Pierre Clarel Catherine

Early CU size determination in HEVC intra prediction using Average Pixel Cost

The HEVC (H.265) standard has brought in significant improvement in terms of coding efficiency. However, this reduction in bit rate (almost half) comes along with an increase in complexity resulting in a very high compression time. This paper proposes a novel method to reduce the complexity in the intra-mode encoding process. We have defined a new term called the Average Pixel Cost (APC) for a CU. When the APC of a CU is below a specified threshold, the splitting process is stopped and therefore the encoder no longer needs to address the smaller CUs in the quad-tree. This results in considerable time saving for the encoder with negligible deterioration in quality and bitrate. Experimental results, based on this method alone, produced an average reduction of 31.3% in compression time in HM 10.0 with an increase of 0.7% in bitrate along with a negligible decrease of PSNR (-0.03 dB) using an APC threshold of 20.

Experimental performance comparison between TCP vs UDP tunnel using OpenVPN

The comparison between TCP and UDP tunnels have not been sufficiently reported in the scientific literature. In this work, we use OpenVPN as a platform to demonstrate the performance between TCP/UDP. The de facto belief has been that TCP tunnel provides a permanent tunnel and therefore ensures a reliable transfer of data between two end points. However the effects of transmitting TCP within a UDP tunnel has been explored and could provide a valuable attempt. The results provided in this paper demonstrates that indeed TCP in UDP tunnel provides better latency. Throughout this paper, a series of tests have been performed, UDP traffic was sent inside UDP tunnel and TCP tunnel successively. The same tests was performed using TCP traffic.

Enhancing the error-correcting performance of LDPC codes for LTE and WiFi

Low-density parity-check (LDPC) codes are one of the most powerful error-correcting codes for wireless communication of high-speed data. This power comes from an efficient decoding scheme, the sum-product algorithm (SPA), which runs over the bipartite graph defining the code. In this work, we propose to use a modified version of the decoding algorithm over the LDPC codes used in Long Term Evolution (LTE) and WiFi and demonstrate that with the same number of iterations, without any increase in time complexity, we can achieve an enhanced error-correcting performance. The only trade off of the system is the necessary storage of the decoding sets, for a total size of ns × n, where ns is the number of decoding sets used and n is the codeword length. In this work, the maximum value of ns used is 5, which makes the trade-off fairly acceptable, considering that the coding gain is obtained virtually free-of-charge.

A modified Rough Mode Decision process for fast High Efficiency Video Coding (HEVC) intra prediction

High Efficiency Video Coding (HEVC/H.265), the latest standard in video compression, aims at half the bit rate while maintaining the same quality compared to its predecessor, AVC/H.264. However, the increase in number of modes (35) for intra prediction in HEVC has significantly impacted on the encoder complexity. In this paper, a reduced number of candidate modes is therefore proposed to improve the encoding time. The most probable modes (MPMs) are inserted in the candidate list based on their computed Rough Mode Decision (RMD) cost rather than appending them to the list. In addition, the number of modes selected for the 4×4 and 8×8 PUs are based on the analysis of the graph obtained by plotting the cost of each mode against the mode number. Using this approach, the number of candidate modes in the RDO process is further reduced. Experimental results show that the average time savings of the proposed method is 38.0% along with an acceptable loss in quality (0.059dB) and a negligible increase in bit rate (0.30%) compared to HM 10.

Performance evaluation and analysis of layer 3 tunneling between OpenSSH and OpenVPN in a wide area network environment

Virtual Private Networks (VPNs) provide a secure encrypted communication between remote networks worldwide by using Internet Protocol(IP) tunnels and a shared medium like the Internet. End-to-end connectivity is established by tunneling. OpenVPN and OpenSSH are cross-platform, secure, highly configurable VPN solutions. The performance comparison however between OpenVPN and OpenSSH VPN has not yet been undertaken. This paper focuses on such comparison and evaluates the efficiency of these VPNs over Wide Area Network (WAN) connections. The same conditions are maintained for a fair comparison. To the best knowledge of the authors, this is the first reported test results of these two commonly used VPN technologies. Three parameters, namely speed, latency and jitter are evaluated. Using a real life scenario with deployment over the Linux Operating System, a comprehensive in-depth comparative analysis of the VPN mechanisms is provided. Results of the analysis between OpenSSH and OpenVPN show that OpenSSH utilizes better the link and significantly improves transfer times.

6to4 tunneling framework using OpenSSH

6to4 tunneling enables IPv6 hosts and routers to connect with other IPv6 hosts and routers over the existing IPv4Internet. The main purpose of IPv6 tunneling is to maintain compatibility with large existing base of IPv4 hosts and routers. OpenSSH VPN tunneling is said to have limitations with numerous IPv6 clients and therefore it is advisable to use OpenVPN. To the best knowledge of the authors, this is the first reported successful implementation of 6to4 tunneling over OpenSSH with more than one client. This proof-of-concept positions OpenSSH therefore as a potential alternative to conventional VPNs.

Fast adaptive inter-splitting decisions for HEVC based on luma residuals

The long encoding time of High Efficiency Video Coding (HEVC) compared to its predecessor, Advanced Video Coding (AVC), is mostly associated with the large number of Coding Units (CUs) to be processed during the quad tree splitting of the 64 × 64 Coding Tree Unit (CTU) along with the improved but intensive Motion Estimation (ME) techniques. In this paper, the unnecessary processing of some CUs during the recursive splitting of the CTU along with some of the two-PUs mode operations are skipped so as to bring significant time reduction for the encoder. Statistical distributions of the HEVC splitting decisions based on the Mean Square (MS) values of each 8 × 8 block within the 2N × 2N luma residuals are adaptively constructed during the starting frames for each sequence. Thereafter, thresholds for early termination of the CU and early identification of the 2N × 2N PU mode based on these distributions are applied during the encoding of subsequent inter frames. The proposed inter-mode scheme significantly reduces the total encoding time with negligible loss of coding efficiency. Experimental results show that the proposed scheme effectively achieves 47.0% encoding time savings with a Bjøntegaard Delta bitrate (BDBR) increase of only 0.57% for various test sequences under random access conditions.

Evaluation of UDP tunnel for data replication in data centers and cloud environment

The era of Data Centers is underway. Cloud is an off-premise form of computing that stores data on the Internet, whereas a data center refers to on-premise. For cloud-hosting purposes, vendors also often own multiple data centers in several geographic locations to safeguard data availability during outages and other data center failures. Data replication and synchronization techniques have recently attracted a lot of attention of researchers from computing community. Data transferred during replication needs to be secure. Tunneling is one way to secure information before sending it to off-premise replication site. The two kinds of tunneling that exists are TCP and UDP tunnel. UDP tunnel is claimed to be faster during the transfer of data when compared to TCP tunnel, the main reason is that UDP does not make use of excessive acknowledgment messages and also UDP does not suffer the tcp-meltdown problem. In situations where bandwidth is limited, UDP is the preferred option. This paper addresses the reliability of UDP tunnel, while measuring the packet drops when sending different packet sizes. The authors want to determine whether UDP tunnel can be used as the mode of transfer during data replication. A series of tests have been performed and the MTU size have been adjusted for a minimal packet loss. The authors demonstrate that UDP tunnel with an MTU size of 1150 bytes can be used as the mode of transfer for data centers.

Fast Intra Mode Decision for HEVC

High Efficiency Video Coding (HEVC/H.265), the latest standard in video compression, aims to halve the bitrate while maintaining the same quality or to achieve the same bitrate with an improved quality compared to its predecessor, AVC/H.264. However, the increase in prediction modes in HEVC significantly impacts on the encoder complexity. Intra prediction methods indeed iterate among 35 modes for each Prediction Unit (PU) to select the most optimal one. This mode decision procedure which consumes around 78 % of the time spent in intra prediction consists of the Rough Mode Decision (RMD), the simplified Rate Distortion Optimisation (RDO) and the full RDO processes. In this chapter considerable time reduction is achieved by using techniques that use fewer modes in both the RMD and the simplified RDO processes. Experimental results show that the average time savings of the proposed method indeed yields a 42.1 % time savings on average with an acceptable drop of 0.075 dB in PSNR and a negligible increase of 0.27 % in bitrate.

A VPN framework through multi-layer tunnels based on OpenSSH

This paper details how to setup and test the new tunneling features of OpenSSH to establish an enhanced SSH Layer 3 VPN between three computers in a Wide Area Network (WAN) environment. The OpenSSH security feature will be explored to provide secure tunneling and different authentication methods. Using OpenSSH to built VPN will cater for security by encrypting the data transmitted across the public network to private networks. OpenSSH VPN is said to have limitations with numerous clients and therefore it is advisable to use OpenVPN when dealing with more than one clients. To the best knowledge of the authors, this is the first reported successful implementation of a wide-area network VPN using OpenSSH tunnels with multiple clients. This proof-of-concept positions OpenSSH therefore as a potential alternative to the more conventional OpenVPN.