| 摘要 |
PURPOSE:To eliminate the unnaturalness of a hearing sensation on the reception side in a soundless section when ADPCM codes only in a sound section are transmitted by sending information on the length of the soundless section and a mean noise level from a transmission side to the reception side. CONSTITUTION:An ADPCM encoder 13 is controlled with the output of a sound detector 10 to perform ADPCM encoding only in the sound section. A noise analyzer 12 generates representative values of soundless-section length information and soundless-section level information, and they are inputted to and encoded by an encoder 15. The output of the encoder 15 is multiplexed by a multiplexing circuit 16 with the output of the encoder 13 and outputted. A demultiplexing circuit 7 on the reception side demultiplexes the receive signal into ADPCM codes and the codes from the encoder 15, and the representative value from the encoder 15 are decoded by a decoder 18 and supplied to a pseudo random noise generator 20 to obtain a random noise with a level based upon the representative value in the soundless section, thereby outputting it from a terminal 4 in the soundless section. |
