A system for retrieving video sequences created by tracking humans in a smart environment, by using spatial queries, is presented. Sketches made with a pointing device on the floor layout of the environment are used to form queries corresponding to locomotion patterns. The sketches are analyzed to identify the type of the query. Directional search algorithms based on the minimum distance between points are applied for finding the best matches to the sketch. The results are ranked according to the similarity and presented to the user. The system was developed in two stages. An initial version of the system was implemented and evaluated by conducting a user study. Modifications were made where appropriate, according to the results and the feedback, to make the system more accurate and usable. We present the details of the initial system, the user study and the results, and the modifications thus made. The overall accuracy of retrieval for the initial system was approximately 93%, when tested on a collection of data from a real-life experiment. This is improved to approximately 97% after the modifications. The user interaction strategy and the search algorithms are usable in any environment for automated retrieval of locomotion patterns. The subjects who evaluated the system found it easy to learn and use. Their comments included several prospective applications for the user interaction strategy, providing valuable insight for future directions.

Gamhewage C. de Silva

Toshihiko Yamasaki

Kiyoharu Aizawa

Sketch-Based Spatial Queries for the Retrieval of Human Locomotion Patterns in Smart Environments

Packet-level Forward Error Control (FEC) for video streaming over a wireless network has received comparatively limited investigation, because of the delay introduced by the need to assemble a group of packets. However, packet-level interleaving when combined with FEC presents a remedy to time-correlated error bursts, though it can further increase delay if this issue is not addressed. This paper proposes adapting the overall degree of interleaved packet-level FEC according to the display deadlines of packets, transmit buffer occupation, and estimated video input to the wireless channel, all of which address the issue of delay. To guard against estimation error, the scheme applies a conservative adaptation policy, which accounts for picture type importance to ensure that display deadlines are met, thus avoiding this defect of interleaving. The paper additionally introduces a greedy algorithm that effectively groups packet-level FEC protection according to packet priority. Priority encoding adds extra protection during deep fades. As feedback is not required, the interleaving scheme is suitable for all forms of video broadcast. A Bluetooth piconet demonstrates the packet-level FEC interleaving scheme, which provides higher quality delivered video compared to the industry-standard Pro-MPEG Cop#3r2 interleaving scheme.

Rouzbeh Razavi

Martin Fleury

Mohammed Ghanbari

Adaptive Packet-Level Interleaved FEC for Wireless  Priority-Encoded Video Streaming

Visual sensor networks have emerged as an important
class of sensor-based distributed intelligent systems,
with unique performance, complexity, and quality of service
challenges. Consisting of a large number of low-power camera nodes,
visual sensor networks support a great number of novel
vision-based applications. The camera nodes provide information
from a monitored site, performing distributed and collaborative
processing of their collected data. Using multiple cameras in the
network provides different views of the scene, which enhances
the reliability of the captured events. However, the large amount
of image data produced by the cameras combined with the
network's resource constraints require exploring new means
for data processing, communication, and sensor management.
Meeting these challenges of visual sensor networks requires
interdisciplinary approaches, utilizing vision processing, communications
and networking, and embedded processing. In this
paper, we provide an overview of the current state-of-the-art in
the field of visual sensor networks, by exploring several relevant
research directions. Our goal is to provide a better understanding
of current research problems in the different research fields of
visual sensor networks, and to show how these different research
fields should interact to solve the many challenges of visual sensor
networks.

Stanislava Soro

Wendi Heinzelman

A Survey of Visual Sensor Networks

The increasing variety of networks and end systems, especially wireless devices, pose new challenges in communication support for, particularly, multicast-based collaborative applications. In traditional multicasting, the sender transmits video at the same rate and resolution to all receivers independent of their network characteristics, end system equipment, and users' preferences about video quality and significance. Such an approach results in resources being wasted and may also result in some receivers having their quality expectations unsatisfied. This
problem can be addressed, near the network edge, by applying dynamic, in-network adaptation (e.g., transcoding) of video streams to meet available connection bandwidth, machine characteristics, and client preferences. In this paper, we extrapolate from earlier work of Shorfuzzaman et al. 2006 in which we implemented and assessed an MPEG-1 transcoding system on the Intel IXP1200 network processor to consider the feasibility of in-network transcoding for other video formats and network processor architectures. The use of “on-the-fly” video adaptation near the edge of the network offers the promise of simpler support for a wide range of end devices with different display, and so forth, characteristics that can be used in different types of environments.

Mohammad Shorfuzzaman

Rasit Eskicioglu

Peter Graham

In-Network Adaptation of Video Streams Using Network Processors

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Advances in Multimedia publishes research on the technologies associated with multimedia systems, including computer-media integration for digital information processing, storage, transmission, and representation.

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Advances in Multimedia - Table of contents 2009

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Advances in Multimedia publishes research on the technologies associated with multimedia systems, including computer-media integration for digital information processing, storage, transmission, and representation.

Advances in Multimedia