Audio processing method, audio processing circuit and audio playing device

Abstract

The present invention discloses an audio processing method, an audio processing circuit and an audio playback device. The audio processing method comprises: determining the gear range of the amplitude of the currently input sound source signal, and selecting the corresponding analog gain based on the determined gear range; and outputting the selected analog gain to a power amplifier for control, and outputting a digital gain in inverse proportion to the selected analog gain to a digital audio processing unit for control, wherein the lower the gear range of the amplitude of the sound source signal, the smaller the corresponding analog gain is set to.

Description

Technical Field

[0001] The present invention relates to the field of audio technology, and in particular to an audio processing method, an audio processing circuit and an audio playing device. Background Art

[0002] With the development of audio playback devices such as Bluetooth headsets and smart speakers, the requirements for sound quality are getting higher and higher while maintaining low power consumption. Dynamic range is one of the important indicators of audio playback devices. The definition of dynamic range is the ratio of the maximum signal to the minimum signal that can be distinguished.

[0003] However, when using an audio player to play audio, there will be noise generated by the current flowing through the electronic components, that is, the background noise. If the signal is above the background noise, it can be distinguished. It can be seen that reducing noise or increasing the volume can effectively improve the dynamic range of the audio. In the prior art, the output amplitude and background noise of the power amplifier in the audio player are usually directly optimized to the extreme. Summary of the invention

[0004] Technical problem to be solved by the invention

[0005] However, in the case of increasing the output amplitude of the power amplifier, the portable audio playback device uses advanced technology, the voltage will not be too high, and the increase is limited.

[0006] On the other hand, in the case of reducing the noise floor of the power amplifier, there are two ways: reducing the analog gain and increasing the current. When reducing the analog gain of the power amplifier, the equivalent input noise of the power amplifier remains unchanged, and the output noise is reduced due to the reduced gain. However, while reducing the noise, the output amplitude is also reduced, which is not beneficial for increasing the dynamic range. When increasing the current, the equivalent input noise of the power amplifier is reduced, but the output amplitude is not reduced. However, increasing the current will affect the power consumption of the portable audio player.

[0007] The present invention is completed to solve the above-mentioned problems, and its purpose is to provide an audio processing method, an audio processing circuit and an audio playback device that can improve the audio playback background noise while ensuring the volume output amplitude, thereby increasing the dynamic range and improving the audio playback quality.

[0008] Technical solutions to technical problems

[0009] A first aspect of the present invention provides an audio processing method for an audio processing circuit, the audio processing circuit comprising a digital audio processing unit with a variable digital gain, a digital-to-analog converter, and a power amplifier with a variable analog gain, the audio processing method comprising the following steps: determining the gear range of the amplitude of a currently input sound source signal, and selecting the corresponding analog gain based on the determined gear range; and outputting the selected analog gain to the power amplifier for control, and outputting a digital gain in inverse proportion to the selected analog gain to the digital audio processing unit for control, wherein the lower the gear range of the amplitude of the sound source signal, the smaller the corresponding analog gain is set to.

[0010] The second aspect of the present invention is that, in the above-mentioned audio processing method, the following steps are also included: the step of presetting a plurality of gear intervals and a plurality of analog gains corresponding to each gear interval for the amplitude of the sound source signal; and the step of establishing and storing a mapping table that corresponds the gear intervals to the analog gains.

[0011] A third aspect of the present invention is that, in the above audio processing method, the amplitude of the sound source signal is divided into a plurality of gear intervals by setting at least one threshold.

[0012] A fourth aspect of the present invention is that, in the above audio processing method, a value obtained by multiplying the analog gain of the power amplifier by the digital gain of the digital audio processing unit is proportional to the output volume set by the user.

[0013] A fifth aspect of the present invention is that in the above-mentioned audio processing method, the audio processing circuit also includes at least one of a digital offset voltage compensation unit that uses a digital offset voltage compensation signal to perform offset voltage compensation, and an analog offset voltage compensation unit that uses an analog offset voltage compensation signal to perform offset voltage compensation, and the audio processing method also includes the following steps: a step of pre-testing the offset voltage under multiple analog gains and the digital offset voltage compensation signal and / or analog offset voltage compensation signal used to offset the offset voltage under silent conditions; a step of selecting the corresponding digital offset voltage compensation signal and / or analog offset voltage compensation signal according to the selected analog gain; and a step of outputting the selected digital offset voltage compensation signal and / or analog offset voltage compensation signal to the digital offset voltage compensation unit and / or the analog offset voltage compensation unit for control.

[0014] The sixth aspect of the present invention is that the above-mentioned audio processing method also includes the following steps: a step of pre-setting a plurality of gear intervals and a plurality of analog gains corresponding to each gear interval for the amplitude of the sound source signal; and a step of establishing and storing a mapping table that corresponds the gear intervals, analog gains, digital offset voltage compensation signals and / or analog offset voltage compensation signals.

[0015] The seventh aspect of the present invention is that in the above-mentioned audio processing method, when only the digital offset voltage compensation unit or the analog offset voltage compensation unit is used to perform offset voltage compensation due to reasons of synchronization with digital gain adjustment or due to quantization noise, the analog offset voltage compensation signal or the digital offset voltage compensation signal is set to 0.

[0016] The eighth aspect of the present invention also provides an audio processing circuit, which includes: a digital audio processing unit with variable digital gain; a digital-to-analog converter; a power amplifier with variable analog gain; and a controller for executing the audio processing method described in any one of the first to fourth aspects above.

[0017] The ninth aspect of the present invention also provides an audio processing circuit, which includes: a digital audio processing unit with a variable digital gain; a digital-to-analog converter; at least one of a digital offset voltage compensation unit that performs offset voltage compensation using a digital offset voltage compensation signal, and an analog offset voltage compensation unit that performs offset voltage compensation using an analog offset voltage compensation signal; a power amplifier with a variable analog gain; and a controller for executing the audio processing method described in any one of the fifth to seventh aspects.

[0018] The tenth aspect of the present invention further provides an audio playback device, comprising: a processor; and a memory, wherein instructions are stored in the memory, and when the instructions are executed by the processor, the audio processing method described in any one of the first to seventh aspects is executed.

[0019] Technical Effects

[0020] According to the present invention, by dynamically switching the analog gain of the power amplifier according to the amplitude of the sound source signal, the volume output amplitude can be guaranteed while improving the audio playback noise floor, thereby increasing the dynamic range and improving the audio playback quality.

[0021] In addition, according to the present invention, by dynamically switching the analog gain of the power amplifier according to the amplitude of the sound source signal, an offset voltage compensation action is performed for each analog gain to offset the offset voltage, so that smooth switching of the analog gain can be achieved without affecting the audio playback quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the audio processing circuit involved in embodiment 1 of the present invention.

[0023] Figure 2 It is a flowchart of the audio processing method involved in embodiment 1 of the present invention.

[0024] Figure 3 It shows the use of Figure 2 A diagram showing an example of changes in the noise floor when the analog gain is switched using the audio processing method shown.

[0025] Figure 4 It is a schematic diagram of the structure of the audio processing circuit involved in embodiment 2 of the present invention.

[0026] Figure 5 It is a flowchart of the audio processing method involved in embodiment 2 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described more fully below with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. However, the present invention may be implemented in different ways and should not be limited to the embodiments set forth herein. Unless otherwise specified, the terms used herein have the same meanings as those generally understood by those of ordinary skill in the art to which the present invention belongs. The terms should be understood to have meanings consistent with those in the context of the relevant art and should not be understood in an idealized or overly formalized manner unless clearly so defined herein.

[0028] <Implementation Method 1>

[0029] The following, combined Figure 1 and Figure 2 , the audio processing circuit and audio processing method involved in embodiment 1 of the present invention are specifically described.

[0030] like Figure 1 As shown, the audio processing circuit 1 includes a digital audio processing unit 11 , a digital-to-analog converter 12 , a power amplifier 13 and a controller 14 .

[0031] The digital audio processing unit (also referred to as a "digital processing system") 11 is a circuit that processes the digital audio signal input as the sound source signal data_in so as to make it suitable for digital-to-analog conversion by the digital-to-analog conversion unit 12. The digital audio processing unit 11 has a variable digital gain. In different application scenarios, the digital audio processing unit 11 can obtain the digital audio signal to be processed in various ways. For example, the digital audio processing unit 11 can directly obtain a locally stored audio file, or download and transmit the audio signal through the network or Bluetooth.

[0032] The processing performed by the digital audio processing unit 11 may include signal processing based on an equalizer (EQ), gain adjustment, code conversion, etc. For example, the equalizer is used to adjust the amplification of various frequency component electrical signals respectively to achieve the purpose of adjusting the timbre. Common EQ modes include pop, rock, jazz, classical and vocal, etc., which each adjust a different frequency band. For example, the classical music EQ enhances both the high and low frequency bands, mainly highlighting the performance of the instrument, while the adjustment of the vocal EQ is mainly concentrated on the mid-frequency part.

[0033] The digital-to-analog converter (DAC) 12 performs digital-to-analog conversion on the processed digital audio signal to obtain an analog audio signal.

[0034] The power amplifier (PA) 13 amplifies the analog audio signal to obtain an output signal out for driving a sound generating unit (not shown) to play the audio. The power amplifier 13 has a variable analog gain. The power amplifier 13 may also be referred to as a "power amplifier" for short.

[0035] The controller 14 may execute the audio processing method described below, and output the obtained analog gain a_gain and digital gain d_gain to the power amplifier 13 and the digital audio processing unit 11 for control, respectively.

[0036] The audio processing method of this embodiment 1 is as follows Figure 2 As shown, the process includes the following steps S11 to S14.

[0037] In step S11, a plurality of gear intervals and a plurality of analog gains a_gain corresponding to each gear interval are pre-set for the amplitude of the sound source signal. Specifically, the amplitude of the sound source signal can be divided into a plurality of gear intervals, for example, by setting at least one threshold. In addition, the lower the gear interval of the amplitude of the sound source signal, the smaller the corresponding analog gain a_gain is set to.

[0038] In step S12, a mapping table that corresponds the gear range to the analog gain a_gain is established and stored.

[0039] In step S13 , the gear range of the amplitude of the currently input audio source signal data_in is determined, and based on the determined gear range, a corresponding analog gain a_gain is selected from a mapping table, for example.

[0040] In step S14, the selected analog gain a_gain is output to the power amplifier 13 for control, and the digital gain d_gain in inverse proportion to the selected analog gain a_gain is output to the digital audio processing section 11 for control.

[0041] The digital gain d_gain is used to compensate for the change of the analog gain a_gain. Because from the audio source signal data_in to the output signal out, as long as the user does not adjust the output volume, it should be a fixed gain. After the analog gain a_gain is switched, the digital gain d_gain should be compensated accordingly to maintain the gain from the audio source signal data_in to the output signal out as a constant. Therefore, the value obtained by multiplying the analog gain of the power amplifier 13 by the digital gain of the digital audio processing unit 11 is a constant and is proportional to the output volume set by the user.

[0042] It should be noted that the above steps S11 and S12 are only an example of selecting the corresponding analog gain according to the gear range. However, the present invention is not limited thereto, and in addition to establishing a mapping table, any other method can be used to establish the corresponding relationship.

[0043] In addition, the above audio processing method can be implemented by the controller 14 disposed in the above audio processing circuit 1, but is not limited thereto. For example, it can also be implemented by a control circuit disposed outside the audio processing circuit.

[0044] Combine the following Figure 3 The principle of the audio processing method of this embodiment is described. Figure 3 1 is a diagram showing an example of changes in the noise floor when the analog gain is switched using the above-mentioned audio processing method. Figure 3 In the example, a threshold value Vth is set for the amplitude of the sound source signal to set two gear ranges and corresponding two analog gains a_gain1 and a_gain2. Figure 3 In the figure, the horizontal axis represents time and the vertical axis represents signal amplitude. As time changes, the amplitude of the sound source signal changes.

[0045] When the amplitude of the sound source signal (signal 1) is greater than Vth, a larger analog gain a_gain1 is used, and the noise floor at this time is noise floor 1. When the amplitude of the sound source signal (signal 2) is less than Vth, since a large output amplitude is no longer required, a smaller analog gain a_gain2 can be used, and the noise floor at this time is noise floor 2. Since the analog gain a_gain2 is lower than the analog gain a_gain1, the noise floor 2 is smaller than the noise floor 1. Therefore, when the amplitude of the sound source signal gradually decreases and crosses the threshold Vth, the noise floor suddenly decreases.

[0046] By dynamically switching the analog gain according to the amplitude of the sound source signal, the background noise is reduced when the sound is reduced, and the part below the background noise 1 and above the background noise 2 can be distinguished by the user. In terms of subjective listening, taking listening to a song as an example, at the climax, the ear itself is affected by the loud volume and cannot distinguish very small details. When the song reaches the climax, the ear can distinguish more details.

[0047] According to the audio processing method and audio processing circuit of this embodiment, by dynamically switching the analog gain of the power amplifier according to the amplitude of the sound source signal, the volume output amplitude can be guaranteed while improving the audio playback noise floor, thereby increasing the dynamic range and improving the audio playback quality.

[0048] <Implementation Method 2>

[0049] In the second embodiment, the problem of offset voltage is further considered in addition to the first embodiment described above.

[0050] The problem of offset voltage is common in analog circuits. The reason for this is that due to the mismatch of semiconductor processes, digital-to-analog converters and power amplifiers do not output 0 exactly when the input is 0, but mostly output a smaller value close to 0. This value is called offset voltage. The offset voltage is mainly related to the device used and is fixed after production is completed.

[0051] Since some components need to be switched when switching analog gain, the offset voltage under different analog gain is also different. The offset voltage is a DC quantity in frequency, and the human ear itself cannot hear the audio of the DC part. However, when the DC quantity changes suddenly, the user will hear a "pop" sound. This sound is called a popping sound. Therefore, it can be predicted that when switching analog gain, a popping sound will also be heard due to the sudden change of the offset voltage.

[0052] In view of the above problem, in the second embodiment, a small reverse signal is set to offset the offset voltage under different analog gains, so that the DC output of the power amplifier is always 0. Therefore, the user will not hear the popping sound whether turning on the power or switching the analog gain. The small reverse signal can be superimposed on the digital signal (called the digital offset voltage compensation signal d_offset), or on the analog signal (called the analog offset voltage compensation signal a_offset), or the two can be mixed and used.

[0053] When only the digital offset voltage compensation signal is used for calibration, a certain amount of quantization noise will be generated, making the background noise slightly larger, but its advantage is that it can easily take effect at the same time as the digital gain adjustment.

[0054] When only the analog offset voltage compensation signal is used for calibration, no quantization noise is generated. However, there is a delay in the digital-to-analog path. To ensure that the actual analog calibration and digital gain adjustment take effect at the same time, a delay needs to be inserted between the output times of the digital gain and analog calibration.

[0055] The following, combined Figure 4 and Figure 5, the audio processing circuit and audio processing method involved in embodiment 2 of the present invention are specifically described.

[0056] like Figure 4 As shown, the audio processing circuit 1A of the second embodiment is provided with a digital offset voltage compensating unit 15 and an analog offset voltage compensating unit 16 in addition to the audio processing circuit 1 of the first embodiment.

[0057] The digital offset voltage compensating unit 15 is arranged before the digital audio processing unit 11, and superimposes the digital offset voltage compensation signal d_offset with the digital audio signal input as the sound source signal to perform offset voltage compensation. The digital audio processing unit 11 processes the compensated digital audio signal.

[0058] The analog offset voltage compensation unit 16 is disposed between the DAC 12 and the power amplifier 13, and performs offset voltage compensation by superimposing the analog offset voltage compensation signal a_offset with the analog audio signal output by the DAC 12. The power amplifier 13 amplifies the compensated analog audio signal to drive the sound unit to play audio.

[0059] The audio processing method of this embodiment 2 is as follows Figure 5 As shown, the process includes the following steps S21 to S25.

[0060] Step S21 is identical to step S11, and therefore repeated description is omitted here.

[0061] In step S22, multiple offset voltages at analog gain a_gain and digital offset voltage compensation signals d_offset and analog offset voltage compensation signals a_offset for offsetting the offset voltage are pre-tested under silent conditions. Specifically, since the offset voltage is fixed after production, a series of d_offset and a_offset only need to be pre-measured and stored. The measurement method can be to use test equipment or chip built-in test (if there are enough resources in the chip).

[0062] In step S23 , a mapping table is established to correspond the gear range, the analog gain a_gain, the digital offset voltage compensation signal d_offset and the analog offset voltage compensation signal a_offset and is stored.

[0063] In step S24, the gear range of the amplitude of the currently input audio source signal is determined, and based on the determined gear range, the corresponding analog gain a_gain, digital offset voltage compensation d_offset signal and analog offset voltage compensation signal a_offset are selected from a mapping table, for example. Specifically, the corresponding analog gain can be selected first, and then, according to the selected analog gain, the corresponding digital offset voltage compensation signal and analog offset voltage compensation signal are selected.

[0064] In step S25, the selected analog gain a_gain, the digital offset voltage compensation signal d_offset and the analog offset voltage compensation signal a_offset are respectively output to the power amplifier 13, the digital offset voltage compensation unit 15 and the analog offset voltage compensation unit 16 for control, and the digital gain d_gain which is inversely proportional to the selected analog gain a_gain is output to the digital audio processing unit 11 for control.

[0065] It should be noted that, when performing offset voltage compensation, in addition to using both the digital offset voltage compensation unit and the analog offset voltage compensation unit, it is also possible to use only the digital offset voltage compensation unit or the analog offset voltage compensation unit for reasons of synchronization with digital gain adjustment or quantization noise. Figure 4 In the structure of, only the digital offset voltage compensation unit 15 or the analog offset voltage compensation unit 16 may be provided. When only the digital offset voltage compensation unit is used to perform offset voltage compensation, the analog offset voltage compensation signal may be set to 0. When only the analog offset voltage compensation unit is used to perform offset voltage compensation, the digital offset voltage compensation signal may be set to 0.

[0066] Similar to Embodiment 1, the above steps S21 and S23 are only an example of selecting the corresponding analog gain, digital offset voltage compensation signal and analog offset voltage compensation signal according to the gear range. However, the present invention is not limited thereto, and in addition to establishing a mapping table, any other method can be used to establish the corresponding relationship.

[0067] In addition, the above audio processing method can be implemented by the controller 14 provided in the above audio processing circuit 1A, but is not limited thereto, and can also be implemented by a control circuit provided outside the audio processing circuit, for example.

[0068] According to the audio processing method and audio processing circuit of the present embodiment, by dynamically switching the analog gain of the power amplifier according to the amplitude of the sound source signal and performing an offset voltage compensation action for each analog gain to offset the offset voltage, smooth switching of the analog gain can be achieved without affecting the audio playback quality.

[0069] Another embodiment of the present invention further provides an audio playback device, which includes a processor and a memory. The audio playback device can be a Bluetooth headset, a smart speaker, a smart watch, a smart phone, a tablet computer, a laptop computer, a desktop computer, etc., but is not limited thereto, as long as it is an audio playback device that can play audio.

[0070] The processor may be implemented in at least one hardware form of digital signal processing (DSP), field-programmable gate array (FPGA), and programmable logic array (PLA).

[0071] The memory may be a read-only memory (ROM), a random access memory (RAM), etc. The memory stores instructions, and when the instructions are executed by the processor, the audio processing method described in the embodiment of the present invention is executed.

[0072] Another embodiment of the present invention further provides a computer-readable storage medium, in which instructions are stored. When the computer-readable storage medium is run on a computer, the computer executes the audio processing method as described in the embodiment of the present invention.

[0073] Another embodiment of the present invention further provides a computer program product comprising instructions, which, when executed on a computer, enables the computer to execute the audio processing method as described in the embodiment of the present invention.

[0074] It should be noted that, for the sake of simplicity, the implementation methods of the above-mentioned audio processing methods are all described as a series of action combinations, but those skilled in the art should be aware that the present invention is not limited by the described order of actions. According to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the implementation methods described in the specification are all preferred implementation methods, and the actions and modules involved are not necessarily required by the present invention.

[0075] A person skilled in the art may understand that all or part of the steps in the implementation of the above-mentioned audio processing method may be completed by hardware related to program instructions, and the program may be stored in a computer-readable storage medium, and the storage medium may include: a flash drive, a read-only memory (ROM), a random access memory (RAM), an EPROM, an EEPROM, a magnetic disk or an optical disk, etc.

[0076] The present invention is described in detail, but the above embodiments are only examples of all embodiments, and the present invention is not limited thereto. The present invention can freely combine the various embodiments within the scope of the invention, or modify any constituent element of each embodiment, or omit any constituent element of each embodiment.

Claims

1. An audio processing method for an audio processing circuit, the audio processing circuit comprising a digital audio processing unit with a variable digital gain, a digital-to-analog converter, and a power amplifier with a variable analog gain, characterized in that: The audio processing method comprises the following steps: The step of determining the range of the amplitude of the currently input audio source signal, and selecting the corresponding analog gain based on the determined range of the amplitude; and The step of outputting the selected analog gain to the power amplifier for control, and outputting the digital gain in inverse proportion to the selected analog gain to the digital audio processing unit for control, The lower the amplitude range of the sound source signal, the smaller the corresponding analog gain is set to. The audio processing circuit further includes at least one of a digital offset voltage compensation unit for performing offset voltage compensation using a digital offset voltage compensation signal and an analog offset voltage compensation unit for performing offset voltage compensation using an analog offset voltage compensation signal. The audio processing method further comprises the following steps: The step of pre-testing the offset voltages at multiple analog gains and the digital offset voltage compensation signals and / or analog offset voltage compensation signals for offsetting the offset voltages under silent conditions; A step of selecting a corresponding digital offset voltage compensation signal and / or an analog offset voltage compensation signal according to the selected analog gain; and The step of outputting the selected digital offset voltage compensation signal and / or analog offset voltage compensation signal to the digital offset voltage compensation unit and / or the analog offset voltage compensation unit for control.

2. The audio processing method according to claim 1, characterized in that: The following steps are also included: The step of presetting a plurality of gear intervals and a plurality of analog gains corresponding to each gear interval for the amplitude of the sound source signal; and The step of establishing and storing a mapping table that corresponds the gear range to the analog gain.

3. The audio processing method according to claim 2, characterized in that: By setting at least one threshold, the amplitude of the sound source signal is divided into a plurality of gear intervals.

4. The audio processing method according to any one of claims 1 to 3, characterized in that: A value obtained by multiplying the analog gain of the power amplifier by the digital gain of the digital audio processing unit is proportional to the output volume set by the user.

5. The audio processing method according to claim 1, characterized in that: The following steps are also included: The step of presetting a plurality of gear intervals and a plurality of analog gains corresponding to each gear interval for the amplitude of the sound source signal; and A step of establishing and storing a mapping table that corresponds the gear range, analog gain, digital offset voltage compensation signal and / or analog offset voltage compensation signal.

6. The audio processing method according to claim 1 or 5, characterized in that: When offset voltage compensation is performed using only the digital offset voltage compensating unit or the analog offset voltage compensating unit due to synchronization with digital gain adjustment or quantization noise, the analog offset voltage compensation signal or the digital offset voltage compensation signal is set to 0.

7. An audio processing circuit, characterized in that: include: A digital audio processing section with variable digital gain; Digital to analog converters; at least one of a digital offset voltage compensation unit for performing offset voltage compensation using a digital offset voltage compensation signal and an analog offset voltage compensation unit for performing offset voltage compensation using an analog offset voltage compensation signal; A power amplifier with variable analog gain; and A controller for executing the audio processing method according to any one of claims 1 to 6.

8. An audio playback device, characterized in that: The audio playback device comprises: processor; and A memory, wherein instructions are stored in the memory, and when the instructions are executed by the processor, the audio processing method according to any one of claims 1 to 6 is executed.

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