Method and an apparatus for processing an audio signal
A method of processing an audio signal is disclosed. The present invention includes receiving, by an audio processing apparatus, coding identification information indicating whether to apply a first coding scheme or a second coding scheme to a current frame; when the coding identification information indicates that the second coding scheme is applied to the current frame, receiving window type information indicating a particular window for the current frame, from among a plurality of windows; 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 includes a gentle long stop window and a steep long stop window; and, when the first coding scheme is applied to a previous frame, applying the gentle long stop window to the current frame, wherein: the gentle long stop window comprise an ascending line with first slope, the steep long stop window comprise an ascending line with second slope, and, the first slope is gentler than the second slope.
1. A method for processing an audio signal, comprising:
receiving, by an audio processing apparatus, 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;
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;
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.
2. The method of the claim 1 , wherein a width of the first slope is equal to two-times a width of the second slope.
3. The method of claim 1 , wherein a width of the first slope corresponds to N/ 4 (where N is frame length).
4. The method of claim 1 , wherein a width of the first slope corresponds to 256 samples, and wherein a width of the first slope is equal to ⅛ of length of the long_stop window.
5. The method of claim 1 , wherein the only_long window is horizontal-symmetry, and the long_stop window is horizontal-asymmetry, the long_stop window has zero part in a left half.
6. The method of claim 1 , wherein center point of the ascending line with the first slope or the second slope is at N/2 distance from a start point of the long_stop window (where N is frame length).
7. 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.
8. The apparatus of the claim 7 , wherein a width of the first slope is equal to two-times a width of the second slope.
9. The apparatus of claim 7 , wherein a width of the first slope corresponds to N/4 (where N is frame length).
10. The apparatus of claim 7 , wherein a width of the first slope corresponds to 256 samples, and wherein a width of the first slope is equal to ⅛ of length of the long_stop window.
11. The apparatus of claim 7 , wherein the only_long window is horizontal-symmetry, and the long_stop window is horizontal-asymmetry, the long_stop window has zero part in a left half.
12. The apparatus of claim 7 , wherein center point of the ascending line with the first slope or the second slope is at N/2 distance from a start point of the long_stop window (where N is frame length).