Alias cancelling during audio coding mode transitions
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, an audio signal including a first data of a first block encoded with a rectangular coding scheme and a second data of a second block encoded with a non-rectangular coding scheme;
generating an output signal for the first block using the first data of the first block based on the rectangular coding scheme;
receiving a compensation signal corresponding to the second block;
obtaining a prediction of an aliasing part by applying a window of the second block to the output signal for the first block; and
obtaining a reconstructed signal for the second block based on the second data, the compensation signal and the prediction of the aliasing part,
wherein, when the first data is encoded with a LPD (Linear Prediction Domain) coding scheme and the window of the second block belongs to a transition window class, the window of the second block has an ascending line with a first slope,
wherein the first slope is gentler than a second slope.
2. The method of claim 1 , wherein, when the first data is encoded with a FD (Frequency Domain) coding scheme and the window of the second block belongs to the transition window class, the window of the second block has an ascending line with the second slope.
3. The method of claim 1 , wherein, when the transition window class comprises a long_stop window and a stop_start window, and
the long_stop window and the stop_start window have horizontal-asymmetry, and have a zero part in a left half.
4. The method of claim 1 , wherein the compensation signal is received, when the first data is encoded with the rectangular coding scheme.
5. The method of claim 1 , wherein the compensation signal is generated based on at least one of a difference related to asymmetry between a rectangular window and a non-rectangular window, and a difference between the aliasing part and a prediction of the aliasing part.
6. An apparatus for processing an audio signal, comprising:
a de-multiplexer receiving an audio signal including a first data of a first block encoded with a rectangular coding scheme and a second data of a second block encoded with a non-rectangular coding scheme, and receiving a compensation signal corresponding to the second block;
a rectangular decoding unit generating an output signal for the first block using the first data of the first block based on the rectangular coding scheme, and obtaining a prediction of an aliasing part by applying a window of the second block to the output signal for the first block; and
a non-rectangular decoding unit obtaining a reconstructed signal for the second block based on the second data, the compensation signal and the prediction of the aliasing part,
wherein, when the first data is encoded with a LPD (Linear Prediction Domain) coding scheme and the window of the second block belongs to a transition window class, the window of the second block has an ascending line with a first slope,
wherein the first slope is gentler than a second slope.
7. The apparatus of claim 6 , wherein, when the first data is encoded with a FD (Frequency Domain) coding scheme and the window of the second block belongs to the transition window class, the window of the second block has an ascending line with the second slope.
8. The apparatus of claim 6 , wherein, when the transition window class comprises a long_stop window and a stop_start window, and
the long_stop window and the stop_start window have horizontal-asymmetry, and have a zero part in a left half.
9. The apparatus of claim 6 , wherein the compensation signal is received, when the first data is encoded with the rectangular coding scheme.
10. The apparatus of claim 6 , wherein the compensation signal is generated based on at least one of a difference related to asymmetry between a rectangular window and a non-rectangular window, and a difference between the aliasing part and a prediction of the aliasing part.