Media Vision

Aureal Semiconductor, Inc.

Bryan J Colvin, Sr

Perry R Cook

Daniel B Gochnauer

Michael S Rovner

Masao Shindo

Exponential and pseudo-exponential decay function values are generated by scaling a fractional decrease per sampling period by a previous decay function value and then subtracting the scaled fractional decrease from the previous decay function value. In one embodiment, a multiplier multiplies the fractional decrease by the previous decay function value and provides a product signal representing the scaled fractional decrease. An adder subtracts the scaled fractional decrease from the previous decay function value. In another embodiment, a shift block replaces the multiplier and approximates multiplication by a binary shift of the fractional decrease. The size of the shift is determined by the previous magnitude of the decay function as indicated by a priority encoder. Shifting generates a pseudo-exponential decay function which is suitable for music synthesis and can be generated quickly using less expensive hardware.

Economical generation of exponential and pseudo-exponential decay

Synthesizer models for emulating musical instruments can be improved using an analysis model that compares the output signal of the model to a recording of a desired sound and derives a residual signal that can be used to correct the model. When the original model is a good one, the residual signal is small and takes much less memory to store than is required for a sampled sound.

Residual excited wave guide

A circuit is provided for filtering asynchronous metastability. The circuit includes two or more output lines that provide signals indicative of the assertion of control or data input signals at a plurality of input lines. Despite the simultaneous assertion of two or more input signals, the circuit prevents the simultaneous assertion of more than one output signal, thereby preventing adverse effects within a digital system connected to the circuit.

Circuit for filtering asynchronous metastability of cross-coupled logic

Synthesizer models for emulating musical instruments are improved to take into account sympathetic string vibrations. One embodiment of the present invention scales an output signal from a sound synthesis model and uses the scaled signal as an input signal for a number of single-string emulations causing the single-string emulations to produce sound signals corresponding to sympathetic string vibrations. The output signals from the synthesis model and from all of the single-string emulations are added together. Another embodiment employs an octave's worth of single-string emulations to emulate the lower strings of an emulated instrument. Still another embodiment is a synthesizer which includes an input bus for accepting a sound signal, scaling means, a plurality of single-string emulations, and means for summing output signals from the string emulations. Embodiments preferably employ waveguide synthesis or the plucked string model to emulate single-strings.

Sound synthesis model incorporating sympathetic vibrations of strings

A timing generator contains an oscillator section (10) formed with a plural number of stages (S.sub.1 -S.sub.N) for respectively producing a like number of stage signals (V.sub.S1 -V.sub.SN) that sequentially change signal values at a basic oscillator frequency (f.sub.O). The oscillator section is typically implemented as a ring oscillator. In response to the stage signals, a timing-signal generating section (14) generates one or more timing signals (V.sub.T1 -V.sub.TM), each having at least two transitions corresponding to transitions of two or more of the stage signals. A control section (12), preferably arranged in a phase-locked loop, causes the oscillator frequency and a reference frequency (f.sub.R) to have a substantially fixed relationship.

Timing generator

An audio power amplifier is provided that includes circuitry to prevent popping noises when the amplifier is turned on and turned off. The amplifier can be powered with a single-ended voltage power supply, and thus may be used within systems such as personal computer. The amplifier includes a control circuit that prevents the fast charging of the output AC coupling capacitor when the amplifier is turned on and turned off. The control circuit controls a driver stage such that the output transistors turn on slowly when power is first applied, and such that the output transistors turn off quickly when the supply voltage is removed.

Audio power amplifier with noise prevention at turn-on and turn-off

An anti-clipping mixer circuit is provided within an integrated circuit. The mixer circuit allows for the independent level control of each input signal, thereby allowing the optimization of the signal-to-noise ratio. A master level control is provided to limit the overall combined output signal to a level below the operational amplifier's maximum voltage level. A control circuit may be used to automatically adjust the input signal levels as well as the combined output signal level.

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San Jose, CA, United States of America

Bryan J Colvin, Sr