ME algorithm which is considered to be one of the fastest ME algorithms and was implemented in HEVC reference software HM8.0. Experimental results show an improvement that can reach 8% up to 49% compared to the basic TZSearch.

Fast coding unit selection and motion estimation algorithm based on early detection of zero block quantified transform coefficients for high-efficiency video coding standard

High-efficiency video coding (HEVC) is the newest video coding standard developed by the joint video team, consisting of ITU-T video coding experts group and ISO/IEC Moving Picture Experts Group. The HEVC standard has aggregated an exhaustive algorithm for mode decision based on a recursive quad-tree structured coding tree block. Moreover, several specific features have been incorporated into the motion estimation (ME) process to improve its coding efficiency. However, they resulted in very high computational complexity. To accelerate the encoding process, fast mode decision algorithms for the partitioning module and also for the ME module were proposed in this study. These algorithms are based on early zero block detection technique. To improve the efficiency of these algorithms, an overall algorithm which combines the two techniques has been implemented. The performance of the proposed algorithm was checked through a comparative analysis in terms of encoding time and compression rate. Compared to HEVC test model 10.0, the authors’ proposed algorithms bring a great reduction of the HEVC complexity encoder with a saving time, which can reach 25% in average for different tested videos and a slight coding loss in terms of image quality and compression rate.

Fast motion estimation for HEVC video coding

In this paper, a fast configuration for Motion Estimation (ME) is described in order to reduce the computational time of the new High Efficient Video Coding (HEVC). This configuration uses the Coded Block Flag (CBF) Fast Method (CFM), the Early Coding Unit (CU) termination (ECU) and the Early Skip Detection (ESD) modes. The Diamond Pattern is used as a search algorithm for ME in the encoding process. Compared to the latest original reference software test model (HM) 16.2 of the HEVC, experimental results had showed that the complexity is reduced, in average, by 56.75% with a small bit-rate and PSNR degradation.

A fast coding algorithm based on fast mode decision for HEVC standard

As the new generation standard of video coding, the High Efficiency Video Coding (HEVC) is intended to provide significantly better coding efficiency than all existing video coding standards. One of his improvements is the encoding process of the structure block. It was established that this process requires high computing power because it is performed using all the possible depth levels and prediction modes to find the one with the least rate distortion (RD) cost using Lagrange multiplier. To reduce the computational complexity, fast coding unit size decision algorithms were proposed and implemented in HM. These algorithms can significantly reduce computational complexity while maintaining almost the same performance as the original HEVC encoder.

Fast intra-prediction algorithms for high efficiency video coding standard

Abstract. High efficiency video coding (HEVC) is the latest video compression standard that provides significant performance improvement on the compression ratio compared to all existing video coding standards. The intra-prediction procedure plays an important role in the HEVC encoder, and it is being achieved by providing up to 35 intra-modes with a larger coding unit requiring a high computational complexity that needs to be alleviated. Toward this end, the paper proposes two fast intra-mode decision algorithms that exploit the features of video sequences. First, an early detection of zero transform and quantified coefficients method is applied to generate threshold values employed for early termination of the intra-decision process and hence accelerates the encoding procedure. Another fast intra-mode decision algorithm is elaborated that relies on a refinement technique. Based on statistical analyses of frequently chosen modes, only a small part of the candidate modes is chosen for intra-prediction process, which reduces the complexity of the intra-encoding procedure. The performance of the proposed algorithms is verified through comparative analysis of encoding time, visual image quality, and compression ratio. Compared to HM 10.0, the encoding time reduction can reach 69% with only a slight degradation of image quality and compression ratio.

A fast CU Partitionning algorithm based on early detection of zero block quantified transform coefficients for HEVC standard

In this paper, a fast Coding Unit (CU) partitioning algorithm is proposed to reduce encoding time of HEVC test model (HM). HEVC is the new generation video codec which improves the coding efficiency significantly and provides more than 50% bit rate reduction while maintaining the same image quality compared to its predecessor H.264/AVC. Different sizes of CUs are adopted during encoding which makes the encoding process time consuming. To reduce this computational complexity, a fast CU partitioning method is proposed based on early zero block detection technique. The performance of the proposed algorithm is verified through comparative analysis of encoding time and rate compression. Comparing to HM 10, our method saves the encoding time from 2% to 56% for different test videos with negligible coding loss.

Free multiplication integer transformation for the HEVC standard

This paper presents an optimized algorithm to compute the 4×4, 8×8 and 16×16 efficient one-dimensional (1-D) transform. The suggested algorithm is based on fast integer transform algorithms for the HEVC standard. Based on the similarity in the transform matrix operations and the symmetric properties, the efficient fast 1-D algorithms are developed. The developed architecture is designed only with adders and shifters. Therefore, the computational complexities of the proposed algorithm are smaller than those of the direct method while keeping similar quality.

Low-complexity algorithm using DCT approximation for POST-HEVC standard

Under development by the Joint Collaborative Team on Video Coding (JCT-VC), the recent standardization proposal beyond HEVC known as POST-HEVC (or Future Video Coding FVC) proposition was designated to improve the coding efficiency compared to the HEVC. In order to respond to users’ requests for high quality videos in 4k and 8k, this standard is planned to cover a wide range of multimedia applications. When compared with its predecessor, the postHEVC standard should be capable of providing a bit rate reduction of approximately 30% at the same subjective quality given by HEVC. However, this efficiency comes with additional complexity which shall be taken into consideration. In fact, FVC encoders should be capable of trading off complexity and coding efficiency in order to meet real-time requirements or non-real-time requirements when an important coding efficiency is achieved. More specifically, the increased complexity cognized per the transform module should be reconsidered. This complexity can be seen on the introduction of a new approach called Adaptive Multiple Transform (AMT) involving five different transformation types from DCT/DST family for sizes ranging from 4x4 to 128x128. This can be a real issue since the majority of image and video transmission and processing applications are subject to real-time constraints. Hence, to meet these requirements, a large amount of effort has been devoted to eliminate multiplication operations in order to insure low-complexity transform. In this context, the approximation technique can provide eloquent estimations at low-complexity requirements. The contributions of this method can be mainly seen on the reduction of the device utilization and power consumption in addition to lower computational complexity. This gain comes from the elimination of multiplications which require a great number of logical resources. Furthermore, it has been demonstrated in the literature that some approximation transforms can decrease dramatically the hardware resources with slight degradation of the video quality. Accordingly, the approximation technique seems to be an efficient solution offering an adequate compromise between precision and complexity. This work benefits from the DCT-II approximations evoked in previous works in order to minimize the computation time of the transform module as well as its complexity. This idea comes after a statistical analysis done on 4k videos for different quantization parameters which shows that the DCT-II utilization can reach 60% of the total of possible transformation types. In the last version of the paper, we will provide extensive statistical studies on the compressed bitstream. Then, we will use that to detect bottlenecks of the transformations in order to specify the computation elements that should be optimized and approximate.

Statistical analysis of Post-HEVC encoded videos

The Post-HEVC is the emerging video coding standard beyond the High Efficiency Video Coding (HEVC) standard. It is more complex in transformation and prediction steps but it offers the opportunity of 3D and 360° videos coding and compression. This paper presents different statistical analyzes of Post-HEVC encoded videos especially analysis on 1D and 2D transformation types and analysis on intra and inter prediction types of some test videos for different classes and resolutions. Analyzes are carried out at the decoder level where the coding decision has already been taken by the encoder. Results show that the choice of transformation (type and size) and the prediction type (intra or inter) depends on the nature of video: motion and texture. This work can be considered as a milestone for proposing intelligent algorithms based on video characteristics to perform fast decision in the Post-HEVC encoding process.

Adaptive motion estimation search window size for HEVC standard

Recently standardized by the Joint Video Team (JVT) of ITU-T Video Coding Experts Group (VCEG) and ISO/IEC Moving Picture Experts Group (MPEG), the High Efficiency Video Coding (HEVC) was adopted to replace the H264/AVC with better compression performance that facilitates video transmission and storage while maintaining the same reconstructed video quality. This excellent coding efficiency is performed through an exhaustive algorithm for mode decision that requires a huge computational complexity. To accelerate the encoding process, fast motion estimation (ME) algorithms are proposed in this paper. Firstly, according to statistical results of the motion vector difference prediction distribution, an adaptive search range selection algorithm based on a depth level is presented. In addition, several motion estimation search patterns were designed to reduce the calculation redundancy of motion estimation process. Experimental results show that the proposed algorithm schemes can save the ME time up to 88% while upholding almost the same rate-distortion performances.