CROSS-REFERENCE TO RELATED APPLICATION

This application is a national phase of PCT patent application No.: PCT/CN2018/117766 filed on Nov. 27, 2018, which claims priority to Chinese Patent Application No. 201811053050.0, filed on Sep. 10, 2018 and entitled “METHOD AND APPARATUS FOR RECOVERING AUDIO SIGNALS”, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the field of audio technology, and more particularly, relates to a method for recovering audio signals, a terminal and a storage medium.

BACKGROUND

In the audio field, in order to save audio data transmission resources, audio data is generally subjected to low-pass filtering first to filter high-frequency signals that are insensitive to the human auditory system, and the audio data subjected to low-pass filtering is then compressed to increase the compression ratio and reduce the amount of audio data.

SUMMARY

Embodiments of the present disclosure provide a method for recovering audio signals, a terminal and a storage medium.

In a first aspect, a method for recovering audio signals is provided. The method includes:

determining a first frequency point in an audio signal having a high-frequency signal to be recovered by power spectrum scanning, wherein the first frequency point is a frequency point having a minimum frequency of the high-frequency signal to be recovered in the audio signal;

among a plurality of frequency subbands having equal width of the audio signal having the high-frequency signal to be recovered, recovering, according to the audio signal of a previous frequency subband of a target frequency subband, the audio signal of the target frequency subband and the audio signals of the frequency subbands after the target frequency subband in the plurality of frequency subbands, wherein the target frequency subband is a frequency subband to which the first frequency point belongs;

synthesizing the audio signals of the frequency subbands before the target frequency subband in the plurality of frequency subbands, the audio signal of the target frequency subband, and the audio signals of the frequency subbands after the target frequency subband in the plurality of frequency subbands;

separating the synthesized audio signal according to the first frequency point to obtain high-frequency signals and low-frequency signals, and performing phase recovery on the high-frequency signals; and

superimposing the high-frequency signals subjected to phase recovery and the low-frequency signals to obtain an audio signal in which the high-frequency signals are recovered.

Optionally, the method further includes:

if the first frequency point is not present in the audio signal having a high-frequency signal to be recovered, converting the audio signal having a high-frequency signal to be recovered into a plurality of frequency subbands having an equal width, and synthesizing the audio signals of the plurality of frequency subbands;

separating the audio signal obtained by synthesizing the audio signals of the plurality of frequency subbands according to a preset third frequency point to obtain high-frequency signals and low-frequency signals; and

superimposing the high-frequency signals and the low-frequency signals obtained by separating according to the preset third frequency point to obtain the audio signal in which the high-frequency signals are recovered.

Optionally, separating the synthesized audio signal according to the first frequency point to obtain high-frequency signals and low-frequency signals includes:

performing linear high-pass filtering on the synthesized audio signal to obtain the high-frequency signals, and performing linear low-pass filtering on the synthesized audio signal to obtain the low-frequency signals, wherein a frequency of each of the signals subjected to linear high-pass filtering is greater than or equal to the frequency of the first frequency point, and a frequency of each of the signals subjected to linear low-pass filtering is less than the frequency of the first frequency point.

Optionally, performing phase recovery on the high-frequency signals includes:

performing all-pass biquad infinite impulse response (IIR) filtering on the high-frequency signals to obtain the high-frequency signals subjected to phase recovery.

Optionally, the method further includes:

determining a coefficient of the biquad IIR filtering according to the frequency of the first frequency point and sampling rates.

Optionally, determining a first frequency point in an audio signal having a high-frequency signal to be recovered by power spectrum scanning includes:

buffering an audio signal which is sampled at a preset number of sampling points;

performing fast Fourier transform (FFT) on the sampled audio signal to obtain an FFT result;

according to the FFT result, finding a first frequency point that satisfying preset conditions, wherein the preset conditions are that a difference between frequencies of the first frequency point and a second frequency point is less than a first preset value, a difference between powers of the first frequency point and the second frequency point is greater than a second preset value, a power of a frequency point having a frequency greater than the frequency of the first frequency point is zero, and the frequency of the second frequency point is less than the frequency of the first frequency point.

Optionally, prior to the performing FFT on the sampled audio signal to obtain an FFT result, the method further includes:

windowing the sampled audio signal to obtain audio signal subjected to windowing; and

wherein performing FFT on the sampled audio signal to obtain an FFT result includes:

performing the FFT on the audio signal subjected to windowing to obtain the FFT result.

In a second aspect, an apparatus for recovering audio signals is provided. The apparatus includes:

a buffering module, configured to buffer an audio signal sampled at a preset number of sampling points;

a fast Fourier transform (FFT) module, configured to perform FFT on the sampled audio signal to obtain an FFT result;

a converting module, configured to, according to the FFT result, if a first frequency point satisfying preset conditions is present, convert the audio signal sampled at the preset number of sampling points into audio signals of a plurality of frequency subbands having an equal width;

a determining module, configured to determine a target frequency subband to which the first frequency point belongs, wherein the preset conditions are that a difference between frequencies of the first frequency point and a second frequency point is less than a first preset value, a difference between powers of the first frequency point and the second frequency point is greater than a second preset value, a power of a frequency point having a frequency greater than the frequency of the first frequency point is zero, and the frequency of the second frequency point is less than the frequency of the first frequency point;

a recovering module, configured to recover, according to the audio signal of a previous frequency subband of the target frequency subband, the audio signal of the target frequency subband in the plurality of frequency subbands and the audio signals of the frequency subbands after the target frequency subband;

a synthesizing module, configured to synthesize the audio signals of the frequency subbands before the target frequency subband in the plurality of frequency subbands, the audio signal of the target frequency subband, and the audio signals of the frequency subbands after the target frequency subband in the plurality of frequency subbands;

a separating module, configured to separate the synthesized audio signal according to the first frequency point to obtain high-frequency signals and low-frequency signals, wherein the recovery module is further configured to perform phase recovery on the high-frequency signals; and

a superimposing module, configured to superimpose the high-frequency signals subjected to phase recovery and the low-frequency signals obtained by separating to obtain sampled audio signal in which the high-frequency signals are recovered.

Optionally, the converting module is further configured to, according to the FFT result, if the first frequency point is not present, convert the audio signal sampled at the preset number of sampling points into a plurality of frequency subbands having an equal width;

the synthesizing module is further configured to synthesize the audio signals of the plurality of frequency subbands;

the separating module is further configured to separate the audio signal obtained by synthesizing the audio signals of the plurality of frequency subbands according to a preset third frequency point to obtain high-frequency signals and low-frequency signals; and

the superimposing module is further configured to superimpose the high-frequency signals and the low-frequency signals according to the preset third frequency point to obtain the sampled audio signal.

Optionally, the separating module is configured to:

perform linear high-pass filtering on the synthesized audio signal to obtain the high-frequency signals, and perform linear low-pass filtering on the synthesized audio signal to obtain the low-frequency signals, wherein a frequency of each of the signals subjected to linear high-pass filtering is greater than or equal to the frequency of the first frequency point, and a frequency of each of the signals subjected to linear low-pass filtering is less than the frequency of the first frequency point.

Optionally, the recovering module is configured to:

perform all-pass biquad IIR filtering on the high-frequency signals to obtain high-frequency signals subjected to phase recovery.

Optionally, the determining module is further configured to:

determine a coefficient of the biquad IIR filtering according to the frequency of the first frequency point and sampling rates.

Optionally, the apparatus further includes:

a windowing module, configured to, prior to performing FFT on the sampled audio signal to obtain an FFT result, windowing the sampled audio signal to obtain audio signal subjected to windowing; and

the FFT module is configured to:

perform the FFT on the audio signal subjected to windowing to obtain the FFT result.

In a third aspect, a terminal is provided. The terminal includes a memory and a processor, the memory is used to store at least one instruction, and the processor is used to implement any method according the first aspect when executing the at least one instruction.

In a fourth aspect, a non-transitory computer-readable storage medium is provided. The storage medium stores at least one instruction, and the at least one instruction, when being executed by a processor, implements any method according the first aspect.

The technical solutions according to the embodiments of the present disclosure at least achieve the following beneficial effects.

In the embodiments of the present disclosure, in case of an audio with a lossy format, after an audio signal sampled at a preset number of sampling points is buffered each time, the sampled audio signal may be subjected to FFT to obtain an FFT result. According to the FFT result, if a first frequency point satisfying preset conditions is present, the audio signal sampled at the preset number of sampling points are converted into audio signals of a plurality of frequency subbands having an equal width. A target frequency subband including the first frequency point is determined. Then, based on the audio signal of a previous frequency subband of the target frequency subband, the audio signal of the target frequency subband in the plurality of frequency subbands and the audio signals of the frequency subbands after the target frequency subband are recovered. Next, the audio signals of the frequency subbands before the target frequency subband, the audio signal of the target frequency subband, and the audio signals of the frequency subbands after the target frequency subband in the plurality of frequency subbands are synthesized. The synthesized audio signal are separated according to the first frequency point to obtain high-frequency signals and low-frequency signals, and the high-frequency signals are subjected to phase recovery. The high-frequency signals subjected to phase recovery and the low-frequency signals are superimposed to obtain sampled audio signal in which the high-frequency signals are recovered. As such, since the high-frequency signals in the sampled audio signal may be recovered, the sampled audio signal are recovered as well. Therefore, the method for recovering audio signals is provided.

