共查询到10条相似文献,搜索用时 171 毫秒
1.
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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2.
In this paper, an improved quantization technology with low-complexity is presented for H.264/AVC video codec. Multiplication
factors of H.264/AVC quantizer are modified. Therefore, it is possible to reduce the bit width of the quantization and substitute
large bit-width multiplier by some small bit-width adders without noticeable rate-distortion degradation in integrated circuits
(ICs) design. Quantization error introduced by the modified multiplication factors is not only theoretically but also experimentally
analyzed. Quantizer is optimized on register transfer level of IC design, and under the same cell CMOS technology, about 75.2%
area and 76.3% dynamic power consumption are saved in each quantization unit on average compared with original H.264/AVC quantization.
Experimental video coding results show that the Bjontegaard delta peak signal-to-noise ratio (PSNR) and Bjontegaard delta
bit rate between the improved and original H.264/AVC quantization are very slight, which means that the improved quantization
scheme is approximately the same as the original quantization scheme of H.264/AVC in rate-distortion performance.
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3.
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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4.
Stream processors can achieve high performance in stream applications that share stream characteristics of large parallelism,
intensive computation and little data reuse. Transform coding, as a core component in video compression, is widely used in
video storage and video transmission. This paper summarizes stream execution mechanism and explores design approaches of programmable
stream processors including the Imagine stream processor and graphics processing unit (GPU). Based on the stream processing
model, stream algorithms for block-based and frame-based (nonblock-based) transform coding are presented and mapped onto stream
processors. Especially, an Interleaved Streaming Transform (IST) algorithm on Imagine and a Row-wise Zonal Transform (RZT)
algorithm on GPU for 4×4 integer transform in H.264 are proposed to exploit great potential of stream processing for block-based
transform. Our experiments of transform coding suite on Imagine and GPU show that the coding efficiency of stream processors
is far beyond the real-time requirements of current video applications, dealing with a variety of different video resolutions
ranging from QCIF to high definition (HD). The performance evaluation of stream implementations discusses the architectural
supports for transform coding, and presents the significant improvements over other programmable platforms. Transform coding
may take advantage of the flexibility of programmable stream processors with high performance to play an important role in
the future.
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5.
Networked robotic cameras are becoming popular in remote observation applications such as natural observation, surveillance,
and distance learning. Equipped with a high optical zoom lens and agile pan-tilt mechanisms, a networked robotic camera can
cover a large region with various resolutions. The optimal selection of camera control parameters for competing observation
requests and the on-demand delivery of video content for various spatiotemporal queries are two challenges in the design of
such autonomous systems. For camera control, we introduce memoryless and temporal frame selection models that effectively
enable collaborative control of the camera based on the competing inputs from in-situ sensors and users. For content delivery, we design a patch-based motion panorama representation and coding/decoding algorithms
(codec) to allow efficient storage and computation. We present system architecture, frame selection models, user interface,
and codec algorithms. We have implemented the system and extensively tested our design in real world applications including
natural observation, public surveillance, distance learning, and building construction monitoring. Experiment results show
that our frame selection models are robust and effective and our on-demand content delivery codec can satisfy a variety of
spatiotemporal queries efficiently in terms of computation time communications bandwidth.
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6.
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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7.
Tracking location is challenging due to the numerous constraints of practical systems including, but not limited to global
cost, device volume and weight, scalability and accuracy; these constraints are typically more severe for systems that should
be wearable and used indoors. We investigate the use of wearable solar cells to track changing light conditions (a concept
that we named LuxTrace) as a source of user displacement and activity data. We evaluate constraints of this approach and present
results from an experimental validation of displacement and activity estimation. The results indicate that a distance estimation
accuracy of 21 cm (80% quantile) can be achieved. A simple method to combine LuxTrace with complementary absolute location
estimation methods is also presented. We apply carpet-like distributed RFID tags to demonstrate online learning of new lighting
environments.
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8.
In order to provide high data availability in peer-to-peer (P2P) DHTs, proper data redundancy schemes are required. This paper
compares two popular schemes: replication and erasure coding. Unlike previous comparison, we take user download behavior into
account. Furthermore, we propose a hybrid redundancy scheme, which shares user downloaded files for subsequent accesses and
utilizes erasure coding to adjust file availability. Comparison experiments of three schemes show that replication saves more
bandwidth than erasure coding, although it requires more storage space, when average node availability is higher than 47%;
moreover, our hybrid scheme saves more maintenance bandwidth with acceptable redundancy factor.
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9.
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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10.
This paper revisits the concept of fractal image coding and the contractivity conditions of the fractal transform operator.
All such existing conditions are only sufficient. This paper formulates a necessary and sufficient condition for the contractivity
of the fractal transform operator associated to a fractal code. Furthermore, analytical results on the convergence of the
fractal image decoding will be derived.
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