Wassim Hamidouche

Parallel SHVC decoder: Implementation and analysis

The new Scalable High efficiency Video Coding (SHVC) standard is based on a multi-loop coding structure which requires the total decoding of all intermediate layers. The decoding complexity becomes then a real issue, especially for a real time decoding of ultra high video resolutions. A parallel processing architecture is proposed to reduce both the decoding time and the latency of the SHVC decoder. The proposed solution combines the high level parallel processing solutions defined in the HEVC standard with an extension of the frame-based parallelism. The latter solution enables the decoding of several spatial and temporal SHVC frames in parallel to enhance both decoding frame rate and latency. The wavefront parallel processing solution is used for more coarse level of granularity. The proposed hybrid parallel processing approach achieves a near optimal speedup and provides a good trade-off between decoding time, latency and memory usage. On a 6 cores Xeon processor, the parallel SHVC decoder performs a real time decoding of 1600p60 video resolution.

4K Real-Time and Parallel Software Video Decoder for Multilayer HEVC Extensions

Two High Efficiency Video Coding (HEVC) extensions, namely, the scalable HEVC (SHVC) extension and multiview HEVC (MV-HEVC) extension, have been finalized in July 2014 by the Moving Picture Experts Group and Video Coding Experts Group. These two extensions enable additional features not covered in the first version of the HEVC standard such as spatial, fidelity, bitdepth, and color gamut scalability, as well as stereoscopic and multiview representations. In this paper, we propose a software parallel decoder architecture for the HEVC standard and its multilayer extensions, including SHVC and MV-HEVC extensions. The decoder consists of multiple instances of the OpenHEVC decoder, one instance to decode each layer with a communication between dependent layers to perform inter-layer predictions. The proposed multilayer HEVC decoder is parallel friendly and supports both wavefront parallelism to simultaneously process adjacent rows of the frame and frame-based parallelism to decode a set of temporal and spatial frames in parallel. Moreover, the most time-consuming operation introduced in the SHVC extension, namely, the resampling of the inter-layer reference picture in spatial scalability, is optimized in single instruction multiple data for x86 platform. We assess the complexity of the multilayer HEVC decoder with respect to the simulcast configuration. The multilayer decoder decoding two SHVC layers introduces in average 40%-71% additional complexity compared with the single layer HEVC decoder. Moreover, the low level optimizations with a hybrid parallel processing solution enable a real-time decoding of 4Kp60 enhancement layer on a 6-core Intel i7 processor running at 3.4 GHz.

Impact of realistic MIMO physical layer on video transmission over mobile Ad Hoc network

In this paper we investigate the impact of a realistic physical layer on the H.264/AVC video transmission over Ad Hoc networks in urban environment. We propose a realistic Multiple Input Multiple Output (MIMO) physical layer which combines a determinist propagation model and a fine-grained model of wireless transmission errors. The determinist propagation model takes into account all the environmental characteristics (geometric and electric) and provides all the information of the multi-path channel (received power, complex impulse response). The wireless transmission errors model is based on a BER computation. The BER is calculated according to 802.11n standard to evaluate MIMO wireless links and, then, is compared to both SISO configuration and an existing wireless errors model using empirical propagation models. In the case of a SISO configuration, the BER is computed according to 802.11a standard. The simulation results show clearly a significant difference in term of QoS for the video transmission using realistic and empirical physical layer. In addition, the MIMO system, compared to a SISO one, improves the quality of links in the network and, thus, provides a better QoS for video transmission over Ad Hoc networks.

A solution to efficient power allocation for H.264/SVC video transmission over a realistic MIMO channel using precoder designs

In this paper we propose a novel scheme for real time SVC-based video transmission over MIMO channels in the context of Joint Source Channel Coding (JSCC). This scheme compares the transmission of the H.264/SVC video over four precoder solutions, namely Max-SNR, WF, QoS and E-dmin. We exploit the high flexibility of the QoS precoder to minimize the total distortion of the received video. The proposed adaptive QoS precoder takes into account the scalability of the H.264/SVC standard jointly with the instantaneous MIMO channel statue. Finally, the proposed scheme is evaluated over both statistical and time Optimal power allocation varying realistic MIMO channels. This study provides the performance of these four precoder designs in term of BER, ML decoder complexity and the quality of the received video. We show that the precoder solutions providing the best BER MIMO channels performance are not usually the most appropriate for real time video transmission. However, the adaptive QoS precoder which uses three configurations, by considering both the importance of the video bit-QoS precoder stream and the channel statue, provides the best Rate-Distortion performance regardless the channel conditions. We assess the accuracy of these four precoder solutions against channel estimation errors over time varying realistic MIMO channel. The results shows that the adaptive QoS precoder remains robust against channel estimation errors even at high mobility speed.

Low power HEVC software decoder for mobile devices

In the context of mobile handheld devices, energy consumption is a primary concern and the process of video decoding is often among the most resource-intensive applications. Recent embedded processors are equipped with advanced features such as dynamic voltage frequency scaling (DVFS) in order to reduce their power consumption. These features can be used to perform low power video decoding when no hardware decoding support is available for a given standard. High efficiency video coding (HEVC) is a recent video standard offering state-of-the-art compression rates and advanced parallel processing solutions. This paper presents strategies for the power optimization of a real-time software HEVC decoder on NEON architecture. These strategies include the exploitation of data and task-level parallelism, as well as the use of a new frequency control system to optimize the processor DVFS, based on an estimation of the decoding complexity. Extensive power measurement results, based on a multi-core ARM big.LITTLE processor, are provided and compared to state-of-the-art. These results show that the proposed open-source implementation can reach an energy consumption below 21 nJ/px for HD decoding at 2.2 Mbits/s.

4K real time video streaming with SHVC decoder and GPAC player

This paper presents the first 4Kp30 end-to-end video streaming demonstration based on the upcoming Scalable High efficiency Video Coding (SHVC) standard. The optimized and parallel SHVC decoder is used under the GPAC player to decode and display in real time the received SHVC layers. The SHVC reference software model (SHM) is used to encode the 4K original video in two spatial scalability layers: the base layer at 1080p resolution and the enhancement layer at 2160p resolution. The SHVC bitstream is encapsulated with the GPAC multimedia library into MP4 file format. The GPAC player at the server side broadcasts the MP4 content in MPEG-2 TS. At the client side, the GPAC player receives the SHVC video packets which are decoded by the SHVC decoder and then rendered in real time by the player. The GPAC player provides an interactive interface enabling to switch between displaying the base and the enhancement layers.

Optimal resource allocation for Medium Grain Scalable video transmission over MIMO channels

In this paper we investigate an optimal solution for adaptive H.264/SVC video transmission over Multiple-Input Multiple-Output (MIMO) channels. We first write the end-to-end distortion of the H.264/SVC video transmission over a diagonal MIMO channel. The total distortion is expressed following three physical layer parameters: power allocation, modulation spectral efficiency and Error Code Correction (ECC) code rate. Minimizing the total distortion is considered as an optimization problem containing both discrete and continuous variables. We use the Lagrangian method associated with Karush-Kuhn and Tucker conditions to find out the optimal continuous physical layer parameters. Concerting the discrete modulation spectral efficiency and ECC code rate, we exploit information of the MIMO system to remove all suboptimal configurations. Therefore, the optimal power allocation is computed only for a reduced number of discrete configurations. The performance of the proposed solution is evaluated over both statistical and realistic MIMO channels. Results show that the proposed solution performs an optimal resource allocation to achieve the best QoS regardless the channel conditions.

Optimal Bitrate Allocation in the Scalable HEVC Extension for the Deployment of UHD Services

Ultra high definition (UHD) is the latest trend in broadcasting area, which enables new services with 3840×2160 resolution and comes with enhanced color-gamut, frame-rate, dynamic range, and better audio system compared to the currently deployed HD services. The UHD format for broadcasting is already under standardization in the digital video broadcasting consortium which plans to introduce UHD services in three phases. The increase in data brought by these services requires more efficient compression and transmission systems. The recent scalable video coding standard scalable High Efficiency Video Coding (SHVC) is a promising candidate to handle these three phases while ensuring backward compatibility. Moreover, delivering such contents over networks needs an accurate control of the output bitrate from encoder engines to match rigid constraints on bandwidth and QoS. Several contributions have already been proposed to jointly encode scalable stream, but without considering the impact of bitrate ratio between layers on the compression performance. In this paper, the impact of the bitrate ratio between layers on the coding performance is first investigated for several UHD scalable schemes including spatial, color-gamut, and SDR-to-HDR scalability in SHVC. Based on this investigation, an adaptive rate control algorithm which dynamically allocates the bitrate between two layers is proposed to optimize the performance under quality and bitrate constraints. The algorithm has been implemented in the SHVC reference software (SHM9.0) and tested over 15 video sequences under two industrial usecases. The performance shows an average BD-BR improvement of 7.51% and 3.35% for these two use-cases.

Real time SHVC decoder: Implementation and complexity analysis

The Scalable High efficiency Video Coding (SHVC) standard is developed to offer spatial and quality scalability with high coding efficiency. In this paper we investigate a complexity analysis of a real time and parallel SHVC decoder. We first provide details on the implementation of the SHVC decoder including its low level optimizations. Furthermore, we introduce parallelism tools integrated in the SHVC software for parallel decoding. These tools include frame-based parallelism to decode a set of temporal and spatial frames in parallel as well as wavefront parallelism to simultaneously process separated regions of a picture. We assessed through experimental results the complexity of the real time SHVC decoder in different coding configurations. The SHVC decoder with two layers introduces in average an additional complexity of 43 to 80% in respect to a simulcast configuration. The low level optimizations together with a hybrid parallelism solution enables a real time decoding of 1600p40 enhancement layer on an Intel i7 processor.

Realistic SISO and MIMO physical layer implemented in two routing protocols for vehicular ad hoc network

In the most of ad hoc network simulators, the physical layer is considered with a simple approach. Moreover, the information routing is realized in order to only minimize the number of hops or the delay. In this paper, the authors propose two contributions: the first one consists in considering a 3D propagation model taking into account the characteristics of the propagation environment for SISO and MIMO physical layers; the second one allows to introduce the BER as a metric of quality of the radio link used in two routing protocols. The impact of these two contributions is evaluated in two environments.