JPH11352967A - Sound effect adder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance an SN ratio by outputting a compressed wave form to the next stage when it is smaller than a limit, and by supplying the limit to the next stage when it exceeds the limit. SOLUTION: A musical sound wave form W from a sound source is multiplied by an output level coefficient α to generate a wave form Wα, in a digital signal processor(DSP). When the wave form Wα is a threshold TH or less, both a threshold determining circuit 22 and a limit determining circuit 28 output select signals SEL1, SEL2 of '0', and a selector 30 selects the wave form Wαsupplied to an input terminal A to output it to the next stage D/A converter. On the other hand, when the waveform Wα exceeds the threshold TH to be the limit LT, the determining circuit 22 outputs the select signal SEL1 of '1', the determining circuit 28 outputs the select signal SEL2 of '0', and the selector 30 selects a wave form Wαβ+γ supplied to an input terminal B to output it to the next stage D/A converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an effect adding device suitable for use in electronic musical instruments and the like.

[0002]

2. Description of the Related Art Conventionally, as an effect adding device for adding a so-called limiter effect to prevent an output waveform distortion by suppressing an input waveform level when the input waveform level is excessive, for example, a configuration shown in FIG. Are known. In this figure, a multiplier 81 multiplies a musical tone waveform W supplied from a sound source side (not shown) by a coefficient out stored in an output level register 80, and outputs a level-set waveform W · out. It is. Reference numeral 82 denotes a limit level determined by the number of conversion bits (dynamic range width) of a D / A converter provided at a subsequent stage of the apparatus, and a waveform W.out.
Is a limit level judging means for generating a select signal SEL according to the result of the comparison between the two. 84 is an input terminal A
Is supplied to the input terminal B, and a fixed limit value read from the limit register 83 is supplied to the input terminal B, and the input terminals A,
A selector that selects and outputs any one of B.

According to the above configuration, the waveform W.out is D /
If it is below the limit level determined by the number of conversion bits of the A converter, the waveform W ·
out is selected and output as it is to the next stage. On the other hand, when the waveform Wout exceeds the limit level, the input terminal B
The fixed limit value supplied to the side is output to the next stage,
By doing so, the input / output characteristics shown in FIG. 14 are realized.

[0004]

In the conventional effect adding device having such input / output characteristics, if there is a waveform W.out that frequently enters the limiter area, the waveform value is changed every time the limit is reached. Since it is replaced with a fixed limit value, there is a problem that musically unnatural noise that is hard to hear is separated from the original waveform. On the other hand, in order to avoid such adverse effects, it is only necessary to set a higher limit value.
For example, in the case of a small sound in which a single sound is played by a pianissimo, a sufficient dynamic range cannot be secured in the next stage D / A converter, and as a result, there is a problem that the SN ratio is reduced.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an effect adding device capable of preventing a decrease in an SN ratio and a waveform distortion.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, the level of the input waveform supplied from the preceding stage exceeds the maximum input level of the D / A converter of the following stage. In such a case, in the effect adding device that replaces the level of the input waveform with a limit value corresponding to the maximum input level and suppresses waveform distortion, it is determined whether the input waveform has exceeded a first level. If the level is smaller than 1, the input waveform is output to the next stage as it is.
First level determining means for converting the input waveform into a compressed waveform when the first level is exceeded, and determining whether the compressed waveform converted by the first level determining means has exceeded the limit value; A second level judging means for judging and outputting the compressed waveform to the next stage when the value is smaller than the limit value, and supplying the limit value to the next stage when the value exceeds the limit value. It is characterized by.

According to the second aspect of the present invention, when the input waveform exceeds the first level, the first level determining means multiplies the input waveform by a multiplication factor. After multiplying by β, an addition coefficient γ is added to convert to a compressed waveform.

According to a preferred aspect of the present invention, the first level determining means changes the first level in accordance with the level of the input waveform. The effect adding device according to the above.

Further, according to the invention described in claim 4,
The first level determining means varies the first level according to the operation amount of a volume operator for adjusting a volume output.

[0010] In addition, according to the invention described in claim 5,
The first level determination unit is characterized in that a multiplication coefficient β and an addition coefficient γ used when converting an input waveform into a compressed waveform are changed according to the level of the input waveform.

According to the present invention, if the input waveform is smaller than the first level, it is output to the next stage as it is, and if it exceeds the first level, it is converted into a compressed waveform, and the maximum input level of the next stage D / A converter is converted. Is compared with the limit value, and if it is smaller than the limit value, the compressed waveform is output to the next stage. If the limit value is exceeded, the limit value is supplied to the next stage. Therefore, even if the input waveform has a level that falls within the limiter area in the past, the level is compressed in the compressor area, so that the waveform distortion can be improved. Moreover, the limit value is set to D /
Since the setting is made higher to match the maximum input level of the A converter, a sufficient dynamic range can be secured in the next stage D / A converter even for an input waveform having a small level, and therefore, the SN ratio can be improved. It becomes possible to plan.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The effect adding device according to the present invention can be applied to a sound control device for controlling sound effects in a concert hall or a studio, in addition to a well-known electronic musical instrument. Hereinafter, an electronic musical instrument according to an embodiment of the present invention will be described as an example, which will be described with reference to the drawings.

A. First Embodiment (1) Overall Configuration FIG. 1 is a block diagram showing a configuration of an electronic musical instrument according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a keyboard for generating performance information such as a key-on / key-off signal corresponding to a key press / release operation, a key code, and a velocity corresponding to a key pressing speed (strength). An operation panel 2 includes a panel switch unit 2a and a display unit 2b. The panel switch unit 2a includes various switches and a volume operator disposed on the panel surface, and generates a switch signal corresponding to each switch operation and an operation signal corresponding to the volume operation, respectively. The display unit 2b includes an LCD panel and a plurality of LEDs (light emitting elements). On the LCD panel side, various set values and operation modes are displayed according to a display control signal supplied from a CPU 3 described later.
The ED indicates the operation state of the panel switch unit 2a.

Reference numeral 3 denotes a CPU for controlling each section of the musical instrument. 4
Is a ROM (program memory) for storing various control programs loaded into the CPU 3. 5 is a RAM (work memory) used as a work area of the CPU 3
And various registers and flag data are temporarily stored. Reference numeral 6 denotes a sound source which is constituted by a well-known waveform memory reading method and has a plurality of simultaneous sounding channels which operate in a time-division manner. The tone generator 6 reads out the waveform data of the designated timbre from the waveform memory 7 in accordance with the musical tone parameters generated by the CPU 3 based on the performance information supplied from the keyboard 1 and synthesizes the musical tone.
To supply.

Reference numeral 8 denotes a digital signal processor (hereinafter abbreviated as DSP) for adding an effect to the tone waveform W supplied from the sound source 6 under the control of the CPU 3, and its characteristic configuration will be described later. Will be described. Reference numeral 9 denotes a tone waveform W added to the effect output from the DSP 8.
Is a D / A converter that converts the sound signal into an analog tone signal. Reference numeral 10 denotes a sound system for filtering a tone signal output from the D / A converter 9 for the purpose of removing noise, amplifying the filtered tone signal in accordance with a volume operation, and then emitting the tone signal from a speaker.

(2) Configuration of DSP 8 Next, the configuration of the DSP 8 will be described with reference to FIG. In this figure, reference numeral 20 denotes an output level register, in which an output level coefficient α corresponding to the bit precision of the D / A converter 9 is stored by the CPU 3. A multiplier 21 multiplies the musical tone waveform W supplied from the sound source 6 by the output level coefficient α read from the output level register 20 to generate a waveform Wα. 22 is a threshold level TH stored in a threshold level register 23
And a waveform Wα, and a threshold level determination circuit for generating a select signal SEL1 of “1” when TH ≦ Wα and “0” otherwise. The threshold level TH stored in the register 23 may be set as a predetermined fixed value in advance, or the threshold value TH may be changed by the CPU 3 according to the level of the musical tone waveform W or the operation amount of the volume control. It is good also as a mode which calculates and sets.

A multiplier 24 multiplies the waveform Wα by a compressor multiplication coefficient β read from the compressor multiplication coefficient register 25 to generate a waveform Wαβ. The compressor multiplication coefficient β takes a value of 0 <β ≦ 1. The value may be set in the register 25 as a predetermined fixed value in advance, or may be set according to the level of the musical tone waveform W. CP as changing value
U3 may be calculated and set. 26 is
This is an adder that adds the compressor addition coefficient γ read from the compressor addition coefficient register 27 to the output of the multiplier 24 and outputs a waveform Wαβ + γ.

Reference numeral 28 denotes a waveform Wαβ + γ output from the adder 26 and the D / A converter 9 at the subsequent stage (see FIG. 1).
Is a limit level judging circuit which compares the magnitude with a limit level LT determined by the number of converted bits, and generates a select signal SEL2 of “1” when LT ≦ Wαβ + γ, and a “0” otherwise. 30 is a select signal SEL1, SE
Based on L2, the selector selects one of the signals supplied to the input terminals A to C and outputs it to the next stage.

In the selector 30, the select signal SE
When both L1 and SEL2 are “0”, that is, the waveform Wα
Is below the threshold level TH, the waveform Wα supplied to the input terminal A is selected and output to the next stage. When the select signal SEL1 is “1” and the select signal SEL2 is
Is “0”, that is, the waveform Wα exceeds the threshold level TH, and the waveform Wαβ + γ
T is equal to or less than T, the waveform Wαβ +
γ is selected and output to the next stage. Further, the select signal S
When EL1 is "1" and the select signal SEL2 is "1", that is, when the waveform Wαβ + γ exceeds the limit level LT, the limit value LMT supplied to the input terminal C is selected and output to the next stage. Here, the limit value LMT is a value corresponding to a limit level determined by the number of conversion bits of the D / A converter 9, and the limit value register 2
Points to a fixed value set to 9.

The DSP 8 configured as described above generates a waveform Wα by multiplying the tone waveform W supplied from the sound source 6 by an output level coefficient α corresponding to the bit precision of the D / A converter 9. When the waveform Wα is equal to or lower than the threshold level TH, the threshold level determination circuit 22 and the limit level determination circuit 28 both output select signals SEL1 and SEL2 of “0”. The supplied waveform Wα is selected and output to the D / A converter 9 at the next stage. On the other hand, the waveform W
When α exceeds the threshold level TH and is equal to or lower than the limit level LT, the threshold level determination circuit 22 outputs the select signal SEL1 of “1” and the limit level determination circuit 28 outputs the select signal SEL2 of “0”. Therefore, the selector 30 selects the waveform Wαβ + γ supplied to the input terminal B and outputs it to the D / A converter 9 at the next stage. When the waveform Wα exceeds the limit level LT, both the threshold level determination circuit 22 and the limit level determination circuit 28 select the select signals SEL1 and SEL1 of “1”.
Since the SEL2 is output, the selector 30 selects the limit value LMT supplied to the input terminal C and selects the limit value LMT at the next stage.
/ A converter 9.

That is, in the DSP 8, as can be seen from the input / output characteristics shown in FIG. 3, the output level coefficient α corresponding to the bit precision of the D / A converter 9 is multiplied up to the threshold level TH. The waveform Wα is output to the D / A converter 9 at the next stage. When the waveform Wα exceeds the threshold level TH and reaches the limit level LT, the waveform Wα is changed to a waveform Wαβ + γ (where 0 ≦ β <1). In the compressor region to be converted, even if the waveform has a level which falls into the limiter region in the past, the level is compressed in the compressor region, so that the waveform distortion can be improved. In addition, since the limit value LMT can be set higher to match the maximum input of the DAC due to the above, for example, even for a waveform having a small level at which a single note is played by pianissimo, the D / A of the next stage is performed.
A sufficient dynamic range can be ensured in the converter 9, and as a result, the SN ratio can be improved.

In this embodiment, the above-mentioned compressor region has been described as being fixed. However, the present invention is not limited to this, and the threshold level TH may be set in correspondence with the tone waveform W supplied to the DSP 8 and the volume operation. By changing the range, the compressor range may be variably controlled. In this way, a sufficient dynamic range can be secured for a waveform whose level rapidly changes, and waveform distortion can be suppressed as much as possible. Further, in the above-described embodiment, the input / output relationship of the waveform in the compressor region is defined by the linear characteristic. However, the present invention is not limited to this, and it is of course possible to define the input / output relationship of the waveform in the compressor region by nonlinear characteristics. It is.

B. 2. Second Embodiment (1) Configuration Next, a configuration of a second embodiment according to the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing the configuration of the second embodiment. Elements common to the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.
The difference between the second embodiment shown in this figure and the first embodiment is that the volume operation position is detected, and the DSP 8 compensates for the volume-dependent human auditory characteristics according to the detected volume operation position. Thus, the compressor effect is added, and such a configuration will be described below.

First, in FIG. 4, reference numeral 10a denotes an analog filter for filtering an analog musical tone waveform output from the D / A converter 9 for the purpose of removing noise. 10b is a volume circuit provided with a volume operator for adjusting the volume output level. A volume position detection circuit 10c detects the operation position of the volume operator. The volume circuit 10b and the volume position detection circuit 10c have a circuit configuration shown in FIG.

That is, as shown in FIG. 5, the volume circuit 10b is provided with dual variable resistors VR1 and VR2.
1 and VR2 slide, the one variable resistor V
R1 controls the level of the output of the analog filter 10a in response to this and supplies the output to the next-stage amplifier 10d. On the other hand, the other variable resistor VR2 divides the reference voltage Vref to divide the A / D provided in the volume position detection circuit 10c.
Input to converter 10c-1. As a result, the A / D converter 10c-1 applies the reference voltage V
It generates voltage data Dref divided from ref. Then, the volume position detection circuit 10c converts the voltage data Dref into a volume operation position and supplies it to the CPU 3.

As a mode of converting the voltage data Dref into a volume operation position, for example, a data table in which the voltage data Dref is associated with the volume operation position is provided in advance using a ROM or the like, and the A / D Converter 1
Each time the voltage data Dref is output from 0c-1, the voltage data Dref may be used as a read address to read the converted volume operation position from the data table, or the A / D converter 10c-1 The voltage data Dref to be output may be directly input to the CPU 3 and the CPU 3 may convert the voltage data Dref into a volume operation position.

Next, referring to FIG. 6, a description will be given of a configuration of the DSP 8 which adds a compressor effect based on the volume operation position detected as described above so as to supplement the human audibility characteristic depending on the volume. In FIG. 6, 4
0 is an output level register, and the CPU 3 stores an output level coefficient α corresponding to the bit precision of the D / A converter 9. A multiplier 41 multiplies the musical tone waveform W supplied from the sound source 6 by the output level coefficient α read from the output level register 40 to generate a waveform Wα. A threshold level determination circuit 42 compares the threshold level TH stored in the threshold level register 43 with the waveform Wα, and generates a select signal SEL of “1” if TH ≦ Wα, and “0” otherwise. It is. The CPU 3 calculates and sets the threshold level TH stored in the register 23 as a value that changes according to the volume operation position.

A multiplier 44 generates a waveform Wαβ by multiplying the waveform Wα by a compressor multiplication coefficient β read from the compressor multiplication coefficient register 45. The compressor multiplication coefficient β takes a value range that varies according to the volume operation position, that is, a value range of 0 ≦ β <1 so as to compensate for the human auditory characteristics depending on the volume.
Set by CPU3. An adder 46 adds the compressor addition coefficient γ read from the compressor addition coefficient register 47 to the output of the multiplier 44 to output a waveform Wαβ + γ. As for the compressor addition coefficient γ, similarly to the compressor multiplication coefficient β,
The CPU 3 calculates and sets the register according to the volume operation position. Reference numeral 48 denotes a waveform Wα supplied to the input terminal A when the select signal SEL supplied from the threshold level determination circuit 42 is “0”, and a waveform Wαβ + γ supplied to the input terminal B when the select signal SEL is “1”. Are respectively selected and output to the D / A converter 9 at the next stage.

(2) Operation Next, the operation of the second embodiment will be described with reference to FIGS. First, when the volume position detection processing routine shown in FIG. 7 is executed via a main routine (not shown), the CPU 3 advances the processing to step SA1, and acquires the volume operation position from the above-described volume position detection circuit 10c. In step SA1, the voltage data Dre output from the A / D converter 10c-1 is output.
f is taken as it is, and the voltage data Dr
ef may be converted to a volume operation position.
Next, in step SA2, it is determined whether the volume operation position acquired this time is the same as that acquired last time, that is, whether the volume operation has been performed. If the currently obtained volume operation position is the same as the previously obtained volume operation position, the determination result is "YES". In this case, since no volume operation has been performed, this routine is completed without performing any processing. .

On the other hand, if the volume operation has been performed, the result of the determination in step SA2 is "NO",
The process proceeds to Step SA3. In step SA3,
The volume operation position obtained this time is set in a predetermined register of the RAM 5. In the subsequent step SA4, the above-described threshold level TH, compressor multiplication coefficient β and compressor multiplication coefficient γ are generated based on the volume operation position set in the register. Is stored in the corresponding registers 43, 45, and 47 in the DSP 8, respectively.

As a method for generating the above-described threshold level TH, compressor multiplication coefficient β and compressor multiplication coefficient γ based on the volume operation position,
For example, as shown in FIG. 8A, a threshold level TH, a compressor multiplication coefficient β, and a compressor multiplication coefficient γ for supplementing the audibility characteristics are obtained experimentally in advance for each volume operation position, and are tabulated. By doing so, as shown in FIG. 11B, by reading out the corresponding coefficients from the table with the obtained volume operation position as the read address, the optimum audibility characteristic according to the volume operation position can be obtained. Compressor effect can be realized. That is, in the case of the example shown in FIG. 8B, if the volume (volume) is low, the threshold level TH is lowered, and if the input exceeds the threshold level TH, the input is compressed so as to have a substantially constant output. This makes it possible to realize a compressor effect that supplements the human audibility characteristics, such as making it harder to hear a smaller sound in a low volume. Then, as the volume (volume) increases, the compression ratio is reduced while the threshold level TH is increased, thereby providing a natural audibility characteristic.

In the second embodiment, a compressor effect for compensating for human hearing characteristics is added by focusing only on the level of the tone waveform W input to the DSP 8, but in addition to this, the tone waveform W is added. A mode in which the auditory characteristics are compensated in a form depending on the frequency of W is also possible. That is, according to the human auditory characteristics, at a certain sound pressure level (volume), the sound tends to be small at low frequencies, loudest (good) at mid frequencies, and difficult to hear at higher frequencies. In view of such audibility characteristics, it is also possible to perform bandpass filtering on the musical tone waveform W and perform level correction for each band to add an effect so that the audibility characteristics desired by the user are obtained. Further, such a technique is not limited to the electronic musical instrument shown in the second embodiment, and may be applied to a hearing aid for elderly people whose hearing has declined.

C. Third Embodiment Next, a configuration of a third embodiment according to the present invention will be described with reference to the drawings. FIG. 9 is a block diagram showing the configuration of the third embodiment. Here, the same elements as those in the above-described second embodiment are denoted by the same reference numerals, and description thereof is omitted. The third embodiment shown in this figure is different from the above-described second embodiment in that a line-out terminal 11 for supplying the output of the amplifier 10d to the outside and an on-state when plugged into this terminal 11 Cable connection detection switch 11a to be set
When the cable connection detection switch 11a is plugged into the line-out terminal 11 and the cable connection detection switch 11a is turned on, the characteristic at the time of the maximum volume near flat is set. On the other hand, when the cable connection detection switch 11a is off, the above-described characteristics are set. As in the case of the second embodiment, the present invention is to add a compressor effect that provides an optimum audibility characteristic according to the volume operation position. That is, the third embodiment is characterized in that the manner in which the effect is added is varied according to the acoustic environment used.

The operation of the third embodiment having such features will be described below with reference to FIGS. Operation of Main Routine First, when the power is turned on in this embodiment, the CPU 3
After loading the predetermined control program stored in M4 into itself, the main routine shown in FIG. 10 is executed, and the process proceeds to step SB1. In step SB1, the RAM
5, the sound source 6 and the D
Initialization processing for instructing initial value setting and zero reset is performed on various registers provided in SP8. Then
In step SB2, in addition to the various switches 2 arranged on the operation panel, a switch processing routine for detecting the individual switch states of the above-described cable connection detection switch 11a is executed.

In step SB3, when it is detected in the switch processing routine that the cable connection detection switch 11a is on, the DSP 8 is instructed to set a nearly flat characteristic at the maximum volume. On the other hand, when it is detected that the compressor is in the off state, the CPU 8 instructs the DSP 8 to set a compressor effect that provides an optimum audibility characteristic according to the volume operation position, as in the second embodiment. Thereafter, in step SB4,
After performing various tone processing such as instructing generation of a tone according to a key press / release operation and adding an effect to the generated tone, the process returns to step SB2 described above. Since then
Until the power switch is turned off, steps SB2 to SB4
repeat.

Operation of Switch Processing Routine When this routine is executed through the above-described step SB2, the CPU 3 advances the processing to step SC1, initializes switch numbers for identifying various switches, and sets the first switch number to the first switch number. Get the status of the corresponding switch. Subsequently, in step SC2, it is determined whether or not the status acquisition has been completed for all the switches. When the status acquisition has been completed, the determination result is “YES”, and this routine is completed. "NO", and the process proceeds to the next Step SC3.

At step SC3, it is determined whether or not the obtained switch state is the ON state. Here, if it is in the off state, the determination result is “NO”, and step SC
4, the ON flag ONF and the NEW ON flag NOF are both set to "0" and both flags OF
Lower NF and NOF. The ON flag ONF mentioned here indicates a flag that is set to "1" when the ON state is maintained, and the NEW ON flag NOF is set to "1" when the ON state is newly turned on. Points to a flag.

On the other hand, if the obtained switch state is the ON state in step SC3, the judgment result is “Y
ES ", the flow advances to the next Step SC5, and it is determined whether the signal has been newly turned on or has been continuously turned on. That is, it is determined whether or not the NEW ON flag NOF is “1”. Where NE
If the W-on flag NOF is not "1", the determination result is "NO". In this case, the process proceeds to step SC6, where the on-state flag ONF and the new-on flag NOF are set so as to indicate that they are newly turned on. Are both set to "1" to set both flags.

On the other hand, when the NEW ON flag NOF is "1", that is, when the ON state is continued, the determination result of step SC5 is "YES", the process proceeds to step SC7, and the ON state is set. The ON flag ONF is set to "1" and the NEW ON flag NOF is set to "0" to indicate that the flag is maintained. When the flag is set to indicate the detected switch state in this way, the CPU 3 advances the processing to step SC8, increments the switch number and steps up to obtain the state of the next switch, and then returns to step SC8.
The process returns to C2, and thereafter, the above-described process is repeated to sequentially acquire the state of the switch corresponding to the stepped switch number.

Therefore, when the external connection cable is not plugged into the line-out terminal 11, the cable connection detection switch 11a maintains the off state, and the on flag ONF corresponding to the switch 11a is maintained.
And the NEW ON flag NOF are both "0". When an external connection cable is plugged into the line out terminal 11 and the cable connection detection switch 11a is newly turned on, both the ON flag ONF and the NEW ON flag NOF corresponding to the switch 11a are set to "1". Become. After being plugged into the line-out terminal 11, the ON state of the cable connection detection switch 11a continues, so that the ON flag ONF is "1" and the NEW ON flag NOF is "0".

Operation of Volume Position Detection Processing Routine When the above switch processing routine is completed, C
PU3 performs the processing in FIG. 12 through step SB3 (see FIG. 10).
And executes the volume position detection processing routine shown in FIG. First, in step SD1, NEW corresponding to the cable connection detection switch 11a is set.
It is determined whether the on-flag NOF is “1”, that is, whether the external connection cable is newly connected to the line-out terminal 11 or not. Here, when the external connection cable is newly connected to the line-out terminal 11, the NEW ON flag NOF is set to "1" in the above-described switch processing routine.
, The determination result is “YES”, and the process proceeds to step SD2.

In step SD2, a predetermined value other than the change range of the A / D converter 10c-1 is stored in a predetermined register of the RAM 5 as the volume operation position. Note that a predetermined value other than the change range of the A / D converter 10c-1 is R
The reason why the data is stored in the predetermined register of the AM 5 is that when the external connection cable is disconnected from the line-out terminal 11, the voltage data Dref output from the A / D converter 10c-1 at that time is used as the volume operation position. That's why. Then, in step SD3, the coefficients corresponding to the maximum volume operation position, that is, the above-described threshold level TH, compressor multiplication coefficient β, and compressor multiplication coefficient γ are set in correspondence with the cable connection to the line-out terminal 11. These are set in the corresponding registers in the DSP 8, respectively. As a result, according to the connection of the cable to the line-out terminal 11, the DSP 8 sets the characteristic at the time of the maximum sound volume which is almost flat.

On the other hand, if the NEW ON flag NOF is not "1", that is, if no external connection cable is connected to the line-out terminal 11, the result of the determination in step SD1 is "NO", and
The process proceeds to D4. In step SD4, it is determined whether the ON flag ONF corresponding to the cable connection detection switch 11a is "1", that is, whether the external connection cable is connected to the line-out terminal 11. When the external connection cable is connected, the ON flag ONF is “1”, and the determination result is “YES”.
In this case, when the cable is connected, the characteristic at the time of the maximum sound volume that is almost flat has already been set through steps SD2 and SD3 described above, so that this routine is completed without any processing.

On the other hand, when the external connection cable is not connected to the line-out terminal 11, the result of determination in steps SD1 and SD4 is "NO", and the process proceeds to step SD5. In step SD5, the voltage data Dre output from the A / D converter 10c-1 is output.
Get the volume operation position based on f. Next, when the process proceeds to step SD6, the CPU 3 determines whether the volume operation position acquired this time is the same as the volume operation position acquired last time, that is, whether the volume operation position has changed. If the volume operation position has not changed, the determination result is "YES". In this case, the threshold level TH, the compressor multiplication coefficient β and the compressor multiplication coefficient γ are newly set in the corresponding registers in the DSP 8, respectively. Since there is no need, this routine is completed without performing any processing.

On the other hand, if the volume operation position has changed, the result of the determination in step SD6 is "NO", the process proceeds to the next step SD7, and the volume operation position acquired this time is stored in a predetermined register of the RAM 5. . Then, thereafter, the process proceeds to step SD8, where the RAM 5
A threshold level TH, a compressor multiplication coefficient β, and a compressor multiplication coefficient γ corresponding to the current volume operation position stored in a predetermined register of
Each generated coefficient is set in a corresponding register in the DSP 8. Thus, as in the second embodiment, a compressor effect that provides optimum audibility characteristics according to the volume operation position is added.

As described above, according to the third embodiment, when the cable is connected to the line-out terminal 11, each coefficient corresponding to the maximum volume operation position is set in the DSP 8, and the characteristic at the time of the maximum volume close to flat is obtained. When the setting is made and the cable is not connected to the line-out terminal 11, a compressor effect that provides an optimal audibility characteristic according to the volume operation position is added, so that the manner in which the effect is added can be changed according to the acoustic environment used. It has become.

[0047]

According to the first aspect of the present invention, if the input waveform is smaller than the first level, it is output to the next stage as it is, and if it exceeds the first level, it is converted to a compressed waveform and converted to a compressed waveform. The magnitude is compared with a limit value corresponding to the maximum input level of the D / A converter. If the compression value is smaller than the limit value, the compression waveform is output to the next stage. If the compression value exceeds the limit value, the limit value is supplied to the next stage.
Therefore, even if the input waveform has a level that falls into the limiter area in the past, the level is compressed in this compressor area. Since the limit value is set high so as to match the maximum input level of the D / A converter, a sufficient dynamic range can be secured in the next stage D / A converter even for an input waveform having a small level. Therefore, the SN ratio can be improved. According to the second aspect of the present invention, when the input waveform exceeds the first level, the first level determination means adds the addition coefficient γ after multiplying the input waveform by the multiplication coefficient β. Thus, the output waveform is converted into a compressed waveform, so that the output waveform distortion can be avoided. According to the third and fourth aspects of the present invention, the first level is made different according to the operation amount of the volume operator for adjusting the level of the input waveform or the volume output. The dynamic range can be secured, and the waveform distortion can be suppressed as much as possible. According to the invention described in claim 5, since the multiplication coefficient β and the addition coefficient γ used when converting the input waveform into the compressed waveform are made different depending on the level of the input waveform, various and optimal compressed waveforms are obtained. Can be generated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a first embodiment according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a DSP 8 according to the first embodiment.

FIG. 3 is a diagram showing input / output characteristics of a DSP 8;

FIG. 4 is a block diagram showing an overall configuration of a second embodiment.

FIG. 5 is a block diagram showing a configuration of a volume circuit 10b and a volume position detection circuit 10c.

FIG. 6 is a block diagram illustrating a configuration of a DSP 8 according to a second embodiment.

FIG. 7 is a flowchart showing an operation of a volume position detection processing routine.

FIG. 8 is a diagram for explaining input / output characteristics.

FIG. 9 is a block diagram showing the overall configuration of the third embodiment.

FIG. 10 is a flowchart showing an operation of a main routine.

FIG. 11 is a flowchart illustrating an operation of a switch processing routine.

FIG. 12 is a flowchart illustrating an operation of a volume position detection processing routine.

FIG. 13 is a diagram for explaining a conventional example.

FIG. 14 is a diagram for explaining a conventional example.

[Explanation of symbols]

 8 DSP 20 Output Level Register 21 Multiplier 22 Threshold Level Judgment Circuit 23 Threshold Level Register 24 Multiplier 25 Compressor Multiplication Coefficient 26 Adder 27 Compressor Addition Coefficient 28 Limit Level Judgment Circuit 29 Limit Value Register 30 Selector

Claims (5)

[Claims] When a level of an input waveform supplied from a preceding stage exceeds a maximum input level of a D / A converter of a next stage, the level of the input waveform is replaced with a limit value corresponding to the maximum input level. In the effect adding apparatus that suppresses waveform distortion, it is determined whether the input waveform has exceeded a first level,
If the input level is lower than the first level, the input waveform is output to the next stage as it is, while if the input level is higher than the first level, the input waveform is converted to a compressed waveform. It is determined whether or not the compressed waveform converted by the first level determining means has exceeded the limit value. If the compressed waveform is smaller than the limit value, the compressed waveform is output to the next stage. And a second level determining means for supplying the limit value to the next stage. 2. When the input waveform exceeds the first level, the first level determination means multiplies the input waveform by a multiplication factor β and adds an addition coefficient γ to convert the input waveform into a compressed waveform. The effect adding device according to claim 1, wherein 3. The effect adding apparatus according to claim 1, wherein said first level determining means changes the first level according to the level of the input waveform. 4. The effect adding apparatus according to claim 1, wherein said first level determining means changes the first level in accordance with an operation amount of a volume operator for adjusting a volume output. 5. The apparatus according to claim 1, wherein the first level determination means changes a multiplication coefficient β and an addition coefficient γ used when converting the input waveform into a compressed waveform according to the level of the input waveform. Item 2. The effect adding device according to Item 1.