Showing papers by "Enrico Masala published in 2014"

Measuring DASH streaming performance from the end users perspective using neubot

Abstract: The popularity of DASH streaming is rapidly increasing and a number of commercial streaming services are adopting this new standard. While the benefits of building streaming services on top of the HTTP protocol are clear, further work is still necessary to evaluate and enhance the system performance from the perspective of the end user. Here we present a novel framework to evaluate the performance of rate-adaptation algorithms for DASH streaming using network measurements collected from more than a thousand Internet clients. Data, which have been made publicly available, are collected by a DASH module built on top of Neubot, an open source tool for the collection of network measurements. Some examples about the possible usage of the collected data are given, ranging from simple analysis and performance comparisons of download speeds to the performance simulation of alternative adaptation strategies using, e.g., the instantaneous available bandwidth values.

Challenges and Issues on Collecting and Analyzing Large Volumes of Network Data Measurements

Abstract: This paper presents the main challenges and issues faced when collecting and analyzing a large volume of network data measurements. We refer in particular to data collected by means of Neubot, an open source project that uses active probes on the client side to measure the evolution of key network parameters over time to better understand the performance of end-users’ Internet connections. The measured data are already freely accessible and stored on Measurement Lab (M-Lab), an organization that provides dedicated resources to perform network measurements and diagnostics in the Internet. Given the ever increasing amount of data collected by the Neubot project as well as other similar projects hosted by M-Lab, it is necessary to improve the platform to efficiently handle the huge amount of data that is expected to come in the very near future, so that it can be used by researchers and end-users themselves to gain a better understanding of network behavior.

Content-based group-of-picture size control in distributed video coding

Abstract: Controlling the group of picture (GOP) size in distributed video coding (DVC) is a difficult but important task since it has a direct impact on the coding performance. This paper presents a framework to adaptively control the size of GOPs in a Wyner-Ziv encoder by means of encoder-side decisions based on support vector machines (SVM) that uses simple features extracted from the original video content. To train the SVM, firstly this work proposes how to compute the sequence of GOP sizes with the best rate-distortion performance given the set of GOP sizes that can be used during the encoding process. Then, an algorithm based on the previously trained SVMs is presented to control the actual GOP size each time a new decision can be taken at the encoder. Results show that the proposed algorithm can achieve a rate distortion performance close to the ideal one. Moreover, comparisons with a reference adaptive GOP size selection algorithm in the literature shows gains up to 2dB PSNR in the best conditions.

Supporting triple-play communications with TDuCSMA and first experiments

Abstract: This work addresses the implications of using the Time-Division Unbalanced Carrier Sense Multiple Access (TDuCSMA) coordination function to support triple-play services. Firstly, the theoretical background of TDuCSMA is reported, presenting its advantages and discussing its full compliance with the IEEE 802.11 standard. Secondly, a prototype of TDuCSMA is discussed in details. Then, a set of experiments with the prototype implementation of TDuCSMA is presented, showing for the first time the advantages of TDuCSMA in a realistic setting with audio, video and elastic data applications. Experimental results show the superiority of TDuCSMA over the legacy 802.11 Medium Access Control (MAC) in terms of both channel utilization and Quality of Experience (QoE) as measured at the application level.

Low-Cost 3D-Supported Interactive Control

Abstract: Devices for stereoscopic vision are gaining increasing diffusion, but their usage is mostly oriented toward entertainment. A prototype based on consumer devices and open software to achieve low-cost 3D-video-supported interactive control is presented here. This research could stimulate the study and implementation of low-cost general-purpose systems that could be used on a wide spectrum of applications, including remote operation, education, training, and surveillance. There are two related Web extras that provide supplemental material. The first video [http://youtu.be/5zApDO3wSq4] shows the building blocks of the proposed teleoperation system based on real-time 3D video feedback. The second video [http://youtu.be/1Olg1oV2fIs] shows the experiment. A smartphone camera was mounted on a radio-controlled toy car, and users were asked to perform an alignment task using the 3D vision system and the car remote controller.

Driving Event Detection by Low-Complexity Analysis of Video-Encoding Features

Abstract: All standard video-encoding algorithms rely on differential encoding with motion compensation to improve the compression. When a video from a front-facing camera onboard a vehicle is compressed, the information computed for compression purposes, in particular motion vectors, can be effectively used to gain some understanding of the driving dynamics and eventually to support driver decisions and improve driving safety. In this chapter an algorithm that can use such side information to detect a number of driving events is presented. Numerous potential applications are envisaged. Since video-encoding software and hardware are usually strongly optimized, it is possible to implement the proposed algorithms in battery-powered embedded devices with strict limits on processing capabilities such as camera-equipped mobile phones mounted on the car dashboard and consequently allow different types of low cost vehicles, which in most cases do not include cameras as a standard equipment, to be fitted with at least a warning device with very low cost. If the video is captured in the context of a video surveillance scenario, differentiating the events could be used to automatically decide which portion of the video should be transferred to a remote monitoring center thus optimizing network resources usage and costs.

High-quality symmetric Wyner–Ziv coding scheme for low-motion videos

Abstract: Traditional Wyner-Ziv video coding (WZVC) structures require either intra (Key) or Wyner-Ziv (WZ) coding of frames Unfortunately, keeping the video quality approximately constant implies drastic bit-rate fluc- tuations because consecutive frames of different types (Key or WZ) present significantly different compression performances Moreover, certain scenarios severely limit rate fluctuation This work proposes a WZVC scheme with low bit-rate fluctuations based on a symmetric coding structure First, this work investigates the performance of a generic nonasymmetric distributed source coding structure, showing that the low-density parity-check accu- mulate channel decoding method is best suited This is used as a basis to design a symmetric WZVC scheme in which every input video frame is divided into four parallel subframes through subsampling, and then the sub- frames are encoded by using a symmetric method Compared with the traditional asymmetric WZVC scheme, the proposed scheme can achieve higher bit-rate stability over time, which is a great advantage to guarantee a reliable transmission in many wireless communication application environments in which bit-rate fluctuations are strongly constrained Simulation results show the effectiveness of the proposed symmetric WZVC scheme in maintaining a steady bit rate and quality, as well as a quality comparison with the traditional WZVC scheme © 2014 SPIE and IS&T (DOI: 101117/1JEI236061112)