Method and an apparatus for processing an audio signal
An apparatus for processing an audio signal and method thereof are disclosed. The present invention includes receiving, by an audio processing apparatus, an audio signal including a first data of a first block encoded with rectangular coding scheme and a second data of a second block encoded with non-rectangular coding scheme; receiving a compensation signal corresponding to the second block; estimating a prediction of an aliasing part using the first data; and, obtaining a reconstructed signal for the second block based on the second data, the compensation signal and the prediction of aliasing part.
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 being based on linear-prediction domain or a second coding scheme being based on frequency domain to a current frame;
when the coding identification information indicates that the second coding scheme being 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 stop_start window based on the window type information, wherein the stop_start window follows one of a long_start window, a short window and a window of the first coding scheme being based on linear-prediction domain for a previous frame, wherein the stop_start window is followed by one of a long_stop window, a short window and a window of the first coding scheme being based on linear-prediction domain for a following frame, wherein the stop_start window comprises an ascending line and a descending line;
determining a slope of the ascending line to be a first slope or a second slope according to the previous frame, and a slope of the descending line to be the first slope or the second slope according to the following frame,
wherein the ascending line is determined to be the first slope when the first coding scheme being based on linear-prediction domain is applied to the previous frame, and is determined to be the second slope when the first coding scheme being based on linear-prediction domain is not applied to the previous frame,
wherein the descending line is determined to be the first slope when the first coding scheme being based on linear-prediction domain is applied to the following frame, and is determined to be the second slope when the first coding scheme being based on linear-prediction domain is not applied to the following 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 stop_start window.
5. The method of claim 1 , wherein the short window is horizontal-symmetry,
the long_start window and the long_stop window are horizontal-asymmetry,
the long_stop window has zero part in a left half, and
the long_start window has zero part in a right 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 stop_start window (where N is frame length),
wherein center point of the descending line with the first slope or the second slope is at 3N/2 distance from a start point of the stop_start 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 being based on linear-prediction domain or a second coding scheme being based on frequency domain to a current frame, and, when the coding identification information indicates that the second coding scheme being 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 identifying that a current window is a stop_start window based on the window type information, wherein the stop_start window follows one of a long_start window, a short window and a window of the first coding scheme being based on linear-prediction domain for a previous frame, wherein the stop_start window is followed by one of a long_stop window, a short window and a window of the first coding scheme being based on linear-prediction domain for a following frame, wherein the stop_start window comprises an ascending line and a descending line, and determining a slope of the ascending line to be a first slope or a second slope according to the previous frame, and a slope of the descending line to be the first slope or the second slope according to the following frame,
wherein the ascending line is determined to be the first slope when the first coding scheme being based on linear-prediction domain is applied to the previous frame, and is determined to be the second slope when the first coding scheme being based on linear-prediction domain is not applied to the previous frame,
wherein the descending line is determined to be the first slope when the first coding scheme being based on linear-prediction domain is applied to the following frame, and is determined to be the second slope when the first coding scheme being based on linear-prediction domain is not applied to the following frame,
wherein the first slope is gentler than the second slope,
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 stop_start window.
11. The apparatus of claim 7 , wherein the short window is horizontal-symmetry,
the long_start window and the long_stop window are horizontal-asymmetry,
the long_stop window has zero part in a left half, and
the long_start window has zero part in a right 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 stop_start window (where N is frame length),
wherein center point of the descending line with the first slope or the second slope is at 3N/2 distance from a start point of the stop_start window (where N is frame length).