JP4522246B2 - Automotive audio system - Google Patents

Description

  The present invention relates to an in-vehicle audio system, and more particularly to a technique for reproducing a multi-channel audio source.

  With the spread of multi-channel software such as DVD, audio systems that reproduce multi-channel audio sources are used. In order to obtain a multi-channel sound effect, the 5.1 channel system or the 6.1 channel system is adopted in the speaker system. Recently, such an audio system has been widely used in spaces in automobiles.

  However, the speaker system in the vehicle interior space is not necessarily equivalent to the speaker system for home use or home theater. Therefore, there is a problem that even if a multi-channel audio source is reproduced as it is, the surround effect by the multi-channel cannot be fully enjoyed. In order to cope with this problem, Patent Document 1 detects that the input from the sound source is a multi-channel audio input by an input detection unit that detects whether the input from the sound source is a multi-channel audio input or a stereo / mono input, and the input detection unit. In some cases, a vehicle-mounted multi-channel audio reproduction device is provided that includes reproduction characteristic correction means for correcting reproduction characteristics in a reproduction circuit to reproduction characteristics suitable for multi-channel audio input. Specifically, when multi-channel audio input is performed, the reproduction characteristics are corrected so that the rear speaker functions as a main rather than a sub.

JP 2001-69598 A

  When listening to audio in a car, if you are exposed to noise such as engine noise or road noise, you will not be able to listen to the music well. For this reason, traveling noise is measured with a microphone installed in the passenger compartment, and correction according to the noise is performed. FIG. 7 shows a configuration example of an audio system having such a noise correction function. In order to obtain a surround effect, speakers 20, 22, 24 are arranged on the front left, center, and right of the passenger compartment, and surround left, center, right speakers 26, 28, 30 are arranged on the rear side. Further, a subwoofer 32 for heavy bass is arranged on the rear side. Between the DVD player 10 and the speakers 20 to 32, noise correction filters 40, 42, 44, 46, 48, 50 and 52 for correcting audio signals according to noise are connected. A microphone 60 is installed in the vehicle interior, and the audio reproduction sound P and noise N in the vehicle interior are detected by the microphone 60. The noise extraction unit 70 extracts the noise N from the audio signal detected by the microphone 60 and corrects the noise correction filters 40 to 52 in accordance with the noise N.

  In order to support multi-channel software such as a DVD, the noise correction filters 40 to 52 are used to perform filtering on a large number of channels as described above, which increases the amount of DSP processing and increases costs. End up. On the other hand, since the noise during driving of the automobile has a spectrum pattern in which the low sound is large and gradually decreases toward the high sound, as shown in FIG. 8, it is necessary to enhance the low sound by the noise correction filters 40 to 52. However, since the surround audio signal contains almost no bass component, even if the bass is boosted, the effect of noise correction is not shown so much, and even if an expensive DSP is used, it can be effectively used. There was a fact that was not made.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a low-cost in-vehicle audio system that can cope with a multi-channel audio source.
A further object of the present invention is to provide an in-vehicle audio system that can improve the utilization efficiency of a DSP or the like and obtain a surround effect compatible with multi-channel software.

  The in-vehicle audio system according to the present invention is connected to a reproducing means for reproducing an audio signal, a plurality of speakers arranged on the front side and the rear side, and the reproducing means and the front side speaker. A signal processing unit that performs signal processing of an audio signal, a switching unit that is connected between the playback unit and the rear speaker, and that selects either the output of the signal processing unit or the output of the playback unit as an input; Multi-channel discriminating means for discriminating whether or not the audio signal to be played is multi-channel, and when it is determined that the audio signal is multi-channel, the output of the reproducing means is selected as input of the switching means, and it is discriminated that it is not multi-channel And switching control means for selecting an output of the signal processing means as an input of the switching means.

  Preferably, the rear speaker includes at least a left and right surround speaker disposed at the rear of the vehicle interior, and the front speaker includes a left and right speaker disposed at the front of the vehicle interior. A 5.1 channel or 6.1 channel speaker system is configured.

  The signal processing means performs correction to boost (enhance) the low frequency of the audio signal in accordance with the noise of the automobile. The signal processing means can be performed by a filter operation by a DSP.

  Furthermore, the in-vehicle audio system of the present invention includes a reproducing means for reproducing an audio signal, a plurality of speakers arranged on the front side and the rear side, and an audio reproduced by being connected between the reproducing means and the plurality of speakers. Signal processing means for performing signal processing, multi-channel discrimination means for determining whether or not the audio signal to be reproduced is multi-channel, and signal processing means connected to a rear speaker, are connected in parallel, and switching control Bypass means for bypassing the signal processing means in accordance with the signal, expansion means for expanding the stereo audio signal to a multi-channel audio signal, and when the multi-channel discrimination means determines that the signal is multi-channel, the bypass means causes the signal processing means to The switching control signal is supplied to be executed, and the stereo channel is supplied. When it is determined that the expansion means is turned on, and if it is on, the processing resources and memory resources used for the signal processing means are allocated to the expansion means, Switching control means for supplying the switching control signal so that the signal processing means is bypassed by the bypass means.

  Furthermore, according to the present invention, there is provided a method for reproducing an audio signal of an in-vehicle audio system that outputs audio reproduction sound from a plurality of speakers arranged on a front side and a rear side in a vehicle interior. When the audio signal is determined to be multi-channel, the noise correction is performed on the audio signal supplied to the front speaker and the noise correction is performed on the audio signal supplied to the rear surround speaker. There are no steps.

  According to the in-vehicle audio system of the present invention, the signal processing means for performing noise correction or the like is connected between the reproducing means and the front speaker, and the audio to the rear surround speaker when the audio signal is multi-channel. Since the signal processing such as noise correction is not performed on the signal, the signal processing means of the audio signal provided to the rear speaker is eliminated, and the cost of the audio system can be reduced. Furthermore, according to the in-vehicle audio system of the present invention, the signal processing means connected to the rear surround speaker can be bypassed, and the signal processing means can be used when expanding a stereo audio signal to a multi-channel audio signal. Since it did in this way, a signal processing means can be utilized effectively.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an in-vehicle audio system according to an embodiment of the invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of an in-vehicle audio system according to an embodiment of the present invention. The in-vehicle audio system 100 includes an audio playback unit 110 for playing back a digital audio source stored in a storage medium such as a CD, a DVD, a hard disk, a semiconductor memory, a Blu-ray disc, and the digital played back by the audio playback unit 110. A DSP (digital signal processor) 120 that receives an audio signal, performs processing necessary for surround reproduction and noise correction, a controller 130 that controls the DSP 120, converts the digital audio signal into an analog audio signal and amplifies it And an amplifier 140 that converts the analog audio signal from the amplifier 140 into an audible sound.

  As will be described later, the controller 130 performs a process of determining whether or not the audio signal is multi-channel, a process of extracting noise based on a sound signal detected by a microphone installed in the vehicle interior, and the like. The DSP 120 is controlled according to the result. The controller 130 is composed of, for example, a microcomputer including a ROM and a RAM, and a program for performing necessary control is stored in the ROM.

  As shown in FIG. 2, the speaker 150 has a full-range main speaker including a front left 20, a front center 22, and a front right 24 on the front side of the vehicle interior, and a rear left 26, a rear center 28, and a rear right 30 on the rear side. And a rear center subwoofer 32 for heavy bass. As a result, a 6.1-channel speaker system is realized.

  FIG. 3 is a block diagram showing an internal configuration of the audio system of FIG. In the figure, the amplifier 140 is omitted, and the same components as those in FIG. 7 used in the conventional description are given the same numbers. The audio system 100 includes a DVD player 10, noise correction filters 40, 42, 44, 52, changeover switches 160, 162, 164, and speakers 20-32 as audio playback units. In the present embodiment, the noise correction filters 40, 42, 44, and 52 are used for the front left output F / L, the front center output F / C, the front right output F / R, and the subwoofer output S / W of the DVD player 10, respectively. A noise correction filter is not connected to the surround rear left output R / L, rear center output R / C, and rear right output R / R. This is because the surround audio signal does not contain much bass component, and even if the bass is increased, the effect of the correction is not exhibited so much. The noise correction filters 40, 42, 44 and 52 are implemented by digital signal processing of the DSP 120.

  The changeover switch 160 selects either the output of the noise correction filter 40 or the rear left output R / L of the DVD player 10 as an input, and outputs this to the rear left speaker 26. Similarly, the changeover switch 162 selects either the output of the noise correction filter 42 or the rear center output R / C of the DVD player 10 as an input, and outputs this to the rear center speaker 28. The changeover switch 164 selects either the output of the noise correction filter 44 or the rear light output R / R of the DVD player 10 as an input, and outputs this to the rear light speaker 30. Operation control of the changeover switches 160, 162, and 164 is performed by a changeover control signal C from the multichannel discrimination unit 170.

The audio reproduction sound P and the noise N in the passenger compartment are input to the microphone 60 and supplied to the noise extraction unit 70. Furthermore, the audio signal from the DVD player 10 is input to the noise extraction unit 70, and the noise N is extracted from the difference between these two signals. The noise extraction unit 70 outputs a correction coefficient corresponding to the noise N to the noise correction filters 40, 42, 44, and 52, and controls their operations. The noise extraction unit 70 and the multi-channel determination unit 170 are included in the controller 130 .

  The multi-channel discriminating unit 170 decodes the audio signal from the DVD player 10 and discriminates whether or not the reproduced audio signal is multi-channel. The multi-channel is, for example, a 5.1 channel or 6.1 channel digital audio signal by Dolby Digital. A non-multi-channel audio signal is a mono or stereo audio signal. In addition to this, for example, when a multi-channel input is different from a signal line to which a monaural / stereo input is applied, the method of determining whether the signal is multi-channel is detected. You may make it discriminate | determine by.

  The multichannel discriminating unit 170 outputs a change control signal C to the changeover switches 160, 162, and 164 according to the discrimination result, and controls their operations. When it is determined that the audio signal is multi-channel, the changeover switches 160, 162 and 164 input the rear left output R / L, rear center output R / C and rear right output R / R of the DVD player 10 by the change control signal C. Choose as. On the other hand, when it is determined that the audio signal is monaural or stereo, the changeover switches 160, 162, and 164 select the outputs of the noise correction filters 40, 42, and 44 as inputs based on the changeover control signal C.

  Next, the operation of the audio system of the present embodiment will be described with reference to the flowchart of FIG. When the audio signal is reproduced by the DVD player 10 (step S101), the reproduced audio signal is supplied to the multi-channel determination unit 170. The multi-channel determination unit 170 decodes the audio signal and determines whether the audio signal is multi-channel (step S102).

  When it is determined that the audio signal is multi-channel, the multi-channel determination unit 170 outputs the switching control signal C having the logic level “1” to the change-over switches 160, 162, and 164 (step S103). In response to the switching control signal C, the selector switches 160, 162, and 164 select the rear left output R / L, rear center output R / C, and rear right output R / R of the DVD player 10 as inputs (step S104). .

  On the other hand, the front left output F / L, the front center output F / C, and the front right output F / R of the DVD player 10 are input to the noise correction filters 40, 42, and 44. As a result, for the audio signal to the front speaker, correction in response to the noise extracted by the noise extraction unit 70, that is, correction for enhancing the bass is performed. Similarly, the audio signal to the subwoofer 32 is also corrected by the noise correction filter 52. On the other hand, the audio signal to the rear side surround speakers 26, 28, 30 is not corrected according to the noise (step S105). This is because the effectiveness of the correction is poor as described above.

  When it is determined that the audio signal is a monaural / stereo signal, the multi-channel determination unit 170 outputs a switching control signal C having a logic level “0” to the change-over switches 160, 162, and 164 (step S106). In response to the switching control signal C, the selector switches 160, 162, and 164 select the outputs of the noise correction filters 40, 42, and 44 as inputs (step S107).

  As a result, a common audio signal subjected to noise correction is supplied to the front speaker and the rear speaker. That is, the audio signals corrected by the noise correction filter 40 are supplied to the front and rear left speakers 20 and 26, and the audio signals corrected by the noise correction filter 42 are supplied to the front and rear center speakers 22 and 28. A signal is supplied, and the audio signals corrected by the noise correction filter 44 are supplied to the front and rear light speakers 26 and 30. Further, the audio signal corrected by the noise correction filter 52 is supplied to the subwoofer speaker 32 (step S108). As a result, the audio reproduction sound whose noise has been corrected is output from the front and rear speakers.

  As described above, according to this embodiment, when the audio signal is multi-channel, the noise correction of the audio signal to the surround speaker on the rear side is not performed, so that it is compared with the conventional audio system. The noise correction filter can be reduced, and the cost can be reduced. If the audio signal is not multi-channel, the signal corrected with respect to the front audio signal can be shared by the rear surround speakers, so that the same acoustic effect as before can be maintained. it can.

  Next, a second embodiment of the present invention will be described. In the second embodiment, an example in which resources of the DSP 120 are used effectively will be described. FIG. 5 shows the internal configuration of the in-vehicle audio system according to the second embodiment. As shown in the figure, the DSP 120 includes a surround expansion function 12 such as Pro Logic 2 by Dolby and Neo 6 by DTS. Pro Logic 2 or Neo 6 is a function that expands and reproduces stereo sound to 5.1 channel or 6.1 channel sound, and this function can be turned on / off by an input 180 from the user, for example. .

  Noise correction filters 40, 42, 44, 52 are connected between the speakers 20, 22, 24, 32 corresponding to the output on the front side and the subwoofer side of the DVD player 10 as in the conventional case, and these are the noises. The audio signal is corrected according to the noise extracted by the extraction unit 70. On the other hand, noise using DSP computing resources and memory resources between the rear left output R / L, the rear center output R / C, the rear right output R / R, and the surround speakers 26, 28, 30 on the rear side. Correction filters 46a, 48a and 50a are connected. The DSP can execute the expansion process by the prologic 2 or Neo6 using the DSP processing resources and memory resources used for the noise correction filters 46a, 48a, and 50a. Further, bypass switches 190, 192, 194 are connected in parallel with the noise correction filters 46a, 48a, 50a. The bypass switches 190, 192, 194 bypass the noise correction filters 46a, 48a, 50a in response to the switching control signal C from the multi-channel discriminating unit 170.

  Next, the operation of the second embodiment will be described with reference to the flowchart of FIG. The audio signal is reproduced (step S201), and it is determined whether or not the reproduced audio signal is multi-channel (step S202). In the case of multi-channel, the multi-channel determination unit 170 outputs a switching control signal C of logic “0” to the bypass switches 190, 192, 194 (step S203). In response to the switching control signal C, the bypass switches 190, 192, 194 open contacts, whereby the rear-side rear left output R / L, rear center output R / C, and rear right output R / R are converted to the noise correction filter 46a. , 48a, 50a (step S204). As a result, the noise-corrected audio signal is also output from the surround rear speakers 26, 28 and 30 (step S205).

  On the other hand, if the audio signal is not multi-channel, it is determined whether or not the surround expansion function 12 such as the prologic 2 is turned on (step S206). When the extended function is off, the same processing as that for multi-channel is performed. That is, the bypass switches 190 to 196 are opened, and the noise-corrected audio signal is also supplied to the surround speakers 26, 28, and 30 on the rear side. In this case, as in the first embodiment, the outputs of the front-side noise correction filters 40, 42, and 44 may be supplied to the rear-side speakers 26, 28, and 30.

  When the extended function 12 is on, the multi-channel determination unit 170 outputs a switching control signal C having a logic “1” (step S207). In response to this, the contacts of the bypass switches 190, 192, 194 are closed, and the rear left output R / L, the rear center output R / C, and the rear right output R / R are bypassed through the noise correction filters 46a, 48a, 50a ( Step S208). As a result, DSP processing resources and memory resources used in the noise correction filters 46a, 48a, and 50a are switched to the surround expansion function 12, and audio signal expansion processing corresponding to Pro Logic 2 and Neo 6 is performed. Is supplied to the rear speakers 26, 28, 30. As a result, a surround-enhanced multi-channel audio output can be obtained.

  As described above, according to the second embodiment, DSP processing resources and memory resources can be effectively used for expansion processing such as Pro Logic 2 and Neo6 and noise correction processing.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments according to the present invention, and various modifications can be made within the scope of the gist of the present invention described in the claims. Deformation / change is possible.

  In the above embodiment, the 6.1-channel speaker system is used in the passenger compartment, but this may be 5.1 channel. The audio playback unit 110 includes all electronic devices including a function of playing back an audio signal.

  The in-vehicle audio system according to the present invention can be widely used in an audio system equipped in a moving body such as a vehicle, an AV device that combines audio and video, and an in-vehicle electronic device that combines a navigation function. .

It is a block diagram which shows the structure of the vehicle-mounted audio system which concerns on the Example of this invention. It is a figure which shows arrangement | positioning of the speaker in a vehicle interior. It is a block diagram which shows the internal structure of the audio system of FIG. It is a flowchart explaining the operation | movement of the audio system of a 1st Example. It is a block diagram which shows the internal structure of the vehicle-mounted audio system of a 2nd Example. It is a flowchart explaining the operation | movement of the audio system of a 2nd Example. It is a block diagram which shows the internal structure of the conventional vehicle-mounted audio system. It is a figure which shows the noise spectrum at the time of driving | running | working of a motor vehicle.

Explanation of symbols

20: Front left 22: Front center 24: Front right 26: Rear left 28: Rear center 30: Rear right 32: Subwoofer 40, 42, 44, 46, 48, 50, 52: Noise correction filter 60: Microphone 70: Noise extraction Unit 100: in-vehicle audio system 110: audio reproduction unit 120: DSP 130: controller 140: amplifier 150: speakers 160, 162, 164: changeover switch 170: multi-channel discrimination unit 190, 192, 194: bypass switch

Claims (5)

Playback means for playing back an audio signal;
A plurality of speakers arranged on the front side and rear side;
A microphone for inputting audio reproduction sound and noise in the passenger compartment output by the plurality of speakers, and noise from the difference between the audio reproduction sound and noise input from the microphone and the audio signal reproduced by the reproduction means; Noise extraction means for extracting;
Audio that is connected between the reproduction means and a front-side speaker , inputs a front-side audio signal reproduced by the reproduction means, and is reproduced by the reproduction means based on noise extracted by the noise extraction means Signal processing means for performing signal processing for signal noise correction ;
The rear audio signal is connected between the reproduction means and the rear speaker and is reproduced by the reproduction means without passing through the signal processing means, and the output of the signal processing means or the reproduction means Switching means for selecting one of the outputs as an input;
Multi-channel discriminating means for discriminating whether or not the audio signal reproduced by the reproducing means is multi-channel;
When it is determined that the channel is multi-channel, the audio signal output from the reproduction unit is selected as the input of the switching unit, and when it is determined that the channel is not multi-channel , the noise is detected by the signal processing unit as the input of the switching unit. Switching control means for selecting the corrected audio signal ;
An in-vehicle audio system. The rear speaker includes at least a left and right surround speaker disposed at the rear of the vehicle interior, and the front speaker includes a left and right speaker disposed at a front of the vehicle interior. Item 2. The in-vehicle audio system according to Item 1. The in-vehicle audio system according to claim 2, wherein a 5.1 channel or 6.1 channel speaker is arranged in the vehicle interior. The in-vehicle audio system according to claim 1, wherein the signal processing unit performs correction to increase a low frequency of the audio signal in accordance with automobile noise. A method for reproducing an audio signal of an in-vehicle audio system that outputs audio reproduction sound from a plurality of speakers arranged on a front side and a rear side in a vehicle interior,
Play the audio signal,
Inputting audio reproduction sound and noise in the passenger compartment output from the plurality of speakers from a microphone, and extracting noise from the difference between the audio reproduction sound and noise input from the microphone and the reproduced audio signal,
Input the reproduced front audio signal , perform signal processing for noise correction of the reproduced audio signal based on the extracted noise,
Determine whether the audio signal to be played is multi-channel,
When it is determined that the audio signal is multi-channel, the front-side speaker is supplied with the noise-corrected front-side audio signal , and the rear-side surround speaker is reproduced with the noise-corrected rear side. When an audio signal is provided and it is determined that the audio signal is not multi-channel, the front-side speaker is provided with a noise-corrected front-side audio signal , and the rear-side surround speaker is provided with a noise-corrected front signal. A method for reproducing an audio signal, wherein the audio signal of the side is provided .

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