| 摘要 |
PURPOSE: To improve a problem of a pseudo background noise for a silence interval of receiver side causing unnatural sound quality when a sound detection flag is outputted by mistake for the silence interval from the sender side in the receiver side voice decoder for the adaptive differential PCM coding system communication. CONSTITUTION: An auxiliary controller 6 is provided between a controller 5 receiving a sound detection flag (b) separated from a reception demodulation signal (a) to provide an output of a signal (e) representing discrimination of sound/silence and a reset signal (d) at a change point of the sound/silence and a predict,ion coefficient storage device 7 extracting a prediction coefficient (g) from an ADPCM decoder 4 decoding a coded signal (c), calculating an average for each frame, storing and updating it and providing an output of a stored value (h) just before the change from the silence interval into the sound interval. The auxiliary controller 6 outputs continuously a flag (f) representing the silence interval for nearly 5 frames even when the input flag (e) indicates the change of the silence interval into the sound interval so that the sound quality of pseudo background noise generated and decoded by the decoder 4 for the silence interval is not disturbed. |
