共查询到10条相似文献,搜索用时 125 毫秒
1.
Periodic broadcasting can be used to support near-video-on-demand for popular videos. For a given bandwidth allocation, pyramid
broadcasting schemes substantially reduce the viewer latency (waiting) time compared to conventional broadcasting schemes.
Nevertheless, such pyramid schemes typically have substantial storage requirements at the client end, and this results in
set-top boxes needing disks with high transfer rate capabilities. In this paper, we present a permutation-based pyramid scheme
in which the storage requirements and disk transfer rates are greatly reduced, and yet the viewer latency is also smaller.
Under the proposed approach, each video is partitioned into contiguous segments of geometrically increasing sizes, and each
segment is further divided into blocks, where a block is the basic unit of transmission. As in the original pyramid scheme,
frequencies of transmission for the different segments of a video vary in a manner inversely proportional to their size. Instead
of transmitting the blocks in each segment in sequential order, the proposed scheme transmits these blocks in a prespecified
cyclic permutation to save on storage requirements in the client end. Performance analyses are provided to quantify the benefits
of the new scheme. 相似文献
2.
An optimal bandwidth allocation strategy for the delivery of compressed prerecorded video 总被引:1,自引:0,他引:1
The transportation of prerecorded, compressed video data without loss of picture quality requires the network and video
servers to support large fluctuations in bandwidth requirements. Fully utilizing a client-side buffer for smoothing bandwidth
requirements can limit the fluctuations in bandwidth required from the underlying network and the video-on-demand servers.
This paper shows that, for a fixed-size buffer constraint, the critical bandwidth allocation technique results in plans
for continuous playback of stored video that have (1) the minimum number of bandwidth increases, (2) the smallest peak bandwidth
requirements, and (3) the largest minimum bandwidth requirements. In addition, this paper introduces an optimal bandwidth allocation algorithm which, in addition to the three critical bandwidth allocation properties, minimizes the total number of bandwidth
changes necessary for continuous playback. A comparison between the optimal bandwidth allocation algorithm and other critical
bandwidth-based algorithms using 17 full-length movie videos and 3 seminar videos is also presented. 相似文献
3.
Bogdan S. Chlebus Leszek Gasieniec Alan Gibbons Andrzej Pelc Wojciech Rytter 《Distributed Computing》2002,15(1):27-38
We consider the problem of distributed deterministic broadcasting in radio networks of unknown topology and size. The network
is synchronous. If a node u can be reached from two nodes which send messages in the same round, none of the messages is received by u. Such messages block each other and node u either hears the noise of interference of messages, enabling it to detect a collision, or does not hear anything at all, depending on the model. We assume that nodes know neither the topology nor the size of
the network, nor even their immediate neighborhood. The initial knowledge of every node is limited to its own label. Such
networks are called ad hoc multi-hop networks. We study the time of deterministic broadcasting under this scenario.
For the model without collision detection, we develop a linear-time broadcasting algorithm for symmetric graphs, which is
optimal, and an algorithm for arbitrary n-node graphs, working in time . Next we show that broadcasting with acknowledgement is not possible in this model at all.
For the model with collision detection, we develop efficient algorithms for broadcasting and for acknowledged broadcasting
in strongly connected graphs.
Received: January 2000 / Accepted: June 2001 相似文献
4.
The Personal Presence System (PPS) is an experimental research prototype platform to support advanced broadband applications,
including multimedia conferencing and distance learning. It supports the user's presentation control of advanced network elements
(multimedia bridges). The multimedia bridge provides for a single contact point per user, who receives only one combined video
stream, which minimizes access bandwidth. This architecture solves the -squared transmission problem of multipoint video conferencing and makes customer terminal equipment simpler and cheaper than
high-end desktop workstations. The PPS provides each user with flexible presentation control of a feature-rich video bridge.
The PPS also supports advanced features such as object extraction and multimedia object associations. 相似文献
5.
On fast microscopic browsing of MPEG-compressed video 总被引:1,自引:0,他引:1
Boon-Lock Yeo 《Multimedia Systems》1999,7(4):269-281
MPEG has been established as a compression standard for efficient storage and transmission of digital video. However, users
are limited to VCR-like (and tedious) functionalities when viewing MPEG video. The usefulness of MPEG video is presently limited
by the lack of tools available for fast browsing, manipulation and processing of MPEG video.
In this paper, we first address the problem of rapid access to individual shots and frames in MPEG video. We build upon the
compressed-video-processing framework proposed in [1, 8], and propose new and fast algorithms based on an adaptive mixture
of approximation techniques for extracting spatially reduced image sequence of uniform quality from MPEG video across different frame types and also under different motion activities in the scenes. The algorithms
execute faster than real time on a Pentium personal computer. We demonstrate how the reduced images facilitate fast and convenient
shot- and frame-level video browsing and access, shot-level editing and annotation, without the need for frequent decompression
of MPEG video. We further propose methods for reducing the auxiliary data size associated with the reduced images through
exploitation of spatial and temporal redundancy. We also address how the reduced images lead to computationally efficient algorithms for video analysis based
on intra- and inter-shot processing for video database and browsing applications. The algorithms, tools for browsing and techniques
for video processing presented in this paper have been used by many in IBM Research on more than 30 h of MPEG-1 video for
video browsing and analysis. 相似文献
6.
The paper investigates efficient bandwidth allocation schemes for the transmission of MPEG-2 video traffic on high-speed
networks. To this end we performed an extensive analysis of the traffic generated by an MPEG-2 encoder. Specifically, we encoded
“The Sheltering Sky” movie according to the MPEG-2 standard. By the analysis of the generated traffic it results that a constant-quality
transmission can be performed with a poor bandwidth utilization. In the paper we identified that the low bandwidth utilization
is caused by rare high-rate periods in the codec bitstream. Hence, we identified the source scalability as a promising approach
to achieve a “quasi-constant” quality transmission and an efficient bandwidth utilization. The effectiveness of this approach
is evaluated in the paper via simulation. Specifically, by defining a Markovian model for an MPEG-2 scalable source we performed
a set of simulation experiments which indicate that the source scalability approach significantly increases the utilization,
while maintaining the quality of the video signal at the highest value for most of the time, e.g., a 50% of the network utilization
with the highest quality for the 99.7% of the time. 相似文献
7.
Igor D.D. Curcio Antonio Puliafito Salvatore Riccobene Lorenzo Vita 《Multimedia Systems》1998,6(6):367-381
The relative simplicity of access to digital communications nowadays and the simultaneous increase in the available bandwidth
are leading to the definition of new telematic services, mainly oriented towards multimedia applications and interactivity
with the user. In the near future, a decisive role will be played in this scenario by the providers of interactive multimedia
services of the on-demand type, which will guarantee the end user a high degree of flexibility, speed and efficiency. In this
paper, some of the technical aspects regarding these service providers are dealt with, paying particular attention to the
problems of storing information and managing service requests. More specifically, the paper presents and evaluates a new storage
technique based on the use of disk array technology, which can manage both typical multimedia connections and traditional
requests. The proposed architecture is based on the joint use of the partial dynamic declustering and the information dispersal
algorithm, which are employed for the allocation and retrieval of the data stored on the disk array. We also define efficient
strategies for request management in such a way as to meet the time constraints imposed by multimedia sessions and guarantee
good response times for the rest of the traffic. The system proposed is then analyzed using a simulation approach. 相似文献
8.
As the number of video streams to be supported by a digital video delivery system (DVDS) increases, an improved understanding
of the necessity for reliable and cost-efficient support for a considerable number of video streams (in the magnitude of tens
of thousands), and the dependency largely on software capabilities emerges. Even in the presence of an optimal hardware configuration,
or model, and associated costs, using software to exploit the underlying hardware capabilities is of paramount importance.
Although a number of DVDSs have become operational, their ability to deliver the required services mainly depends on the small
number of streams supported and the hardware trade-offs. It is imperative that current software developments account for
the eventual scalability of the number of video streams without commensurate increase in hardware. In this paper, we present
strategies for the management of video streams in order to maintain and satisfy their space and time requirements. We use
a DVDS architectural model with functionally dichotomized nodes: a single-node partition is responsible for data retrieval,
while the remaining partition of nodes accepts user requests, determines object locations, and routes requests through the
network that connects both partitions. We present a detailed analysis of the issues related to queuing I/O requests and data
buffering. The discussion includes the requirements for arranging and scheduling I/O requests and data buffers, with the objective
of guaranteeing the required data availability rates for continuous media display. 相似文献
9.
In a video-on-demand (VOD) environment, disk arrays are often used to support the disk bandwidth requirement. This can pose
serious problems on available disk bandwidth upon disk failure. In this paper, we explore the approach of replicating frequently
accessed movies to provide high data bandwidth and fault tolerance required in a disk-array-based video server. An isochronous
continuous video stream imposes different requirements from a random access pattern on databases or files. Explicitly, we
propose a new replica placement method, called rotational mirrored declustering (RMD), to support high data availability for disk arrays in a VOD environment. In essence, RMD is similar to the conventional
mirrored declustering in that replicas are stored in different disk arrays. However, it is different from the latter in that
the replica placements in different disk arrays under RMD are properly rotated. Combining the merits of prior chained and
mirrored declustering methods, RMD is particularly suitable for storing multiple movie copies to support VOD applications.
To assess the performance of RMD, we conduct a series of experiments by emulating the storage and delivery of movies in a
VOD system. Our results show that RMD consistently outperforms the conventional methods in terms of load-balancing and fault-tolerance
capability after disk failure, and is deemed a viable approach to supporting replica placement in a disk-array-based video
server. 相似文献
10.
The broadband integrated services digital networks (B-ISDN) based on asynchronous transfer mode (ATM) technology can support
a wide range of applications such as voice, video, still images, and data. Compression techniques increase the effective bandwidth
utilization, but the bursty and asynchronous nature of the traffic can still lead to congestion in the network, and degradation
of image quality and quality of service (QOS). Some of the features to provide better coding schemes for ATM networks are
layered coding, resynchronization, buffering, interleaved schemes, constrained bit rate due to buffers, encapsulation with
the RTP or AAL1 for clock recovery, lapped transforms, motion compensation, and optimal bit allocation for coders based on
wavelet transforms. We review various techniques forimage and video coding such as transforms, motion compensation, vector
quantization, and subband coding. We outline the impact of the cell loss ratio (CLR), delay and cell delay variation (CDV)
on video coding: blocking effects, loss of frame synchronization, motion vectors, and vector quantization codewords. The open
problems include tuning coding parameters to the available QOS provided by the network. 相似文献