JP2001007670A - Signal processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the circuit configuration of a signal processing unit and to control volume, while ensuring dynamic range of an audio signal. SOLUTION: When a call tone of a mobile phone or the like rings, a pattern recognition circuit 7 outputs a pattern recognition understanding signal P to a DSP 2. The DSP 2 compresses number of bits of an input audio digital signal through 1st volume processing and electronic volume circuits 4L, 4R conduct attenuation processing as 2nd volume processing. When the mobile phone or the like rings a call end tone, the 1st and 2nd volume processing sets are released, and the tone volume is restored to the original tone volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus for automatically adjusting the volume of an audio device in an automobile in which an audio device such as a car stereo and a telephone such as a mobile phone or a cellular phone coexist.

[0002]

2. Description of the Related Art In general, an automobile is equipped with an MD player as well as a radio receiver, a tape deck and a CD player. The volume of such an acoustic device can be arbitrarily determined by the user, and the volume level is manually changed when varying the volume level.

[0003] On the other hand, mobile phones have become widespread, and because of their portability, they can be carried anywhere, and there is the convenience of being able to talk from anywhere. For this reason, the chance of using a mobile phone in a car is increasing.

[0004]

However, since the volume of the audio device can be set arbitrarily in the automobile, if the volume is set high, the ringing sound of a car phone or a mobile phone will not be heard. There were no cases. In addition, there is a problem that the telephone call becomes difficult to hear due to the volume of the audio equipment even if the telephone rings and the telephone is picked up.

[0005]

SUMMARY OF THE INVENTION The present invention provides a pattern recognition circuit for recognizing a sound pattern generated from a portable telephone or an automobile telephone, and a volume control for controlling an output volume in accordance with the recognition result of the pattern recognition circuit. And a circuit.

[0006] It is characterized in that the volume is turned off or down by recognizing the ringing tone of various telephones, and the volume is returned or raised by recognizing the end tone.

Further, in the front speaker and the rear speaker of the vehicle-mounted audio apparatus, the output of the front speaker is stopped or reduced during a telephone call, and sound is output only from the rear speaker.

[0008] In particular, the sound volume control circuit is arranged before the speaker. Further, the volume control circuit includes an arithmetic unit that performs signal processing on a digital audio signal, a D / A conversion circuit that converts the digital audio into an analog audio signal, and a volume circuit that controls the level of the analog audio signal. ,
The arithmetic unit performs a first volume process for changing a level of the digital audio signal, and outputs a volume control signal for causing the volume circuit to perform a second volume process. It is characterized in that an analog audio signal level is changed by a volume control signal.

According to the present invention, only when a call is being made by a mobile phone or a car phone, the volume is reduced or reduced so that the telephone ringing tone and the call can be heard more easily.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of the present invention. Reference numeral 1 denotes an A / D for A / D converting an audio signal AS from, for example, a CD, MD or DVD playback device into a digital audio signal. The conversion circuit 2 performs signal processing such as equalization processing and sound field correction on the digital audio signal, performs first volume processing for controlling the level of the digital audio signal, and performs first volume processing on the subsequent electronic volume circuit. DSP, 3L that outputs a volume control signal CONT for performing the volume processing of No. 2
And 3R output digital signals DL and D from DSP2.
D / A conversion circuits for analog-converting R into analog audio signals L and R, 4L and 4R are electronic volume circuits for controlling the levels of audio signals L and R according to a volume control signal CONT, and 5L and 5R are level-controlled. A speaker that emits sound in accordance with the audio signals L and R, 6 is a microcomputer, and 7 is a pattern recognition circuit that detects ringing and ending sounds of a mobile phone or a car phone.

The DSP 2 is composed of circuits as shown in FIG. 6. By storing various programs in a program ROM, the DSP 2 can perform not only equalization processing and sound field correction but also bass treble, loudness, low It is possible to realize functions necessary for audio, such as a boost function and a surround effect function. In the present invention, a program for performing the first and second volume processing is stored in the DSP 2, the DSP 2 controls the level of the digital audio signal, and the electronic volume circuits 4L and 4R
And adjust the levels of the analog audio signals L and R to desired levels.

In FIG. 1, it is assumed that each circuit operates and that sound is generated from the speakers 5L and 5R. In this state, when a ringing tone sounds from a mobile phone or a car phone (not shown), the pattern of the ringing tone is matched in the pattern recognition circuit 7. When the ringing tone is recognized, the pattern recognition acknowledgment signal P is generated from the pattern recognition circuit 7. The DSP 2 receives the pattern recognition acknowledgment signal and controls the electronic volumes 4L and 4R, which are the first volume processing and the second volume processing. By this volume processing, the volume from the speaker is stopped or reduced. Thereafter, when an end tone sounds from a mobile phone or a car phone, the pattern recognition circuit 7 recognizes the end tone and generates a pattern recognition acknowledgment signal. The DSP 2 receives the pattern recognition acknowledgment signal and cancels the first and second volume processing. By canceling the volume processing, the volume from the speaker returns to the state before being stopped or reduced or becomes higher. As described above, the volume processing is performed immediately when the ringing tone is recognized by the pattern recognition circuit 7, so that
Ring tones and conversations are easier to hear.

Here, the pattern recognition circuit 7 matches a pattern of a ringing tone and a termination tone, and stores a reference pattern to be compared with a tone ringing from a telephone. In this storage, the ringing tone and the ending tone of all the existing mobile phones and car phones may be stored, or a sound pattern for each maker may be stored. Further, the sound pattern of the telephone owned by the user may be optionally temporarily stored or preset.

Next, the volume processing of FIG. 1 will be described with reference to the flowchart of FIG. In FIG. 1, an analog audio signal AS is digitally converted into a digital audio signal DS by an A / D converter 1, and then input to a DSP 2. In the DSP 2, signal processing desired by the listener, such as equalization processing and sound field correction of the audio signal, is executed (S1). DS
When P2 receives the pattern recognition acknowledgment signal P, DSP2 starts volume processing by an interrupt command (S2).
2).

Incidentally, the level of the audio signal in the volume processing is changed by both the DSP 2 and the electronic volume circuits 4L and 4R. The attenuation in DSP2 is 0
The electronic volume circuits 4L and 4L are set to -48 dB.
The amount of attenuation of R is also set to 0 to -48 dB.

First, when the first volume processing of the DSP 2 is executed, the digital signal is attenuated by compressing the 24-bit digital signal in accordance with the amount of attenuation. When trying to attenuate an audio signal by an attenuation of -48 dB, a 24-bit digital signal becomes 16 bi.
The signal is compressed to a signal equivalent to t, which corresponds to about 96 dB in terms of dynamic range. Generally, the dynamic range of an audio signal is determined by an A / D converter,
The advantage of being limited by the D / A converter and other peripheral analog circuits is that the audio signal of the DSP 2 needs a dynamic range of about 90 to 100 dB. Therefore, if the attenuation is set to about 0 to -48 dB, the DSP 2 can secure an audio signal having a sufficient dynamic range. Conversely, in order to secure a dynamic range, the amount of attenuation is -48d.
It can be said that it cannot be made larger than B. In addition, DS
If the dynamic range of the output of P2 can be ensured, the maximum attenuation is not limited to -48 dB, and the attenuation can be arbitrarily set.

When the total amount of attenuation is set to 0 to -48 dB, this is achieved by the first volume processing of the DSP 2, but when the total amount of attenuation is set to be larger than -49 dB, it is further combined with the first volume processing. Electronic volume circuit 4
Attenuated at L and 4R. For example, when the entire attenuation is set to −60 dB, the DSP 2 executes the −48 dB attenuation process, and executes the −12 dB attenuation process in the electronic volume circuits 4L and 4R. If the DSP 2 and the electronic volume circuit are combined, an attenuation of -96 dB can be obtained.

Therefore, as shown in FIG. 3, when the total attenuation is 0 to -48, the first volume processing is operated, and when the entire attenuation is -49 to -96 dB, the first volume processing is performed.
The second volume processing is operated while the attenuation amount of the volume processing is set to -48 dB.

Returning to the flowchart of FIG. 2, when the DSP 2 receives the pattern recognition acknowledgment signal P in S2, the DSP 2 reads the attenuation amount data from the data RAM in the DSP 2 based on the instruction for the attenuation amount for the audio signal. (S3). The data RAM has a first
And data on the amount of attenuation used for the second volume processing. For example, as shown in FIG. 4, a combination of attenuation amounts in the first and second volume processes with respect to the entire attenuation amount is stored. In this case, data is read out in which the total attenuation is -96 dB or the vicinity thereof. At the same time, the DSP 2 stores the data of the attenuation before receiving the pattern recognition acknowledgment signal.

The read data of the attenuation is stored in the DSP2
, And transferred as a volume control signal to the electronic volume circuits 4L and 4R. In this step, only the attenuation data is transferred to the electronic volume, and the attenuation of the electronic volume is not updated to the new attenuation.

Thereafter, the DSP 2 starts detecting a zero crossing point where the input audio signal crosses the bias level (S4). When the zero crossing point is detected, the DSP 2 updates the attenuation in the first volume processing to the attenuation read from the data RAM. At the same time, the DSP 2 operates the electronic volume circuits 4L and 4R.
A timing signal T, and the attenuation of the electronic volume circuits 4L and 4R is changed to the data R in accordance with the timing signal T.
It is updated to the attenuation read out from AM, and the speaker 5L
And the volume from 5R is stopped or reduced (S5).

The timing signal T indicates the timing at which the amount of attenuation in the DSP 2 is switched, by the electronic volume circuits 4L and 4L.
R is controlled so that the switching of the attenuation amount in the first and second volume processes is performed at the same timing. As a result, an unnatural level change due to a change in the amount of attenuation shifted with time can be prevented, and the listener can be prevented from feeling uncomfortable. Further, if the switching of the amount of attenuation is performed at the timing when the audio signal crosses zero, the level is changed in a state where the audio signal is substantially absent even if the audio signal level changes, so that it is possible to further prevent a sense of incongruity in hearing. .

After the attenuation is changed, the digital audio signal undergoes level adjustment with the new attenuation, and is output from the DSP 2 (S6). Then the audio signals DL and DR are D
The signals are input to the / A converters 3L and 3R and are converted into analog audio signals L and R. Further, the analog audio signals L and R are input to the electronic volume circuits 4L and 4R, respectively, so that the audio signals are attenuated by a new amount of attenuation, and the volume from the left and right speakers 5L and 5R is stopped or reduced.

Further, the case where an end sound is heard from a portable telephone or a car telephone will be described with reference to the flowchart of FIG. D
Upon receiving the second pattern recognition acknowledgment signal P (S10), the DSP 2 reads out the stored data of the attenuation amount before the ringing tone sounds (S11).
The read data of the attenuation amount is transferred for the first volume processing in the DSP 2 and is also transferred to the electronic volume circuits 4L and 4R as a volume control signal. Thereafter, the DSP 2 starts detecting a zero cross point where the input audio signal crosses the bias level (S12). When a zero cross point is detected, D
SP2 updates the amount of attenuation in the first volume processing to the amount of attenuation before the ringing tone sounds. At the same time, D
SP2 outputs the timing signal T to the electronic volume circuits 4L and 4R, and the attenuation of the electronic volume circuits 4L and 4R is updated to the attenuation before the ringing tone is sounded according to the timing signal T (S13). After changing the amount of attenuation, the digital audio signal undergoes level adjustment with the new amount of attenuation, and D
Output from SP2 (S14). Thereafter, the volume from the left and right speakers 5L and 5R returns to the original volume or increases.

By the way, in the first and second volume processes, the whole attenuation range is divided into two ranges as shown in FIG. 3, and the first and second volume processes are executed according to their magnitudes. Was. Contrary to the processing of FIG. 3, it is also possible to attenuate by the second volume processing by the electronic volume in a range where the entire attenuation is small, and to attenuate by the first volume processing by the DSP 2 in the large range.
Further, the first and second volume processes can be executed by another method.

As a first method, the amount of attenuation in the first volume processing of the DSP 2 is switched between 0 and -4 dB, and the electronic volume circuits 4L and 4R switch between 0 dB and-
Attenuation amount control of -5 dB steps of 5 dB, -10 dB, -95 dB is performed. In this method, the data R
The AM stores, for example, a table as shown in FIG.

The method shown in FIG. 5 is effective because the dynamic range is secured when the digital / analog signal is 16 bits instead of 24 bits. When the digital audio signal is composed of 18 bits, the amount of attenuation in the first volume processing of the DSP 2 is switched between 0 and -9 dB, and the electronic volume circuit 4L
, And 4R can be switched in -10 dB steps. Also, when the digital audio signal is 24
In the case of a bit, the DSP 2 controls the volume from 0 to -48 dB, and the electronic volume circuits 4L and 4R control the volume.
The amount of attenuation of dB or -48 dB can be switched. Therefore, the amount of attenuation can be arbitrarily set according to the number of bits of the digital audio signal so that the dynamic range of the output of the DSP 2 can be sufficiently secured.

FIG. 8 is a diagram showing another embodiment of the present invention, wherein the volume is switched by volume control circuits 8L and 8R arranged in front of the speaker without performing volume processing by the DSP 2. When the ringing tone from the mobile phone or the car phone is recognized, the volume control circuits 8L and 8R receiving the pattern recognition acknowledgment signal switch to the speakers 5L and 5R.
Control is performed so that the output of R is stopped or reduced. Further, when the end sound from the telephone is recognized, the volume control devices 8L and 8R that have received the second pattern recognition acknowledgment signal are controlled so that the outputs of the speakers 5L and 5R return to the original state or increase.

The volume control circuits 8L and 8R are constituted by level changing means such as a volume. Therefore, DS
It may also be used as a volume for controlling the change of the output audio signal level of P2.

In this case, since the processing is not performed by the DSP 2, the control of the sound volume can be promptly performed, and the load on the software of the DSP 2 can be reduced.

By the way, so-called four-speaker systems are mainly used in audio devices in automobiles.
If a cell phone or car phone rings,
It is also possible to reduce or lower only the volume of the front speaker and leave the volume of the rear speaker as it is. As a rule of thumb, simply lowering the volume of the front speaker will lower the perceived volume in the car,
It makes it easier to hear the ringtones and calls of mobile phones and car phones. In this case, since the volume processing is performed only on the front speaker, the circuit configuration can be simplified.

In the description of FIGS. 1 and 8, the volume is turned off when the ringing tone sounds, and the volume is returned to the original state when the end tone sounds. However, the present invention is not limited to this. , The volume may be lowered to a ringing tone or a volume at which a call can be easily heard, and the end tone may be raised to a predetermined volume, for example.

[0033]

According to the present invention, after recognizing the ringing tone of a mobile phone or a car phone, the volume is stopped or reduced, so that the telephone ringing tone and the telephone call can be easily heard. In particular, since the volume is automatically stopped or reduced during a call, a ringing tone and a call can be reliably achieved even if both hands are blocked by driving a car and calling by phone.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of FIG. 1;

FIG. 3 is a diagram for explaining volume processing in the operation of FIG. 1;

FIG. 4 shows the DSP 2 of FIG. 1 in the first and second volume processing.
Is table data stored in.

FIG. 5 shows the DSP 2 of FIG. 1 in the first and second volume processing.
Is other table data stored in the.

FIG. 6 is a block diagram showing a specific circuit of the DSP.

FIG. 7 is another flowchart for explaining the operation of FIG. 1;

FIG. 8 is a block diagram showing another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 A / D converter 2 DSP 3L, 3R D / A converter 4L, 4R Electronic volume 5L, 5R Speaker 6 Microcomputer 7 Pattern recognition circuit 8L, 8R Volume control circuit

Continued on the front page (72) Yoshihiko Ima 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Takashi Kuroda 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Takashi Uchino 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Kanken Sato, 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. F term (reference) 5D015 AA01 AA06 KK01 5J100 JA04 KA05 LA00 QA02 SA02 SA06 9A001 CC05 HH17 HH34 JJ12 JJ77

Claims (5)

[Claims] 1. A pattern recognition circuit for recognizing a pattern of a sound generated from a mobile phone or a mobile phone, and a volume control circuit for controlling an output volume according to a recognition result of the pattern recognition circuit. Signal processing device. 2. The signal processing apparatus according to claim 1, wherein the volume is turned off or down by recognizing a ringing tone of various telephones, and the volume is returned or raised by recognizing an end tone. 3. The signal processing according to claim 1, wherein the front speaker and the rear speaker of the on-vehicle audio device stop or reduce the output of the front speaker during a telephone call and output sound only from the rear speaker. apparatus. 4. The signal processing device according to claim 1, wherein the volume control circuit is arranged at a stage preceding the speaker. 5. An arithmetic unit for processing a digital audio signal, said volume control circuit comprising:
A D / A conversion circuit for converting the digital audio into an analog audio signal; and a volume circuit for controlling a level of the analog audio signal, wherein the arithmetic unit is configured to change a level of the digital audio signal. The volume control circuit outputs a volume control signal for causing the volume circuit to perform a second volume process while performing the processing, and the volume circuit changes an analog audio signal level according to the volume control signal. 2. The signal processing device according to 1.