Audio data is converted into a digital format at a selectable conversion rate and applied through a microprocessor into memory storage. Stored data is selectively recalled and reconverted into an analog format for reconstruction into human speech at a processing rate independent of the input storage rate. The write pointer address and the read pointer address during the storage and retrieval of data are maintained within a selected address differential in accordance with the input data rate and the processing rate. To repeat the retrieval of particular stored data from selected address locations, the data input storage is interrupted thereby holding in memory a selected portion of previously stored data. The amount of data retrieved during the repeat process is varied by controlling the write pointer and the differential address between the write pointer and the read pointer.
Digital delay apparatus for variable delay uses a shift register fixed delay driving a random access memory variable delay. A variable modulus counter controls the read-write addressing, whereby the difference between addresses sets the variable delay of the random access memory. The random access memory capacity is small relative to the shift register for increased efficiency.
There is provided an apparatus which automatically records and reproduces. The digital signal based on the acoustic signal is stored in memory means due to the operation of write control means in response to the recording instruction. When the recording is not instructed, the digital signal stored is read out due to the operation of readout control means, and the acoustic signal is reproduced from this digital signal.
A delay correction circuit is described for use with an elastic store in a PCM time division multiplexed system. The relative position of the read and write addresses supplied to the elastic store are monitored. In the event that either the read or write addresses are overtaking the other and are within a predetermined range of addresses, either the read or write address source will be initialized at a predetermined time such that the read and write addresses have new relative position.
A musical instrument employing probabilistic wavetable-modification method of producing musical sound. A randomly initialized wavetable which is periodically accessed to provide an output signal which determines the musical sound. The output signal from the wavetable is probabilistically modified and stored back into the wavetable as modified data. The modified data, after a delay, is accessed from the wavetable and thereby becomes a new output signal. This process is periodically repeated whereby each new output signal is stored (after possibly being modified) back into the wavetable to produce rich and natural musical sound.
Digital processing of speech signals for compression/expansion pitch change is provided by writing and reading a ROM at different rates and controlling the discard/repeat segments of memory to be integral multiples of the pitch period. The rear pointer jumps a portion of the memory to either skip a portion (in compression) or retrace a portion (in expansion) of the recorded information. The read pointer jumps so as to avoid crossing the write pointer (thereby avoiding reading old recorded information). The jump occurs when a predetermined spacing or condition is reached between read and write pointers.
