Most engineering and scientific phenomena, such as the surface of a landscape or the continuously changing temperature at a location are inherently infinite in space or time or both. We cannot measure all the data. Generally it is possible to record surface elevation values or the temperature only at some specific locations and times.

Interpolation and Approximation

The focus of this demonstration is the performance of streaming video over the mobile wireless channel. We compare two schemes: the standard approach to video which transmits H.264/AVC-encoded stream over 802.11-like PHY, and SoftCast -- a clean-slate design for wireless video where the source transmits one video stream that each receiver decodes to a video quality commensurate with its specific instantaneous channel quality.

/pdf/softcast-one-size-fits-all-wireless-video-3vmoew0u0e.pdf

SoftCast: one-size-fits-all wireless video

Reliability modeling and analysis of communication networks

Current WiFi Access Points (APs) choose transmission parameters when emitting wireless packets based solely on channel conditions. In this work we explore the benefits of deciding packet transmission parameters in a content-dependent manner. We demonstrate the benefits specifically for media delivery applications in WiFi environments by designing, implementing and evaluating a system, called Medusa. In order to keep the APs relatively simple, we implement the Medusa functions in a media-aware proxy. More specifically, when forwarding our media traffic, Medusa requires that APs simply use the WiFi broadcast feature, and that they refrain from making decisions on which wireless packets to retransmit, or what PHY rates such packets should be transmitted at. Instead we combine these typical link layer functions with a few other content-specific choices, in the proxy. Through detailed experiments across diverse mobility and interference conditions we demonstrate the advantages of this scheme for both unicast and multicast media delivery applications. The advantages are particularly substantial in multicast scenarios, where Medusa was able to deliver a 20 Mbps HD video stream simultaneously to 25 clients, using a single 802.11 AP, with good to excellent PSNR.

/pdf/scalable-wifi-media-delivery-through-adaptive-broadcasts-2qqwaup91o.pdf

Scalable WiFi media delivery through adaptive broadcasts

Motivated by recent emerging systems that can leverage partially correct packets in wireless networks, this paper investigates the novel concept of error estimating codes (EEC). Without correcting the errors in the packet, EEC enables the receiver of the packet to estimate the packet's bit error rate, which is perhaps the most important meta-information of a partially correct packet. Our EEC algorithm provides provable estimation quality, with rather low redundancy and computational overhead. To demonstrate the utility of EEC, we exploit and implement EEC in two wireless network applications, Wi-Fi rate adaptation and real-time video streaming. Our real-world experiments show that these applications can significantly benefit from EEC.

/pdf/efficient-error-estimating-coding-feasibility-and-13m1vv6nt1.pdf

Efficient error estimating coding: feasibility and applications

When comparing the performance of different video coding approaches, improvements or new codec designs, one of the most important performance metrics is the Rate/Distortion (R/D), where distortion use to be measured in terms of PSNR (Peak Signal-to- Noise Ratio) values. However, it is well known that this metric not always capture the distortion perceived by the human being. So, a lot efforts were performed to define an objective video quality metric that is able to measure video quality distortion close to the one perceived for the destination user. In this work, we perform a study of different available objective quality metrics in order to evaluate their behaviour, taking as reference the classical PSNR metric. Our purpose is to find, if any, a video quality metric that is able to substitute PSNR for video quality assessment and determine a more accurate R/D performance metric when designing and evaluating video codec proposals.

A Study of Objective Quality Assessment Metrics for Video Codec Design and Evaluation

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.

http://www.grc.upv.es/calafate/download/ACMMV2007.pdf

Quality assessment metrics vs. PSNR under packet lossscenarios in manet wireless networks

This work presents our experience on Android teaching at Miguel Hernandez University (Elche, Spain). We decided to orientate our courses toward Android app development, and encouraged students to carry their Android phones or tablets to the classroom. The results, in terms of student motivation, satisfaction and engagement in programming have been extraordinary.

Improving student engagement on programming using app development with Android devices

The 3D-DWT is a mathematical tool of increasing importance in those applications that require an efficient processing of volumetric info. Other applications like professional video editing, IPTV video surveillance applications, live event IPTV broadcast, multi-spectral satellite imaging, HQ video delivery, etc, would rather use 3D-DWT encoders to reconstruct a frame as fast as possible. However, the huge memory requirement of the algorithms that compute the 3D-DWT is one of the main drawbacks in practical implementations. In this paper, we introduce a fast frame-based 3D-DWT video encoder with low memory usage. In addition, there is no need to divide the input video sequence into group of pictures (GOP), and it can be applied in a continuous manner, so that no boundary effects between GOPs appear.

A fast 3D-DWT video encoder with reduced memory usage suitable for IPTV

Intra-video coding is a common way to process video material for applications like professional video editing systems, digital cinema, video surveillance applications, multi-spectral satellite imaging, HQ video delivery, etc. Most practical intra-coding systems employ JPEG encoders due to their simplicity, low coding delay and low memory requirements. JPEG2000 is the main candidate to replace JPEG in this kind of application due to its excellent rate/distortion (R/D) performance and high coding flexibility. However, its complexity and computational resource requirements for proper operation could be a limitation for certain applications. In this work, we propose an intra-video codec, M-LTW, which is able to obtain very good R/D performance results, as good as JPEG2000 or H.264 INTRA, with faster processing and lower memory usage.

Miguel O. Martínez-Rach

Papers

A Study of Objective Quality Assessment Metrics for Video Codec Design and Evaluation

Quality assessment metrics vs. PSNR under packet lossscenarios in manet wireless networks

Improving student engagement on programming using app development with Android devices

A fast 3D-DWT video encoder with reduced memory usage suitable for IPTV

M-LTW: A fast and efficient intra video codec