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AssigneeOki Electric Industry Co., Ltd.
InventorsHiroshi Sasaki, Masayasu Sato
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A voice recording and reproducing device employing differential vector quantization divides an input voice signal into frames and predicts the sample values of each frame. The first sample value in a frame is predicted from one or more sample values of the preceding frame. Each predicted sample value is then used in predicting the next sample value in the same frame. For example, the predicted sample values may be fed back into a shift register that is initially loaded with sample values from the preceding frame, and prediction may be carried out by an arithmetic operation on the shift-register contents. This scheme reduces the amount of arithmetic circuitry needed for making the predictions, and reduces the cost of the device.
A method of using a codebook of frame patterns identified by index numbers to code a voice signal by sampling the voice signal to obtain sample values, grouping the sample values into frames, predicting the sample values in each frame, taking differences between the sample values and the predicted sample values in each frame to obtain a differential frame, searching the codebook to find a frame pattern most closely matching the differential frame, and writing the index number of the most closely matching frame pattern in a memory device as a coded value of the frame, each frame including a predetermined number of consecutive sample values from a first sample value to a last sample value, each sample value except the last sample value having a next sample value in the frame, wherein predicting the sample values in each frame comprises the steps of:
A voice recording and reproducing device of the type that samples a voice signal, divides the sampled voice signal into frames, predicts sample values of each frame, takes differences between the predicted sample values and actual sample values of the frame, codes the differences by vector quantization with reference to a codebook, stores resulting coded data in a memory device, and decodes the coded data with reference to the codebook, having a prediction unit comprising:
A voice recording and reproducing device of the type that samples a voice signal, divides the sampled voice signal into frames, predicts sample values of each frame, takes differences between the predicted sample values and actual sample values of the frame, codes the differences by vector quantization with reference to a codebook, stores resulting coded data in a memory device, and decodes the coded data with reference to the codebook, wherein the predicted sample values of each frame are all equal to a last sample value of an immediately preceding frame.
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