A headphone amplifier for calibrating frequency deviation of a sound source

Abstract

The present invention relates to a headphone amplifier for calibrating the frequency deviation of a sound source. The amplifier uses sampling rate information to input a frequency switching control parameter output by a mode controller to a LUT. Simultaneously, the sliding mode filter is controlled to operate in a fast frequency switching mode. The filtered control data is sent to a low-noise DAC, passed through an analog loop filter, and then output to a VCO. The VCO output is sent to a synchronous frequency divider and then to a frequency measuring device consisting of a counting window generator and a counter to complete the frequency measurement. The frequency measurement result is sent to the LUT and the mode controller, which controls the loop. 20kHz audio is superimposed on the input sound source. After the superimposed audio is loaded, it is processed together with the original audio. The processed audio is then passed through an amplifier and detected by a detection module. The frequency offset, broadening, and loudness changes caused by the processing can be fully detected, thereby displaying the operating status in real time on a display module, allowing users to understand the device's operating status at all times.

Description

Technical Field

[0001] The present invention relates to the field of headphone amplifiers, and in particular to a headphone amplifier for calibrating the frequency deviation of a sound source. Background Art

[0002] In real-world devices, audio sources often exhibit frequency deviations due to multiple replications and compression processes. In particular, clock offsets relative to the ideal clock can sometimes lead or lag, which doesn't accumulate over time. In practice, it's often desirable to precisely time a periodic waveform (especially a clock) when it crosses a specific threshold.

[0003] Application number CN201310287918.4 discloses a method and device for processing the deviation, specifically step 1: receiving an analog signal z(t); step 2: providing a clock signal h(t) to an analog-to-digital conversion module, and at the same time adding the product of the clock signal h(t) and a single-tone signal m(t) as a reference signal q(t) to the analog signal z(t) to obtain a composite signal r(t); step 3: the analog-to-digital conversion module performs analog-to-digital conversion on the composite signal r(t) to obtain two completely identical composite digital signals rjit(n); step 4: performing jitter sequence estimation on one of the composite digital signals rjit(n) to obtain a clock jitter sequence; step 5: using the clock jitter sequence to eliminate clock jitter on the other of the composite digital signal rjit(n), thereby obtaining a pure digital signal y(n) with clock jitter eliminated.

[0004] Although it can reduce the deviation to a certain extent, on the one hand, it is not suitable for audio playback processing. On the other hand, during audio playback, users often want to know the working status of the device so that they can adjust various playback parameters at any time. Based on this, a headphone amplifier that can calibrate the frequency deviation of the sound source is needed. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a headphone amplifier for calibrating the frequency deviation of a sound source, comprising an input interface, an output interface, a calibration module, and an amplification module;

[0006] It also includes a sound source module, a superposition module, a detection module and a display module;

[0007] The sound source module sends digital audio data to the superposition module, in which high-frequency tracer audio is superimposed. The superimposed audio data is sent to the input interface and enters the calibration module;

[0008] The calibration module is set between the input interface and the amplification module to calibrate the frequency deviation of the sound source;

[0009] The amplifier module is connected to the output interface, and the output interface is connected to the device that plays the sound;

[0010] The amplification module is also connected to the detection module, which detects and extracts high-frequency tracer audio from the audio amplified by the amplification module, analyzes the high-frequency tracer audio, and displays the analysis results on the display module.

[0011] The superposition module is equipped with a high-precision clock of 20MHz. After obtaining the audio data sent by the sound source module, the superposition module superimposes the audio data of a fixed frequency F with the audio data sent by the sound source; the value range of F is 20kHz-24kHz.

[0012] The specific methods of audio overlay are one of the following two:

[0013] Method 1: The superposition module obtains the clock signal of the digital audio sent by the sound source module and generates digital audio data with a fixed frequency F according to the clock signal of the sound source;

[0014] Then, the generated digital audio data of the fixed frequency F is directly added to the digital audio format data sent by the sound source module on the data track to obtain superimposed mixed audio data, which contains audio of the fixed frequency F;

[0015] Method 2: Set up ADC and DAC modules in the superposition module, first perform digital-to-analog conversion on the digital audio sent by the sound source module, and then directly superimpose the audio of the fixed frequency F pre-stored in the superposition module with the audio of the sound source module to obtain a mixed audio of the analog signal, and then perform analog-to-digital conversion before output.

[0016] The calibration module includes a reference clock, a sampling rate input, an I2S input, a buffer module, a frequency synthesis module and an output module;

[0017] The reference module and the sampling rate input are both connected to the frequency synthesis module, which locks the sampling rate to the local clock frequency and performs local clock frequency detection. The frequency synthesis module calculates the difference between the sampling rate and the I2S input clock and the local clock, and further sets the cache sequence direction and cache depth based on this difference to correct clock deviation.

[0018] 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 broadband VCO 11;

[0019] The reference module outputs a 10MHz high-precision reference clock to the counting window generator 2;

[0020] The sampling rate information is fed into the mode controller 1, which then outputs the frequency switching control parameters to the LUT 5. At the same time, the sliding mode filter 8 is controlled to operate in a fast frequency switching mode. The filtered control data is sent to the low-noise DAC 9, passes through the analog loop filter 10, and is then output to the VCO 11.

[0021] The VCO output is sent to the synchronous frequency divider 4, and then to the frequency measurement 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;

[0022] 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 LUT5 unit, and sets the buffer sequence direction and buffer depth of the FIFO according to the difference;

[0023] The maximum depth of the bulk cache 15 ensures that a 74-minute CD can be played to completion without leakage. A silence detection module is also provided. Silence detection is a protection mechanism that resets the bulk cache 15 during silent segments. By resetting the bulk cache 15, the system can ensure continuous and stable operation.

[0024] The detection module obtains an analog signal from the output of the amplification module, which is a replica of the output signal of the amplification module, and digitizes the analog signal to obtain detection data. The detection module time-segments the obtained detection data, that is, generates a small segment of fragmented audio data every fixed time T. The generated fragmented audio data is converted into the frequency domain to obtain the spectrum of the fragmented audio data.

[0025] The detection module retains the data with the center frequency F and width W in the fragmented audio data and deletes the rest to obtain the tracer fragment audio data; the tracer fragment audio data is processed to obtain its center frequency F n and half-height width W n and the center frequency intensity H n ; Where n is the number of the fragmented audio data, that is, the nth tracer fragmented audio data.

[0026] The center frequency F n and half-height width W n and the center frequency intensity H n Generate three curves, the horizontal axis is n, the vertical axis is the center frequency F n and half-height width W n and the center frequency intensity H n value.

[0027] The detection module detects the center frequency F n and half-height width W n and the center frequency intensity Hn Whether the change is not within the threshold range, the threshold includes an upper threshold and a lower threshold;

[0028] The detection module calculates the center frequency F that exceeds the threshold n and half-height width W n Or center frequency intensity H n duration;

[0029] The vertical axis displayed on the display module is the center frequency F n and half-height width W n and the center frequency intensity H n The three curves show the center frequency F that exceeds the threshold n and half-height width W n Or center frequency intensity H n The duration of the calibration is calculated and the curves that are not within the threshold range are marked to show the working status of the calibration module.

[0030] The beneficial effects of the present invention are:

[0031] The present invention superimposes 20kHz audio on the input sound source. This frequency is selected because the upper limit of the response frequency of general headphones or speakers is around 20kHz. Therefore, even if a 20kHz audio speaker is loaded, basically no response will be generated; at the same time, since the resolution limit of the human ear is less than 20kHz, even if a 20kHz sound is played, the human ear basically cannot hear it; in addition, since the general audio sampling rate is 44.1kHz, 48kHz, and 96kHz, the 20kHz audio can be processed in the circuit.

[0032] After the superimposed audio is loaded, it is processed together with the original audio. The processed audio is detected by the detection module after passing through the amplifier. The frequency offset, broadening, and loudness changes caused by the processing process can be fully detected, so that the working status can be displayed in real time on the display module, making it convenient for users to always understand the working status of the device.

[0033] The present invention uses sampling rate information to input the frequency switching control parameters output by the mode controller to the LUT, and at the same time controls the mode of the sliding mode filter to fast frequency switching. The filtered control data is sent to the low-noise DAC, and then output to the VCO after passing through the analog loop filter; the VCO output is sent to the synchronous divider, and then to the frequency measuring device composed of the counting window generator and the counter to complete the frequency measurement. The frequency measurement result is sent to the LUT and the mode controller, and the mode controller controls the loop. The input I2S data is sent to a large-capacity cache, and the mode controller obtains the difference between the local frequency clock frequency and the I2S input clock through the LUT unit, and sets the cache sequence direction and cache depth of the FIFO based on the difference. The maximum depth of the FIFO can ensure that a 74-minute CD disc is played to completion without leakage. Silence detection is a protection mechanism that resets the FIFO in the silent segment. By resetting the FIFO, the system can be ensured to work continuously and stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Attachment Figure 1 This is a schematic diagram of the overall architecture of the present invention;

[0036] Attachment Figure 2 This is a schematic diagram of the connection structure of the calibration module of the present invention;

[0037] Attachment Figure 3 Schematic diagram of the circuit structure of the present invention. DETAILED DESCRIPTION

[0038] Example 1:

[0039] See also Figure 1 , the present invention provides a headphone amplifier for calibrating the frequency deviation of a sound source, comprising an input interface, an output interface, a calibration module, and an amplification module;

[0040] It also includes a sound source module, a superposition module, a detection module and a display module;

[0041] The sound source module sends digital audio data to the superposition module, in which high-frequency tracer audio is superimposed. The superimposed audio data is sent to the input interface and enters the calibration module;

[0042] The calibration module is set between the input interface and the amplification module to calibrate the frequency deviation of the sound source;

[0043] The amplifier module is connected to the output interface, and the output interface is connected to the device that plays the sound;

[0044] The amplification module is also connected to the detection module, which detects and extracts high-frequency tracer audio from the audio amplified by the amplification module, analyzes the high-frequency tracer audio, and displays the analysis results on the display module.

[0045] The superposition module is equipped with a high-precision clock of 20MHz. After obtaining the audio data sent by the sound source module, the superposition module superimposes the audio data of a fixed frequency F with the audio data sent by the sound source; the value range of F is 20kHz-24kHz.

[0046] The specific methods of audio overlay are one of the following two:

[0047] Method 1: The superposition module obtains the clock signal of the digital audio sent by the sound source module and generates digital audio data with a fixed frequency F according to the clock signal of the sound source;

[0048] Then, the generated digital audio data of the fixed frequency F is directly added to the digital audio format data sent by the sound source module on the data track to obtain superimposed mixed audio data, which contains audio of the fixed frequency F;

[0049] Method 2: Set up ADC and DAC modules in the superposition module, first perform digital-to-analog conversion on the digital audio sent by the sound source module, and then directly superimpose the audio of the fixed frequency F pre-stored in the superposition module with the audio of the sound source module to obtain a mixed audio of the analog signal, and then perform analog-to-digital conversion before output.

[0050] The calibration module includes a reference clock, a sampling rate input, an I2S input, a buffer module, a frequency synthesis module and an output module;

[0051] The reference module and the sampling rate input are both connected to the frequency synthesis module, which locks the sampling rate to the local clock frequency and performs local clock frequency detection. The frequency synthesis module calculates the difference between the sampling rate and the I2S input clock and the local clock, and further sets the cache sequence direction and cache depth based on this difference to correct clock deviation.

[0052] 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 broadband VCO 11;

[0053] The reference module outputs a 10MHz high-precision reference clock to the counting window generator 2;

[0054] The sampling rate information is fed into the mode controller 1, which then outputs the frequency switching control parameters to the LUT 5. At the same time, the sliding mode filter 8 is controlled to operate in a fast frequency switching mode. The filtered control data is sent to the low-noise DAC 9, passes through the analog loop filter 10, and is then output to the VCO 11.

[0055] The VCO output is sent to the synchronous frequency divider 4, and then to the frequency measurement 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;

[0056] 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 LUT5 unit, and sets the buffer sequence direction and buffer depth of the FIFO according to the difference;

[0057] The maximum depth of the bulk cache 15 ensures that a 74-minute CD can be played to completion without leakage. A silence detection module is also provided. Silence detection is a protection mechanism that resets the bulk cache 15 during silent segments. By resetting the bulk cache 15, the system can ensure continuous and stable operation.

[0058] The detection module obtains an analog signal from the output of the amplification module, which is a replica of the output signal of the amplification module, and digitizes the analog signal to obtain detection data. The detection module time-segments the obtained detection data, that is, generates a small segment of fragmented audio data every fixed time T. The generated fragmented audio data is converted into the frequency domain to obtain the spectrum of the fragmented audio data.

[0059] The detection module retains the data with the center frequency F and width W in the fragmented audio data and deletes the rest to obtain the tracer fragment audio data; the tracer fragment audio data is processed to obtain its center frequency F n and half-height width W n and the center frequency intensity H n ; Where n is the number of the fragmented audio data, that is, the nth tracer fragmented audio data.

[0060] The center frequency F n and half-height width W n and the center frequency intensity H n Generate three curves, the horizontal axis is n, the vertical axis is the center frequency F n and half-height width W n and the center frequency intensity H n value.

[0061] The detection module detects the center frequency F n and half-height width W n and the center frequency intensity Hn Whether the change is not within the threshold range, the threshold includes an upper threshold and a lower threshold;

[0062] The detection module calculates the center frequency F that exceeds the threshold n and half-height width W n Or center frequency intensity H n duration;

[0063] The vertical axis displayed on the display module is the center frequency F n and half-height width W n and the center frequency intensity H n The three curves show the center frequency F that exceeds the threshold n and half-height width W n Or center frequency intensity H n The duration of the calibration is calculated and the curves that are not within the threshold range are marked to show the working status of the calibration module.

[0064] Example 2:

[0065] See also Figure 2-3 ,

[0066] The circuit example specifically includes a mode controller 1, a count 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 broadband VCO 11; it also includes a silence detection 13, a FIFO control 14, a large-capacity cache FIFO 15 and an I2S timing generation 12.

[0067] The I2S timing and data are divided into three paths after input. One path enters the mute 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. Input I2S_MCLK enters the counter 3.

[0068] The 10MHz high-precision reference clock enters the count window generator 2 and then enters the counter 3. The sampling rate is input into the mode controller 1 and then enters the count window generator 2, LUT 5 and sliding mode filter 8 (FIR+IIR).

[0069] The mode controller is connected to the FIFO control 14, the LUT 5, and the sliding mode filter 8 (FIR+IIR);

[0070] The output of counter 3 is to LUT5 and subtractor 6, the output of LUT5 is to subtractor and sliding mode filter 8 (FIR+IIR), and the output of subtractor is to FIR filter 7;

[0071] The sliding mode filter 8 (FIR+IIR) outputs to the low noise DAC 9, then to the analog loop filter 10, and then to the broadband VCO 11;

[0072] The broadband VCO output is sent to the synchronous frequency divider 4, the I2S timing generator 12 and the MCLK output;

[0073] The I2S timing generation 12 outputs to the FIFO control 14 and the I2S output; the FIFO control 14 is connected to the large-capacity buffer FIFO 15; and the large-capacity buffer FIFO 15 is connected to the I2S timing generation 12.

[0074] Thus far, the description of the above-described embodiments has been provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the present disclosure. The individual elements or features of a particular embodiment are generally not limited to the particular embodiment, but when applicable, they can be interchanged and used for selected embodiments even if not specifically shown or described. In many aspects, the same elements or features can also be changed. Such changes are not considered to depart from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

[0075] Example embodiments are provided so that the present disclosure will be thorough and will fully convey the scope to those skilled in the art. In order to thoroughly understand the embodiments of the present disclosure, numerous details are set forth, such as examples of specific parts, devices, and methods. It will be apparent to those skilled in the art that specific details need not be used, and the example embodiments may be implemented in many different forms, and neither should be construed as limiting the scope of the present disclosure. In certain example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0076] Here, professional vocabulary is used only for the purpose of describing specific example embodiments and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "a" and "the" used herein may be intended to include the plural forms as well. The terms "including" and "having" are inclusive and therefore specify the presence of the claimed features, wholes, steps, operations, elements and / or components, but do not exclude the presence or additional presence of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof. Unless the order of execution is explicitly indicated, the method steps, processes and operations described herein are not to be interpreted as necessarily needing to be performed in the specific order discussed and shown. It should also be understood that additional or optional steps may be adopted.

Claims

1. A headphone amplifier for calibrating the frequency deviation of a sound source, comprising an input interface, an output interface, a calibration module, and an amplification module; characterized in that: It also includes a sound source module, a superposition module, a detection module and a display module; The sound source module sends digital audio data to the superposition module, in which high-frequency tracer audio is superimposed. The superimposed audio data is sent to the input interface and enters the calibration module; The calibration module is set between the input interface and the amplification module to calibrate the frequency deviation of the sound source; The amplifier module is connected to the output interface, and the output interface is connected to the device that plays the sound; The amplification module is also connected to the detection module, which detects and extracts high-frequency tracer audio from the audio amplified by the amplification module, analyzes the high-frequency tracer audio, and displays the analysis results on the display module; The calibration module includes a reference clock, a sampling rate input, an I2S input, a buffer module, a frequency synthesis module and an output module; The reference module and the sampling rate input are both connected to the frequency synthesis module, which locks the sampling rate to the local clock frequency and performs local clock frequency detection. The frequency synthesis module calculates the difference between the sampling rate and the I2S input clock and the local clock, and further sets the cache sequence direction and cache depth based on this difference to correct clock deviation. 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 10 MHz high-precision reference clock to the counting window generator (2); The sampling rate information is fed into the mode controller (1) to output the frequency switching control parameters to the LUT (5), and the sliding mode filter (8) is controlled to be in the fast frequency switching mode. The filtered control data is sent to the low noise DAC (9), passes through the analog loop filter (10), and 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; The input I2S data is sent to a large-capacity cache (15), and 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 cache depth of the FIFO according to the difference.

2. The headphone amplifier for calibrating the frequency deviation of a sound source according to claim 1, characterized in that: The superposition module is equipped with a high-precision clock of 20MHz. After obtaining the audio data sent by the sound source module, the superposition module superimposes the audio data of a fixed frequency F with the audio data sent by the sound source; the value range of F is 20kHz-24kHz.

3. The headphone amplifier for calibrating the frequency deviation of a sound source according to claim 2, characterized in that: The specific methods of audio overlay are one of the following two: Method 1: The superposition module obtains the clock signal of the digital audio sent by the sound source module and generates digital audio data with a fixed frequency F according to the clock signal of the sound source; Then, the generated digital audio data of the fixed frequency F is directly added to the digital audio format data sent by the sound source module on the data track to obtain superimposed mixed audio data, which contains audio of the fixed frequency F; Method 2: Set up ADC and DAC modules in the superposition module, first perform digital-to-analog conversion on the digital audio sent by the sound source module, and then directly superimpose the audio of the fixed frequency F pre-stored in the superposition module with the audio of the sound source module to obtain a mixed audio of the analog signal, and then perform analog-to-digital conversion before output.

4. The headphone amplifier for calibrating the frequency deviation of a sound source according to claim 1, characterized in that: The maximum depth of the large-capacity cache (15) can ensure that a 74-minute CD disc can be played to completion without leakage; at the same time, a silence detection module is provided. The silence detection is a protection mechanism that resets the large-capacity cache (15) in a silent segment; by resetting the large-capacity cache (15), the system can be ensured to work continuously and stably.

5. The headphone amplifier for calibrating the frequency deviation of a sound source according to claim 1, characterized in that: The detection module obtains an analog signal from the output of the amplification module, which is a replica of the output signal of the amplification module, and digitizes the analog signal to obtain detection data. The detection module time-segments the obtained detection data, that is, generates a small segment of fragmented audio data every fixed time T. The generated fragmented audio data is converted into the frequency domain to obtain the spectrum of the fragmented audio data. The detection module retains the data with the center frequency F and width W in the fragmented audio data and deletes the rest to obtain the tracer fragmented audio data; Process the tracer fragment audio data to obtain its center frequency F n and half-height width W n and the center frequency intensity H n ; Where n is the number of the fragment audio data, that is, the nth tracer fragment audio data; The center frequency F n and half-height width W n and the center frequency intensity H n Generate three curves, the horizontal axis is n, the vertical axis is the center frequency F n and half-height width W n and the center frequency intensity H n value.

6. The headphone amplifier for calibrating the frequency deviation of a sound source according to claim 5, characterized in that: The detection module detects the center frequency F n and half-height width W n and the center frequency intensity H n Whether the change is not within the threshold range, the threshold includes an upper threshold and a lower threshold; The detection module calculates the center frequency F that exceeds the threshold n and half-height width W n Or center frequency intensity H n duration; The vertical axis displayed on the display module is the center frequency F n and half-height width W n and the center frequency intensity H n The three curves show the center frequency F that exceeds the threshold n and half-height width W n Or center frequency intensity H n The duration of the calibration is calculated and the curves that are not within the threshold range are marked to show the working status of the calibration module.

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