| 摘要 |
PURPOSE: To improve the coding efficiency and to prevent the occurrence of pre-echoes without complicating a signal coding device by converting a waveform signal into plural frequency components and then coding the control information used for the gain control and also those frequency components. CONSTITUTION: A signal coding device consists primarily of a window circuit 32, an attack part detection circuit 33, a gain control circuit 34, a forward spectrum conversion circuit 35, a normalization/quantization circuit 36, and a coding circuit 37. When a waveform signal is coded, an attack part where the levels of elements of the waveform signal suddenly rise is detected. Then one of plural gain controlled variables expressed in two prescribed powers is adaptively selected in response to the characteristic of the waveform signal. This selected gain controlled variable is used to give the gain control to at least those waveform elements preceding the attack part. Then the waveform signal is converted into plural frequency components, and the control information used for the gain control and these frequency components are coded. |
