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1.
In this paper, we study the bandwidth allocation problem for serving video requests in a mobile real-time video player system.
One of the main issues to maintain the quality of services (QoS) in mobile video playback is to ensure sufficient number of
video frames available at the client side while a video is being played. However, due to the limited bandwidth of a mobile
network and variable workload streaming video, this is not easy to achieve in practice. In addition, the communication link
between mobile clients and a video server is subject to frequent errors and temporary disconnection. In this paper, we propose
to use the notion of buffered bandwidth in addition to the network bandwidth to support real-time playback of videos at mobile clients. Based on this, we designed
a bandwidth allocation scheme called Cooperative Pre-Fetching (CP) in which the amount of bandwidth to be allocated to serve a video request depends on the current buffer level of the
video at the client relative to the target buffer level of the client. In determining the target buffer level, we consider
the errors in communication to the client as well as the other clients who are concurrently served by the system. The buffered
video frames at the clients are then used to minimize the impact of error in communications on the overall QoS of video playbacks
in the whole system.
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2.
Periodic broadcast is a cost-effective solution for large-scale distribution of popular videos. Regardless of the number of
video requests, this strategy guarantees a constant worst service latency to all clients, making it possible to serve a large
community with a minimal amount of broadcast bandwidth. Although many efficient periodic broadcast techniques have been proposed,
most of them impose rigid requirements on client receiving bandwidth. They either demand clients to have the same bandwidth
as the video server, or limit them to receive no more than two video streams at any one time. In our previous work, we addressed
this problem with a Client-Centric Approach (CCA). This scheme takes into consideration both server broadcast bandwidth and client receiving bandwidth and allows clients
to use all their receiving capability for prefetching broadcast data. As a result, given a fixed broadcast bandwidth, a shorter
broadcast period can be achieved with an improved client communication capability. In this paper, we present an enhanced version
of CCA to further leverage client bandwidth for more efficient video broadcast. The new scheme reduces the broadcast latency
up to 50% as compared to CCA. We prove the correctness of this new technique and provide an analytical evaluation to show
its performance advantage as compared with some existing techniques.
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3.
To investigate the benefits of scalable codecs in the case of rate adaptation problem, a streaming system for scalable H.264
videos has been implemented. The system considers congestion level in the network and buffer status at the client during adaptation
process. The rate adaptation algorithm is content adaptive. It selects an appropriate substream from the video file by taking
into account the motion dynamics of video. The performance of the system has been tested under congestion-free and congestion
scenarios. The performance results indicate that the system reacts to congestion properly and can be used for Internet video
streaming where losses occur unpredictably.
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4.
Multicast Video-on-Demand (VoD) systems are scalable and cheap-to-operate. In such systems, a single stream is shared by
a batch of common user requests. In this research, we propose multicast communication technique in an Enterprise Network where
multimedia data are stored in distributed servers. We consider a novel patching scheme called Client-Assisted Patching where clients’ buffer of a multicast group can be used to patch the missing portion of the clients who will request the same
movie shortly. This scheme significantly reduces the server load without requiring larger client cache space than conventional
patching schemes. Clients can join an existing multicast session without waiting for the next available server stream which
reduces service latency. Moreover, the system is more scalable and cost effective than similar existing systems. Our simulation
experiment confirms all these claims.
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5.
Video streaming is vital for many important applications such as distance learning, digital video libraries, and movie-on-demand.
Since video streaming requires significant server and networking resources, caching has been used to reduce the demand on
these resources. In this paper, we propose a novel collaboration scheme for video caching on overlay networks, called Overlay Caching Scheme (OCS), to further minimize service delays and loads placed on an overlay network for video streaming applications. OCS is not a
centralized nor a hierarchical collaborative scheme. Despite its design simplicity, OCS effectively uses an aggregate storage
space and capability of distributed overlay nodes to cache popular videos and serve nearby clients. Moreover, OCS is light-weight
and adaptive to clients’ locations and request patterns. We also investigate other video caching techniques for overlay networks
including both collaborative and non-collaborative ones. Compared with these techniques on topologies inspired from actual
networks, OCS offers extremely low average service delays and approximately half the server load. OCS also offers smaller
network load in most cases in our study.
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6.
The MPEG-4 fine granularity scalability (FGS) video coding standard offers flexible adaptation to varying network bandwidths
and different application needs. This paper presents a MPEG-4 FGS video CODEC based watermarking scheme to embed watermark
during encoding. Watermark is embedded into base layer, and can be extracted from both base layer and enhanced video through
eliminating the influence of enhancement layer on watermark. This scheme eliminates error propagation caused by watermark
for normal video, and utilizes error propagation caused by watermark adjustment to protect the video content. This scheme
provides dual protection for intellectual property rights (IPR): watermark and video content protection utilizing error propagation
in temporal motion compensation prediction. Watermark is embedded into I-VOP, and is adjusted before I-VOP is reconstructed
as reference VOP. Only customers with authorization can adjust the watermark correctly during decoding to get good video quality.
Illegal customers can also access the video, but with bad quality. This scheme has the virtue of providing dual protection
with a little expense. Theoretical bounds of watermark embedding strength to keep watermark invisibility and of watermark
adjustment strength to get enough protective effect are calculated. Some experimental results are given and analyzed.
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7.
Providing video on demand (VoD) service over the Internet in a scalable way is a challenging problem. In this paper, we propose
P2Cast—an architecture that uses a peer-to-peer approach to cooperatively stream video using patching techniques, while only relying on unicast connections among peers. We address the following two key technical issues in P2Cast:
(1) constructing an application overlay appropriate for streaming; and (2) providing continuous stream playback (without glitches)
in the face of disruption from an early departing client. Our simulation experiments show that P2Cast can serve many more
clients than traditional client-server unicast service, and that it generally out-performs multicast-based patching if clients
can cache more than 10% of a stream’s initial portion. We handle disruptions by delaying the start of playback and applying
the shifted forwarding technique. The threshold in P2Cast, i.e., the length of time during which arriving clients form a single
session, can serve as a “knob” to adjust the balance between the scalability and the clients’ viewing quality.
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8.
The complexity of group dynamics occurring in small group interactions often hinders the performance of teams. The availability
of rich multimodal information about what is going on during the meeting makes it possible to explore the possibility of providing
support to dysfunctional teams from facilitation to training sessions addressing both the individuals and the group as a whole.
A necessary step in this direction is that of capturing and understanding group dynamics. In this paper, we discuss a particular
scenario, in which meeting participants receive multimedia feedback on their relational behaviour, as a first step towards
increasing self-awareness. We describe the background and the motivation for a coding scheme for annotating meeting recordings
partially inspired by the Bales’ Interaction Process Analysis. This coding scheme was aimed at identifying suitable observable
behavioural sequences. The study is complemented with an experimental investigation on the acceptability of such a service.
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9.
An important research issue in video streaming is how to efficiently utilize the network resources to provide clients instant
access to multiple video objects. Caching strategy and transmission scheme are the two essential points inside the video streaming
framework. Recent research efforts on them are not sufficient due to their inflexible support for scalable encoded video streams
and heterogeneous requests from clients. In this paper, we propose an optimized caching strategy (OCS) and a scalable transmission
scheme (STS) for scalable coded video streaming. By exploring the characteristics of video streaming workload and system design
objectives, OCS and STS work efficiently to minimize both network bandwidth cost and user access latency. Firstly, we analyze
the caching problem for the proxy-assisted video streaming system and derive a maneuverable caching scenario. Secondly, we
develop an efficient transmission scheme for scalable coded videos. Thirdly, we formulate a multi-objective optimization model
with closed-form expressions to obtain the optimized caching strategy. Finally, with designed algorithms, an excellent compromise
between two competing objectives (minimizing the bandwidth cost and the access latency) is achieved. We start our evaluation
by studying the optimized caching strategy for a single video object. Then we apply the strategy to multiple video objects
and illustrate the tradeoff between the optimization objectives. Our evaluation results show that compared with other caching
strategies, the proposed optimized scalable caching strategy can achieve a significant reduction in bandwidth cost with even
a small proxy cache size. Meanwhile, the best performance (in terms of bandwidth cost) is obtained together with the proposed
scalable batch-patching transmission scheme.
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10.
In this paper, we propose a new real-time content filtering framework for live broadcasts in TV terminals. Content filtering
in TV terminals is a necessary provision of personalized broadcasting services in that it enables a TV viewer to obtain desired
scenes from multiple channel broadcasts. In this paper, a stable and reliable filtering structure and an algorithm for multiple
inputs are proposed. Moreover, real-time filtering requirements such as frame sampling rate per channel, number of input channels,
and buffer condition are analyzed to achieve real-time processing in terminals with limited computing power. Based on queueing
theory, we model the system and resolve the filtering requirements. To verify the proposed system and analysis, a filtering
algorithm for soccer videos is applied which is modified for real-time processing. Through analysis of visual features (e.g.,
dominant color and edge components) and detection of spatial objects (e.g., a score board), it recognizes a temporal pattern
between successive video frames and filters desired scenes. Experiments on soccer videos have been performed and the results
validate the effectiveness of the proposed approach and system.
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11.
This paper addresses the problem of ensuring the integrity of a digital video and presents a scalable signature scheme for
video authentication based on cryptographic secret sharing. The proposed method detects spatial cropping and temporal jittering
in a video, yet is robust against frame dropping in the streaming video scenario. In our scheme, the authentication signature
is compact and independent of the size of the video. Given a video, we identify the key frames based on differential energy
between the frames. Considering video frames as shares, we compute the corresponding secret at three hierarchical levels.
The master secret is used as digital signature to authenticate the video. The proposed signature scheme is scalable to three
hierarchical levels of signature computation based on the needs of different scenarios. We provide extensive experimental
results to show the utility of our technique in three different scenarios—streaming video, video identification and face tampering.
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12.
Providing scalable VoD streaming services has recently become a hot issue, and many approaches have been proposed. Because
video streaming services through the Internet are widely used, the need to support VCR operations also increases. However,
there are few approaches to supporting VCR operations on the Internet. We propose a service scheme based on chaining, in which
clients as well as the server provide streaming services. In the proposed scheme, services are provided by unicast and managed
locally using node lists. In addition, our scheme can support frequent VCR operations without incurring significant overhead
in the server workload. We have evaluated our scheme through simulation with real traces from a content distribution network
(CDN) company and with various parameters. The results show that the proposed scheme reduces server workload significantly.
The results also verify that frequent VCR operations can be served smoothly without causing too much overhead.
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13.
Providing scalable video services in a peer-to-peer (P2P) environment is challenging. Since videos are typically large and
require high communication bandwidth for delivery, many peers may be unwilling to cache them in whole to serve others. In
this paper, we address two fundamental research problems in providing scalable P2P video services: (1) how a host can find
enough video pieces, which may scatter among the whole system, to assemble a complete video; and (2) given a limited buffer
size, what part of a video a host should cache and what existing data should be expunged to make necessary space. We address
these problems with two new ideas: Cell caching collaboration and Controlled Inverse Proportional (CIP) cache allocation. The Cell concept allows cost-effective caching collaboration in a fully distributed environment and
can dramatically reduce video lookup cost. On the other hand, CIP cache allocation challenges the conventional caching wisdom
by caching unpopular videos in higher priority. Our approach allows the system to retain many copies of popular videos to
avoid creating hot spots and at the same time, prevent unpopular videos from being quickly evicted from the system. We have
implemented a Gnutella-like simulation network and use it as a testbed to evaluate the proposed technique. Our extensive study
shows convincingly the performance advantage of the new scheme.
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14.
In this paper, an adaptive framework for video streaming over the Internet is presented. The framework is a joint design of
packet scheduling and rate control with optimal bandwidth resource allocation. The transmission rate is dynamically adjusted
to obtain maximal utilization of the client buffer and minimal allocation of the bandwidth. Under the constraint of the transmission
rate, a prioritized packet scheduling is designed to provide a better visual quality of video frames. The packet scheduling
is a refined bandwidth allocation which takes into account of varying importance of the different packets in a compressed
video stream. Moreover, the proposed approach is scalable with increasing multimedia flows in the distributed Internet environment.
Comparisons are made with the most current streaming approaches to evaluate the performance of the framework using the H.264
video codec. The extensive simulation results show that the average Peak Signal to Noise Ratio (PSNR) increases in our proposed
approach. It provides a better quality of the decoded frames, and the quality of the decoded frames changes more smoothly.
The achieved video quality among different users also has a lower fluctuation, which indicates a fair sharing of network resources.
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15.
This paper proposes a framework to aid video analysts in detecting suspicious activity within the tremendous amounts of video
data that exists in today’s world of omnipresent surveillance video. Ideas and techniques for closing the semantic gap between
low-level machine readable features of video data and high-level events seen by a human observer are discussed. An evaluation
of the event classification and detection technique is presented and a future experiment to refine this technique is proposed.
These experiments are used as a lead to a discussion on the most optimal machine learning algorithm to learn the event representation
scheme proposed in this paper.
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16.
Listening to music on personal, digital devices whilst mobile is an enjoyable, everyday activity. We explore a scheme for
exploiting this practice to immerse listeners in navigation cues. Our prototype, ONTRACK, continuously adapts audio, modifying
the spatial balance and volume to lead listeners to their target destination. First we report on an initial lab-based evaluation
that demonstrated the approach’s efficacy: users were able to complete tasks within a reasonable time and their subjective
feedback was positive. Encouraged by these results we constructed a handheld prototype. Here, we discuss this implementation
and the results of field-trials. These indicate that even with a low-fidelity realisation of the concept, users can quite
effectively navigate complicated routes.
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17.
This paper describes the simulated car racing competition that was arranged as part of the 2007 IEEE Congress on Evolutionary
Computation. Both the game that was used as the domain for the competition, the controllers submitted as entries to the competition
and its results are presented. With this paper, we hope to provide some insight into the efficacy of various computational
intelligence methods on a well-defined game task, as well as an example of one way of running a competition. In the process,
we provide a set of reference results for those who wish to use the simplerace game to benchmark their own algorithms. The paper is co-authored by the organizers and participants of the competition.
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18.
Quantitative usability requirements are a critical but challenging, and hence an often neglected aspect of a usability engineering process. A case study is described where quantitative usability requirements played a key role in the development of a new user interface of a mobile phone. Within the practical constraints of the project, existing methods for determining usability requirements and evaluating the extent to which these are met, could not be applied as such, therefore tailored methods had to be developed. These methods and their applications are discussed. 相似文献
19.
Grouping video content into semantic segments and classifying semantic scenes into different types are the crucial processes
to content-based video organization, management and retrieval. In this paper, a novel approach to automatically segment scenes
and semantically represent scenes is proposed. Firstly, video shots are detected using a rough-to-fine algorithm. Secondly,
key-frames within each shot are selected adaptively with hybrid features, and redundant key-frames are removed by template
matching. Thirdly, spatio-temporal coherent shots are clustered into the same scene based on the temporal constraint of video
content and visual similarity between shot activities. Finally, under the full analysis of typical characters on continuously
recorded videos, scene content is semantically represented to satisfy human demand on video retrieval. The proposed algorithm
has been performed on various genres of films and TV program. Promising experimental results show that the proposed method
makes sense to efficient retrieval of interesting video content.
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20.
A video streaming proxy server needs to handle hundreds of simultaneous connections between media servers and clients. Inside,
every video arrived at the server and delivered from it follows a specific arrival and delivery schedule. While arrival schedules
compete for incoming network bandwidth, delivery schedules compete for outgoing network bandwidth. As a result, a proxy server
has to provide sufficient buffer and disk cache for storage, together with memory space, disk space and disk bandwidth. In
order to optimize the throughput, a proxy server has to govern the usage of these resources. In this paper, we first analyze
the property of a traditional smoothing algorithm and a video staging algorithm. Then we develop, based on the smoothing algorithm,
a video staging algorithm for video streaming proxy servers. This algorithm allows us to devise an arrival schedule based
on the delivery schedule. Under this arrival and delivery schedule pair, we can achieve a better resource utilization rate
gracefully between different parameter sets. It is also interesting to note that the usage of the resources such as network
bandwidth, disk bandwidth and memory space becomes interchangeable. It provides the basis for inter-resource scheduling to
further improve the throughput of a video streaming proxy server system.
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