Angel Groba

Distortion-Energy Analysis of an OMAP-Based H.264/SVC Decoder

This paper describes a Pareto frontier estimate of a scalable video decoder embedded in an OMAP-based multimedia terminal within the distortion-energy optimization space. A metric to estimate video distortion has been introduced. In addition, energy consumption estimates are obtained from real time measurements of the computational load. Finally, test-bench operation is successfully demonstrated with different H.264/SVC-compliant sets of sequences.

A Real-Time H.264 BP Decoder based on a DM642 DSP

In this paper, the implementation of a Main Profile H.264 decoder based on a DM642 digital signal processor is described. An initial standard compliant raw-C decoder has been optimized in speed for the target processor. The parallelism between algorithm execution and data movement has been fully exploited using DMA. Also, critical parts of the algorithm have been encoded directly in assembly code to increase the number of instructions per cycle. The decoder has been tested in simulation with actual (transcoded) DVD and digital TV streams. According to these tests, standard definition (Dl) real time decoding can be obtained with a DM642@720 MHz.

Response time of streaming chains: analysis and results

The analysis of systems executing a set of transactions composed by a number of tasks is required in some application domains, such as distributed systems or many audio/video streaming systems. The paper deals with the time response analysis of such systems, considering periodic uniprocessor transactions, and tasks, characterized by their fixed priority and execution time, connected in series through bounded buffers. The scheduling policy allows several transaction jobs to be active at a time, which is possible by putting intermediate task results in the buffers. When the output buffer of a task is full, the task becomes blocked and priority inversion arises. An analysis method is described that allows one to calculate the worst-case response time of the transactions in order to be compared with their end-to-end deadlines. The results of the method application show how task priorities or buffer sizes influence the transaction response times.

OS-level power consumption estimator for multimedia mobile devices

In this paper, an OS level power estimator based on monitored system events for multimedia mobile devices is presented. The OS level power estimator periodically obtains significant-events count values and calculates power-consumption estimations through mathematical models. We have implemented this power estimator in a Linux kernel and evaluated it while running a video decoder application on an embedded development platform. Experiments results show that the accuracy of power estimations is high with regard to the real measured power consumption, i.e., the error between them is less than 1% in average.

Real-time power consumption control system for multimedia mobile devices

Energy consumption in battery operated mobile devices is a critical issue. Autonomy periods are increasingly compromised as the complexity of tasks, such as the widespread video decoding ones, is also increased. While new higher-capacity batteries are being developed, techniques to control, i.e. save, the energy consumption can provide a significant benefit. This paper presents the proposal, implementation and test of a real-time closed-loop control system applicable to the power-consumption regulation of multimedia mobile devices. The novel closed loop does not need any specific power sensor but only standard performance monitoring counters (PMCs) available in common mobile processors. From them, the power consumption is estimated with an algorithm to be included into the operating system, along with the control system itself. A theoretical system model has been first developed to (1) enable the design of some controllers and (2) validate the actual results obtained from the control system prototype into a given low-cost development board. These results prove the control-system stability and the comparative suitability of classic controllers to keep the multimedia-system consumption close to the desired value in steady state with settling times as short as a single sample interval.

Real-time power-consumption control system for multimedia mobile devices

This paper presents a real-time closed-loop system to regulate the power consumption of multimedia mobile devices. The system feedback is an OS-level power estimator based on monitored events of the target system, i.e., an embedded development platform executing a video decoder. The implementation results match the expected ones from simulation and confirm that the system works with a suitable controller to reach null average steady-state error in short settling times.

High-level specification languages for embedded system design

In this chapter we show how to use three complementary languages, SDL, Statecharts and the language of MATRIX X, for the modelling and design of embedded systems. We base our approach on the fact that there is no perfect language for the design of embedded systems, and that one therefore has to find ways in which several formalisms, each with its own strength, can be used in conjunction. We present three ways of achieving this.

Closed-loop power-control governor for multimedia mobile devices

The micro-electronics industry has been boosting the capabilities of multimedia mobile devices, but the battery, which is the only power source of most mobile devices, is experiencing relatively slow development. Therefore, determining how to optimize the energy consumption of mobile devices under a predefined performance requirement has become a critical issue. The video decoder, as one of the main energyconsuming multimedia applications, is the target application of this manuscript. This paper presents control algorithms for power regulation under the limited battery capacities of multimedia hand-held devices while executing a decoder application and maintaining a reasonable quality of user experience. A control system, which includes a real-time closedloop control subsystem and a power-control governor (PCG), has been implemented in the operating system of a low-cost development board. Instead of using any specific power sensor, a PMC (performance monitoring counter)-based estimator is used as the feedback signal in the closed-loop subsystem. After a theoretical system model has been obtained, classic controllers have been implemented in the development board. The control system is able to regulate the power consumption and the battery discharge rate in the presence of fluctuations in the decoder power-consumption demand. The proposed PCG can extend the battery lifetime by 15.5% and 12.8% in comparison with the conservative and ondemand governors of Linux, respectively.

A Simulation Model for a Linear Variable Gap-Reluctance Drive With Resonant Load

A simulation model for a linear variable gap-reluctance drive with resonant load, a device widely used in automobile horns, is developed. The model, simulable with common electrical simulators, allows fast and accurate computation of: current and voltage waveforms, gap-width; and supplied, lost, and delivered power. A method to obtain model parameters is described. The model is validated comparing simulations against measurements upon real devices. The model can be used to ascertain the behavior of new devices prior to manufacturing and also to guide later device developments.

UF: Architecture and semantics for system-level multiformalism descriptions

In many industrial cases, the design of complex systems results in descriptions of the system that make use of different specification languages. In this paper we present a language, for the description of the global architecture of a system specified using such multilanguage approach.