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1.
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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2.
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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3.
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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4.
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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5.
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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6.
Video-over-IP applications have recently attracted a large number of users on the Internet. Traditional client-server based
video streaming solutions incur expensive bandwidth provision cost on the server. Peer-to-Peer (P2P) networking is a new paradigm
to build distributed network applications. Recently, several P2P streaming systems have been deployed to provide live and
on-demand video streaming services on the Internet at low server cost. In this paper, we provide a survey on the existing
P2P solutions for live and on-demand video streaming. Representative P2P streaming systems, including tree, multi-tree and
mesh based systems are introduced. We describe the challenges and solutions of providing live and on-demand video streaming
in P2P environment. Open research issues on P2P video streaming are also discussed.
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7.
Indexing and segmenting of video content by motion, color and texture has been intensively explored leading to a commonly used representation in a storyboard. In this paper, a novel method of visualization of video content is proposed. First of all, the content is segmented into shots, and then a spatio-temporal color signature of shots, based on color distribution in the frames, is proposed. This spatio-temporal color signature serves as a basis for graph clustering and graph visualization tools. Those, integrated in a platform for visualization of huge graphs, Tulip, supply an exciting graph-based navigation interface for multimedia content. The results obtained on feature documentaries are promising. 相似文献
8.
The mushroom growth of video information, consequently, necessitates the progress of content-based video analysis techniques.
Video summarization, aiming to provide a short video summary of the original video document, has drawn much attention these
years. In this paper, we propose an algorithm for video summarization with a two-level redundancy detection procedure. By
video segmentation and cast indexing, the algorithm first constructs story boards to let users know main scenes and cast (when
this is a video with cast) in the video. Then it removes redundant video content using hierarchical agglomerative clustering
in the key frame level. The impact factors of scenes and key frames are defined, and parts of key frames are selected to generate
the initial video summary. Finally, a repetitive frame segment detection procedure is designed to remove redundant information
in the initial video summary. Results of experimental applications on TV series, movies and cartoons are given to illustrate
the proposed algorithm.
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9.
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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10.
We present a real-time implementation of 2D to 3D video conversion using compressed video. In our method, compressed 2D video
is analyzed by extracting motion vectors. Using the motion vector maps, depth maps are built for each frame and the frames
are segmented to provide object-wise depth ordering. These data are then used to synthesize stereo pairs. 3D video synthesized
in this fashion can be viewed using any stereoscopic display. In our implementation, anaglyph projection was selected as the
3D visualization method, because it is mostly suited to standard displays.
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11.
In this paper, we study the important issues in the design of an efficient wireless real-time visual surveillance system (WISES).
Two important considerations are to minimize: (1) the video workload on the wireless network; and (2) the processing workload
at the front-end video capturing unit. To achieve the first objective, we propose a cooperative framework for semantic filtering of video frames instead of forwarding every video frame to the back-end server for analysis and monitoring query evaluation.
To minimize the processing workload at the front-end unit, a hierarchical object model (HOM) is designed to model the status
of the objects, and their temporal and spatial properties in the video scene. With the information provided from the back-end
server, the front-end unit pre-analyses the current status of the objects in the HOM by comparing the selection conditions
in the submitted monitoring queries following the adaptive object-based evaluation (APOBE) scheme which is proposed to reduce
the processing workload at the front-end unit. In APOBE, a higher evaluation frequency is given to the object which is closer
to satisfy the condition in the monitoring queries. The performance of WISES has been studied to demonstrate the efficiency
of the proposed scheme.
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12.
In conventional motion compensated temporal filtering based wavelet coding scheme, where the group of picture structure and
low-pass frame position are fixed, variations in motion activities of video sequences are not considered. In this paper, we
propose an adaptive group of picture structure selection scheme, which the group of picture size and low-pass frame position
are selected based on mutual information. Furthermore, the temporal decomposition process is determined adaptively according
to the selected group of picture structure. A large amount of experimental work is carried out to compare the compression
performance of proposed method with the conventional motion compensated temporal filtering encoding scheme and adaptive group
of picture structure in standard scalable video coding model. The proposed low-pass frame selection can improve the compression
quality by about 0.3–0.5 dB comparing to the conventional scheme in video sequences with high motion activities. In the scenes
with un-even variation of motion activities, e.g. frequent shot cuts, the proposed adaptive group of picture size can achieve
a better compression capability than conventional scheme. When comparing to adaptive group of picture in standard scalable
video coding model, the proposed group of picture structure scheme can lead to about 0.2~0.8 dB improvements in sequences
with high motion activities or shot cut.
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13.
Recently, electronic auctions have been receiving more and more attention in the world of electronic commerce. The security
and efficiency of electronic auctions are becoming important. We shall propose a securely sealed-bid auction scheme that uses
our group signature scheme with the function of authenticated encryption. It can achieve the following goals: secrecy of bidding
price, anonymity, verifiability, non-repudiation, and better performance.
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14.
Mobile ad hoc networks without centralized infrastructure change their topology rapidly because of node mobility, making multimedia
applications difficult to run across wireless networks. Moreover, video transmission over ad hoc networks causes frequent
transmission loss of video packets owing to end-to-end transmission with a number of wireless links, and requires essential
bandwidth and restricted delay to provide quality-guaranteed display. This paper presents an architecture supporting transmission
of multiple video streams in ad hoc networks by establishing multiple routing paths to provide extra video coding and transport
schemes. This study also proposes an on-demand multicast routing protocol to transport layered video streams. The multicast
routing protocol transmits layered video streaming based on a weight criterion, which is derived according to the number of
receivers, delay and expiration time of a route. A simulation is performed herein to indicate the viability and performance
of the proposed approach. The simulation results demonstrate that the proposed transport scheme is more effective than other
video transport schemes with single or multiple paths.
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15.
A video encryption scheme combining with advanced video coding (AVC) is presented and analyzed in this paper, which is different
from the ones used in MPEG1/2 video encryption. In the proposed scheme, the intra-prediction mode and motion vector difference
are encrypted with the length-kept encryption algorithm (LKE) in order to keep the format compliance, and the residue data
of the macroblocks are encrypted with the residue data encryption algorithm (RDE) in order to keep low cost. Additionally,
a key distribution scheme is proposed to keep the robustness to transmission errors, which assigns sub-keys to different frames
or slices independently. The encryption scheme’s security, time efficiency and error robustness are analyzed in detail. Experimental
results show that the encryption scheme keeps file format unchanged, is secure against replacement attacks, is efficient in
computing, and is robust to some transmission errors. These properties make it a suitable choice for real-time applications,
such as secure IPTV, secure videoconference or mobile/wireless multimedia, etc.
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16.
This paper deals with monitoring user perception of multimedia presentations in a Universal Multimedia Access (UMA) enabled
system using objective no-reference (NR) metrics. These NR metrics are designed for an UMA-enabled system, in a novel architecture,
for a multimedia viewer. The first metric measures block-edge impairments in a video frame at the receiver end, based on the
observation that they occur in regions with low spatial activity. The second metric evaluates the quality of the reconstructed
video frame in the event of packet loss. Here, the structure of the artifact is itself exploited for the evaluation. Both
the metrics involve low computational complexity and are feasible for real-time monitoring of streaming video in a multimedia
communication scenario. Further, in rate-adaptive streaming of video, these metrics could serve as feedback parameters to
dynamically adapt the bit rates based on network congestion.
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17.
Although scalable video coding can achieve coding efficiencies comparable with single layer video coding, its computational
complexity is higher due to its additional inter-layer prediction process. This paper presents a fast adaptive termination
algorithm for mode selection to increase its computation speed while attempting to maintain its coding efficiency. The developed
algorithm consists of the following three main steps which are applied not only to the enhancement layer but also to the base
layer: a prediction step based on neighboring macroblocks, a first round check step, and a second round check step or refinement
if failure occurs during the first round check. Comparison results with the existing algorithms are provided. The results
obtained on various video sequences show that the introduced algorithm achieves about one-third reduction in the computation
speed while generating more or less the same video quality.
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18.
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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19.
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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20.
As typical wireless sensor networks (WSNs) have resource limitations, predistribution of secret keys is possibly the most
practical approach for secure network communications. In this paper, we propose a key management scheme based on random key
predistribution for heterogeneous wireless sensor networks (HSNs). As large-scale homogeneous networks suffer from high costs
of communication, computation, and storage requirements, the HSNs are preferred because they provide better performance and
security solutions for scalable applications in dynamic environments. We consider hierarchical HSN consisting of a small number
high-end sensors and a large number of low-end sensors. To address storage overhead problem in the constraint sensor nodes,
we incorporate a key generation process, where instead of generating a large pool of random keys, a key pool is represented
by a small number of generation keys. For a given generation key and a publicly known seed value, a keyed-hash function generates
a key chain; these key chains collectively make a key pool. As dynamic network topology is native to WSNs, the proposed scheme
allows dynamic addition and removal of nodes. This paper also reports the implementation and the performance of the proposed
scheme on Crossbow’s MicaZ motes running TinyOS. The results indicate that the proposed scheme can be applied efficiently
in resource-constrained sensor networks. We evaluate the computation and storage costs of two keyed-hash algorithms for key
chain generation, HMAC-SHA1 and HMAC-MD5.
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