In this paper, we address the problem of the efficient encoding of object boundaries. This problem is becoming increasingly important in applications such as content-based storage and retrieval, studio and television postproduction, and mobile multimedia applications. The MPEG-4 visual standard will allow the transmission of arbitrarily shaped video objects. The techniques developed for shape coding within the MPEG-4 standardization effort are described and compared first. A framework for the representation of shapes using their contours is presented next. Such representations are achieved using curves of various orders, and they are optimal in the rate-distortion sense. Last, conclusions are drawn.
W e discuss the architecture and technical viability of transporting real-time voice over packet-switched networks such as the Internet. The value of integrating voice and data networks onto a common platform is well known. The telephony industry has proposed the ATM standard as a means of upgrading the Internet to provide both real-time and data services. In contrast, voice services may be added to traditional IP networks that were originally designed for data transmission alone. Here, we consider the feasibility and expected qualit of service of audio a plications tures for voice over IP and discuss measured Internet delay and loss characteristics. over IP networks such as the Internet. In particu Y ar, we examine possib P e architeche concept of an integrated services network with both real-time and data services is not new. In fact, two alternate schemes are currently contending to provide all the services seen in Fig. 1. From one point of view, a new backbone from the telephony world -interexchange carrier (1XC)iasynchronous transfer mode (ATM) or frame relay (FR) -would provide all the required quality of service (QoS) levels for integrated services. From the other point of view, the existing Internet and corporate intranets would carry real-time voice traffic in addition to data.Traditionally, the networking world has been divided along such lines. There has long been a telecommunications network that is circuit-switched and designed for point-to-point communication of real-time audio. Subsequently it has been adapted for the growing needs of data communication via modem technologies, ISDN, digital carriers, and, most recently, integrated services ATM and FR backbones. In contrast, there also exists a data networking world of store-and-forward packet technologies created primarily for data transport over local and wide areas. These networks are the vast collection of small and large IP networks that are intertwined in the form of the Internet and many partitioned intranets. Data networks comprise links, routers, bridges, and switches in the form of local and wide area networks.Although these two networking worlds are coming together in a model of shared data, voice, and video, proponents of each view are looking at the future as an extension of their own technology. The telecommunications world has envisioned an integrated network via a large-scale ATM backbone that supports many levels of QoS, including traditional n x 64 kbis voice. Since the telecommunications world has always been very QoS-focused, ATM is provisioned with mechanisms to provide different QoS levels. From the IP community, the long-term view is that real-time voice and video services can multiplex with existing data traffic. However, QoS has not been considered with the same intensity -the current Internet service model is flat, offering a classless,, best-effort delivery service. As such, QoS is an ad hoc extension to the IP infrastructure. The next generation of IP, version 6, includes support for '(flows" of packets between one or mor...
In this paper, we review a general framework for the optimal bit allocation among dependent quantizers based on the minimum maximum (MINMAX) distortion criterion. Pros and cons of this optimization criterion are discussed and compared to the well-known Lagrange multiplier method for the minimum average (MINAVE) distortion criterion. We argue that, in many applications, the MINMAX criterion is more appropriate than the more popular MINAVE criterion. We discuss the algorithms for solving the optimal bit allocation problem among dependent quantizers for both criteria and highlight the similarities and differences. We point out that any problem which can be solved with the MINAVE criterion can also be solved with the MINMAX criterion, since both approaches are based on the same assumptions. We discuss uniqueness of the MINMAX solution and the way both criteria can be applied simultaneously within the same optimization framework. Furthermore, we show how the discussed MINMAX approach can be directly extended to result in the lexicographically optimal solution. Finally, we apply the discussed MINMAX solution methods to still image compression, intermode frame compression of H.263, and shape coding applications.
We present a prototype compressive video camera that encodes scene movement using a translated binary photomask in the optical path. The encoded recording can then be used to reconstruct multiple output frames from each captured image, effectively synthesizing high speed video. The use of a printed binary mask allows reconstruction at higher spatial resolutions than has been previously demonstrated. In addition, we improve upon previous work by investigating tradeoffs in mask design and reconstruction algorithm selection. We identify a mask design that consistently provides the best performance across multiple reconstruction strategies in simulation, and verify it with our prototype hardware. Finally, we compare reconstruction algorithms and identify the best choice in terms of balancing reconstruction quality and speed.
In this paper, we present fast and efficient methods for the lossy encoding of object boundaries that are given as eight-connect chain codes. We approximate the boundary by a polygon, and consider the problem of finding the polygon which leads to the smallest distortion for a given number of bits. We also address the dual problem of finding the polygon which leads to the smallest bit rate for a given distortion. We consider two different classes of distortion measures. The first class is based on the maximum operator and the second class is based on the summation operator. For the first class, we derive a fast and optimal scheme that is based on a shortest path algorithm for a weighted directed acyclic graph. For the second class we propose a solution approach that is based on the Lagrange multiplier method, which uses the above-mentioned shortest path algorithm. Since the Lagrange multiplier method can only find solutions on the convex hull of the operational rate distortion function, we also propose a tree-pruning-based algorithm that can find all the optimal solutions. Finally, we present results of the proposed schemes using objects from the Miss America sequence.
Artificial light at night (ALAN) is a relatively new and rapidly increasing global change driver. While evidence on adverse effects of ALAN for biodiversity and ecosystem functioning is increasing, little is known on the spatial extent of its effects. We therefore tested whether ALAN can affect ecosystem functioning in areas adjacent to directly illuminated areas. We exposed two phytometer species to three different treatments of ALAN (sites directly illuminated, sites adjacent to directly illuminated sites, control sites without illumination), and we measured its effect on the reproductive output of both plant species. Furthermore, in one of the two plant species, we quantified pre-dispersal seed predation and the resulting relative reproductive output. Finally, under controlled condition in the laboratory, we assessed flower visitation and oviposition of the main seed predator in relation to light intensity. There was a trend for reduced reproductive output of one of the two plant species on directly illuminated sites, but not of the other. Compared to dark control sites, seed predation was significantly increased on dark sites adjacent to illuminated sites, which resulted in a significantly reduced relative reproductive output. Finally, in the laboratory, the main seed predator flew away from the light source to interact with its host plant in the darkest area available, which might explain the results found in the field. We conclude that ALAN can also affect ecosystem functioning in areas not directly illuminated, thereby having ecological consequences at a much larger scale than previously thought. Artificial light at night (ALAN) is a relatively new global change driver, which is worldwide rapidly increasing 1. It has various ecological consequences as it can cause alterations in physiology and behaviour of organisms, thereby increasing mortality, reducing reproduction as well as altering species abundances and community composition 1-5. For example, many animals have been shown to be attracted 6,7 or repelled 8-11 by light. There is increasing evidence that ALAN has also consequences for species interactions: ALAN has been shown to alter mutualistic interactions, for example to disrupt nocturnal plant-pollinator interactions with negative consequences for the pollination service the nocturnal pollinators provide to the plants 12. However, most of the research so far has focused on the effect of ALAN on predation. 8,11,13-16. These studies show that ALAN can reduce or increase species interactions and ecosystem functioning, and that the effect often depends on light quality and quantity 5,17. However, so far, research has mostly focused on the impact ALAN has on species interactions and ecosystem functioning in directly illuminated areas 5,12,18,19 , ignoring what happens in areas in the surroundings of the illuminated area. Yet animals such as moths, might be attracted from long distances to the illuminated area potentially leading to lowered densities, interaction frequencies and ecosystem functioning in ...
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