Speech production by unconverted digital signals
AssigneeFirst Byte
InventorsKevin R. Kachikian, William J. Arthur, Richard P. Sprague
Life of this patent
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Abstract
Improved speech sounds are produced from an all-software speech generating program on a computer which does not have a digital-to-analog converter by polling a first timer connected to the computer's speaker until a time-out is found, then applying a sample time value to a second timer so connected, and restarting the first timer. This results in the generation of a variable-duty-cycle carrier without interfering with the computer's operation. In an alternative embodiment, the first timer is used to generate an interrupt at regular intervals, and a sample time value from a storage buffer is then applied to the second timer.
Claims4
Apparatus for producing speech from digitally encoded speech samples without the use of a digital-to-analog converter, comprising:
- (a) speech computation means for producing a sequence of said digitally encoded samples;
- (b) a computer central processing unit;
- (c) a speaker;
- and
- (d) control means connected to said central processing unit and said speaker for applying to said speaker a square wave signal having a duty cycle controlled by said speech computation means in accordance with the values of said samples;
- (e) said square wave signal having a constant frequency in the ultrasonic range;
- and
- (f) said control means including:
- (i) first and second timers;
- (ii) means for causing said first timer to count a first predetermined time interval;
- (iii) means for continually polling said first timer to detect the end of said time interval;
- (iv) means for causing said second timer to count a second time interval when said end of said first interval is detected, said second interval being a function of said sample values, and to put out said square wave signal in response thereto.
Apparatus for producing speech from digitally encoded speech samples without the use of a digital-to-analog converter, comprising:
- (a) speech computation means for producing a sequence of said digitally encoded samples;
- (b) a computer central process unit;
- (c) a speaker;
- and
- (d) control means connected to said central processing unit and said speaker for applying to said speaker a square wave signal having a duty cycle controlled by said speech computation means in accordance with the values of said samples;
- (e) said square wave signal having a constant frequency in the ultrasonic range;
- and
- (f) said control means including:
- (i) first and second timers;
- (ii) a buffer for storing said sample values;
- (iii) means for causing said first timer to cyclically count first predetermined time intervals;
- (iv) means for interrupting said central processing unit in synchronization with said time intervals to apply a sample value stored in said buffer to said second timer so as to cause it to count a second interval which is a function of said stored sample value, and to put out said square wave signal in response thereto;
- and
- (v) means for causing sad central processing unit to compute and store and sample values in said buffer between interrupts.
Dependencies are inferred from the claim text.