Generation of wave functions by storage of parameters for piecewise linear approximations
AssigneeLucent Technologies Inc.
InventorsEduardo Abreu, Jalil Fadavi-Ardekani
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Abstract
An improved method for generating various wave functions for use in musical tone generation in FM synthesis so as to substantially reduce computational and storage requirements. The waveform desired to be used is mathematically modeled using piecewise linear approximation. A reduced number of coefficients of the piecewise linear approximation, representing the angles and offsets of the linear segments, are stored in memory.
Claims24
An integrated circuit that includes an operator circuit employed in a FM synthesizer to generate a frequency modulated, FM signal, said operator circuit comprising:
- an envelope generator configured to generate a signal corresponding to a desired envelope shape associated with a predetermined sound;
- a phase buffer that stores data samples corresponding to a predetermined phase representing the phase of a carrier signal of said FM signal;
- a temporary buffer for storing the signals generated by said operator circuit;
- an adder coupled to said phase buffer and said temporary buffer for adding the contents of said phase buffer to data stored in said temporary buffer representing the modulating signal of signal of said FM signal;
- and
- a sine signal estimator configured to generate a piecewise linear approximation of a desired waveform, said sine signal estimator coupled to said envelope generator and said adder so that the signal provided by said envelope generator defines the amplitude of said desired waveform, and the signal provided by said adder defines the phase of said desired waveform.
A method for generating a desired FM signal by employing an FM synthesizer comprising the steps of:
- generating an envelope signal corresponding to a desired envelope shape associated with a predetermined sound;
- storing in a phase buffer data samples corresponding to a predetermined phase representing the phase of a carrier signal of said FM signal;
- adding the contents of said phase buffer to phase data stored in a temporary buffer representing the modulating signal of said FM signal;
- and
- generating a piecewise linear approximation of a desired waveform, such that said envelope signal defines the amplitude of said desired waveform, and said modulating signal defines the phase of said desired waveform.
A method for generating a waveform for use in FM synthesis, comprising the following steps:
- (a) identifying a desired waveform to be generated for use;
- (b) creating a piecewise linear approximation of the desired waveform;
- (c) storing the coefficients of the piecewise linear approximation in a memory device;
- and
- (d) retrieving said coefficients upon demand for use in generating a waveform for use in FM synthesis.
An integrated circuit that includes a signal estimator to generate a desired waveform, as a function of a variable, said signal estimator comprising:
- a memory device configured to store a plurality of coefficients representing a plurality of lines, wherein each line corresponds to a predetermined segment that represents a set of said variable;
- and
- waveform generating means coupled to said memory device configured to retrieve at least one of said coefficients so as to generate a linear approximated value for said desired waveform corresponding to one of said variables.
The signal estimator in accordance with claim 22 further comprising an envelope generator coupled to said waveform generating means configured to generate a signal corresponding to a desired envelope shape associated with said desired waveform.
Dependencies are inferred from the claim text.