PURPOSE: To suppress the deterioration of quantity and to attain a low bit rate by compressing the time base of an input sound signal prior to the execution of a code excited LPC(CELP) encoding and extending the time base of a CELP-decoded sound signal.
CONSTITUTION: The time base compression of an integral multiple is applied to an input sound signal, the sampling period of an input signal to the CELP encoder is set up to an integral multiple of the original sampling period and the frequency band of a signal is reduced to 1/integer times. The time base compressed sound signal is CELP-encoded by using plural samples as one vector and transmitted as a code consisting of plural bits. On the transmitting side, a time base compressing circuit 1 executes time base compression and a CELP encoding circuit 2 executes CELP encoding, and on the receiving side, a CELP decoding circuit 3 decodes CELP decoding and a time axis extending circuit 4 executes time base extension. In addition, pitch period information indicating how many samples are used for each time base compression on the transmitting side is informed to the receiving side.
FUJINO SHOJI
MATSUO NAOJI
NOBUMOTO TOSHIAKI
EGUCHI OSAHIDE
OTA TOSHIYUKI
MURAKAWA MIKI
