Pitch control system

DETAILED DESCRIPTION It is an object of the present invention to provide a pitch control system for suppressing the generation of tremolo sounds.
Another object of the invention is to provide a pitch control system, which has a common clock for determining writing timing and reading timing.
The interval control system according to a first aspect of the present invention comprises interpolating means for decreasing from a plurality of consecutive inputted data of digitized audio signal obtained through sampling at predetermined sampling intervals a predetermined number of data when a pitch is to be raised, and for increasing a predetermined number of data when the pitch is to be lowered, a ring buffer with a predetermined memory size, writing and reading means for simultaneously writing one or more continuous interpolated data at a write memory position of a specified write address on the ring buffer at intervals of the period of sampling and for reading from a read memory position of at least one specified read address of the ring buffer at intervals of the sampling period, and address specifying means for specifying write address and read address at each of the above intervals, whereby the address is corrected to exclude empty space for the written data if the data are decreased when the pitch is to be raised, and the address is corrected so that the written data are not in excess if the data are increased when the pitch is to be lowered.
The interval control system according to a second aspect of the present invention comprises writing and reading means for writing inputted data of digitized audio signal at predetermined sampling intervals to a write memory position of a specified write address of a ring buffer having a predetermined memory size and for reading the data stored in the ring buffer from a plurality of memory positions of the ring buffer at intervals different from intervals corresponding to the sampling interval in the order of the data, coefficient setting means for setting coefficients according to address spacing with a write memory position of he ring buffer for each of a plurality of read memory positions of the ring buffer, and computing means for multiplying the read data for each of a plurality of read memory positions by the corresponding coefficients and for summing up the resultant data and using this as an output data, whereby the address spacing between a plurality of read memory positions is different from each other