8440598
A rate control algorithm for wireless video transmission using perceptual tuning
In video transmission over two-way wireless channel automatic repeat request (ARQ) retransmission has been used to protect packets from losing, which also causes the channel throughput varying and brings more challenges to rate control of the video compression. This paper proposes a new rate control algorithm based on regions of interest (ROI), PID buffer controlling and perceptual tuning techniques, etc. It intelligently allocates bit budget among different regions and adapts to time-varying wireless channel so as to achieve better perceptual quality in ROI and depress the frame skipping. Simulation results illustrate that our algorithm effectively enhances the perceptual quality for ROI, significantly reduces the number of frame skipping, and thereby improves the smoothness of the video.
16523105
Region-based rate control and bit allocation for wireless video transmission
In this paper, we propose a joint source-channel region-based rate control algorithm for real-time video transmissions over wireless systems. During the video transmission, the channel throughput available to the video encoder in the wireless systems is inherently variable, due to the retransmission of the error packets using the automatic repeat request (ARQ) error control. The variable data rate of the wireless system is characterized by the packet-level Gilbert two-state Markov Model, the parameters of which are extracted from the statistical properties of the channel information obtained from the wireless channel simulator. The proposed algorithm adopts a fast but effective block-based segmentation method to extract the regions of interest. Unlike traditional bit allocation methods used in the region/content-based rate control, the algorithm exploits the most effective criteria "coding qualities" as quantitative factors to directly control bit allocation among different regions so as to achieve better visual quality in the regions of interest. The computational complexity of the algorithm is low making it suitable for real-time applications. Compared with the MPEG-4 rate control algorithm, our algorithm can effectively enhance the perceptual quality for the regions of interest and significantly reduce the number of frame skipping; thereby, improve the smoothness of the video.
2733368
Low delay rate-control in video transcoding
In order to obtain optimal visual quality while meeting the bit rate requirements, a video transcoder needs efficient rate-control with fine and dynamic adjustments. This paper proposes a new frequency domain complexity estimation scheme and an algorithm for adaptive bit allocation during transcoding. In conjunction with frame skipping mechanism, the proposed algorithm adaptively determines spatial coding parameters to realize very low target bitrate for MPEG-2 to MPEG-4 transcoding. Experiments show that the proposed algorithm performs accurate target bit rate transcoding, improves the visual quality and effectively alleviates visual quality degradation during scene changes.
7298536
A multistage fast motion estimation scheme for video compression
This paper presents a novel multistage motion estimation (ME) scheme called content adaptive search technique (CAST). The proposed scheme consists of four stages: motion vector field (MVF) prediction, block-based segmentation, motion parameter extraction, and adaptive search strategy. Through pre-processing the MVF of the previous reference frame in the first three stages, CAST extracts the motion parameters for each region. The 4th stage is a combination of various techniques including MV prediction, search area decision and an adaptive fast search algorithm that is adjusted by a mathematical model for the block distortion surface (BDS). Experiment shows that the proposed scheme improves the visual quality, while yielding a faster speed, comparing with the other predictive ME algorithms.
9615760
Asynchronous rate control for multi-object videos
Object-based coding can potentially achieve a higher degree of compression and better visual quality. The objects in a scene are not always synchronous, that is, they have different temporal resolutions. In some applications, it is more efficient to transmit asynchronous objects with different temporal rates so as to achieve a better tradeoff between temporal and spatial resolutions. This requires to balance the qualities of individual objects while ensuring an overall visual quality with a given bit rate. This paper proposes a rate control algorithm for multiple video object encoding, which is suitable for both synchronous and asynchronous transmissions. The algorithm aims to maximize scene quality with an accurate bit rate, while efficiently handling buffer fullness. Using an efficient bit allocation strategy, the algorithm achieves accurate target bit rates, provides good coding quality, and decreases buffer overflow/underflow. The proposed algorithm also allows flexible priority adjustment among multiple objects to ensure overall better visual perception. Designed primarily for asynchronous objects, the algorithm treats the synchronous objects as a special case. Experimental results demonstrate that, when giving suitable asynchronous video object planes rates, the proposed algorithm achieves good temporal-spatial tradeoff while yielding accurate rate regulation and effective buffer control.
11930112
Fast motion estimation using hierarchical motion intensity structure
The embedded motion compensation model of the new H.264/AVC video coding standard dramatically increases the computational complexity of motion estimation. We propose a fast motion estimation algorithm using a hierarchical motion intensity structure to lower the computational complexity of the motion estimation in H.264/AVC. The proposed algorithm is mainly based on a multi-level motion intensity structure. It determines the motion intensity at three levels and, accordingly, uses different motion estimation techniques to find a more accurate, and faster, motion vector (MV). Experimental results show that the proposed algorithm provides promising performance in terms of the computational speedup and video reconstruction quality.
12119839
Performance analysis of maximum intensity projection algorithm for display of MRA images
The maximum intensity projection (MIP) is a popularly used algorithm for display of MRA images, but its performance has not been rigorously analyzed before. In this paper, four measures are proposed for the performance of the MIP algorithm and the quality of images projected from three-dimensional (3-D) data, which are vessel voxel projection probability, vessel detection probability, false vessel probability, and vessel-tissue contrast-to-noise ratio (CNR). As side products, vessel-missing probability, vessel receiver operating characteristics (ROC's), and mean number of false vessels are also studied. Based on the assumptions that the intensities of vessel, tissue, and noise along a projection path are independent Gaussian, these measures are derived and obtained all in closed forms. All the measures are functions of explicit parameters: vessel-to-tissue noise ratio (VTNR) and CNR of 3 D data prior to the MIP, vessel diameter, and projection length. It is shown that the MIP algorithm increases the CNR of large vessels whose CNR prior to the MIP is high and whose diameters are large. The increase in CNR increases with projection path length. On the other hand, all the proposed measures indicate that the small vessels that have low CNR prior to the MIP and small diameters suffer from the MIP. The performance gets worse as projection path length increases. All measures demonstrate a better performance when the vessel diameter is larger. Other properties and possible applications of the derived measures are also discussed.
1423209
Scalable load balancing on distributed web servers using mobile agents
Distributed web servers on the immensely expanding Internet require high scalability and availability to provide efficient services to millions of clients on the web. To provide rapid responses to enormous number of client requests, load balancing is an important technique to evenly distribute the requests to web servers. In this paper, we propose a framework called Mobile Agent based LoaD balancing (MALD) that uses mobile agents technology to implement scalable load balancing on distributed web servers. The web servers can dispatch mobile agents to collect system-wide load information and accomplish load redistribution on all servers. Various load-balancing policies can be incorporated with versatile mobile agents in the framework. Compared with the traditional message-passing-based load-balancing methods, the mobile-agent-based approaches have the merits of high flexibility, low network traffic and high asynchrony. The performance evaluation demonstrates that the MALD framework provides a foundation to develop efficient load-balancing schemes on wide range of web server systems from cluster to the Internet.
2008945
Finger Force Direction Recognition by Principal Component Analysis of Fingernail Coloration Pattern
A method based on principal component analysis of the fingernail coloration pattern is presented to infer fingertip force direction during planar contact. Images from 7 subjects were registered and normalized to each other. Results show that the fingernail coloration patterns are similar for the 7 subjects, but the feature centroids vary. It is concluded that there are common features for all people. But accurate detection of fingertip force direction requires individually calibrated centroids
2615609
EigenNail for Finger Force Direction Recognition
This paper presents a technique termed eigennails to classify fingertip force during contact based on the coloration patterns in the fingernail and surrounding skin. Fingertip force is classified into six directions: no force, normal force only, two directions (left/right) of lateral shear force, and two directions (forward/backward) of longitudinal shear forces. Based on the face recognition technique eigenfaces, a small number of eigennails are sufficient to express the color pattern features for shear force direction classification. Results show that 98% of 960 fingernail images of 8 different subjects are correctly classified. The lowest imaging resolution without sacrificing classification accuracy is found to be 10-by-10.
3124333
Stochastic iterative algorithms for signal set design for Gaussian channels and optimality of the L2 signal set
We propose a stochastic iteration approach to signal set design. Four practical stochastic iterative algorithms are proposed with respect to equal and average energy constraints and sequential and batch modes. By simulation, a new optimal signal set, the L2 signal set (consisting of a regular simplex set of three signals and some zero signals), is found under the strong simplex conjecture (SSC) condition (equal a priori probability and average energy constraint) at low signal-to-noise ratios (SNR). The optimality of the L1 signal set, the confirmation of the weak simplex conjecture, and two of Dunbridge's (1967) theorems are some of the results obtained by simulations. The influence of SNR and a priori probabilities on the signal sets is also investigated via simulation. As an application to practical communication system design, the signal sets of eight two-dimensional (2-D) signals are studied by simulation under the SSC condition. Two signal sets better than 8-PSK are found. Optimal properties of the L2 signal set are analyzed under the SSC condition at low SNRs. The L2 signal set is proved to be uniquely optimal in 2-D space. The class of signal sets S(M, K) (consisting of a regular simplex set of K signals and M-K zero signals) is analyzed. It is shown that any of the signal sets S(M, K) for 3/spl les/K/spl les/M-1 disproves the strong simplex conjecture for M/spl ges/4, and if M/spl ges/7, S(M, 2) (the L1 signal set) also disproves the strong simplex conjecture. It is proved that the L2 signal set is the unique optimal signal set in the class of signal sets S(M, K) for all M/spl ges/4. Several results obtained by Steiner (see ibid., vol.40, no.5, p.721-31, 1994) for all M/spl ges/7 are extended to all M/spl ges/4. Finally, we show that for M/spl ges/7, there exists an integer K'