Papers by Otoniel López Granado
Computers, Jan 3, 2024
When working with the Wireless Access in Vehicular Environment (WAVE) protocol stack, the multi-c... more When working with the Wireless Access in Vehicular Environment (WAVE) protocol stack, the multi-channel operation mechanism of the IEEE 1609.4 protocol may impact the overall network performance, especially when using video streaming applications. In general, packets delivered from the application layer during a Control Channel (CCH) time slot have to wait for transmission until the next Service Channel (SCH) time slot arrives. The accumulation of packets at the beginning of the latter time slot may introduce additional delays and higher contention when all the network nodes try, at the same time, to obtain access to the shared channel in order to send the delayed packets as soon as possible. In this work, we have analyzed these performance issues and proposed a new method, which we call SkipCCH, that helps the MAC layer to overcome the high contention produced by the packet transmission bursts at the beginning of every SCH slot. This high contention implies an increase in the number of packet losses, which directly impacts the overall network performance. With our proposal, streaming video in vehicular networks will provide a better quality of reconstructed video at the receiver side under the same network conditions. Furthermore, this method has particularly proven its benefits when working with Quality of Service (QoS) techniques, not only by increasing the received video quality but also because it avoids starvation of the lowerpriority traffic.
HEVC is the latest video coding standard aimed to compress double to that its predecessor standar... more HEVC is the latest video coding standard aimed to compress double to that its predecessor standard H.264. Motion Estimation is one of the critical parts in the encoder due to the introduction of asymmetric motion partitioning and higher size of coding tree unit. In this paper, a design for an Integer Motion Estimator of HEVC is presented over specific hardware architecture for real time implementation. The implementation shows a new IME unit supporting asymmetric partitioning mode which significantly reduce the overall motion estimation processing time. The prototyped architecture has been designed in VHDL, synthesized and implemented using the Xilinx FPGA, Zynq-7000 xc7z020 clg484-1. The proposed design is able to process 30 fps at Full-HD and 15 fps at 2K resolution.
Evaluación del módulo de estimación de movimiento basado en FPGA para el codificador de vídeo HEVC
Heterogeneous Parallel Approaches for HEVC Encoder
Hybrid Computing for Intra Prediction in HEVC
Civil-Comp Proceedings
Advances in Engineering Software, 2016
In this paper, we focus on applying parallel processing techniques to HEVC encoder in order to si... more In this paper, we focus on applying parallel processing techniques to HEVC encoder in order to significantly reduce the computational power requirements without disturbing its coding efficiency. So, we propose several, synchronous and asynchronous, parallelization approaches working at a coarse grain parallelization level, based on the Group Of Pictures (GOP), which we call GOP-based level. GOP-based approaches encode simultaneously several groups of consecutive frames. Depending on how these GOPs are conformed and distributed it is critical to obtain good parallel performance. The results show that near ideal efficiencies are obtained using up to 10 cores. Furthermore, when the computational load is unbalanced, the asynchronous versions outperform the synchronous ones. The parallel algorithms developed in this work support all standard coding modes proposed by the reference software.
Análisis combinado de texture y contrast masking en HEVC
En este articulo se pretende recoger la experiencia realizada en la asignatura "Sistemas Ope... more En este articulo se pretende recoger la experiencia realizada en la asignatura "Sistemas Operativos" de segundo curso de Ingenieria Tecnica en Informatica de Gestion, impartida en la Escuela Politecnica Superior de Orihuela de la Universidad Miguel Hernandez. En concreto la experiencia se ha realizado sobre la parte del temario de la asignatura que cubre los conceptos de concurrencia, exclusion mutua y sincronizacion de procesos. La utilizacion de las nuevas tecnologias no garantiza unos mejores resultados en el aprendizaje de los alumnos. Lo que si desempena un papel crucial en la obtencion de buenos resultados es, especialmente, la forma en la que la tecnologia es puesta en practica y utilizada [9]. Con este ejemplo proponemos una metodologia para la inclusion de las nuevas tecnologias en el aula cuyos objetivos principales son intentar garantizar un buen rendimiento en las practicas de la asignatura asi como obtener una mayor motivacion del alumnado, una mejor comprensi...
Emulador HEVC INTRA en Matlab
2010 IEEE International Conference on Mechatronics and Automation, 2010
High-Efficiency Video Coding (HEVC) was developed to improve its predecessor standard, H264/AVC, ... more High-Efficiency Video Coding (HEVC) was developed to improve its predecessor standard, H264/AVC, by doubling its compression efficiency. As in previous standards, Motion Estimation (ME) is one of the encoder critical blocks to achieve significant compression gains. However, it demands an overwhelming complexity cost to accurately remove video temporal redundancy, especially when encoding very high-resolution video sequences. To reduce the overall video encoding time, we propose the implementation of the HEVC ME block in hardware. The proposed architecture is based on (a) a new memory scan order, and (b) a new adder tree structure, which supports asymmetric partitioning modes in a fast and efficient way. The proposed system has been designed in VHDL (VHSIC Hardware Description Language), synthesized and implemented by means of the Xilinx FPGA, Virtex-7 XC7VX550T-3FFG1158. Our design achieves encoding frame rates up to 116 and 30 fps at 2 and 4K video formats, respectively.
The Journal of Supercomputing
It is well-known that each new video coding standard significantly increases in computational com... more It is well-known that each new video coding standard significantly increases in computational complexity with respect to previous standards, and this is particularly true for the HEVC and VVC video coding standards. The development of techniques for reducing the required complexity without affecting the rate/distortion (R/D) performance is therefore always a topic of intense research interest. In this paper, we propose a combination of two powerful techniques, deep learning and parallel computing, to significantly reduce the complexity of the HEVC encoding engine. Our experimental results show that a combination of deep learning to reduce the CTU partitioning complexity with parallel strategies based on frame partitioning is able to achieve speedups of up to 26$$\times$$ × when 16 threads are used. The R/D penalty in terms of the BD-BR metric depends on the video content, the compression rate and the number of OpenMP threads, and was consistently between 0.35 and 10% for the video s...
Influence of Dead Zone Quantization Parameters in the R/D Performance of Wavelet-Based Image Encoders
2017 Data Compression Conference (DCC), 2017
Uniform quantization schemas with dead zone are commonly used in image and video codecs. The desi... more Uniform quantization schemas with dead zone are commonly used in image and video codecs. The design of these quantizers affects to the final R/D performance, being two of the quantizer parameters, the responsible for that variations: (a) the dead zone size and (b) the reconstruction point location inside each quantization step. We analyze how variations of these parameters, by means of a variable dead zone quantizer, affect to the R/D performance of wavelet-based image encoders, using three different quality metrics. We tune the quantizer for each image to obtain the optimum parameters that provide the best R/D behavior for each of the metrics for different rate ranges, without altering the rest of the encoder stages. We provide a general parameter set for each metric and rate range, to be used with other images to obtain important rate savings and better quality values for each metric.
Journal of Visual Communication and Image Representation, 2017
Uniform quantization schemas with dead zone are widely used in image and video codecs. The design... more Uniform quantization schemas with dead zone are widely used in image and video codecs. The design of these quantizers affects to the final R/D performance, being two of the quantizer parameters the responsible for that variations: the dead zone size and the reconstruction point location inside each quantization step. In this work we tune the quantizer to obtain the optimum quantization parameters that provide the best R/D behavior for different quality metrics and rate ranges. Based on a representative image set, we provide the quantization parameters to encode general imagery, with a R/D performance close to the optimum one. The same study was done including the Contrast Sensitivity Function in the quantization stage. After an exhaustive experimental test, the results show that the estimated quantization parameters are able to provide bit rate savings up to 11% at low and moderate bit rates without additional computational cost.
GPU-based HEVC intra-prediction module
The Journal of Supercomputing, 2016
The HEVC video coding standard requires nearly 70 % more time than H.264/AVC to encode a video se... more The HEVC video coding standard requires nearly 70 % more time than H.264/AVC to encode a video sequence. Manycore architectures can considerably help to reduce the coding time. In this paper, we propose the use of GPUs to perform the intra-picture prediction without any R/D loss. We have evaluated our proposal and compared the results with the ones obtained when running on a CPU. The results show that a time reduction of up to 85 % can be obtained without any R/D loss.
The Journal of Supercomputing, 2018
In 2016, 73% of total Internet traffic came from video transmission and this percentage is expect... more In 2016, 73% of total Internet traffic came from video transmission and this percentage is expected to reach 82% by 2021. These figures show the importance of using video compression standards that maximize video quality while minimizing the necessary bandwidth. In 2013, the HEVC standard was released accounting for an approximate 50% bit rate saving compared to H.264/AVC while maintaining the same reconstruction quality. To address increases in video IP traffic, a new generation of video coding techniques is required that achieve higher compression rates. Compression improvements are being implemented in a software package known as the Joint Exploration Test Model. In this work, we present two parallel JEM model solutions specifically designed for distributed memory platforms for both All Intra and Random Access coding modes. The proposed parallel algorithms achieved high levels of efficiency, in particular for the All Intra mode. They also showed great scalability.
Simulation Framework for Evaluating Video Delivery Services Over Vehicular Networks
2018 IEEE 88th Vehicular Technology Conference (VTC-Fall), 2018
Vehicular Ad-hoc Networks contribute to the Intelligent Transportation Systems by providing a set... more Vehicular Ad-hoc Networks contribute to the Intelligent Transportation Systems by providing a set of services related to traffic, mobility, safe driving, and infotainment applications. One of the most challenging applications is video delivery, since it has to deal with several hurdles typically found in wireless communications, like high node mobility, bandwidth limitations and high loss rates. In this work, we propose an integrated simulation framework that will provide a multilayer view of a particular video delivery session with a bunch of simulation results at physical (i.e., collisions), MAC (i.e., packet delay), application (i.e., % of lost frames), and user levels (i.e., perceptual video quality). With this tool, we can analyze the performance of video streaming over vehicular networks with a high level of detail, giving us the keys to better understand and, as a consequence, improve video delivery services.
Article URL
This Provisional PDF corresponds to the article as it appeared upon acceptance. Fully formatted P... more This Provisional PDF corresponds to the article as it appeared upon acceptance. Fully formatted PDF and full text (HTML) versions will be made available soon. Enhancing LTW image encoder with perceptual coding and GPU-optimized 2D-DWT transform
The Journal of Supercomputing, 2016
The HEVC video coding standard launched on 2013, is able to reduce to the half, on average, the b... more The HEVC video coding standard launched on 2013, is able to reduce to the half, on average, the bit stream size produced by H.264/AVC encoder at the same video quality, but it requires nearly 70 % more time than H.264/AVC to encode a video sequence. In this paper we propose several parallelization approaches to the HEVC encoder. Our proposals, for distributed memory platforms, work at a coarse grain level parallelization, being one group of pictures (GOP) the basic structure. These approaches encode simultaneously several GOPs. To obtain good parallel performance, a right GOP conformation and distribution should be applied.
Performance analysis of frame partitioning in parallel HEVC encoders
The Journal of Supercomputing, 2016
The new video coding standard HEVC includes two concepts that allow to partition a frame into reg... more The new video coding standard HEVC includes two concepts that allow to partition a frame into regions that can be independently encoded and decoded. These two concepts are named “Tiles” and “Slices”. In this paper, we present and analyze optimized parallel versions of the HEVC encoder based on tile and slice partitioning. We have evaluated the benefits and drawbacks of both approaches in terms of computational times and rate distortion performance. The results show that both approaches obtain good speed-ups, being the parallel version based on tiles the one that obtains the best trade-off between speed-up achieved (up to 9.3$$\times $$×) and rate distortion performance loss (1.6% BD rate for AI mode and 2.2% for LB mode on average).
Proceedings of the international workshop on Workshop on mobile video - MV '07, 2007
It is well known that PSNR does not always rank quality of an image or video sequence in the same... more It is well known that PSNR does not always rank quality of an image or video sequence in the same way that a human being. There are many other factors considered by the human visual system and the brain. So, a lot of efforts were required to find an objective video quality metric that is able to measure the quality distortion similarly to the one perceived by the destination user. We analyze the behaviour of some of the most relevant objective quality metrics when they are applied to video compressed by a H264/AVC codec at different bit-rates and with error resilience options enabled. Video data is transmitted in a wireless MANET environment and packet losses are modelled for different scenarios including variable congestion and mobility states. We take as reference the PSNR metric and try to find out if there is a more accurate metric in terms of human quality perception that could substitute PSNR in the performance evaluation of different coding proposals under packet loss scenarios.
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Papers by Otoniel López Granado