Apparatus and method for encoding or decoding an audio signal using a transient-location dependent overlap

Decoder for decoding an audio signal comprising a sequence of blocks of converted windowed samples and associated window information identifying a specific window function for a block out of at least three different window functions, comprising:

• a processor for providing a sequence of blocks of spectral values;
• a controllable converter for converting the sequence of blocks of spectral values into a time domain representation using an overlap-add processing,
• wherein the controllable converter is controlled by the window information to apply window functions indicated by the window information to the corresponding block to calculate a decoded audio signal,
• wherein the window is selected from a group of at least three windows comprising a first window having a first overlap length, a second window having a second overlap length, and a third window having a third overlap length or having no overlap, wherein the first overlap length is greater than the second overlap length, and wherein the second overlap length is greater than the third overlap length or greater than an overlap of zero.

Method for encoding an audio signal, comprising:

• windowing the audio signal to provide a sequence of blocks of windowed samples;
• converting the sequence of blocks of windowed samples into a spectral representation comprising a sequence of frames of spectral values;
• identifying a location of a transient within a transient look-ahead region of a frame;
• and
• controlling the windowing to apply a specific window having a specified overlap length to the audio signal in response to an identified location of the transient, wherein the specific window is selected from a group of at least three windows comprising a first window having a first overlap length, a second window having a second overlap length, and a third window having a third overlap length or having no overlap,
• wherein the first overlap length is greater than the second overlap length, and wherein the second overlap length is greater than the third overlap length 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 comprises first window coefficients at the location of the transient and the other of the two time-adjacent overlapping windows comprises second window coefficients at the location of the transient, wherein the second coefficients are at least nine times greater than the first coefficients.

Method for decoding an audio signal comprising a sequence of blocks of converted windowed samples and associated window information identifying a specific window function for a block out of at least three different window functions, comprising:

• providing a sequence of blocks of spectral values;
• converting the sequence of blocks of spectral values into a time domain representation using an overlap-add processing,
• wherein the converting is controlled by the window information to apply window functions indicated by the window information to the corresponding block to calculate a decoded audio signal,
• wherein the window is selected from a group of at least three windows comprising a first window having a first overlap length, a second window having a second overlap length, and a third window having a third overlap length or having no overlap, wherein the first overlap length is greater than the second overlap length, and wherein the second overlap length is greater than the third overlap length or greater than an overlap of zero,