CN106023998B - Camera audio input device, denoising method and camera - Google Patents

Camera audio input device, denoising method and camera Download PDF

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CN106023998B
CN106023998B CN201610365949.0A CN201610365949A CN106023998B CN 106023998 B CN106023998 B CN 106023998B CN 201610365949 A CN201610365949 A CN 201610365949A CN 106023998 B CN106023998 B CN 106023998B
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module
gain
value
gain value
coding
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CN106023998A (en
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熊道云
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Beijing Vision World Technology Co., Ltd.
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Beijing Vision World Technology Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/50—Constructional details
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L19/008—Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
    • G10L21/0208—Noise filtering
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/50—Constructional details
    • H04N23/54—Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Computational Linguistics (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Human Computer Interaction (AREA)
  • Quality & Reliability (AREA)
  • Mathematical Physics (AREA)
  • Amplifiers (AREA)

Abstract

the invention discloses a camera audio input device, a denoising method and a camera. The camera audio input device includes: the audio acquisition module is used for acquiring environmental sound and converting the environmental sound into an analog audio signal; the encoding module is used for converting the analog audio signal into a digital audio signal and performing encoding output; the power amplification module is used for amplifying and outputting the coded digital audio signal; the processing module is used for outputting a first gain value to the coding module according to a first trigger condition so as to reduce the gain of the coding module, and outputting a second gain value to the power amplification module according to the first trigger condition so as to improve the gain of the power amplification module. The invention reduces the noise of the audio signal and improves the tone quality.

Description

Camera audio input device, denoising method and camera
Technical Field
The invention relates to the technical field of audio circuits, in particular to a camera audio input device, a denoising method and a camera.
Background
the camera is also called a computer camera, a computer eye, an electronic eye and the like, is a video input device, and is widely applied to the field of monitoring safety. With the development of camera technology, it gradually extends from the commercial field to the civil field. The common people can install the camera in private places such as families and the like, and the camera is connected with mobile terminals such as mobile phones and the like through a wireless communication technology, so that the picture shot by the camera can be watched at any time, and the method is very convenient.
The function of camera also becomes diversified at its development in-process day by day, and the microphone is installed more to current camera, still can record the sound of shooing the scene when shooing, has further promoted safety monitoring's ability. The existing camera microphone circuit comprises a codec (coder/decoder) and a power amplifier, wherein the codec encodes and compresses an acquired original audio signal, and then the signal is amplified by the power amplifier to complete audio input. The disadvantage of this circuit is that the noise of the audio signal is relatively large without corresponding denoising measures.
Disclosure of Invention
In view of the above problems, the invention provides a camera audio input device, a denoising method and a camera, which solve the problem of large noise of an audio signal of the existing camera.
according to a first aspect of the present invention, an embodiment of the present invention provides a camera audio input device, which includes: the audio acquisition module is used for acquiring environmental sound and converting the environmental sound into an analog audio signal; the encoding module is used for converting the analog audio signal into a digital audio signal and performing encoding output; the power amplification module is used for amplifying and outputting the coded digital audio signal; the processing module is used for outputting a first gain value to the coding module according to a first trigger condition so as to reduce the gain of the coding module, and outputting a second gain value to the power amplification module according to the first trigger condition so as to improve the gain of the power amplification module.
Preferably, the first trigger condition includes a preset first gain threshold and a preset second gain threshold respectively corresponding to the coding module and the power amplifier module, and when the processing module detects that the gain of the coding module is higher than the first gain threshold, the processing module outputs the first gain value; and when the processing module detects that the gain of the power amplification module is lower than the second gain threshold value, outputting the second gain value.
Preferably, the first trigger condition includes a first preset value and a second preset value which are preset and respectively correspond to the coding module and the power amplifier module, and the processing module outputs the first preset value and the second preset value when being powered on, so as to limit the gain ranges of the coding module and the power amplifier module.
Preferably, the first trigger condition includes a first trigger signal generated when the audio acquisition module acquires the environmental sound, and the processing module is configured to output a first gain value to the encoding module according to the first trigger signal and output a second gain value to the power amplifier module according to the first trigger signal.
Preferably, the first gain value and the second gain value are respectively included in the first control signal and the second control signal, and the first control signal and the second control signal respectively drive the encoding module and the power amplifier module to operate within a gain range defined by the first gain value and the second gain value.
Preferably, the processing module is provided with registers corresponding to the coding module and the power amplifier module, the first gain value and the second gain value are respectively stored in the corresponding registers, the processing module writes the first gain value and the second gain value into the corresponding registers to complete the output of the registers, and the coding module and the power amplifier module perform adaptive gain adjustment according to the first gain value and the second gain value of the corresponding registers.
Preferably, the processing module is further configured to output the first sampling value to the encoding module according to a second trigger condition to increase the sampling rate.
Preferably, the second trigger condition includes a preset first sampling threshold corresponding to the coding module, and when the processing module detects that the sampling rate of the coding module is lower than the first sampling threshold, the processing module outputs the first sampling value.
Preferably, the second trigger condition includes a preset sampling value corresponding to the encoding module, and the processing module outputs the preset sampling value when powered on, so as to limit the sampling rate range of the encoding module.
Preferably, the second trigger condition includes a second trigger signal generated when the audio acquisition module acquires the environmental sound, and the processing module is configured to output the first sampling value to the encoding module according to the second trigger signal.
Preferably, the product of the gain of the coding module after being reduced and the gain of the power amplifier module after being increased is greater than or equal to the product of the gain of the coding module before being reduced and the gain of the power amplifier module before being increased.
Preferably, the digital audio signal processing device further comprises a band-pass filtering module for performing band-pass filtering on the amplified digital audio signal, wherein the pass-band frequency of the band-pass filtering module is 2K-20 KHz.
Preferably, the passband frequency of the bandpass filtering module is 5K-8 KHz.
According to a second aspect of the present invention, an embodiment of the present invention provides a camera audio denoising method, including the following steps: converting the ambient sound into an analog audio signal by using an audio acquisition module; converting the analog audio signal into a digital audio signal by using an encoding module, and performing encoding output; amplifying the coded digital audio signal by using a power amplifier module and then outputting the amplified digital audio signal; and outputting a first gain value by using a processing module according to a first trigger condition to reduce the gain of the coding module, and outputting a second gain value by using the first trigger condition to improve the gain of the power amplification module.
Preferably, the first trigger condition includes a preset first gain threshold and a preset second gain threshold respectively corresponding to the coding module and the power amplifier module; outputting, by a processing module, the first gain value when the processing module detects that the gain of the coding module is higher than the first gain threshold; and when the processing module detects that the gain of the power amplification module is lower than the second gain threshold value, outputting the second gain value by using the processing module.
Preferably, the first gain value and the second gain value are respectively included in the first control signal and the second control signal; correspondingly, the processing module is used for driving the coding module and the power amplifier module to work in the gain range limited by the first gain value and the second gain value respectively according to the first control signal and the second control signal.
according to a third aspect of the present invention, an embodiment of the present invention provides a camera including the above camera audio input device.
Compared with the prior art, based on the scheme provided by the invention, the processing module is used for outputting a first gain value to the coding module according to a first trigger condition so as to reduce the gain of the coding module, and outputting a second gain value to the power amplification module according to the first trigger condition so as to improve the gain of the power amplification module. Because the coding module is more sensitive to noise, the invention reduces the gain of the coding module, and the noise is reduced along with the reduction of the gain, thereby reducing the noise of the audio signal and improving the tone quality of the audio signal.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.
drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an audio input device with a camera according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of an encoding module according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of an L-order Σ Δ modulator according to an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a power amplifier module according to an embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a power amplifier module according to another embodiment of the present invention.
Fig. 6 is a schematic structural diagram of an audio input device with a camera according to an embodiment of the present invention.
Fig. 7 is a flowchart of a camera audio denoising method according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
In some of the flows described in the present specification and claims and in the above figures, a number of operations are included that occur in a particular order, but it should be clearly understood that these operations may be performed out of order or in parallel as they occur herein, with the order of the operations being indicated as 101, 102, etc. merely to distinguish between the various operations, and the order of the operations by themselves does not represent any order of performance. Additionally, the flows may include more or fewer operations, and the operations may be performed sequentially or in parallel. It should be noted that, the descriptions of "first", "second", etc. in this document are used for distinguishing different messages, devices, modules, etc., and do not represent a sequential order, nor limit the types of "first" and "second" to be different.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic structural diagram of an audio input device with a camera according to an embodiment of the present invention.
A camera audio input device is shown in figure 1 and comprises an audio acquisition module 10, an encoding module 20 and a power amplifier module 30 which are connected in sequence. The audio capture module 10 is used to capture ambient sound and convert the ambient sound into an analog audio signal. Specifically, the audio collection module 10 may be an electret microphone, a sound collector, a sound sensor, a sound pickup, an audio collection circuit, or the like.
The encoding module 20 is configured to convert the analog audio signal output by the audio acquisition module 10 into a digital audio signal, and encode and compress the digital audio signal. In particular, the digital audio signal is also filtered and amplified accordingly before being converted into the digital audio signal. The encoding module 20 may be a codec chip, or may be a circuit module including circuits having the above functions.
The power amplifier module 30 is configured to amplify the audio signal processed by the encoding module 20 to make the audio signal reach a required signal strength. The amplified audio signal may be stored to a memory. The power amplifier module 30 may be a power amplifier chip, or may be a circuit module having a signal amplifying function.
the camera audio input device further comprises a processing module 40, and the processing module 40 is respectively connected with the encoding module 20 and the power amplifier module 30. Specifically, the processing module 40 may be a DSP chip, a single chip, or other circuit modules having the above functions.
when the first trigger condition occurs, the processing module 40 is configured to output a first gain value to the encoding module 20 according to the first trigger condition, and the encoding module 20 is configured to reduce its gain according to the first gain value. The processing module 40 is further configured to output a second gain value to the power amplifier module 30 according to the first trigger condition, and the power amplifier module 30 is configured to increase the gain of the power amplifier module according to the second gain value. Accordingly, the noise of the audio signal is reduced as the gain of the encoding module 20 is reduced, thereby reducing the noise of the audio signal. Meanwhile, the gain of the power amplifier module is improved, and the strength of the output signal is ensured.
in an implementation manner, the processing module 40 is provided with registers corresponding to the encoding module 20 and the power amplifier module 30, the first gain value and the second gain value are respectively stored in the corresponding registers, the processing module 40 writes the first gain value and the second gain value into the corresponding registers, and the encoding module 20 and the power amplifier module 30 respectively read the first gain value and the second gain value from the corresponding registers and respectively perform adaptive gain adjustment according to the first gain value and the second gain value.
In another implementation manner, the encoding module 20 and the power amplifier module 30 are respectively provided with corresponding registers, the processing module 40 writes the first gain value and the second gain value into the corresponding registers after outputting the first gain value and the second gain value, and the encoding module 20 and the power amplifier module 30 respectively read the first gain value and the second gain value from their own registers and perform adaptive gain adjustment according to the first gain value and the second gain value.
It should be noted that the gain value reduced by the coding module 20 and the gain value increased by the power amplifier module 30 are determined by those skilled in the art in combination with actual details, and are not described herein again. The processing module 40 is also configured to obtain the current gains of the coding module 20 and the power amplifier module 30 in a timing manner or in real time, so as to ensure that the gains of the coding module 20 and the power amplifier module 30 are within a reasonably controllable range.
in one embodiment, the product of the gain of the coding module 20 after being reduced and the gain of the power amplification module 30 after being increased is greater than or equal to the product of the gain of the coding module 20 before being reduced and the gain of the power amplification module 30 before being increased. Since the coding module 20 reduces the gain thereof and the signal strength of the audio signal is weakened, the product of the gain of the coding module 20 after being reduced and the gain of the power amplification module 30 after being increased should be at least equal to the product of the gain of the coding module 20 before being reduced and the gain of the power amplification module 30 before being increased, so that the strength of the audio signal is equal to the strength of the signal before being changed.
In one embodiment, the first trigger condition includes a preset first gain threshold and a preset second gain threshold corresponding to the encoding module 20 and the power amplifier module 30, respectively. The processing module 40 obtains the gains of the coding module 20 and the power amplifier module 30 in real time or in a timing manner. Taking the codec chip and the power amplifier chip as examples, the registers in the codec chip and the power amplifier chip store the current gains of the codec chip and the power amplifier chip, and the processing module 40 obtains the gains of the codec chip and the power amplifier chip through the respective registers.
When the processing module 40 detects that the gain of the encoding module 20 is higher than the first gain threshold, the first gain value is output. When the processing module 40 detects that the gain of the power amplifier module 30 is lower than the second gain threshold, a second gain value is output.
In one embodiment, the first trigger condition includes a first preset value and a second preset value that are preset and respectively correspond to the encoding module 20 and the power amplifier module 30. When the processing module 40 is powered on, the processing module outputs a first preset value to the encoding module 20 and outputs a second preset value to the power amplifier module 30, so as to limit the gain of the encoding module 20 to be reduced to the first preset value, and the gain of the power amplifier module 30 to be increased to the second preset value.
specifically, after receiving the first preset value, the encoding module 20 writes the first preset value into the register corresponding to the self gain, thereby reducing the self gain to the first preset value. After receiving the second preset value, the power amplifier module 30 writes the second preset value into the register corresponding to the self gain, so as to increase the self gain to the second preset value.
In one embodiment, the first trigger condition includes a first trigger signal generated when the audio capture module 10 captures the ambient sound, and the first trigger signal may be a level signal to indicate that the audio capture module 10 captures the ambient sound. The processing module 40 outputs a first gain value to the encoding module 20 according to the first trigger signal, and is configured to output a second gain value to the power amplifier module 30 according to the first trigger signal, that is, when the audio acquisition module 10 acquires a sound, the first gain value and the second gain value are output.
In one embodiment, the processing module 40 is configured to output a first control signal to the encoding module 20 and a second control signal to the power amplifier module 30. The first gain value and the second gain value are respectively included in the first control signal and the second control signal. The first gain value and the second gain value define a variable gain range of the encoding module 20 and the power amplifier module 30.
Specifically, the coding module 20 and the power amplifier module 30 adjust their gains based on a negative feedback manner. After receiving the first control signal, the encoding module 20 extracts a first gain value from the first control signal, and gradually decreases its gain within a range larger than the first gain value based on a negative feedback manner. After receiving the second control signal, the power amplifier module 30 extracts a second gain value from the second control signal, and gradually increases its gain within a range smaller than the second gain value based on a negative feedback manner.
Fig. 2 is a schematic structural diagram of an encoding module according to an embodiment of the present invention.
as shown in fig. 2, in the present embodiment, the encoding module 20 is a codec chip, and includes a pre-filtering module 201, an AD conversion module 202, an AGC (automatic gain control) module 203, and an encoding and compressing module 204, which are connected in sequence.
the pre-filtering module 201 is used for performing a primary filtering on the analog audio signal output by the audio acquisition module 10. The AD conversion module 202 is configured to convert the audio signal from an analog signal to a digital signal. The AGC block 203 is embodied as an AGC loop for changing the gain of the coding block 20. The encoding and compressing module 204 is used for encoding and compressing the audio signal.
In one implementation, the AGC block 203 changes the gain of the coding block 20 by changing the dc operating state of its transistors. In another implementation, the AGC module 203 reduces its own gain parameter, and reduces the signal amplification factor according to the reduced gain parameter, thereby reducing the gain of the encoding module 20.
In the AD conversion process, there is a difference between the encoded signal and the original signal due to the quantization of the amplitude and time, that is, there is quantization noise, and the quantization noise also causes large interference to the audio signal, so it is necessary to consider removing the quantization noise.
In this embodiment, the processing module 40 is further configured to output the first sampling value to the encoding module 20 according to a second trigger condition to increase the sampling rate. Specifically, when the AD conversion module 202 of the encoding module 20 performs AD conversion, the audio signal needs to be sampled, so that the encoding module 20 increases the sampling rate of the AD conversion module 202 according to the first sampling value.
the AD conversion module 202 may employ a second-order Σ Δ modulator. The sigma delta modulator employs oversampling, eliminating the need for sample and hold circuitry and reducing the design requirements of the filter.
Fig. 3 is a schematic diagram of an L-order Σ Δ modulator according to an embodiment. Which includes several integrators and quantizers. Where Q (nT) represents quantization noise, the z-domain transfer function of which is:
Y(z)＝z-L·X(z)+(1-z-1)L·Q(z)
It can be seen that the Σ Δ modulator transmits a signal without distortion, transmits quantization noise with an L-order difference, and performs high-pass filtering in terms of frequency domain, that is, quantization noise in the baseband of the Σ Δ modulator shifts to an out-of-band high frequency band, while baseband low-frequency noise is suppressed, and the higher the order L is, the stronger the suppression effect is. Therefore, increasing the order L can reduce the quantization noise.
Assuming that the quantization noise is white noise, the output dynamic range DR of the L-order Σ Δ modulator with the oversampling ratio M is: dR＝3(2L+1)·M2L+1/(2π2L)
Where the relationship between the convertible digit precision n and the dynamic range DR of the AD conversion module 202 is DR 3 × 22n-1, then:
It can be seen that the sampling rate M also affects the signal noise, and increasing the sampling rate M reduces the signal noise accordingly and can improve the conversion accuracy. Therefore, the encoding module 20 is further configured to increase the sampling rate of the AD conversion module 202 according to the first sampling value, so as to further reduce the noise of the audio signal.
In one embodiment, the second trigger condition comprises a preset first sampling threshold corresponding to the encoding module 20. The processing module 40 obtains the sampling rate of the encoding module 20 in real time or on a timed basis. Taking the codec chip as an example, a register in the codec chip stores the current sampling rate of the codec chip, and the processing module 40 obtains the sampling rate of the codec chip through the register. When the processing module 40 detects that the sampling rate of the encoding module 20 is lower than the first sampling threshold, the first sampling value is output.
In one embodiment, the second trigger condition comprises a preset sampling value corresponding to the encoding module 20. The processing module 40 outputs the preset sampling value when being powered on, so as to limit the encoding module 20 to increase the sampling rate within a range smaller than the first preset value.
in one embodiment, the second trigger condition includes a second trigger signal generated when the audio capture module 10 captures the ambient sound, and the second trigger signal may be a level signal to indicate that the audio capture module 10 captures the ambient sound. The processing module 40 outputs the first sampling value to the encoding module 20 according to the second trigger signal, that is, outputs the first sampling value when the audio acquisition module 10 acquires sound.
fig. 4 is a schematic structural diagram of the power amplifier module 30 according to an embodiment.
As shown in fig. 4, the power amplifier module 30 includes a gain control module 301 and a variable gain amplifier module 302 connected to each other, and the gain control module 301 is provided with a gain control interface. The gain control module 301 changes the gain of the variable gain amplification module 302 according to the voltage of the input signal of the gain control interface. Therefore, the processing module 40 is connected to the gain control interface, and the second control signal sent by the processing module 40 is specifically an output signal after voltage increase, so that the power amplifier module 30 increases its gain according to the output signal after voltage increase.
Fig. 5 is a schematic structural diagram of a power amplifier module 30 according to another embodiment.
As shown in fig. 5, the power amplifier module 30 includes a gain control module 301, an attenuation module 303, and a fixed gain amplification module 304, which are connected in sequence. The gain of the fixed gain amplification module 304 is fixed, and the gain control module 301 is provided with a gain control interface. The attenuation of the attenuation module 303 is determined by the voltage of the signal applied to the gain control interface, and the higher the voltage of the signal, the greater the attenuation, and the attenuated signal is amplified again by the fixed gain amplification module 304. Therefore, the processing module 40 is connected to the gain control interface, and the second control signal sent by the processing module 40 is specifically an output signal after the voltage is reduced, so that the attenuation of the attenuation module 303 is reduced, and the power amplifier module 30 can improve the gain of itself.
In an embodiment, the encoding module may share the same power supply with a CPU, a MEMORY, and other devices with relatively high noise, and particularly in the field of cameras applied to the present invention, the product size is small, the integration level of the devices is relatively high, the encoding module may share the same power supply with other chips, and at this time, the encoding module is easily interfered by noise.
Therefore, in the embodiment, a voltage stabilizer is added between the encoding module and the power supply thereof, and specifically, a low dropout regulator and the like can be selected, so that the stability of the input power supply is ensured, the interference of other devices is reduced, and the noise is reduced.
Furthermore, an independent power supply is preferably provided for the coding module to be separated from power supplies of other devices, so that interference of the devices can be better avoided, and noise is reduced.
In one embodiment, an RC filter is added between the encoding module and a power supply thereof, and the RC filter has the advantages of simple circuit, strong anti-interference performance, better low-frequency performance and capability of filtering noise generated by other devices.
The internal circuit of the coding module has a ground terminal, and the ground terminal of the coding module may be connected to the ground terminals of other devices, for example, the ground terminal of the power amplifier module. On the ground line, return currents of various signals generally flow. The variation in ground return current is large and if the ground is not properly treated, the ground potential will significantly float. This ground potential variation is also a significant noise for the coding module and is often difficult to remove, thus requiring the ground of the coding module to be distinguished from the grounds of other devices.
In one embodiment, an isolation device is disposed between the ground terminal of the encoding module and the ground terminal of the other device, and specifically, the isolation device may be a resistor or a magnetic bead. In this way, the return current of the coding module flows only in the network of coding modules and then returns to ground via a resistor or a bead. And the return currents of other devices are restricted in the network of the device, so that the coding module cannot be interfered, and the effect of reducing noise is achieved.
Furthermore, the grounding end of the coding module is preferably separated from the grounding ends of other devices, so that the interference of the other devices is completely avoided.
in one embodiment, the encoding module is a codec chip. In order to reduce noise and obtain better audio performance, a filter capacitor is connected to a power input pin of the codec chip, and the filter capacitor can be a ceramic capacitor.
Taking the es8388 chip as an example, the chip has four power input pins, namely AVDD, HPVDD, DVDD and PVDD, and the four pins are connected with filter capacitors, so that the capacitance value is minimum 4.7 uF. When the codec chip is mounted on a PCB, the filter capacitor is arranged on the same PCB layer as the codec chip, so that the inductive reactance effect of the via hole does not exist on the routing lines of AVDD, HPVDD, DVDD and PVDD, and a better filtering effect can be ensured.
Fig. 6 is a schematic structural diagram of an audio input device of a camera according to an embodiment.
As shown in fig. 6, the output end of the power amplifier module 30 is further connected to a band-pass filter 50, and the band-pass frequency of the band-pass filter 50 is 2K-20KHz, which is close to the hearing range of human ears, so that only the signal of this frequency band is retained, and signals of other frequency bands are filtered out, which can play a role in removing noise.
Furthermore, the band pass frequency of the band pass filter 50 is 5K-8KHz, which is close to the audio band of the sound emitted by a person, so that only the person's voice is retained, and other sounds are filtered out, which can further play a role in removing noise.
The embodiment of the invention also provides a camera which comprises the camera audio input device of the embodiment.
fig. 7 is a flowchart of a camera audio denoising method according to an embodiment of the present invention.
A camera audio denoising method is implemented by utilizing an audio acquisition module, an encoding module, a power amplifier module and a processing module. The audio acquisition module, the coding module and the power amplifier module are sequentially connected, and the processing module is respectively connected with the coding module and the power amplifier module. As shown in fig. 7, it includes the following steps:
S101: and converting the ambient sound into an analog audio signal by using an audio acquisition module.
The audio acquisition module acquires surrounding environmental sounds and converts the environmental sounds into analog audio signals. Specifically, the audio acquisition module may be an electret microphone, a sound collector, a sound sensor, a sound pickup, an audio acquisition circuit, or the like.
S102: and converting the analog audio signal into a digital audio signal by using an encoding module, and encoding and outputting the digital audio signal.
the coding module converts the analog audio signal output by the audio acquisition module into a digital audio signal and codes and compresses the digital audio signal. The digital audio signal may also be filtered and amplified accordingly before being converted into a digital audio signal. The coding module can be a codec chip, and can also be a circuit module consisting of circuits with the functions.
S103: and amplifying the coded digital audio signal by using a power amplifier module and then outputting the amplified digital audio signal.
The power amplification module amplifies the audio signal processed by the coding module to enable the audio signal to reach the required signal intensity. The amplified audio signal may be stored to a memory. The power amplifier module can be a power amplifier chip or a circuit module with a signal amplification function.
S104: and outputting a first gain value by using a processing module according to a first trigger condition to reduce the gain of the coding module, and outputting a second gain value by using the first trigger condition to improve the gain of the power amplification module.
When the first trigger condition occurs, the processing module outputs a first gain value to the coding module according to the first trigger condition, and the coding module reduces the self gain according to the first gain value. And the processing module outputs a second gain value to the power amplification module according to the first trigger condition, and the power amplification module improves the self gain according to the second gain value. Accordingly, noise of the audio signal is reduced as the gain of the coding module is reduced, thereby reducing the noise of the audio signal. Meanwhile, the gain of the power amplifier module is improved, and the strength of the output signal is ensured.
In one embodiment, the first trigger condition includes a preset first gain threshold and a preset second gain threshold respectively corresponding to the coding module and the power amplifier module; outputting, by a processing module, the first gain value when the processing module detects that the gain of the coding module is higher than the first gain threshold; and when the processing module detects that the gain of the power amplification module is lower than the second gain threshold value, outputting the second gain value by using the processing module.
in one embodiment, the first gain value and the second gain value are included in the first control signal and the second control signal, respectively; correspondingly, the processing module is used for driving the coding module and the power amplifier module to work in the gain range limited by the first gain value and the second gain value respectively according to the first control signal and the second control signal.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the system, the apparatus and the module described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the modules is merely a logical division, and in actual implementation, there may be other divisions, for example, multiple modules or components may be combined or integrated into another system, or some features may be omitted, or not implemented. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or modules, and may be in an electrical, mechanical or other form.
The modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical modules, may be located in one place, or may be distributed on a plurality of network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
In addition, functional modules in the embodiments of the present invention may be integrated into one processing module, or each of the modules may exist alone physically, or two or more modules are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode.
Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable storage medium, and the storage medium may include: a Read Only Memory (ROM), a Random Access Memory (RAM), a magnetic or optical disk, or the like.

Claims (15)

1. A camera audio input device, comprising:
The audio acquisition module is used for acquiring environmental sound and converting the environmental sound into an analog audio signal;
The encoding module is used for converting the analog audio signal into a digital audio signal and performing encoding output;
The power amplification module is used for amplifying and outputting the coded digital audio signal;
The processing module is used for outputting a first gain value to the coding module according to a first trigger condition so as to reduce the gain of the coding module, and outputting a second gain value to the power amplification module according to the first trigger condition so as to improve the gain of the power amplification module; the first trigger condition comprises a preset first gain threshold and a preset second gain threshold which respectively correspond to the coding module and the power amplifier module, and when the processing module detects that the gain of the coding module is higher than the first gain threshold, the processing module outputs a first gain value; and when the processing module detects that the gain of the power amplification module is lower than the second gain threshold value, outputting the second gain value.
2. The apparatus of claim 1, wherein:
The first trigger condition comprises a first preset value and a second preset value which are preset and respectively correspond to the coding module and the power amplifier module, and the first preset value and the second preset value are output when the processing module is powered on so as to limit the gain ranges of the coding module and the power amplifier module.
3. The apparatus of claim 1, wherein:
The first trigger condition comprises a first trigger signal generated when the audio acquisition module acquires environmental sound, and the processing module is used for outputting a first gain value to the coding module according to the first trigger signal and outputting a second gain value to the power amplification module according to the first trigger signal.
4. The apparatus of claim 1, wherein:
the first gain value and the second gain value are respectively contained in a first control signal and a second control signal, and the first control signal and the second control signal respectively drive the coding module and the power amplifier module to work in a gain range limited by the first gain value and the second gain value.
5. The apparatus of claim 1, wherein:
The processing module is provided with registers corresponding to the coding module and the power amplifier module, the first gain value and the second gain value are respectively stored in the corresponding registers, the processing module writes the first gain value and the second gain value into the corresponding registers to complete the output of the registers, and the coding module and the power amplifier module carry out self-adaptive gain adjustment according to the first gain value and the second gain value of the corresponding registers.
6. The apparatus of any one of claims 1-5, wherein:
The processing module is further used for outputting the first sampling value to the encoding module according to a second trigger condition so as to improve the sampling rate of the encoding module.
7. The apparatus of claim 6, wherein:
The second trigger condition comprises a preset first sampling threshold corresponding to the coding module, and when the processing module detects that the sampling rate of the coding module is lower than the first sampling threshold, the first sampling value is output.
8. The apparatus of claim 6, wherein:
The second trigger condition comprises a preset sampling preset value corresponding to the coding module, and the processing module outputs the preset sampling value when being powered on so as to limit the sampling rate range of the coding module.
9. The apparatus of claim 6, wherein:
The second trigger condition comprises a second trigger signal generated when the audio acquisition module acquires the environmental sound, and the processing module is used for outputting a first sampling value to the encoding module according to the second trigger signal.
10. The apparatus of any one of claims 1-5, wherein:
The product of the gain of the coding module after reduction and the gain of the power amplification module after improvement is larger than or equal to the product of the gain of the coding module before reduction and the gain of the power amplification module before improvement.
11. The apparatus of any one of claims 1-5, wherein:
The band-pass filtering device also comprises a band-pass filtering module used for carrying out band-pass filtering on the amplified digital audio signal, and the passband frequency of the band-pass filtering module is 2K-20 KHz.
12. The apparatus of claim 11, wherein:
The passband frequency of the band-pass filtering module is 5K-8 KHz.
13. A camera audio denoising method is characterized by comprising the following steps:
converting the ambient sound into an analog audio signal by using an audio acquisition module;
Converting the analog audio signal into a digital audio signal by using an encoding module, and performing encoding output;
Amplifying the coded digital audio signal by using a power amplifier module and then outputting the amplified digital audio signal;
Outputting a first gain value by a processing module according to a first trigger condition to reduce the gain of the coding module, and outputting a second gain value by the first trigger condition to improve the gain of the power amplification module; the first trigger condition comprises a preset first gain threshold and a preset second gain threshold which respectively correspond to the coding module and the power amplifier module;
Outputting, by a processing module, the first gain value when the processing module detects that the gain of the coding module is higher than the first gain threshold; and when the processing module detects that the gain of the power amplification module is lower than the second gain threshold value, outputting the second gain value by using the processing module.
14. the method of claim 13, wherein:
The first gain value and the second gain value are respectively contained in a first control signal and a second control signal;
correspondingly, the processing module is used for driving the coding module and the power amplifier module to work in the gain range limited by the first gain value and the second gain value respectively according to the first control signal and the second control signal.
15. A camera, its characterized in that: a camera audio input device comprising any of claims 1-12.
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