APPARATUS AND METHOD FOR ENCODING OR DECODING AN AUDIO SIGNAL USING A TRANSIENT-LOCATION DEPENDENT OVERLAP

摘要

An apparatus for encoding an audio or image signal, comprises: a controllable windower (102) for windowing the audio or image signal to provide the sequence of blocks of windowed samples; a converter (104) for converting the sequence of blocks of windowed samples into a spectral representation comprising a sequence of frames of spectral values; a transient location detector (106) for identifying a location of a transient within a transient look-ahead region of a frame; and a controller (108) for controlling the controllable windower (102) to apply a specific window having a specified overlap length to the audio or image signal in response to an identified location (210-213) of the transient, wherein the controller (108) is configured to select the specific window from a group of at least three windows comprising a first window (201) having a first overlap length (203), a second window (215) having a second overlap length (218), and a third window (224) having a third overlap length (229) or having no overlap, wherein the first overlap length (203) is greater than the second overlap length (218), and wherein the second overlap length (218) is greater than the third overlap length (229) or greater than an overlap of zero, wherein the specific window is selected based on the transient location such that one of two time-adjacent overlapping windows has coefficients at the location of the transient and the other of the two time-adjacent overlapping windows has second window coefficients at the location of the transient, wherein the second coefficients are at least nine times greater than the first coefficients.