A digital audio dithering-stable headphone amplifier

Abstract

A kind of digital audio removes the stable earphone amplifier of jitter, including correction module, correction module is set between input interface and amplification module, for correcting the deviation of clock jitter.It is also provided with storage module, energy analysis module, detection module and amplification control module;Storage module obtains digital audio file from player, and is stored in storage module;Energy analysis module extracts the waveform vibration curve of audio file to be played or being played from storage module, and carries out analysis, extracts waveform feature and sends to detection module;Detection module extracts waveform data from the signal output by amplification module, and extracts the features of waveform data;Detection module compares the waveform features sent by energy analysis module with the waveform features actually played by amplification module, and outputs comparison result, solves the volume variation and instability caused by correction module.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of digital audio processing, in particular to a digital audio jitter removal stable earphone amplifier. BACKGROUND

[0002] Clock jitter refers to the temporary change of clock period at a given point, so that the clock period may be lengthened or shortened at different periods. Clock jitter can cause frequency changes, misalignment, instability, etc. when playing audio files.

[0003] Application No. CN202221369584.6 discloses a circuit for eliminating clock jitter generated during digital audio transmission using PLL technology. A digital receiving module is provided for receiving input audio and generating an LRCK signal, which is output to a phase detection module. A digital phase-locked loop module is used to generate a same frequency signal as the LPCK signal, which is output to the phase detection module. The output audio signal is processed by the phase difference between the digital receiving module and the digital phase-locked loop module, and fed back to the digital phase-locked loop module to eliminate clock jitter.

[0004] However, correcting clock jitter can cause some degree of misalignment and widening of the original signal, and the processing process can also cause delay, large data volume changes, unstable amplifier temperature, etc. which can also cause some degree of unstable volume during actual amplification. SUMMARY

[0005] To solve the above problems, the present application provides a digital audio jitter removal stable earphone amplifier, which comprises an input interface, a correction module, an amplification module and an output interface. It also comprises a storage module, an energy analysis module, a detection module and an amplification control module.

[0006] The input interface is connected to the correction module, the correction module is connected to the amplification module, and the amplification module is connected to the output interface. The digital audio signal input from the input interface is corrected for clock jitter by the correction module, and the corrected audio data is sent to the amplification module for amplification and output through the output interface.

[0007] The storage module obtains digital audio files from the player and stores them in the storage module. The energy analysis module extracts the waveform vibration curve of the audio file to be played or being played from the storage module and analyzes it, extracts the waveform features and sends them to the detection module.

[0008] The detection module extracts waveform data from the signal output by the amplification module and extracts features of the waveform data. The detection module compares the waveform features sent by the energy analysis module with the waveform features actually played by the amplification module and outputs the comparison result.

[0009] The amplification control module is connected to the amplification module to control the amplification rate of the amplification module, thereby controlling the volume of the amplification module.

[0010] The storage module is directly connected to the sound source through data in a wired or wireless manner or is connected to the sound source through an input interface; and the entire audio file played by the sound source is directly obtained from the sound source.

[0011] The energy analysis module obtains the audio file from the storage module and extracts the vibration curve thereof; the waveform vibration curve is extracted for features in the energy analysis module; the extracted features include an energy change curve varying with time; wherein the energy change curve includes a plurality of sub-energy change curves after frequency division.

[0012] The energy change curve is obtained in the following manner: first, the vibration curve of the audio file is divided into a plurality of audio segments at a time interval T; the audio segments are converted into a frequency domain to obtain a frequency spectrum curve of the audio segments; the frequency spectrum of the audio segments is divided into N segments according to frequency, and then the frequency spectrum curves of the same segment of frequency in different audio segments are taken as a group to obtain N groups of frequency spectrum curves of the audio segments; the total energy of the frequency spectrum curves in each group is calculated to vary with time; and N energy change curves varying with time are obtained, which are denoted as standard energy change curves.

[0013] The detection module obtains audio data from the amplification module, and divides the vibration curve of the obtained audio into a plurality of audio segments at a time interval T; the audio segments are converted into a frequency domain to obtain a frequency spectrum curve of the audio segments; the frequency spectrum of the audio segments is divided into N segments according to frequency, and then the frequency spectrum curves of the same segment of frequency in different audio segments are taken as a group to obtain N groups of frequency spectrum curves of the audio segments; the total energy of the frequency spectrum curves in each group is calculated to vary with time; and N energy change curves varying with time are obtained, which are denoted as actual energy change curves.

[0014] The actual energy change curves and the standard energy change curves are compared in the detection module, and the comparison method is as follows:

[0015] H n (t)=F n (t)-G n (t);

[0016] wherein F n (t) represents the nth actual energy change curve, G n (t) represents the nth standard energy change curve, and H n (t) represents the difference between the nth actual energy change curve and the nth standard energy change curve; n ranges from 1 to N, and t represents a time independent variable; that is, the difference between the nth actual energy change curve and the nth standard energy change curve at each time is compared.

[0017] After that:

[0018] H(t)=k1·H1(t)+k2·H2(t)+…+k n ·H n (t)+k N ·H N (t);

[0019] Wherein k1, k2, k3, …, k N , represents the weight corresponding to different frequency bands;

[0020] The detection module outputs H(t) to the amplification control module; the amplification control module adjusts the amplification rate of the amplification module according to the positive and negative and size of H(t), the larger H(t) corresponds to the adjustment of the amplification rate of the amplification module to decrease, and the smaller H(t) corresponds to the adjustment of the amplification rate of the amplification module to increase, so that the time amplification module is consistent with the original energy change in the sound source, and the volume change caused by the correction module is reduced.

[0021] The correction module includes a reference clock, a sampling rate input, an I2S input, a cache module, a frequency synthesis module and an output module;

[0022] The reference module and the sampling rate input are connected to the frequency synthesis module, the frequency synthesis module performs local clock frequency locking on the sampling rate, and performs local clock frequency detection; the difference between the sampling rate and the I2S input clock and the local clock is calculated, and the cache sequence direction and the cache depth are further set according to the difference, so as to realize the correction of the clock deviation.

[0023] The frequency synthesis module includes a mode controller 1, a counting window generator 2, a counter 3, a synchronous frequency divider 4, a LUT 5, a subtractor 6, a FIR filter 7, a sliding mode filter 8, a low noise DAC 9, an analog loop filter 10 and a wideband VCO 11;

[0024] The reference module outputs a 10MHz high-precision reference clock to the counting window generator 2;

[0025] The sampling rate information is sent to the mode controller 1, so as to output the frequency switching control parameter to the LUT 5, and at the same time control the mode of the sliding mode filter 8 to be fast frequency switching; the filtered control data is sent to the low noise DAC 9, and after passing through the analog loop filter 10, it is output to the VCO 11;

[0026] The VCO output is sent to the synchronous frequency divider 4, and then to the frequency measurer composed of the counting window generator 2 and the counter 3 to complete the frequency measurement; the frequency measurement result is sent to the LUT 5 and the mode controller 1, and the mode controller 1 controls the loop;

[0027] The input I2S data is sent to the large capacity buffer 15, the mode controller 1 obtains the difference between the sampling rate information and the I2S input clock through the LUT 5 unit, and sets the buffer sequence direction and the buffer depth of the FIFO through the difference;

[0028] The maximum depth of the large capacity buffer 15 can ensure that a 74-minute CD disc is played completely without leakage; meanwhile, a mute detection module is arranged, the mute detection is a protection mechanism, the large capacity buffer 15 is reset in the mute segment; through the reset of the large capacity buffer 15, the continuous and stable work of the system can be ensured.

[0029] The beneficial effects of the present application are:

[0030] The present application comprises a correction module arranged between the input interface and the amplification module, which is used for correcting the deviation of clock jitter. A storage module, an energy analysis module, a detection module and an amplification control module are further arranged; the storage module obtains a digital audio file from the player and stores it in the storage module; the energy analysis module extracts the waveform vibration curve of the audio file to be played or being played from the storage module, analyzes it, extracts the waveform features and sends them to the detection module; the detection module extracts the waveform data from the signal output by the amplification module and extracts the features of the waveform data; the detection module compares the waveform features sent by the energy analysis module with the waveform features actually played by the amplification module and outputs the comparison result, solving the volume change and instability caused by the correction module. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0032] FIG. 1 is a schematic diagram of the overall architecture of the present application; Fig. 1 FIG. 1 is a schematic diagram of the overall architecture of the present application;

[0033] FIG. 2 is a schematic diagram of the connection structure of the correction module of the present application; Fig. 2 FIG. 2 is a schematic diagram of the connection structure of the correction module of the present application;

[0034] FIG. 3 is a schematic diagram of the circuit structure of the present application. Fig. 3 FIG. 3 is a schematic diagram of the circuit structure of the present application. DETAILED DESCRIPTION

[0035] Embodiment 1:

[0036] FIG. 1 is a schematic diagram of the overall architecture of the present application; Figs. 1-3The application provides a stable earphone amplifier for removing jitter of digital audio, which comprises an input interface, a correction module, an amplification module and an output interface; further comprises a storage module, an energy analysis module, a detection module and an amplification control module.

[0037] The input interface is connected to the correction module, the correction module is connected to the amplification module, and the amplification module is connected to the output interface; the digital audio signal input from the input interface is corrected by the correction module for clock jitter, the corrected audio data is sent to the amplification module for amplification, and the amplified signal is output through the output interface.

[0038] The storage module obtains a digital audio file from a player and stores it in the storage module; the energy analysis module extracts the waveform vibration curve of the audio file to be played or being played from the storage module, analyzes it, extracts the waveform features and sends them to the detection module.

[0039] The detection module extracts the waveform data from the signal output by the amplification module and extracts the features of the waveform data; the detection module compares the waveform features sent by the energy analysis module with the waveform features actually played by the amplification module and outputs the comparison result.

[0040] The amplification control module is connected to the amplification module to control the amplification rate of the amplification module, thereby controlling the volume of the amplification module.

[0041] The storage module is directly connected to the sound source by wired or wireless data or connected to the sound source through the input interface; and the entire audio file played by the sound source is directly obtained from the sound source.

[0042] The energy analysis module obtains the audio file from the storage module and extracts its vibration curve; the waveform vibration curve is extracted in the energy analysis module; the extracted features include the energy change curve changing with time; wherein the energy change curve includes a plurality of sub-energy change curves after frequency division.

[0043] The energy change curve is obtained by first dividing the vibration curve of the audio file into a plurality of audio segments at a time interval T; the audio segments are converted into frequency domain to obtain the frequency spectrum curve of the audio segments; the frequency spectrum of the audio segments is divided into N segments according to frequency, and then the frequency spectrum curves of the same segment in different audio segments are taken as a group to obtain N groups of frequency spectrum curves of the audio segments; the total energy of the frequency spectrum curve in each group is calculated to change with time; N energy change curves changing with time are obtained, which are denoted as standard energy change curves.

[0044] The detection module obtains audio data from the amplification module, and divides the vibration curve of the obtained audio into multiple audio segments at a time interval T; the audio segments are subjected to frequency domain conversion to obtain the frequency spectrum curve of the audio segments; the frequency spectrum of the audio segments is divided into N segments according to frequency, and then the frequency spectrum curves of the same frequency segment in different audio segments are taken as a group to obtain N groups of frequency spectrum curves of the audio segments; the total energy of the frequency spectrum curves in each group is calculated with respect to time; N energy change curves with respect to time are obtained, denoted as actual energy change curves;

[0045] In the detection module, the actual energy change curves and the standard energy change curves are compared, and the comparison method is:

[0046] H n (t)=F n (t)-G n (t);

[0047] Wherein F n (t) represents the nth actual energy change curve, G n (t) represents the nth standard energy change curve, and H n (t) represents the difference between the nth actual energy change curve and the nth standard energy change curve; n ranges from 1 to N, and t represents the time independent variable; that is, the difference between the nth actual energy change curve and the nth standard energy change curve at each time is compared;

[0048] Then:

[0049] H(t)=k1·H1(t)+k2·H2(t)+…+k n ·H n (t)+k N ·H N (t);

[0050] Wherein k1, k2, k3, …, k N , represent the weights corresponding to different frequency bands;

[0051] H(t) is output to the amplification control module in the detection module; the amplification control module adjusts the amplification rate of the amplification module according to the positive and negative and size of H(t), the larger H(t) corresponds to the adjustment of the amplification rate of the amplification module to decrease, and the smaller H(t) corresponds to the adjustment of the amplification rate of the amplification module to increase, so that the amplification module is consistent with the original energy change in the sound source, and the volume change caused by the correction module is reduced.

[0052] The correction module includes a reference clock, a sampling rate input, an I2S input, a buffer module, a frequency synthesis module and an output module;

[0053] The reference module and the sampling rate input are connected to the frequency synthesis module, the frequency synthesis module carries out local clock frequency locking and local clock frequency detection to the sampling rate, and calculates the difference between the sampling rate and the I2S input clock and the local clock, and further sets the cache sequence direction and the cache depth according to the difference, so as to realize the correction of the clock deviation.

[0054] The frequency synthesis module comprises a mode controller 1, a counting window generator 2, a counter 3, a synchronous frequency divider 4, a LUT 5, a subtractor 6, a FIR filter 7, a sliding mode filter 8, a low-noise DAC 9, an analog loop filter 10 and a wideband VCO 11.

[0055] The reference module outputs a 10MHz high-precision reference clock to the counting window generator 2.

[0056] The sampling rate information is input into the mode controller 1, so as to output the frequency switching control parameter to the LUT 5, and at the same time, the mode of the sliding mode filter 8 is controlled to be fast frequency switching, the filtered control data is sent to the low-noise DAC 9, and after passing through the analog loop filter 10, it is output to the VCO 11.

[0057] The VCO output is sent to the synchronous frequency divider 4, and then to the frequency measurer composed of the counting window generator 2 and the counter 3 to complete the frequency measurement; the frequency measurement result is sent to the LUT 5 and the mode controller 1, and the loop is controlled by the mode controller 1.

[0058] The input I2S data is input into the large-capacity cache 15, the mode controller 1 obtains the difference between the sampling rate information and the I2S input clock through the LUT 5 unit, and sets the cache sequence direction and the cache depth of the FIFO through the difference.

[0059] The maximum depth of the large-capacity cache 15 can ensure that a 74-minute CD disc is played to the end without leakage; at the same time, a mute detection module is provided, and the mute detection is a protection mechanism, which resets the large-capacity cache 15 in the mute segment; through the resetting of the large-capacity cache 15, the continuous and stable work of the system can be ensured.

[0060] Embodiment 2:

[0061] Referring to Figs. 2-3 , the circuit example specifically comprises a mode controller 1, a counting window generator 2, a counter 3, a synchronous frequency divider 4, a LUT 5, a subtractor 6, a FIR filter 7, a sliding mode filter 8, a low-noise DAC 9, an analog loop filter 10 and a wideband VCO 11; and further comprises a mute detection 13, a FIFO control 14, a large-capacity cache FIFO 15 and an I2S timing generation 12.

[0062] The I2S timing and data input are divided into 3 paths. One path enters the silence detection 13 and then enters the FIFO control 14. The second path enters the large-capacity buffer FIFO 15. The third path enters the counter 3. The input I2S_MCLK enters the counter 3.

[0063] A 10MHz high-precision reference clock enters the counting window generator 2, and then enters the counter 3; the sampling rate is input to the mode controller 1 and then enters the counting window generator 2, LUT5 and sliding mode filter 8 (FIR+IIR);

[0064] The mode controller is connected to FIFO control 14, LUT5, and sliding mode filter 8 (FIR+IIR);

[0065] Counter 3 outputs to LUT5 and subtractor 6, LUT5 outputs to subtractor and sliding mode filter 8 (FIR+IIR), and subtractor outputs to FIR filter 7.

[0066] The output of sliding mode filter 8 (FIR+IIR) is sent to low noise DAC9, then to analog loop filter 10, and finally to broadband VCO 11.

[0067] The broadband VCO output is connected to the synchronous divider 4, the I2S timing generator 12, and the MCLK output;

[0068] I2S timing generator 12 outputs to FIFO control 14 and I2S output; FIFO control 14 is connected to large-capacity buffer FIFO 15; large-capacity buffer FIFO 15 is connected to I2S timing generator 12.

[0069] Thus far, the description of the above embodiments has been provided for illustrative and descriptive purposes. This is not intended to be exhaustive or limiting of the present disclosure. Individual elements or features of particular embodiments are generally not limited to those particular embodiments, but may be interchanged and used in selected embodiments where applicable, even if not specifically shown or described. In many respects, the same elements or features may also be varied. Such variations are not considered a departure from this disclosure, and all such modifications are intended to be included within the scope of this disclosure.

[0070] Example embodiments are provided so that this disclosure will become thorough and will fully convey the scope to those skilled in the art. Numerous details, such as examples of specific parts, apparatus, and methods, are set forth to provide a thorough understanding of embodiments of this disclosure. It will be apparent to those skilled in the art that the specific details are not required, and the example embodiments may be implemented in many different forms, neither of which should be construed as limiting the scope of this disclosure. In some example embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

[0071] Professional terms are used herein only for the purpose of describing particular example embodiments and are not intended to be limiting as to a scope of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order in which they are discussed. It is also to be understood that additional or alternative steps can be employed.

Claims

1. A digital audio jitter-reducing stabilized headphone amplifier, comprising an input interface, a correction module, an amplification module, and an output interface; characterized in that: It also includes a storage module, an energy analysis module, a detection module, and an amplification control module; The input interface connects to the correction module, the correction module connects to the amplification module, and the amplification module connects to the output interface. The digital audio signal input from the input interface is corrected for clock jitter by the correction module. The corrected audio data is then sent to the amplification module for amplification and output through the output interface. The storage module retrieves digital audio files from the player and stores them in the storage module; The energy analysis module extracts the waveform vibration curve of the audio file to be played or currently playing from the storage module, analyzes it, extracts waveform features, and sends them to the detection module. The detection module extracts waveform data from the signal output by the amplification module and extracts the features of the waveform data; The detection module compares the waveform characteristics sent by the energy analysis module with the waveform characteristics actually played by the amplification module, and outputs the comparison results. The amplification control module is connected to the amplification module and controls the amplification rate of the amplification module, thereby controlling the volume of the amplification module; The storage module connects directly to the audio source via wired or wireless means or via an input interface; and directly obtains the entire audio file to be played from the audio source. The energy analysis module retrieves the audio file from the storage module and extracts its vibration curve; the waveform vibration curve is used to extract features in the energy analysis module; the extracted features include the energy change curve over time; the energy change curve includes multiple sub-energy change curves after frequency division; The method for obtaining the energy change curve is as follows: First, the vibration curve of the audio file is divided into multiple audio segments by time interval T; the audio segments are frequency domain transformed to obtain the spectral curve of the audio segment; the spectrum of the audio segment is divided into N segments according to frequency, and then the spectral curves of the same frequency in different audio segments are grouped together to obtain N groups of audio segment spectral curves; the total energy change of the spectral curve in each group over time is calculated. N energy change curves that change with time are obtained, and these are denoted as the standard energy change curves. The detection module acquires audio data from the amplification module and divides the vibration curve of the acquired audio into multiple audio segments by time interval T; the audio segments are frequency domain transformed to obtain the spectral curve of the audio segment; the spectrum of the audio segment is divided into N segments according to frequency, and then the spectral curves of the same frequency in different audio segments are grouped together to obtain N groups of audio segment spectral curves; the total energy of the spectral curve in each group changes with time. We obtain N energy change curves that vary with time, which are denoted as the actual energy change curves. The actual energy change curve and the standard energy change curve are compared in the detection module. The comparison method is as follows: H n (t)=F n (t)-G n (t); Where F n (t) represents the nth actual energy change curve, G n (t) represents the nth standard energy change curve, H n (t) represents the difference between the nth actual energy change curve and the nth standard energy change curve; n ranges from 1 to N, and t represents the time variable; that is, comparing the difference between the nth actual energy change curve and the nth standard energy change curve at each moment. after: H(t)=k1·H1(t)+k2·H2(t)+…+k n ·H n (t)+k N ·H N (t); Where k1, k2, k3, ..., k N , representing the weights corresponding to different frequency bands; The detection module outputs H(t) to the amplification control module. The amplification control module adjusts the amplification rate of the amplification module according to the sign and magnitude of H(t). The larger H(t) is, the smaller the amplification rate of the amplification module is, and the smaller H(t) is, the larger the amplification rate of the amplification module is. Therefore, the amplification module is consistent with the original energy change in the sound source, reducing the volume change caused by the correction module.

2. The digital audio jitter removal stabilized headphone amplifier according to claim 1, characterized in that: The correction module includes a reference clock, sampling rate input, I2S input, buffer module, frequency synthesis module, and output module; The reference module and the sampling rate input are both connected to the frequency synthesis module. The frequency synthesis module locks the sampling rate to the local clock frequency and performs local clock frequency detection. It calculates the difference between the sampling rate and the I2S input clock and the local clock, and further sets the buffer sequence direction and buffer depth based on the difference to correct the clock deviation.

3. A stable headphone amplifier for digital audio jitter removal according to claim 2, characterized in that: The frequency synthesis module includes a mode controller (1), a counting window generator (2), a counter (3), a synchronous frequency divider (4), a LUT (5), a subtractor (6), an FIR filter (7), a sliding mode filter (8), a low-noise DAC (9), an analog loop filter (10), and a broadband VCO (11). The reference module outputs a 10MHz high-precision reference clock to the counting window generator (2); The sampling rate information is sent to the mode controller (1) to output frequency switching control parameters to the LUT (5), and at the same time, the mode of the sliding filter (8) is controlled to be fast frequency switching. The filtered control data is sent to the low noise DAC (9), and after passing through the analog loop filter (10), it is output to the VCO (11). The VCO output is sent to the synchronous frequency divider (4), and then to the frequency measuring device composed of the counting window generator (2) and the counter (3) to complete the frequency measurement; the frequency measurement result is sent to the LUT (5) and the mode controller (1), and the mode controller (1) controls the loop. Input I2S data is sent to a large-capacity buffer (15). The mode controller (1) obtains the difference between the sampling rate information and the I2S input clock through the LUT (5) unit, and sets the buffer sequence direction and buffer depth of the FIFO through this difference. The maximum depth of the large-capacity cache (15) can ensure that a 74-minute CD can be played without leakage; at the same time, a silence detection module is set up. The silence detection is a protection mechanism that resets the large-capacity cache (15) in the silence segment; by resetting the large-capacity cache (15), the system can be ensured to work continuously and stably.

4. A stable headphone amplifier for digital audio jitter removal according to claim 1, characterized in that: The value of T ranges from 50ms to 100ms.

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