Quality Control for Scalable Media Processing Applications

Many media processing applications create a load that varies significantly over time. Hence, if such an application is assigned a lower processing-time budget than needed in its worst-case load situation, deadline misses are likely to occur. This problem can be dealt with by designing media processing applications in a scalable fashion. A scalable media processing application can run in multiple qualities, leading to correspondingly different resource demands. The problem we consider is to find an accompanying quality control strategy, which minimizes both the number of deadline misses and the number of quality changes, while maximizing the quality of processing. We present an initial approach to the above problem by modeling it as a Markov decision process (MDP). Our model is based on measuring relative progress at milestones. Solving the MDP results in a quality control strategy that can be applied during runtime with only little overhead. We evaluate our approach by means of a practical example, which concerns a scalable MPEG-2 decoder.     

Worst-case response time analysis of real-time tasks under fixed-priority scheduling with deferred preemption

Fixed-priority scheduling with deferred preemption (FPDS) has been proposed in the literature as a viable alternative to fixed-priority pre-emptive scheduling (FPPS), that obviates the need for non-trivial resource access protocols and reduces the cost of arbitrary preemptions. This paper shows that existing worst-case response time analysis of hard real-time tasks under FPDS, arbitrary phasing and relative deadlines at most equal to periods is pessimistic and/or optimistic. The same problem also arises for fixed-priority non-pre-emptive scheduling (FPNS), being a special case of FPDS. This paper provides a revised analysis, resolving the problems with the existing approaches. The analysis is based on known concepts of critical instant and busy period for FPPS. To accommodate for our scheduling model for FPDS, we need to slightly modify existing definitions of these concepts. The analysis assumes a continuous scheduling model, which is based on a partitioning of the timeline in a set of non-empty, right semi-open intervals. It is shown that the critical instant, longest busy period, and worst-case response time for a task are suprema rather than maxima for all tasks, except for the lowest priority task. Hence, that instant, period, and response time cannot be assumed for any task, except for the lowest priority task. Moreover, it is shown that the analysis is not uniform for all tasks, i.e. the analysis for the lowest priority task differs from the analysis of the other tasks. These anomalies for the lowest priority task are an immediate consequence of the fact that only the lowest priority task cannot be blocked. To build on earlier work, the worst-case response time analysis for FPDS is expressed in terms of known worst-case analysis results for FPPS. The paper includes pessimistic variants of the analysis, which are uniform for all tasks, illustrates the revised analysis for an advanced model for FPDS, where tasks are structured as flow graphs of subjobs rather than sequences, and shows that our analysis is sustainable.     

Smoothing Streams in an In-Home Digital Network: Optimization of Bus and Buffer Usage

In an in-home digital network it may be expected that several data streams (audio, video) run simultaneously over a shared communication device, e.g., a bus. The burstiness of a data stream can be reduced by buffering data at the sending and receiving side, thereby allowing a lower bus share allocation for the stream. In this paper we present an algorithm that determines how much of the bus capacity and buffer space should be allocated to each stream, in order to have a feasible transmission schedule for each stream. Furthermore, the algorithm determines a transmission schedule for each stream, indicating how much data is transmitted over time. We show how this multiple-stream problem can be solved by repeatedly solving single-stream problems. We present efficient algorithms to solve these single-stream problems. Furthermore, we present some experimental results. This revised version was published online in September 2006 with corrections to the Cover Date.     

Architectural strategies for high-throughput applications

In this article an architecture is presented which allows efficient ASIC implementations of high throughput applications. Examples of these applications can be found in real time video applications such as EDTV, IDTV and HDTV. A key issue in the architecture is to provide a balance between memory resources and processing resources. Special attention is paid to the communication between these two types of resources. Architectural techniques are proposed to solve bottlenecks in the memory bandwidth and conflicts between memory accesses. Architectures for address generation in combination with location assignment are presented. The flexibility of the architectural model allows an efficient hardware realization on an ASIC exploiting the inherent parallelism of a particular application. This is illustrated in the article using a complex video algorithm for Progressive Scan Conversion. The proposed architecture is used as a target architecture which drives the high-level synthesis approach of the PHIDEO compiler.     

Mpeg2 Video Encoding in Consumer Electronics

Only very recently, single-chip MPEG2 video encoders are being reported. They are a result of additional interest in encoding in consumer products, apart from broadcast encoding, where a video encoder contains several expensive chips. Only single-chip solutions are cost-effective enough to enable digital recording for the consumer. The professional broadcast encoders are expensive because they use the full MPEG toolkit to guarantee good image quality, at the lowest possible bit-rate. Some MPEG tools are costly in hardware and these are therefore not feasible in single-chip solutions. This results in higher bit-rates, that can be accepted because of the available channel and storage capacity of the latest consumer storage media, harddisk, digital tape (D-VHS) and Digital Versatile Disk (DVD). A consumer product is I.McIC, a single-chip MPEG2 video encoder. It operates in ML@SP mode which can be decoded by all MPEG2 decoders. The IC is highly-integrated, as it contains motion-estimation and compensation, adaptive temporal noise filtering and buffer/bit-rate control. The high-throughput functions of the MPEG algorithm are mapped onto pipelined dedicated hardware, whereas the remaining functions are processed by an application-specific instruction-set processor. Software for this processor can be downloaded, in order to suit the IC for different applications and operating conditions. The IC consists of several communicating processors which were designed using high-level synthesis tools, PHIDEO and DSP Station.     

Urinary Bladder Cancer Susceptibility Markers. What Do We Know about Functional Mechanisms?

Genome-wide association studies (GWAS) have been successful in the identification of the several urinary bladder cancer (UBC) susceptibility loci, pointing towards novel genes involved in tumor development. Despite that, functional characterization of the identified variants remains challenging, as they mostly map to poorly understood, non-coding regions. Recently, two of the UBC risk variants (PSCA and UGT1A) were confirmed to have functional consequences. They were shown to modify bladder cancer risk by influencing gene expression in an allele-specific manner. Although the role of the other UBC risk variants is unknown, it can be hypothesized—based on studies from different cancer types—that they influence cancer susceptibility by alterations in regulatory networks. The insight into UBC heritability gained through GWAS and further functional studies can impact on cancer prevention and screening, as well as on the development of new biomarkers and future personalized therapies.     

Best-Case Response Times and Jitter Analysis of Real-Time Tasks

In this paper, we present a simple recursive equation and an iterative procedure to determine the best-case response times of periodic tasks under fixed-priority preemptive scheduling and arbitrary phasings. The approach is of a similar nature as the one used to determine worst-case response times (Joseph and Pandya, 1986) in the sense that where a critical instant is considered to determine the latter, we base our analysis on an optimal instant. Such an optimal instant occurs when all higher priority tasks have a simultaneous release that coincides with the completion of an execution of the task under consideration. The resulting recursive equation closely resembles the one for worst-case response times. The iterative procedure is illustrated by means of a small example. Next, we apply the best-case response times to analyze jitter in distributed multiprocessor systems. To this end, we discuss the effect of the best-case response times on completion jitter, as well as the effect of release jitter on the best-case response times. The newly derived best-case response times generally result in tighter bounds on jitter, in turn leading to tighter worst-case response time bounds.     

Mohs' method of micrographic surgery as treatment for recurrent basal cell carcinoma

OBJECTIVE: Evaluation of Mohs' micrographic surgery as treatment for recurrent basal cell carcinoma of the skin. DESIGN: Retrospective. SETTING: University Hospital Maastricht, the Netherlands. METHOD: In the period April 1992 to December 1995, 91 recurrent basal cell carcinomas (88 patients) were treated by Mohs' micrographic surgery. Medical records were analysed retrospectively with respect to different aspects. RESULTS: The mean age of the patients was 69 years. The recurrent basal cell carcinomas, with an mean diameter of 19.7 mm, were mainly localized on the nose and forehead. There were equal numbers of solid and morphea-like types of basal cell carcinomas. Most of these tumours had been treated by means of surgical excision in the past. The last treatment had taken place 3 years previously on average. Reconstruction was performed by means of primary closure, a graft or a flap. The mean follow-up period after Mohs' micrographic surgery was 12 months, in which one tumour recurred. CONCLUSION: Mohs' micrographic surgery is a surgical technique which provides the best prospect of total tumour removal together with maximal functional and cosmetic preservation. Mohs' micrographic surgery is of particular value for the treatment of recurrent basal cell carcinomas.     

PHIDEO: High-level synthesis for high throughput applications

This paper describes a new approach to high-level synthesis for high throughput applications. Such applications are typically found in real-time video systems such as HDTV. The method is capable of dealing with hierarchical flow graphs containing loops with manifest boundaries and linear index expressions. The algorithm is based on the model of periodic operations which allows optimizations across loop boundaries. Processing units and storage units are minimized simultaneously. The algorithm is implemented in thePHIDEO system. The major parts of this system are the processing unit synthesis, the scheduler and the memory synthesis including address generation.     

In-game assessment and training of nonverbal cognitive skills using TagTiles

We present a field study with a game for children called ‘Tap the little hedgehog’, which is played on the TagTiles console, a tangible electronic interface. The game was developed to train and assess cognitive skills and includes tasks which, in isolation, exhibit a high correlation with a number of subtests from the Wechsler Intelligence Scale for Children (WISC-III-NL). The tasks address a range of nonverbal skills by requiring children to perform different operations on abstract patterns such as copying, reproducing sequences from memory and mirroring patterns. In the current study, we tested whether these tasks kept their ability to address these skills if included in a gaming context, whether children are able to play the game independently and whether they are motivated to play the game. The results of the study support the hypothesis that nonverbal IQ-scores, as measured by the Wechsler Intelligence Scale for Children, can improve by training with a game. Hence, games like ‘Tap the little hedgehog’ can be used to train specific skills and serve as a screening tool for these skills. The results also confirm that children can play the game independently and that they enjoy it. We further found that children quickly learn how to play the game and use the interface.