Method and apparatus for audio decoding
A method for decoding an audio signal includes: obtaining a lower-band signal component of an audio signal corresponding to a received code stream when the audio signal switches from a first bandwidth to a second bandwidth which is narrower than the first bandwidth; extending the lower-band signal component to obtain higher-band information; performing a time-varying fadeout process on the higher-band information to obtain a processed higher-band signal component; and synthesizing the processed higher-band signal component and the obtained lower-band signal component. With the methods provided in the embodiments of the invention, when an audio signal has a switch from broadband to narrowband, a series of processes such as bandwidth detection, artificial band extension, time-varying fadeout process, and bandwidth synthesis, may be performed to make the switch to have a smooth transition from a broadband signal to a narrowband signal so that a comfortable listening experience may be achieved.
1. A method for decoding an audio signal, comprising:
obtaining a lower-band signal component of an audio signal in a received code stream when the audio signal switches from a first bandwidth to a second bandwidth which is narrower than the first bandwidth;
extending the lower-band signal component to obtain higher-band information; performing a time-varying fadeout process on the higher-band information obtained through extension to obtain a processed higher-band signal component; and
synthesizing the processed higher-band signal component and the obtained lower-band signal component;
wherein performing a time-varying fadeout process on the higher-band information further comprises:
performing a separate time-varying fadeout process on the higher-band information;
or
performing a hybrid time-varying fadeout process on the higher-band information;
wherein the higher-band information is a higher-band signal component and the step of performing a separate time-varying fadeout process on the higher-band information further comprises:
performing a time-domain shaping on the higher-band signal component obtained through extension by using a time-domain gain factor;
or
performing a frequency-domain higher-band signal component obtained through extension by using time-varying filtering; and
wherein after performing a time-domain shaping on the higher-band signal component obtained through extension by using a time-domain gain factor, the method further comprises:
performing a frequency-domain time-domain shaped higher-band signal component by using time-varying filtering.
2. The audio signal decoding method according to claim 1 , wherein after performing a frequency-domain shaping on the higher-band signal component obtained through extension by using time-varying filtering, the method further comprises:
performing a time-domain shaping on the frequency-domain shaped higher-band signal component by using a time-domain gain factor.
3. The audio signal decoding method according to claim 1 , wherein performing a hybrid time-varying fadeout process on the higher-band information further comprises:
when the higher-band information is a higher-band coding parameter, performing a frequency-domain shaping on the higher-band coding parameter obtained through extension by using a frequency-domain higher-band parameter time-varying weighting method, to obtain a time-varying fadeout spectral envelope, and obtaining a higher-band signal component through decoding; or
when the higher-band information is a higher-band signal component, dividing the higher-band signal component obtained through extension into sub-bands, performing a frequency-domain higher-band parameter time-varying weighting on the coding parameter for each sub-band to obtain a time-varying fadeout spectral envelope, and obtaining a higher-band signal component through decoding.
4. An apparatus for decoding an audio signal, comprising a processor, an obtaining unit, an extending unit, a time-varying fadeout processing unit, and a synthesizing unit; wherein:
the obtaining unit is configured to obtain a lower-band signal component of an audio signal in a received code stream when the audio signal switches from a first bandwidth to a second bandwidth which is narrower than the first bandwidth, and transmit the lower-band signal component to the extending unit;
the extending unit is configured to extend the lower-band signal component to obtain higher-band information, and transmit the higher-band information obtained through extension to the time-varying fadeout processing unit;
the time-varying fadeout processing unit is configured to perform a time-varying fadeout process on the higher-band information obtained through extension to obtain a processed higher-band signal component, and transmit the processed higher-band signal component to the synthesizing unit; and
the synthesizing unit is configured to synthesize the received processed hither-band signal component and the lower-band signal component obtained by the obtaining unit;
wherein the time-varying fadeout processing unit further comprises a separate processing sub-unit or a hybrid processing sub-unit; wherein:
the separate processing sub-unit is configured to perform a time-domain shaping and/or frequency-domain shaping on the higher-band signal component obtained through extension when the higher-band information obtained through extension is a higher-band signal component, and transmit the processed higher-band signal component to the synthesizing unit; and
the hybrid processing sub-unit is configured to:
when the higher-band information obtained through extension is a higher-band coding parameter, perform a frequency-domain shaping on the higher-band coding parameter obtained through extension; or
when the higher-band information obtained through extension is a higher-band signal component divide the higher-band signal component obtained through extension into sub-bands, perform a frequency-domain shaping on the coding parameter for each sub-band, and transmit the processed higher-band signal component to the synthesizing unit;
wherein the separate processing sub-unit further comprises at least one of a first sub-unit, a second sub-unit, a third sub-unit, and a fourth sub-unit; wherein:
the first sub-unit is configured to perform a time-domain shaping on the higher-band signal component obtained through extension by using a time-domain gain factor, and transmit the processed higher-band signal component to the synthesizing unit;
the second sub-unit is configured to perform a frequency-domain shaping on the higher-band signal component obtained through extension by using time-varying filtering, and transmit the processed higher-band signal component to the synthesizing unit;
the third sub-unit is configured to perform a time-domain shaping on the higher-band signal component obtained through extension by using a time-domain gain factor, perform a frequency-domain shaping on the time-domain shaped higher-band signal component by using time-varying filtering, and transmit the processed higher-band signal component to the synthesizing unit; and
the fourth sub-unit is configured to perform a frequency-domain shaping on the higher-band signal component obtained through extension by using time-varying filtering, perform a time-domain shaping on the frequency-domain shaped higher-band signal component by using a time-domain gain factor, and transmit the processed higher-band signal component to the synthesizing unit.