Gabriel is a software system intended to manage the complete development of real-time digital signal processing (DSP) applications, from conception and experimentation to implementation in real-time hardware. It performs non-real-time simulations as well as code synthesis for real-time hardware. It is intended to ease code development for architectures that are not easy targets for conventional compilers, such as multiprocessor systems built with very high-performance microcoded DSPs. The system is designed to be retargetable in two ways. First, it can synthesize code for a variety of multi-DSP architectures where the user specifies the salient features of the architecture. Second, it can target different DSPs. The authors have concentrated on code generation for the Motorola DSP56001, although code generation for the AT&T DSP32 has been demonstrated. At the highest level, an algorithm is described using a hierarchical block diagram. At the lowest level, the user can either simulate the algorithm locally on the workstation, simulate the target architecture running the generated code, or download the code into hardware and run it in real time. Gabriel is capable of handling multiple sample rates, iteration, and recurrences. >

Gabriel: a design environment for DSP

We detail a method for the partitioning of a single application specified in synchronous dataflow (SDF) into multiple independently-synthesizable, communicating VHDL hardware modules. Either synchronous or asynchronous communication is allowed, and the clock timing and control are automatically generated. We show that this method guarantees the preservation of correct functional behavior as specified in the original SDF graph, and that many choices of partitioning into multiple hardware modules are possible. The ability to break up a larger application into smaller synthesizable hardware modules can lead to efficiencies in hardware synthesis, which is faster when performed on smaller VHDL specifications. We illustrate this new method with some practical example applications that have been constructed in Ptolemy.

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Synthesis of parallel hardware implementations from synchronous dataflow graph specifications

Gabriel, a second-generation digital signal-processing (DSP) design environment, is described The Gabriel experimental signal-processing software performs non-real-time algorithm simulations and code synthesis for real-time hardware based on programmable DSPs Gabriel eases code development for architectures that are not easy targets for conventional compilers The model of compilation used by Gabriel is discussed at length Modification of the model to run in real time, target architectures, and scheduling are examined >

An overview is presented of the object-oriented programming (OOP) methodology in general and the ways it may be applied to integrate digital signal processing (DSP) software. Examples are given to show how the approach is used to solve signal-processing problems in the QuickSig system. The most important existing OOP languages and programming environments are discussed and compared form the point of view of DSP research and development. It is shown that OOP is a proper methodology for DSP programming and that much further work is needed to find the best tools and ways to build highly advanced programming environments. >

DSP software integration by object-oriented programming: a case study of QuickSig

Gabriel is a retargetable software system for the development of assembly code and microcode for single or multiple programmable DSPs. It is intended to ease code development even for processors that are not easy targets for conventional compilers. Code generation for the Motorola DSP56001 is emphasized. A Thor-based simulator supplies a variety of target multi-DSP architectures based on the DSP56001. The top-level algorithm description is a large grain data flow graph, and a graphical interface using OCT and VEM provides a natural representation of the high level structure of the algorithm.

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Gabriel: A Design Environment for Programmable DSPs

In an effort to produce more efficient means of transforming new algorithm concepts into working models, this paper describes the development of a digital signal processing workstation accepting input entirely in graphic form. This Graphic Oriented Signal Processing Language (GOSPL) accepts flow graph information in block diagram form using a mouse input device. The researcher uses the mouse to describe graph connections and create function blocks in the flow graph by selecting them from a menu. The system executes a broad class of flow graphs and provides virtual instruments to monitor signals throughout the graph during real-time execution.

Graphic oriented signal processing language-GOSPL

This paper examines the capabilities of cubic spline approximation in the representation of speech spectra as compared to the widely used linear predictive coding method. The LPC technique has proven robust in many applications, but certain difficulties remain when modeling speech signals. In particular the issues raised include the modeling of zeros in nasal sounds, model stability for sinusoidal inputs, global reaction of the model to a localized input disturbance, and interpretation of coded parameter values for purposes of editing and recognition. The cubic spline model addresses each of these problem areas. The approach used here to model each frame of speech data consists of fitting a cubic spline function to the local peaks of a log-magnitude FFT spectrum.

C. Covington

Papers

Graphic oriented signal processing language-GOSPL

Cubic spline modeling of speech spectra