Processor and method for processing an audio signal using truncated analysis or synthesis window overlap portions

Method of processing an audio signal, comprising:

• deriving a window control signal from the audio signal,
• the window control signal indicating a change from a first asymmetric window comprising a first overlap portion and a second overlap portion to a second window comprising a first overlap portion, the second overlap portion of the first asymmetric window overlapping with the first overlap portion of the second window, or
• the window control signal indicating a change from a third window comprising a second overlap portion to a fourth asymmetric window comprising a first overlap portion and a second overlap portion, the second overlap portion of the third window overlapping with the first overlap portion of the fourth asymmetric window,
• wherein the second window is shorter than the first asymmetric window, or wherein the third window is shorter than the fourth asymmetric window;
• constructing the second window using a first overlap portion of the first asymmetric window, wherein the constructing comprises determining the first overlap portion of the second window using a truncated first overlap portion of the first asymmetric window, or
• constructing the third window using the second overlap portion of the fourth asymmetric window, wherein the constructing comprises calculating the second overlap portion of the third window using a truncated second overlap portion of the fourth asymmetric window;
• and
• applying the first asymmetric window and the second window or the third window and the fourth asymmetric window to obtain windowed audio signal portions.

Non-transitory storage medium having stored thereon a computer program for performing, when running on a computer or a processor, the method of processing an audio signal, the method comprising:

• deriving a window control signal from the audio signal,
• the window control signal indicating a change from a first asymmetric window comprising a first overlap portion and a second overlap portion to a second window comprising a first overlap portion, the second overlap portion of the first asymmetric window overlapping with the first overlap portion of the second window, or
• the window control signal indicating a change from a third window comprising a second overlap portion to a fourth asymmetric window comprising a first overlap portion and a second overlap portion, the second overlap portion of the third window overlapping with the first overlap portion of the fourth asymmetric window,
• wherein the second window is shorter than the first asymmetric window, or wherein the third window is shorter than the fourth asymmetric window;
• constructing the second window using a first overlap portion of the first asymmetric window, wherein the constructing comprises determining the first overlap portion of the second window using a truncated first overlap portion of the first asymmetric window, or
• constructing the third window using the second overlap portion of the fourth asymmetric window, wherein the constructing comprises calculating the second overlap portion of the third window using a truncated second overlap portion of the fourth asymmetric window;
• and
• applying the first asymmetric window and the second window or the third window and the fourth asymmetric window to obtain windowed audio signal portions.