Speech decoding device to update the synthesis postfilter and prefilter during unvoiced speech or noise

摘要

In the disclosed speech decoding device, activation of a postfilter process is halted during unvoiced sections. However, the updating process of the internal states of the postfilter continues even though the postfilter process is not activated during unvoiced sections. At changes between voiced and unvoiced sections, output signals outputted during voiced sections that have been subjected to a postfilter process and output signals outputted during unvoiced sections that have not been subjected to a postfilter process are interpolated and outputted. In one embodiment, a prefilter controller activates a prefilter state updater for unvoiced sections to update the internal state of the filter of a prefilter section based on excited signals to decrease any perception of noncontinuity in an output signal switching between activation and deactivation of the prefilter when changing between voiced and unvoiced sections.