José Tribolet

A new phase unwrapping algorithm

A new phase unwrapping algorithm is proposed that combines the information contained in both the phase derivative and the principal value of the phase into an adaptive numerical integration scheme. This new algorithm has proven itself to be very reliable and it can be easily incorporated in standard homomorphic signal processors.

A study of complexity and quality of speech waveform coders

This paper presents the results of a pilot study comparing four different speech waveform coding techniques of varying complexity. Coder transmission rates of 24, 16, and 9.6 Kb/s were used in the experiment. Subjective ratings and objective measurements of quality are obtained and compared. A number of conclusions are drawn concerning the quality and complexity, of different coding techniques. By comparing the objective measurements to the subjective ratings a number of conclusions are also drawn concerning the strengths and weaknesses of various (objective) quality measures of speech waveform coders.

Nonstationary spectral modeling of voiced speech

The main purpose of this paper is to present a novel model for voiced speech. The classical model, which is being used in many applications, assumes local stationarity, and consequently imposes a simple and well known line structure to the short-time spectrum of voiced speech. The model derived in this paper allows for local non-stationarities not only in terms of pitch perturbations, but in terms of vocal tract variations as well. The resulting structure of the short-time spectrum becomes more complex, but can still be interpreted in terms of generalized lines. The proposed model supports new forms of spectral prediction, which can be put to advantage in speech coding applications. Experimental results are presented supporting the validity of both the model itself and the prediction relationships. Finally, a new class of speech coders, denoted harmonic coders, based on the presented model, is proposed, and a specific implementation is presented.

The discipline of enterprise engineering

A century ago, Taylor published a landmark in the organisational sciences: his Principles of Scientific Management. Many researchers have elaborated on Taylor’s principles, or have been influenced otherwise. The authors of the current paper evaluate a century of enterprise development, and conclude that a paradigm shift is needed for dealing adequately with the challenges that modern enterprises face. Three generic goals are identified. The first one, intellectual manageability, is the basis for mastering complexity; current approaches fall short in assisting professionals to master the complexity of enterprises and enterprise changes. The second goal, organisational concinnity, is conditional for making strategic initiatives operational; current approaches do not, or inadequately, address this objective. The third goal, social devotion, is the basis for achieving employee empowerment as well as knowledgeable management and governance; modern employees are highly educated knowledge workers; yet, the mindset of managers has not evolved accordingly. The emerging discipline of Enterprise Engineering, as conceived by the authors, is considered to be a suitable vehicle for achieving these goals. It does so by providing new, powerful theories and effective methodologies. A theoretical framework is presented for positioning the theories, goals, and fundamentals of enterprise engineering in four classes: philosophical, ontological, ideological and technological.

Improved pitch prediction with fractional delays in CELP coding

A scheme is discussed for long-term prediction in CELP (code-excited linear predictive) coding using fractional delay prediction. This technique permits a more accurate representation of voiced speech and achieves an improvement of synthetic quality for female speakers. The higher complexity of this type of predictor relative to the classical one is its major disadvantage. Suboptimal schemes in which the search for the functional pitch delay is restricted to a neighborhood of an integer pitch estimate can be envisaged to decrease the computational load.<<ETX>>

Harmonic coding at 4.8 kb/s

A harmonic coder designed for operation at 4.8 kb/s is presented. Sinusoidal modeling of speech is reviewed and the use of harmonically related frequencies is extended to unvoiced and transition regions. The estimation of the fundamental frequency with emphasis on the fine tuning of the pitch estimates is discussed. The structure of the 4.8-kbit/s harmonic coder is described, and a detailed discussion of phase quantization issues is presented. Experimental results are presented which reveal a reverberant character in many speech utterances and difficulties in some classes of sounds (plosives, liquids, and voiced fricatives). These distortions are mostly produced by the quantization of phase, but they are also explained by the difficulties of the sinusoidal analysis/synthesis in transition regions when the frame length is large.<<ETX>>

Harmonic coding: A low bit-rate, good-quality speech coding technique

Low bit-rate, good-quality speech coding is one of the fundamental goals of todays speech processing research. Present-day coding techniques, like APC and ATC, are able to achieve good-quality transmission only down to about 12 kb/s. Below this rate, their quality degrades rapidly. On the other hand, the various kinds of vocoders, which operate up to about 5 kb/s, have inherent quality limitations which cannot be overcome by an increase of the bit rate. In this paper, a new coding scheme is presented, which is based on a recently developed spectral model for nonstationary voiced speech, and it forms the basis of a waveform coder and a vocoder which are introduced in this paper, and which share the same basic structure. Experimental results are presented, which show that both systems yield significant bit-rate reductions relative to present-day schemes of equivalent quality.

Signal analysis by homomorphic prediction

Two commonly used signal analysis techniques are linear prediction and homomorphic filtering. Each has particular advantages and limitations. This paper considers several ways of combining these methods to capitalize on the advantages of both. The resulting techniques, referred to collectively as homomorphic prediction, are potentially useful for pole-zero modeling and inverse filtering of mixed phase signals. Two of these techniques are illustrated by means of synthetic examples.

Using roles and business objects to model and understand business processes

Business process modeling focus on describing how activities interact with other business objects while sustaining the organizations strategy. Business objects are object-oriented representations of organizational concepts, such as resources and actors, which collaborate with one another in order to achieve business goals. These objects exhibit different behavior according to each specific collaboration context. This means the perception of a business object depends on its collaborations with other objects. Business process modeling techniques do not clearly separate the multiple collaborative aspects of a business object from its internal aspects, making it difficult to understand objects which are used in different contexts, thus hindering reuse. To cope with such issues, this paper proposes using role modeling as a separation of concerns mechanism to increase the understandability and reusability of business process models. The approach divides a business process model into a business object model and a role model. The business object models deals with specifying the structure and intrinsic behavior of business objects while the role model specifies its collaborative aspects.

A framework for modeling strategy, business processes and information systems

In order to continuously improve its knowledge and to identify problems and possible solutions, an organization requires understanding of the way business is aligned with the organizational strategy and how information systems are supporting the business. The paper presents a framework for describing and associating organizational concepts at multiple levels of detail using three separate areas of concerns: goals and strategy, business processes, and information systems. The framework is presented as an extension to the Unified Modeling Language (UML) using a standard UML Profile. The framework concepts are illustrated by modeling the purchase and sales business operations of a retail store from the strategic, process and information systems viewpoints.