Method and an apparatus for processing an audio signal

An apparatus for processing an audio signal, comprising:

• a de-multiplexer receiving coding identification information indicating whether to apply a first coding scheme based on linear-prediction domain or a second coding scheme based on frequency domain to a current frame, and when the coding identification information indicates that the second coding scheme based on frequency domain is applied to the current frame, receiving window type information indicating a particular window for the current frame, from among a plurality of windows;
• and,
• a second coding unit and identifying that a current window is a long_stop window based on the window type information, wherein the long_stop window is followed by only_long window of a following frame, wherein the long_stop window comprises an ascending line and, determining a slope of the ascending line to be either a first slope or a second slope according to a previous frame,
• wherein the ascending line is determined to be the first slope gentler than the second slope when the first coding scheme based on linear-prediction domain is applied to the previous frame, and is determined to be the second slope when the first coding scheme based on linear-prediction domain is not applied to the previous frame,
• wherein the first slope is gentler than the second slope, and
• wherein a width of the long_stop window is 2N (where N is frame length) regardless of whether the ascending line is determined to be the first slope or not.