High-band encoding method and device, and high-band decoding method and device

1. A method for encoding an audio signal, the method comprising:

generating an envelope of a low band of a spectrum based on a sub-band configuration of a full band, and quantizing the envelope of the low band;

generating an envelope of a high band of the spectrum based on a sub-band configuration of the high band and quantizing the envelope of the high band;

generating a mapped envelope of the high band by mapping the envelope of the high band into a sub-band configuration of the full band, and quantizing the mapped envelope;

generating an envelope of the full band by combining the quantized mapped envelope of the high band with the quantized envelope of the low band;

determining to perform envelope refinement if there is any sub-band to which a bit is allocated in the high band based on bit allocation information of the envelope of the full band; and

in response to determining to perform the envelope refinement, calculating a delta of norm which is a difference between the mapped envelope and an envelope from an original spectrum for the sub-band to which the bit is allocated in the high band, and generating a bitstream including the delta of norm.

2. The method of claim 1 , further comprising generating an excitation class based on signal characteristics of the high band and encoding the excitation class.

3. The method of claim 1 , further comprising updating the bit allocation information based on bits used for the envelope refinement for the sub-band to which a bit is allocated.

4. The method of claim 3 , wherein the updated bit allocation information is provided to be used for spectrum coding.

5. The method of claim 1 , wherein the calculating of the delta of norm comprises calculating the delta of norm by using a maximum limit and a minimum limit.

6. The method of claim 1 , wherein generating of the bitstream comprises generating the bitstream including necessary bits for representing the delta of norm and a value of the delta of norm.

7. A method for decoding an audio signal, the method comprising:

generating an envelope of a low band of a spectrum based on a sub-band configuration of a full band, and quantizing the envelope of the low band;

generating an envelope of a high band of the spectrum based on a sub-band configuration of the high band and quantizing the envelope of the high band;

generating a mapped envelope of the high band by mapping the envelope of the high band into a sub-band configuration of the full band, and quantizing the mapped envelope;

generating an envelope of the full band by combining the quantized mapped envelope of the high band with the quantized envelope of the low band;

determining to perform envelope update if there is any sub-band to which a bit is allocated in the high band based on bit allocation information of the envelope of the full band; and

in response to determining to perform the envelope update, decoding a delta of norm which is a difference between the mapped envelope and an envelope from an original spectrum for the sub-band to which the bit is allocated in the high band, and updating the envelope by using the delta of norm.

8. The method of claim 7 , further comprising decoding an excitation class.

9. The method of claim 7 , further comprising updating the bit allocation information based on bits used for the envelope update for the sub-band to which a bit is allocated.

10. The method of claim 9 , the updated bit allocation information is provided to be used for spectrum decoding.

11. An apparatus for encoding an audio signal, the apparatus comprising:

at least one processor configured to:

generate an envelope of a low band of a spectrum based on a sub-band configuration of a full band, and quantize the envelope of the low band;

generate an envelope of a high band of the spectrum based on a sub-band configuration of the high band and quantize the envelope of the high band;

generate a mapped envelope of the high band by mapping the envelope of the high band into thea sub-band configuration of the full band, and quantize the mapped envelope;

generate an envelope of the full band by combining the quantized mapped envelope of the high band with the quantized envelope of the low band;

determine to perform envelope refinement if there is any sub-band to which a bit is allocated in the high band based on bit allocation information of the envelope of the full band; and

in response to determining to perform the envelope refinement, calculate a delta of norm which is a difference between the mapped envelope and an envelope from an original spectrum for the sub-band to which the bit is allocated in the high band, and generate a bitstream including the delta of norm.

12. An apparatus for decoding an audio signal, the apparatus comprising:

at least one processor configured to:

generate an envelope of a low band of a spectrum based on a sub-band configuration of a full band, and quantize the envelope of the low band;

generate an envelope of a high band of the spectrum based on a sub-band configuration of the high band, and quantize the envelope of the high band;

generate a mapped envelope of the high band by mapping the envelope of the high band into a sub-band configuration of the full band, and quantize the mapped envelope;

generate an envelope of the full band by combining the quantized mapped envelope of the high band with the quantized envelope of the low band;

determine to perform envelope update if there is any sub-band to which a bit is allocated in the high band based on bit allocation information of the envelope of the full band; and

in response to determining to perform the envelope update, decode a delta of norm which is a difference between the mapped envelope and an envelope from an original spectrum for the sub-band to which the bit is allocated in the high band, and update the envelope by using the delta of norm.