Abstract: 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 approximately integral multiples of the pitch period with means to track the pitch period as it is changing and modify the discard/repeat segments accordingly.

Abstract: 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.

Abstract: An analog signal stacking method and apparatus permits transmission of n analog signals of given spectrum width over a narrow band communication circuit having bandwidth approximately equal to the spectrum width of one analog signal by compressing the spectrum of each signal by a factor of 1/n and frequency offsetting the compressed signals to occupy contiguous frequency bands within the bandwidth of the circuit. Received signals are processed to remove the frequency offset and expand the baseband signals to restore each analog signal to its normal spectrum. A dial through circuit permits application of the stacking feature to place two conventional dialed calls on a single line of the telephone network using a circuit for processing both dial and voice signals.

Abstract: A time compression audio reproduction system has two stereo channels with means for synchronously operating the pitch correction means in each channel to obtain time coincidence between corresponding portions of the signal output from each channel. Features include switching for alternately selecting delay elements.

Abstract: A time compression/expansion system for recorded programs provides time change on playback with pitch correction free of gaps or processing noise due to splicing and discard. A dual memory delay system operated to inversely vary delay is used to provide an interval during which to detect the start of the next program sample with matched signal amplitude and sign. During this interval pitch correction is a continuous extension of the current sample. The system can include individual processing of contiguous frequency bands.

Abstract: A time compression/expansion audio reproduction system of the type that provides pitch correction by repetitive variable time delay achieves improved performance by separating the reproduced signal from a recording into components which are separately delayed. For studio quality reproduction the signal is separated into contiguous frequency bands which are each delayed synchronously and the processing noise in each band is eliminated by filtering each band signal after delay to eliminate high frequency components. Bandpass filtering prior to recombination as well as blanking and amplitude compression and expansion are also disclosed.