JP7672267B2 - Signal processing device, signal processing method, and signal processing system - Google Patents

Description

The present invention relates to a signal processing device, a signal processing method, and a signal processing system.

Conventionally, audio systems installed in vehicles are equipped with a loudness correction function (see, for example, Patent Document 1), an automatic volume adjustment function (AVC: Automatic Volume Control), and a tone control function as functions for correcting the playback frequency characteristics.

The loudness correction function compensates for the human hearing characteristic whereby low and high sounds become harder to hear when the playback volume is low, by adjusting the frequency characteristics to increase low and high sounds when the playback volume is low.

Here, the loudness correction function that responds to the user's volume operation is called the static loudness correction function. Also, the loudness correction function that responds to the characteristics of the audio signal is called the dynamic loudness correction function.

The AVC function is also designed to avoid the masking effect caused by driving noise when playing music, and adjusts the volume and frequency characteristics of the playback sound according to the vehicle's conditions, such as driving speed.

The tone control function allows users to adjust the frequency response to suit their preferences.

JP 2009-111538 A

However, conventional technology has the problem that loudness correction for audio signals may not be performed as intended.

Figure 10 is a diagram showing a conventional signal processing device. As shown in Figure 10, (4) tone control (user variable frequency characteristic correction unit 102a) and (5) AVCEQ (masking avoidance unit 103a) are arranged downstream (on the output side) of (2) dynamic loudness compensation.

The dynamic loudness correction function performs nonlinear processing. This results in harmonic components in the audio signal processed by the dynamic loudness correction function.

Figure 11 is a diagram explaining the problems with conventional signal processing devices. As shown in Figure 11, there may be areas where the control bands of (4) tone control and (2) dynamic loudness compensation overlap.

In this case, the harmonic components that arise in the design of the loudness correction function will be emphasized by the tone control function.

The tone control and AVC adjustments are determined by the user's settings and external factors such as the vehicle's speed, while the dynamic loudness correction function adjusts according to the design intent.

Therefore, when harmonic components are emphasized by the loudness correction function, the output audio signal may deviate from what was intended in the design.

The present invention has been made in consideration of the above, and aims to provide a signal processing device, a signal processing method, and a signal processing system that can perform loudness correction on an audio signal as designed.

In order to solve the above-mentioned problems and achieve the object, the signal processing device according to the present invention has a first correction unit and a second correction unit. The first correction unit corrects the frequency characteristics of an input audio signal according to the contents of settings made by a user and the state of the vehicle in which the audio signal is played back. The second correction unit performs loudness correction on the audio signal corrected by the first correction unit according to the characteristics of the audio signal.

The present invention makes it possible to perform loudness correction on audio signals as intended.

FIG. 1 is a functional block diagram showing an example of the configuration of a signal processing device according to the first embodiment. FIG. 2 is a diagram showing a detailed configuration of the signal processing device according to the first embodiment. FIG. 3 is a diagram for explaining linear processing and nonlinear processing. FIG. 4 is a diagram illustrating the effects of the first embodiment. FIG. 5 is a flowchart showing a procedure of processing executed by the signal processing device according to the first embodiment. FIG. 6 is a diagram showing a detailed configuration of the signal processing device according to the second embodiment. FIG. 7 is a diagram showing a detailed configuration of a signal processing device according to the third embodiment. FIG. 8 is a diagram showing a process flow for calculating the correction amount. FIG. 9 is a diagram for explaining the arbitration process of the correction amount. FIG. 10 is a diagram showing a conventional signal processing device. FIG. 11 is a diagram for explaining a problem with the conventional signal processing device.

Below, embodiments of the signal processing device, signal processing method, and signal processing system disclosed in the present application will be described in detail with reference to the attached drawings. Note that the present invention is not limited to the embodiments described below.

[First embodiment]
The configuration of a signal processing device according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a functional block diagram showing an example of the configuration of a signal processing device according to the first embodiment.

The signal processing device 1 is assumed to be mounted on a vehicle. The signal processing device 1 accepts an input of an audio signal. In addition, the signal processing device 1 outputs a processed audio signal.

Furthermore, the signal processing device 1 accepts input of user operation information, vehicle speed information, etc.

For example, the audio signal may relate to music to be played in a vehicle. In this case, the signal processing device 1 processes the input audio signal to improve the quality of the music playback.

For example, the signal processing device 1 performs AVC, tone control, dynamic loudness compensation, and static loudness compensation on the audio signal.

Here, as shown in FIG. 10, in conventional signal processing devices, tone control and AVC are performed after dynamic loudness compensation.

As a result, as mentioned above, there was a problem in the past in that loudness correction of audio signals could not be performed as intended by the design.

On the other hand, the signal processing device of the first embodiment avoids the problem of loudness correction not being able to be performed as intended by performing tone control and AVC before dynamic loudness compensation.

As shown in FIG. 1, the signal processing device 1 has a volume adjustment unit 101, a user-variable frequency characteristic correction unit 102, a masking avoidance unit 103, a playback volume level detection unit 104, a dynamic loudness correction amount calculation unit 105, a dynamic loudness correction unit 106, a static loudness correction unit 107, and a frequency characteristic correction unit 108.

Furthermore, the signal processing device 1 has a volume gain calculation unit 201, a user variable frequency correction amount calculation unit 202, a masking avoidance correction amount calculation unit 203, and a static loudness correction amount calculation unit 204.

The volume gain calculation unit 201 calculates the amount of adjustment of the playback volume by the volume adjustment unit 101 based on the user's operation information.

The volume adjustment unit 101 adjusts the playback volume based on the calculation results of the volume gain calculation unit 201.

The user variable frequency correction amount calculation unit 202 calculates the amount of adjustment of the frequency characteristics in the tone control based on the user's operation information.

The user variable frequency characteristic correction unit 102 performs tone control based on the calculation results by the user variable frequency correction amount calculation unit 202.

The masking avoidance correction amount calculation unit 203 calculates the amount of adjustment of the frequency characteristics in AVC based on the user's operation information and vehicle speed information. The masking avoidance unit 103 performs AVC based on the calculation result by the masking avoidance correction amount calculation unit 203.

The playback volume level detection unit 104 detects the playback volume level after adjustment by the volume adjustment unit 101.

The dynamic loudness correction amount calculation unit 105 calculates the amount of correction for a specific frequency band in dynamic loudness compensation based on the detection result of the playback volume level detection unit 104.

The dynamic loudness correction unit 106 performs dynamic loudness compensation based on the calculation results by the dynamic loudness correction amount calculation unit 105.

The static loudness correction amount calculation unit 204 calculates the correction amount for a specific frequency band in static loudness compensation based on user operation information (e.g., the amount of adjustment of the playback volume).

The static loudness correction unit 107 performs static loudness compensation based on the calculation results by the static loudness correction amount calculation unit 204.

The frequency characteristic correction unit 108 performs other processing to correct the frequency characteristics. However, the frequency characteristic correction unit 108 performs processing that is not based on user operation information.

Figure 2 is a diagram showing a detailed configuration of the signal processing device according to the first embodiment. For the purpose of explanation, Figure 2 shows an excerpt of the main processing units described in Figure 1.

First, (1) the volume adjustment unit 101 is a function for adjusting the volume.

(4) The user variable frequency characteristic correction unit 102 performs tone control.

(2) Dynamic loudness compensation is performed by the playback volume level detection unit 104, the dynamic loudness correction amount calculation unit 105, and the dynamic loudness correction unit 106.

(3) Static loudness compensation is performed by the static loudness correction unit 107 and the static loudness correction amount calculation unit 204 provided in the host microcomputer.

Dynamic loudness compensation and static loudness compensation are processes that correct certain high- and low-frequency components.

In this case, with dynamic loudness compensation, the amount of compensation is determined according to the detected playback volume level, whereas with static loudness compensation, the amount of compensation is determined by the set volume value.

In addition, dynamic loudness compensation uses linear processing, whereas static loudness compensation uses nonlinear processing.

Figure 3 is a diagram explaining linear processing and nonlinear processing. As shown in Figure 3, the relationship between the input signal level and the output signal level in linear processing is linear, just like before processing. On the other hand, the relationship between the input signal level and the output signal level in nonlinear processing is different from before processing.

Furthermore, in nonlinear processing (dynamic loudness compensation), by adding a smoothing gain to the correction amount, it is possible to make the changes in the audio signal during the transient period natural and smooth.

Here, in the first embodiment, the user variable frequency correction amount calculation unit 202 and the masking avoidance correction amount calculation unit 203 correspond to the first correction unit.

That is, the user variable frequency correction amount calculation unit 202 and the masking avoidance correction amount calculation unit 203 correct the frequency characteristics of the input audio signal according to the contents of the user settings and the state of the vehicle in which the audio signal is played.

In addition, the dynamic loudness correction unit 106 performs loudness correction according to the level of the audio signal after the volume has been adjusted.

In the first embodiment, the dynamic loudness correction unit 106 and the static loudness correction unit 107 correspond to the second correction unit.

That is, the dynamic loudness correction unit 106 performs loudness correction according to the characteristics of the audio signal on the audio signal corrected by the user variable frequency correction amount calculation unit 202 and the masking avoidance correction amount calculation unit 203.

The characteristics of the audio signal are information obtained from the audio signal itself, regardless of the user's actions and the vehicle's state, e.g. the detected level.

On the other hand, the static loudness correction unit 107 performs loudness correction using linear processing on the audio signal corrected by nonlinear processing.

In this way, by placing the processing whose results change depending on the user's operation and the vehicle's state prior to dynamic loudness compensation (on the input side), loudness correction can be performed as designed.

In particular, the first embodiment makes it possible to prevent harmonic components generated by dynamic loudness compensation from being emphasized by tone control and AVC.

Figure 4 is a diagram explaining the effect of the first embodiment. As shown in Figure 4, in the first embodiment, even if the control bands of tone control and dynamic loudness compensation overlap, the harmonic components due to dynamic loudness compensation are not emphasized by tone control.

Figure 5 is a flowchart showing the processing steps executed by the signal processing device according to the first embodiment.

As shown in FIG. 5, the signal processing device 1 receives an input of an audio signal (step S101). For example, the signal processing device 1 receives an input of an audio signal stored as an audio file in a storage device provided in the vehicle.

Next, the signal processing device 1 performs tone control on the audio signal (step S102).

Then, the signal processing device 1 performs AVC on the audio signal to avoid the masking phenomenon (step S103).

Then, the signal processing device 1 performs dynamic loudness compensation on the audio signal (step S104).

Then, the signal processing device 1 performs static loudness compensation on the audio signal (step S105).

Then, the signal processing device 1 outputs the processed audio signal (step S106). For example, the signal processing device 1 outputs the audio signal to a speaker of the vehicle.

The signal processing device 1 can also form a signal processing system together with a vehicle.

In this case, the vehicle has a storage unit that stores the audio signal before processing, and an output unit that converts the audio signal processed by the signal processing device 1 into sound and outputs it.

The signal processing device 1 accepts input of an audio signal stored in a memory unit and outputs a processed audio signal to an output unit.

The storage unit may be realized by a storage medium such as an optical medium or a flash memory. The storage unit may also be a storage area of a mobile terminal connected to the vehicle so as to be able to communicate data with the vehicle, or a server connected to the vehicle via a network.

For example, the output unit is a speaker.

Second Embodiment
In the second embodiment, the signal processing device 1 performs noise-sensitive dynamic noise compensation in addition to the processing described in the first embodiment.

Figure 6 is a diagram showing a detailed configuration of a signal processing device according to the second embodiment. As shown in Figure 6, the dynamic noise compensation unit 304 is arranged after (on the output side of) the dynamic loudness correction unit 106.

The dynamic noise compensation unit 304 performs volume compensation for the part masked by noise on the audio signal corrected by dynamic loudness compensation based on the level calculation result (noise volume) of the noise signal collected by the microphone installed in the vehicle.

This means that users no longer need to change the volume value each time they need to respond to noise such as road noise.

To prevent the playback sound from becoming difficult to hear inside the vehicle due to driving noise, a static noise compensation function linked to vehicle speed, such as AVC, is known.

On the other hand, driving noise varies greatly depending not only on the vehicle speed but also on the driving location and conditions. For this reason, in the second embodiment, a sensor that monitors driving noise is added, and dynamic noise compensation is performed based on noise monitoring information obtained from the sensor information.

In the example of Figure 6, both vehicle speed and microphone input are used to calculate the noise level. Vehicle speed is information that is highly correlated with driving noise. The microphone is also a means for sensing noise.

Here, the masking avoidance unit 103 (AVCEQ) corresponds to static noise compensation that reduces noise based on vehicle speed information and volume value.

As shown in FIG. 6, the masking avoidance unit 103 calculates the correction amount by referring to the Volume Tables corresponding to the adjustment amount of the playback volume by the volume adjustment unit 101 and the AVC Tables corresponding to the vehicle speed pulse.

On the other hand, dynamic noise compensation is based on the results of analyzing noise inside the vehicle that is actually recorded with a microphone.

Specifically, the dynamic noise compensation correction amount calculation unit 303 calculates the correction amount based on the result of the reproduced sound component removal unit 301 removing the reproduced sound components by E/C processing from the noise signal input by the microphone.

Furthermore, the dynamic noise compensation correction amount calculation unit 303 may correct the audio signal obtained by removing the playback sound components from the audio collected by the microphone, using the components for each band obtained by filtering.

This allows for precise equalizer control for each frequency band.

The method of calculating the noise level is not limited to using the voice recorded by the microphone. The dynamic noise compensation correction amount calculation unit 303 may calculate the noise level based on information obtained from either or both of a vehicle signal that is highly correlated with the driving noise and the sensing results from the actuator.

Vehicle signals that are highly correlated with driving noise include vehicle speed, engine RPM, torque, etc. The actuator may be a microphone or a vibration sensor.

Furthermore, the signal processing device 12 may utilize actuators installed for other purposes, such as a microphone for hands-free calling and a sensor for ANC (Active Noise Control).

The signal processing device 12 convolves a transfer function with the audio signal to be played back and predicts the audio signal components to be input to the actuator in order to detect only the actual noise volume from the signal input from the actuator.

Then, the signal processing device 12 subtracts the predicted audio signal components from the input signal.

When a microphone is used as an actuator as in Figure 6, the signal processing device 12 determines and applies the transfer characteristics in the reproduction space (inside the vehicle) from the speaker output to the microphone input.

In addition, when a vibration sensor is used as an actuator, the signal processing device 12 determines and applies the vehicle body propagation characteristics from the speaker to the vibration sensor.

In addition, a band-limiting filter for reducing the tap length of the FIR (Finite Impulse Response) filter used in the transfer function convolution of FIG. 6 may be provided in front of the FIR filter.

In addition, to improve the accuracy of noise level detection, a filter similar to the band-limiting filter described above can be inserted on the noise signal side (microphone input side) to eliminate the relative phase difference.

In addition, the microphone input can be filtered according to frequency or time characteristics, and the control content can be adjusted according to the respective detection results, thereby increasing sensitivity to specific types of noise.

[Third embodiment]
In the third embodiment, the signal processing device performs processing that integrates dynamic loudness compensation and dynamic noise compensation.

This is because dynamic loudness compensation and dynamic noise compensation have similar processing content and both function as equalizers. This makes it possible to prevent a reduction in the effects of dynamic loudness compensation and dynamic noise compensation due to competition, and reduce the processing load.

In addition, in the third embodiment, the signal processing device performs processing that integrates static loudness compensation, tone control, and AVC.

Figure 7 is a diagram showing the detailed configuration of a signal processing device according to the third embodiment.

As shown in FIG. 7, the signal processing device 13 performs static loudness compensation, tone control, and AVC in the front-stage portion (static audio control integrated block: user variable frequency correction amount calculation unit 202, masking avoidance correction amount calculation unit 203, static loudness correction amount calculation unit 204, static control correction amount arbitration unit 401, static control correction unit 402).

The signal processing device 13 also performs dynamic loudness compensation and dynamic noise compensation in the latter stages (dynamic sound control integrated block: dynamic loudness correction amount calculation unit 105, reproduced sound component removal unit 301, noise level detection unit 302, dynamic noise compensation correction amount calculation unit 303, dynamic control correction amount arbitration unit 403, static control correction unit 402).

In other words, the static audio control integrated block performs loudness correction using linear processing on the input audio signal in addition to correcting the frequency characteristics according to the user settings and the state of the vehicle in which the audio signal is being played.

The dynamic audio control integrated block also performs loudness correction according to the characteristics of the audio signal for the audio signal corrected by the static audio control integrated block, and determines the overall correction amount based on the noise level obtained by the same means as in the second embodiment.

The correction amount in the static audio control integrated block is calculated by referring to the Volume Tables and AVC Tables as well as the Tone Table and Loudness Table.

Figure 8 is a diagram showing the process flow for calculating the correction amount. Steps S201, S202, S203, S204, and S205 in Figure 8 are processes for calculating the correction amount in the dynamic voice control integrated block.

In addition, steps S301, S302, S303, S304 and S305 are processes for calculating the correction amount in the static voice control integrated block.

As shown in FIG. 8, the dynamic audio control integrated block detects the playback volume from the playback sound (step S201).

Then, the dynamic audio control integrated block calculates the loudness correction amount based on the detected playback volume (step S202).

The dynamic sound control integrated block also performs a process to compare the noise volume from the noise and vehicle speed signals obtained through microphone input (step S203).

Then, the dynamic sound control integrated block calculates the noise compensation correction amount based on the matched noise amount (step S204).

Furthermore, the dynamic voice control integrated block determines the correction amount A to be adopted from the correction amounts x1 and y1 calculated in steps S202 and S204, respectively (step S205).

Next, the static audio control integrated block checks the AVC Table based on the vehicle speed signal and volume step (step S301).

Then, the static audio control integrated block calculates the masking avoidance correction amount (AVC correction amount) based on the AVC Table matching result (step S302).

The static sound control integrated block also checks the Loudness Table based on the settings of tone control, etc. (step S303).

Then, the static audio control integrated block calculates the loudness correction amount based on the result of matching with the Loudness Table (step S304).

Furthermore, the static voice control integrated block determines the correction amount B to be adopted from the correction amounts x2 and y2 calculated in steps S302 and S304, respectively (step S305).

Figure 9 is a diagram explaining the arbitration process of the correction amount. In the example of Figure 9, it is assumed that in step S205 of Figure 8, the correction amount x2 of the static loudness compensation is calculated to be 6 dB, and the correction amount y2 of the AVCEQ is calculated to be 4 dB.

In this case, since x2 is greater than y2, the static control correction amount arbitration unit 401 adopts x2 as the correction amount.

The dynamic control correction amount arbitration unit 403 also performs arbitration processing for x1 and y1 similar to that shown in FIG. 9.

The arbitration method is not limited to that shown in FIG. 9, and may be, for example, a method of assigning weights to each calculation result. For example, if a weight of 2 is assigned to x1 and a weight of 1 is assigned to y1, the calculation is A = (2/3) x x1 + (1/3) x y1.

By performing this type of arbitration process, the correction amount calculated in each process can be reflected in the final correction.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

REFERENCE SIGNS LIST 1 Signal processing device 101 Volume adjustment unit 102 User variable frequency characteristic correction unit 103 Masking avoidance unit 104 Playback volume level detection unit 105 Dynamic loudness correction amount calculation unit 106 Dynamic loudness correction unit 107 Static loudness correction unit 108 Frequency characteristic correction unit 201 Volume gain calculation unit 202 User variable frequency correction amount calculation unit 203 Masking avoidance correction amount calculation unit 204 Static loudness correction amount calculation unit

Claims (12)

a first correction unit that corrects a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction unit that performs loudness correction by nonlinear processing to generate harmonic components on the audio signal corrected by the first correction unit, and further performs loudness correction by linear processing on the audio signal corrected by the nonlinear processing;
A signal processing device comprising: The signal processing device according to claim 1 , wherein the second correction unit performs loudness correction according to a level of the audio signal after the volume has been adjusted. a first correction unit that corrects a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit according to characteristics of the audio signal;
a third correction unit that performs volume correction on the audio signal corrected by the second correction unit based on a noise amount collected by a microphone provided in the vehicle;
A signal processing device comprising: The signal processing device according to claim 3 , wherein the third correction unit performs correction using components for each band obtained by filtering a voice signal obtained by removing a reproduced sound component from a noise signal collected by the microphone . a first correction unit that performs loudness correction by linear processing on an input audio signal in addition to correcting a frequency characteristic according to a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit in accordance with a characteristic of the audio signal, and also performs volume correction based on a noise amount collected by a microphone provided in the vehicle;
A signal processing device comprising: the first correction unit corrects the input audio signal with a correction amount calculated from a correction amount of a frequency characteristic according to a content of a user setting and a state of a vehicle in which the audio signal is reproduced, and a correction amount of a loudness correction by linear processing;
6. The signal processing device according to claim 5, wherein the second correction unit corrects the audio signal corrected by the first correction unit using a correction amount calculated from a loudness correction amount according to the characteristics of the audio signal and a volume correction amount based on the noise level . A signal processing method performed by a signal processing device, comprising:
a first correction step of correcting a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction step of performing loudness correction by nonlinear processing that generates harmonic components on the audio signal corrected by the first correction step, and further performing loudness correction by linear processing on the audio signal corrected by the nonlinear processing;
A signal processing method comprising: A signal processing method performed by a signal processing device, comprising:
a first correction step of correcting a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction step of performing loudness correction on the audio signal corrected by the first correction step in accordance with characteristics of the audio signal;
a third correction step of performing a volume correction on the audio signal corrected by the second correction step based on a noise amount collected by a microphone provided in the vehicle;
A signal processing method comprising: A signal processing method performed by a signal processing device, comprising:
a first correction step of correcting a frequency characteristic of an input audio signal according to a user's setting and a state of a vehicle in which the audio signal is reproduced, and also correcting loudness by linear processing;
a second correction step of performing loudness correction on the audio signal corrected by the first correction step in accordance with a characteristic of the audio signal, and also performing volume correction based on a noise amount collected by a microphone provided in the vehicle;
A signal processing method comprising: A signal processing system having a vehicle and a signal processing device,
The signal processing device includes:
a first correction unit that corrects a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction unit that performs loudness correction by nonlinear processing to generate harmonic components on the audio signal corrected by the first correction unit, and further performs loudness correction by linear processing on the audio signal corrected by the nonlinear processing;
having
The vehicle is
a signal processing system further comprising an output section for converting the audio signal corrected by the second correction section into a sound and outputting the sound; A signal processing system having a vehicle and a signal processing device,
The signal processing device includes:
a first correction unit that corrects a frequency characteristic of an input audio signal in accordance with a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit according to characteristics of the audio signal;
a third correction unit that performs volume correction on the audio signal corrected by the second correction unit based on a noise amount collected by a microphone provided in the vehicle;
having
The vehicle is
A signal processing system comprising an output section that converts the audio signal corrected by the second correction section into a sound and outputs the sound. A signal processing system having a vehicle and a signal processing device,
The signal processing device includes:
a first correction unit that performs loudness correction by linear processing on an input audio signal in addition to correcting a frequency characteristic according to a content of a user setting and a state of a vehicle in which the audio signal is reproduced;
a second correction unit that performs loudness correction on the audio signal corrected by the first correction unit in accordance with a characteristic of the audio signal, and also performs volume correction based on a noise amount collected by a microphone provided in the vehicle;
having
The vehicle is
a signal processing system further comprising an output section for converting the audio signal corrected by the second correction section into a sound and outputting the sound;

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