PURPOSE: To attain sound compresion with high sound quality even when a bit rate is low by adaptively selecting the volume of information required for respectively coding and quantizing auxiliary information and main information.
CONSTITUTION: An adaptive bit distributing circuit 7 generates bit distributing information based on a threshold determined by a masking threshold determining circuit 6 and supplies the generated information to a transmission pattern selecting circuit 8. The circuit 8 adaptively selects a transmission pattern similar to a MUSICAM system and a transmission pattern reducing the number of bits to be used for the coding of bit distributing information in each frame. Transmission pattern selecting information expressing the selected transmission pattern is sent from the circuit 8 to a coding circuit 9. The sent information is coded and the coded information is sent to a multiplexing circuit 10 as auxiliary information together with a scale factor and the bit distributing information. The circuit 10 multiplexes the auxiliary information and a quantized sub-band signal being main information similarly to the MUSICAM system and outputs the multiplexed signal to a transmission line 11 as a compression signal.
ENDO KAZUHITO
TSUKAMOTO MANABU
ISHIDA MASAYUKI
ISHIDA SADANOBU
