Intra-prediction Mode Research Articles

The Video Encryption Algorithm for H.264 Based on Hyper Chaotic System

In this paper, pseudo-random sequences are designed as encrypting secret keys by the hyper-chaotic system model. Based on the H.264 coding standard, selecting encryption is designed to encrypt intra-prediction modes, MVD symbols and CAVLC residual coding datum. Experiments show that the encryption algorithm has higher security without changing the structure of code streams.

Effective CU size decision for HEVC intracoding.

In high efficiency video coding (HEVC), the tree structured coding unit (CU) is adopted to allow recursive splitting into four equally sized blocks. At each depth level (or CU size), it enables up to 35 intraprediction modes, including a planar mode, a dc mode, and 33 directional modes. The intraprediction via exhaustive mode search exploited in the test model of HEVC (HM) effectively improves coding efficiency, but results in a very high computational complexity. In this paper, a fast CU size decision algorithm for HEVC intracoding is proposed to speed up the process by reducing the number of candidate CU sizes required to be checked for each treeblock. The novelty of the proposed algorithm lies in the following two aspects: 1) an early determination of CU size decision with adaptive thresholds is developed based on the texture homogeneity and 2) a novel bypass strategy for intraprediction on large CU size is proposed based on the combination of texture property and coding information from neighboring coded CUs. Experimental results show that the proposed effective CU size decision algorithm achieves a computational complexity reduction up to 67%, while incurring only 0.06-dB loss on peak signal-to-noise ratio or 1.08% increase on bit rate compared with that of the original coding in HM.

Fast intra-encoding algorithm for High Efficiency Video Coding

The emerging High Efficiency Video Coding (HEVC) standard provides equivalent subjective quality with about 50% bit rate reduction compared to the H.264/AVC High profile. However, the improvement of coding efficiency is obtained at the expense of increased computational complexity. This paper presents a fast intra-encoding algorithm for HEVC, which is composed of the following four techniques. Firstly, an early termination technique for coding unit (CU) depth decision is proposed based on the depth of neighboring CUs and the comparison results of rate distortion (RD) costs between the parent CU and part of its child CUs. Secondly, the correlation of intra-prediction modes between neighboring PUs is exploited to accelerate the intra-prediction mode decision for HEVC intra-coding and the impact of the number of mode candidates after the rough mode decision (RMD) process in HM is studied in our work. Thirdly, the TU depth range is restricted based on the probability of each TU depth and one redundant process is removed in the TU depth selection process based on the analysis of the HEVC reference software. Finally, the probability of each case for the intra-transform skip mode is studied to accelerate the intra-transform skip mode decision. Experimental results show that the proposed algorithm can provide about 50% time savings with only 0.5% BD-rate loss on average when compared to HM 11.0 for the Main profile all-intra-configuration. Parts of these techniques have been adopted into the HEVC reference software.

Complexity scalable intra‐prediction mode decision algorithm for mobile video applications

© The Institution of Engineering and Technology 2014. The full search scheme employed in H.264/AVC significantly improves the coding performance, but it also introduces a very high computational complexity which limits the applications in resource-constrained mobile devices. In this study, the authors firstly present a discretisation total variation and orientation gradient-based hierarchical intra-prediction mode decision method for mobile video applications. By shrinking the candidate mode set in the rate-distortion optimisation (RDO) process, the proposed algorithm reduces the computational complexity and power consumption of the encoder. Furthermore, they extend the hierarchical algorithm to a complexity scalable version in which the coding complexity is measured on five levels by reserving various numbers of modes for RDO. Experimental results demonstrate that the proposed mode decision algorithm reduces the coding complexity significantly with negligible performance degradation and the proposed complexity scalable algorithm is effective and efficient for mobile video application.

A New Fast Algorithm for Intra Prediction Mode Selection in the High Efficiency Video Coding (HEVC) Standard

In order to meet the trend and consumer demands for video information, the ISO/IEC group and ITU-T video encoding expert group have cooperated in making the new video encoding standard of HEVC. It defines 35 Intra prediction modes and thus has a very high encoding complexity. In order to reduce this complexity, this paper has proposed a new algorithm to effectively reduce the number of the candidate mode which needs to be checked. The edge detection and Hough transform are utilized for the prediction unit (PU) with different sizes. Statistical analysis is utilized for the detected edge line angles to decide the candidate modes that need to be checked. The C++ and OpenCV language have been utilized for the implementation of the proposed algorithm. The proposed algorithm can reduce the encoding time by 43.72 percent at most and 17.06 percent at least with just little increase of the code rate and small decrease of the PSNR.

Efficient parallel HEVC intra‐prediction on many‐core processor

High-efficiency video coding (HEVC) is the state-of-the-art video coding standard, which adopts more complicated and time-consuming intra-prediction (IP) modes. Many-core processors are good candidates for speeding up HEVC IP in the case that HEVC IP can provide sufficient parallelism. Proposed is an efficient parallel framework for HEVC IP. Experiments show that the proposed method dramatically accelerates more than the state-of-the-art parallel method.

An efficient motion reference structure based selective encryption algorithm for H.264 videos

In this study, based on both the prediction mechanism of H.264 encoder and the syntax of H.264 bitstream, an efficient selective video encryption algorithm is proposed. The contributions of the study include two aspects. First, motion reference ratio (MRR) of macroblock (MB) is proposed to describe the inter-frame dependency among the adjacent frames. At the MB layer, MRRs of MBs are statistically analysed, and MBs to be encrypted are selected based on the statistical results. Second, at the bitstream layer of MBs, bit-sensitivity is proposed to represent the degree of importance of each bit in the compressed bitstream for reconstructed video quality. The most significant bits for reconstructed video quality are selected to be encrypted based on the bit-sensitivity of H.264 bitstream. The intra-prediction mode codewords, the sign bits of the non-zero coefficients and the info_suffix of motion vector difference codewords are extracted to be encrypted. The proposed two-layer selection scheme improves the encryption efficiency significantly. Experimental results demonstrate that both perceptual security and cryptographic security are achieved, and compared with the existing SEH264 algorithm, the proposed selective encryption algorithm can reduce the computational complexity by 50% on average.

Implementation and Optimization of 4×4 Luminance Intra Prediction Modes on FPGA

Implementation and Optimization of 4×4 Luminance Intra Prediction Modes on FPGA

Data-Parallelism Based Hardware Architecture for the Intra-Coding Module Used in the H.264/AVC Encoder

In this paper, we propose a hardware architecture for the intra-coding module used in the H.264 encoder. The proposed architecture is based on data-parallelism principles, with a 128-bit data input. This data input is retrieved from a DDR2 memory using an intelligent memory controller specially designed for the H.264 encoder. Unlike other architectures using different intra-prediction modes in parallel, we propose to implement the different modes in series to avoid an excessive use of FPGA resources. This also provides the ability to process data in parallel. In this manner, we can ensure a pipelined architecture to reduce the required number of clock cycles to process each macroblock. Data-Parallelism based hardware architectures are proposed for the intra-prediction, the integer transform, the quantization, the inverse integer transform, the inverse quantization, and the mode decision modules. Results and performance measurements of the intra-coding module were validated on the Xilinx Virtex5-ML501 platform. The proposed architecture occupies 18 % of the FPGA’s resources and operates at a maximum frequency of 155MHz.

Data Hiding in Encrypted H.264/AVC Video Streams by Codeword Substitution

Digital video sometimes needs to be stored and processed in an encrypted format to maintain security and privacy. For the purpose of content notation and/or tampering detection, it is necessary to perform data hiding in these encrypted videos. In this way, data hiding in encrypted domain without decryption preserves the confidentiality of the content. In addition, it is more efficient without decryption followed by data hiding and re-encryption. In this paper, a novel scheme of data hiding directly in the encrypted version of H.264/AVC video stream is proposed, which includes the following three parts, i.e., H.264/AVC video encryption, data embedding, and data extraction. By analyzing the property of H.264/AVC codec, the codewords of intraprediction modes, the codewords of motion vector differences, and the codewords of residual coefficients are encrypted with stream ciphers. Then, a data hider may embed additional data in the encrypted domain by using codeword substitution technique, without knowing the original video content. In order to adapt to different application scenarios, data extraction can be done either in the encrypted domain or in the decrypted domain. Furthermore, video file size is strictly preserved even after encryption and data embedding. Experimental results have demonstrated the feasibility and efficiency of the proposed scheme.

An Improved Fast Mode Decision Method for H.264/AVC Intracoding

An improved fast and efficient mode decision method for H.264/AVC intracoding is proposed, which is based on the analysis of the gravity center method and more efficient mode selection. In contrast to the fast mode decision method where the intramodes are determined by the gravity center of the block, the mass center vector is computed for the block and the subblocks formed by the proposed subsampling techniques. This method is able to determine all correlation directions of the block that correspond to the intraprediction mode directions of the H.264/AVC. On this basis, only a small number of intraprediction modes are chosen as the best modes for rate-distortion optimization (RDO) calculation. Different video sequences are used to test the performance of the proposed method. Experimental results reveal the significant computational savings achieved with slight peak signal-to-noise ratio (PSNR) degradation and bit-rate increase.

Fast mode decision for 3D-HEVC depth intracoding.

The emerging international standard of high efficiency video coding based 3D video coding (3D-HEVC) is a successor to multiview video coding (MVC). In 3D-HEVC depth intracoding, depth modeling mode (DMM) and high efficiency video coding (HEVC) intraprediction mode are both employed to select the best coding mode for each coding unit (CU). This technique achieves the highest possible coding efficiency, but it results in extremely large encoding time which obstructs the 3D-HEVC from practical application. In this paper, a fast mode decision algorithm based on the correlation between texture video and depth map is proposed to reduce 3D-HEVC depth intracoding computational complexity. Since the texture video and its associated depth map represent the same scene, there is a high correlation among the prediction mode from texture video and depth map. Therefore, we can skip some specific depth intraprediction modes rarely used in related texture CU. Experimental results show that the proposed algorithm can significantly reduce computational complexity of 3D-HEVC depth intracoding while maintaining coding efficiency.

新一代视频编码帧内预测模式选择的优化

新一代视频编码帧内预测模式选择的优化

Rate-Distortion Optimized Transforms Based on the Lloyd-Type Algorithm for Intra Block Coding

The directional intra prediction (IP) in H.264/AVC and HEVC tends to cause the residue to be anisotropic. To transform the IP residue, Mode Dependent Directional Transform (MDDT) based on Karhunen Loeve transform (KLT) can achieve better energy compaction than DCT, with one transform assigned to each prediction mode. However, due to the data variation, different residue blocks with the same IP mode may not have the same statistical properties. Instead of constraining one transform for each IP mode, in this paper, we propose a novel rate-distortion optimized transform (RDOT) scheme which allows a set of specially trained transforms to be available to all modes, and each block can choose its preferred transform to minimize the rate-distortion (RD) cost. We define a cost function which is an estimate of the true RD cost and use the Lloyd-type algorithm (a sequence of transform optimization and data reclassification alternately) to find the optimal set of transforms. The proposed RDOT scheme is implemented in HM9.0 software of HEVC. Experimental results suggest that RDOT effectively achieves 1.6% BD-Rate reduction under the Intra Main condition and 1.6% BD-Rate reduction under the Intra High Efficiency (HE) 10bit condition.

Fast Intra-Coding for H.264/AVC by Using Projection-Based Predicted Block Residuals

An efficient intra-prediction mode decision mechanism for H.264/AVC is presented in this research. A projection-based approach, which employs the reconstructed surrounding pixels and block content to compute the predicted block residuals (PBR), can effectively eliminate less probable modes from the computation of Rate Distortion Optimization. Both the projected vectors and corresponding predictors can be formed by shifting/adding the related data so the proposed scheme is suitable for hardware implementation. According to the PBR and coding information acquired during the encoding process, some prediction modes can also be skipped to further accelerate the intra coding. The experimental results show that the proposed scheme can effectively reduce the encoding time with slight video quality degradation and bit-rate increment.

Steganalysis of prediction mode modulated data-hiding algorithms in H.264/AVC video stream

In the intra-frame coding of H.264/AVC, information hiding can be implemented by modulating the prediction modes of 4 × 4 luminance blocks. Because such kind of methods has characteristics of high speed, good concealment, and so on, it is very suitable to build the covert communication system based on video communications and brings a great public security threat. Therefore, it is important to study its steganalysis method. In this paper, we first analyzed the changes of remarkable characteristics in intra-frame coding caused by modulating intra-prediction modes for information hiding, and found that the inherent correlation among the prediction modes in different 4 × 4 luminance blocks belonging to an intra-frame coding macroblock was changed. According to several different positional relationships of the adjacent 4 × 4 blocks in spatial domain, we designed statistical models corresponding to the prediction mode correlation to make quantitative extraction of these correlation characteristics. An information hiding detector was constructed based on the support vector machine. Based on the constructed detector, the experimental results show that the mean of the detection accuracy, recall ratio, and precision ratio are all excellent for different test video sequences.

DCT/DST-Based Transform Coding for Intra Prediction in Image/Video Coding

In this paper, we present a DCT/DST based transform scheme that applies either the conventional DCT or type-7 DST for all the video-coding intra-prediction modes: vertical, horizontal, and oblique. Our approach is applicable to any block-based intra prediction scheme in a codec that employs transforms along the horizontal and vertical direction separably. Previously, Han, Saxena, and Rose showed that for the intra-predicted residuals of horizontal and vertical modes, the DST is the optimal transform with performance close to the KLT. Here, we prove that this is indeed the case for the other oblique modes. The optimal choice of using DCT or DST is based on intra-prediction modes and requires no additional signaling information or rate-distortion search. The DCT/DST scheme presented in this paper was adopted in the HEVC standardization in March 2011. Further simplifications, especially to reduce implementation complexity, which remove the mode-dependency between DCT and DST, and simply always use DST for the 4 × 4 intra luma blocks, were adopted in the HEVC standard in July 2012. Simulation results conducted for the DCT/DST algorithm are shown in the reference software for the ongoing HEVC standardization. Our results show that the DCT/DST scheme provides significant BD-rate improvement over the conventional DCT based scheme for intra prediction in video sequences.

An Effective Selective Encryption Scheme for H.264 Video based on Chaotic Qi System

With the wide use of H.264 in Internet and wireless network, many concerns have been made to the security of it. Aiming at providing an effective content protection method for H.264 video, a novel selective encryption scheme based on chaotic Qi system is proposed in this paper. The unpredictability of chaotic system is implemented to construct a pseudo-random number generator based on the 3-dimensional chaotic Qi system, and then some key data such as intra-prediction modes, residual coefficients and MVD are encrypted by the generated key stream. Experimental results and analysis show that the proposed scheme can achieve a good encryption result, a low computational complexity, little impact on compression ratio, and good format compatibility. It has a great potential to be applied in some real-time applications.

A Fast Intra-Prediction Method in HEVC Using Rate-Distortion Estimation Based on Hadamard Transform

A fast intra-prediction method is proposed for High Efficiency Video Coding (HEVC) using a fast intra-mode decision and fast coding unit (CU) size decision. HEVC supports very sophisticated intra modes and a recursive quadtree-based CU structure. To provide a high coding efficiency, the mode and CU size are selected in a rate-distortion optimized manner. This causes a high computational complexity in the encoder, and, for practical applications, the complexity should be significantly reduced. In this paper, among the many predefined modes, the intra-prediction mode is chosen without rate-distortion optimization processes, instead using the difference between the minimum and second minimum of the rate-distortion cost estimation based on the Hadamard transform. The experiment results show that the proposed method achieves a 49.04% reduction in the intra-prediction time and a 32.74% reduction in the total encoding time with a nearly similar coding performance to that of HEVC test model 2.1.

Review of Proposed High Efficiency Video Coding (HEVC) Standard

The objective of this paper is to provide a review of the recent developments in HEVC standardization, particularly focusing on the key features of hybrid coding tools and gives theoretical analysis, summaries of the technological advancements, and compares its performance with the H.264/ MPEG-4 AVC high-profile standard. High Efficiency Video Coding (HEVC) is a proposed and under development new generation of video compression standard, which enables substantially higher compression capability than the existing state-of-the-art video coding standard and exhibit superior coding performance improvements over its predecessors. Some of the major contributors to the higher compression performance of HEVC are the introduction of quadtree structure, improved techniques to support parallel encoding/decoding, more directional intraprediction modes, support for several integer transforms with square as well as nonsquare transforms, merging of prediction blocks for improved motion information encoding, and extensive In-loop processing on reconstructed pictures. When completed, it unlocks future business not possible with today’s AVC notably suitable for resolutions up to Ultra High Definition (UHD) video coding in the future.