Alva E. Henderson

Speech synthesis system utilizing variable frame rate

Speech synthesis system implementable in an integrated circuit device capable of converting frames of speech data at a variable frame rate into analog signals representative of human speech. The frames of speech data comprise digital representations of values of pitch, energy, filter coefficients and coded frame rate data. The speech synthesis system includes a linear predictive coding filter as a speech synthesizer which utilizes the speech data at a varying frame rate to produce digital speech signals representative of human speech. Frames of digital speech data including coded frame rate data are received by an input, with the frame rate data being decoded to control both the rate at which the incoming variable-length frames of speech data are accepted by the speech synthesizer and the number of interpolation calculations required to define interpolated speech values between adjacent incoming frames of speech data. A frame control circuit accomplishes the foregoing utilization of speech data at a variable frame rate by the speech synthesizer by providing for a variable number of interpolation calculations between adjacent speech frames from last implemented speech data in which the number of interpolation calculations in a given instance is determined by the frame rate data. A microprocessor controls the access of selected speech data which is stored in a memory. The system also includes a digital-to-analog converter for converting the digital speech signals produced by the filter into analog signals and a speaker for generating audible sounds in the form of synthesized human speech from the analog signals provided by the digital-to-analog converter.

Speech synthesis system with variable interpolation capability

A speech synthesis system with a linear predictive filter. The linear predictive filter utilizes coded reflection coefficients to produce digital signals representative of human speech. A variable interpolation circuit within the linear predictive filter allows a variable number of interpolation steps to be calculated between successive values of reflection coefficients. Additionally, a user programmable option allows the user to select a linear, nonlinear, or a combination form of interpolation based on stored scale data. The synthesizer output circuit also functions as a digital-to-analog converter.

Integrated speech synthesis circuit with internal and external excitation capabilities

A speech synthesis circuit implementable in an integrated circuit device, capable of converting frames of data into analog signals representative of human speech. The frames of data are comprised of digital representations of values of pitch, energy and certain filter coefficients, which are stored in non-volatile memory. The filter coefficients are utilized to control a linear predictive filter which is excited by voiced and unvoiced excitations stored in non-volatile memory. A control circuit coupling the excitation signals to the linear predictive filter allows the operator to select an external excitation signal rather than precalculated stored excitation signals. Thus, the synthesizer may be utilized in a vocoder application, wherein a residual excitation signal transmitted from an analysis circuit may be utilized as the excitation signal.

Speech synthesis system with alternative coded or uncoded parameter formats

Speech parameter signals may be coded to consist of fewer bits for data reduction in memory. In this system both coded and uncoded signals are stored with an associated control signal which controls selection of corresponding direct or decoder circuit coupling of memory output to a speech synthesizer.