JPH0258638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an envelope control device suitable for multiplying a sound source waveform and an envelope waveform, such as in an electronic musical instrument.

Conventional structure and its problems Conventionally, in the field of electronic musical instruments, when creating a musical sound waveform with an envelope by multiplying a sound source waveform and an envelope waveform, a digital multiplier of 12 bits x 12 bits or more has been used as a digital multiplier. If one with a width was not used, when the envelope was attenuated, noise due to digitization errors would occur, which would be audible to the ears. Furthermore, the DA converter required a 14-bit to 16-bit one, and the envelope waveform also required a resolution of 14 to 16 bits. As an envelope waveform, instead of using a 16-bit linear code, a binary floating-point representation is shown in Japanese Patent Application Laid-Open No. 54-1609.
For multiplication with the sound source waveform, analog multipliers are used, or linear parallel multipliers such as 16 bits x 16 bits are used as usual. It was something to do.

Furthermore, Japanese Patent Application Laid-Open No. 52-27234 shows an example of floatingly displaying harmonic coefficients, but there is no application to envelopes.

Purpose of the Invention The present invention provides an envelope control device that can perform multiplication between a waveform and an envelope using a multiplier smaller than conventional ones. The present invention aims to provide an envelope control device in which envelope data can be easily generated and a multiplier can be easily constructed by using a reduction function.

Composition of the Invention The envelope control device of the present invention is a device that receives waveform data supplied from a waveform generator and controls the amplitude of the waveform data using the envelope data, and includes an envelope generator, a multiplier, and a shifter. , the envelope generator generates envelope data in the form of a decreasing function consisting of a mantissa part and an exponent part, and inputs the lower code forming the mantissa part and the waveform data to the multiplier. Adding 1 as an additional bit to the upper part of the lower code forming the mantissa, adding the output of the multiplier to the shifter, and shifting the shifter according to the upper code forming the exponent, the attenuation envelope is created. This feature is characterized in that it is given.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a block diagram of an embodiment of the present invention.
Reference numeral 1 denotes a waveform generator that generates waveform data Wi of a musical sound source, which samples one waveform of a musical sound and repeatedly generates electronic data. 3 is a waveform data register. 2 is an envelope generator that generates envelope data Ei. The envelope waveform Ei has a structure that can be separated into lower Pi and upper Qi. 4 is a register for the lower code Pi, and 5 is a register for the upper code Qi. The waveform data Wi and the lower code Pi are added to a multiplier 6. At this time, "1" is added above the most significant bit of the lower code Pi. Therefore, when Pi is 8 bits, multiplier 6 is given 9 bits of data. Waveform data Wi is input to the other input of the multiplier 6. This data will consist of 10 bits. For the output of the multiplier 6, we will use the upper 12 bits out of 10+9=19 bits. This product code Wi is input to the shifter 8. The shifter shifts the bits of the input code and outputs the result.The upper or lower bits to be shifted are specified by the upper code Qi of the envelope data.

Here, assume that the envelope data is represented by {q ₃ q ₂ q ₁ q ₀ p ₇ p ₆ p ₅ p ₄ p ₃ p ₂ p ₁ p ₀ }. {p ₇ to _{p 0} } represents the mantissa part, and {q ₃ to _{q 0} } represents the exponent part.

The magnitude of Ei is expressed as a binary floating value, such as Ei={ ₇ 〓 ^i=o Pi2 ⁱ }2 ₃ 〓 ^j=o qj2 ^j . If "1" is added to the top of Pi, Ei becomes essentially E^i={2 ⁸ + ₇ 〓 ^i=o Pi2 ^j }2 ₃ 〓 ^j=o qj2 ^j . The value inside { } is expressed as P^i.

On the other hand, if Wi is 10 bits, Wi = −w ₉ 2 ⁹ + ₈ 〓 ^i=o wi2 ⁱ . However, this uses two's complement representation of negative numbers.

Wi × E^i is Wi × E^i = Wi × P^i × 2 ₃ 〓 ^j=o qj2 ^j = WPi−2 ₃ 〓 ^j=o qj2 ^j The WPi term is the 10-bit × 9-bit multiplier 6 Calculate with.

2 ₃ 〓 ^j=o qj2 ^{The j} term corresponds to performing 16 shifts depending on the upper code Qi, where Qi = (0000) is no shift, Qi = (0001) is a 1-bit shift to the higher order, and Qi = (0010) shifts 2 bits to the upper position, Qi
= (1111) shifts 15 bits to the upper position. Therefore, if WPi is 12 bits, the output of shifter 8 will have a width of 12+15=27 bits, but only the upper 16 bits will be taken out and input to DA converter 9. In this way, since WPi is 12 bits, the S/N against quantization noise is approximately 72 dB, and the dynamic range is 96 dB, corresponding to 16 bits, to obtain sufficiently high quality sound. be able to.

FIG. 2 is another embodiment of the invention. Differences from the embodiment shown in FIG. 1 will be described. The digital shifter 8 is omitted, and instead, an attenuator 10 corresponding to an analog shifter is provided on the output side of the DA converter 9, and the degree of attenuation AT is switched by the upper code Qi. The degree of attenuation AT is expressed as AT=K2 ₃ 〓 ^j=o qj2 ^j . K is a constant. This arrangement is more advantageous than the embodiment shown in FIG. 1, since the DA converter 9 can be of 12-bit precision.

A in FIG. 3 is an example of P^i and Qi. It shows the attenuation process of the envelope, the so-called release. Since Pi changes from 255 to 0, P^i
varies from 511 to 256. Figure 4A shows Qi,
This is the format of Pi and P^i.

FIG. 5 is another example related to the present invention. The waveform data Wi and the lower code Pi are added to the multiplier 6, and the output thereof is according to the upper code Qi.
It is shifted by shifter 8. The waveform data Wi is also shifted by the shifter 18. shifter 8 and 1
The outputs of 8 are applied to a subtractor 20 where their difference is taken. The output of the subtracter 20 is input to a DA converter.

In FIG. 6, the order of the shifters 8, 9 and subtracter 20 of the embodiment of FIG. 5 is reversed to reduce the number of shifters to one, and the bit width to be handled by the subtracter 20 is reduced.

In the embodiments shown in FIGS. 5 and 6, the envelope data Ei is generated so that it becomes an increasing function in its attenuation process. Figure 3B
Example values are shown below. FIG. 4B shows the format of envelope data.

FIG. 7 is an example of an analog shifter. In FIG. 7, the resistors are a well-known R-2R type ladder network. A switch is provided on the resistor side of 2R to select the flow of current into the +input and -input of the operational amplifier 31. R _F is a feedback resistor that determines the gain, and an inflow current flows into the - input.
30 is a decoder which selects and switches one of the 16 switches to the -input side according to the upper code Qi. With switch S ₀ , there is no attenuation, with switch S ₁ -6 dB, with switch S ₂ -12 dB, and so on. For switch Si, it is -6×i dB. For S ₁₅ , which has the largest attenuation, Qi = (1111). In this case, the switch may be fixed to the + input side so that the input is cut off.

In the example in Figure 7, 16 levels are generated, but
More than enough for normal sounds. Qi may be 3 bits. Even when Qi is set to 4 bits,
Instead of using all 16 bits, only about 10 to 12 bits may be used.

In the case of the code shown in FIG. 3B, the correspondence between the decoder and the switch shown in FIG. 7 may be reversed.

In the embodiments shown in Figs. 1 and 2, Pi and Qi decrease until Qi = (0000), and then when Pi becomes smaller than (00000000), Qi = (1111 ) and BORROW occurs, but in this case, Qi = (1111) or
By detecting BORROW, supplying Q^i = (0000) to the shifter instead of Qi, and switching the higher-order additional bit of Pi from "1" to "0", P^i As, the normal range Qi = (0001)
~ (1110), P^i = 511 ~ 256, and Qi =
(0000), P^i can take values from 511 to 0.

In the above embodiment, a case has been described in which the product of waveform data and envelope data is subjected to DA conversion as it is.

FIG. 8 shows an example in which a difference value regarding i of Wi×Ei is output.

The waveform data Wi and P^i obtained by adding "1" to the lower order data Pi are added to the multiplier 60 to obtain the product Wi. Since the product WPi is applied to the latch 40, the previous product WPi _-1 is held at time i. The upper code Qi of the envelope data Ei is latch 4.
2, a comparator 43, and an attenuator 10, which is an analog shifter. The latch 42 has 1
The previous higher order code Q _i-1 is held and supplied to the comparator 43. The comparator 43 compares Qi and Q _i-1 and outputs an output based on the following conditions.

Qi>Q _i-1 :a Qi=Q _i-1 :b Qi<Q _i-1 :c The output WP _i-1 of the latch 40 is supplied to the shifter 41. The shifter 41 shifts WP _i-1 up or down by 1 bit, and can be constructed from a combination of an AND gate and an AO gate. The signal entering input terminal A is shifted one bit lower. Input terminal B
The input signal is output as is. The signal entering input terminal C is shifted one bit upwards.
Therefore, input WP _i-1 will be converted as follows.

a: Select A: 1/2WP _i-1 b: Select B: WP _i-1 c: Select C: 2WP _i-1 The output of the shifter 41 and the product are supplied to the subtracter 61, and the difference is Calculated. The differential output is as follows.

When Qi＞Q _i-1 △WPi=1/2WP _i-1 −WPi When Qi=Q _i -1 △WPi=WP _i-1 −WPi When Qi＜Q _i-1 WPi=2WP _i-1 -WPi The output △WPi of the subtracter 61 passes through the DA converter 9 and the attenuator 10, and then the capacitor C and the operational amplifier 11.
is added to an integrator consisting of . The difference value △WPi is
Since it corresponds to the differential value of WPi, the output of the integrator is
The waveform is the product of Wi and Ei.

The comparator 43 and shifter 41 use the upper code Qi
and Q _i-1 are different. In other words, P^i and P^ _i-1 when the ranges of the index display part of the envelope data are different.
This is to correct the difference between the two and obtain the correct difference value △WPi.

Since △WPi is the difference between WPi and WP _i-1 ,
Even with WPi and 12 bits, the word width of △WPi is usually small. Therefore, in this embodiment for calculating the difference, the word width of the DA converter 9 is set to 12
It can be less than 1 bit.

FIG. 9 shows another example of the DA converter 9 used in FIG. 8. The difference value △WPi is shifter 70,
The signal is outputted via a DA converter 71 and an analog shifter 72, and applied to the attenuator 10 in FIG.
The shifter 70 and shifter 72 are supplied with the upper 3 bits of the 7-bit data of ΔWPi to control the shift operation. When the upper 3 bits of △WPi are "0" as shown in FIG. 10A, the lower 4 bits are directly applied to the DA converter 71, and the shifter 72 is
The gain is 1/4, or -12dB. As shown in Figure 10B, when the upper 3 bits are “001”,
The middle 4 bits are output by the shift operation of the shifter 70, and are applied to the DA converter 71, so that the shifter 72 has a gain of 1/2, that is, -6 dB. As shown in Figure 10C, the upper two bits of △WPi are “01”
In this case, the upper 4 bits excluding the MSB (most significant bit) are applied to the DA converter 71, and the shifter 72 has an attenuation of 0 dB.

The above explanation applies when △WPi is positive. △WPi
FIG. 11 shows a case in which the two's complement representation is performed when is negative. In FIG. 11, when the upper 3 bits are "11", the lower 4 bits shown in FIG. 11D are directly applied to the DA converter 71. shifter 72
is -2dB. When the upper 3 bits are "110", the middle 4 bits in FIG. 11E are transferred to the shifter 70.
outputs. At this time, the shifter 72 becomes -6 dB. When the upper two bits are "10", the four bits shown in FIG. 11F are output from the shifter 70.
At this time, the shifter 12 becomes 0 dB. Of the △WPi7 bits, the MSB is inverted and sent to the DA converter 71.
Given on MSB input. In this way, this complement representation is converted to an offset binary representation.

The waveform generator 1 outputs a digital sound source waveform, and may be one that sequentially reads out data written in a storage device. envelope generator 2
, an up-down counter or the like is used.

It goes without saying that even when using increasing function type envelope data Ei as in the embodiments of FIGS. 5 and 6, it is possible to adopt a configuration that calculates the difference value as shown in FIG.

Effects of the Invention As is clear from the above description, the present invention is a device that receives waveform data supplied from a waveform generator as input and controls the amplitude of the waveform data using envelope data. The envelope generator generates envelope data in the form of a decreasing function consisting of a mantissa part and an exponent part, and inputs the lower code forming the mantissa part and the waveform data to the multiplier. At this time, 1 is added as an additional bit to the upper part of the lower code forming the mantissa, the output of the multiplier is added to the shifter, and the shifter is shifted according to the upper code forming the exponent. By adding an attenuation envelope, an output waveform obtained by multiplying the waveform and the envelope is obtained, which has the effect that the multiplier can be made smaller than the conventional envelope control device. It will be done. Furthermore, since an attenuation function is used as the envelope data, generating the envelope data is easy, and simply adding additional bits to the upper bits of the mantissa simplifies multiplication and shift processing.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a block diagram of the second embodiment of the present invention, FIG. 3 is a diagram showing an example of envelope data used in each of the above embodiments, FIG. 4 is a diagram showing an example of the format of envelope data, FIG. FIG. 6 is a block diagram of an envelope control device related to the present invention, FIG. 7 is a circuit diagram showing an example of a shifter used in each of the above embodiments, and FIG. 8 is a block diagram of an embodiment configured to output a difference value. 9 is a block diagram when the DA converter in the embodiment shown in FIG.
It is a figure which shows the code table of a figure. 1... Waveform generator, 2... Envelope generator, 6... Multiplier, 8... Shifter, 9... DA converter, 10... Analog shifter.

Claims (1)

[Claims] 1 A device that receives waveform data supplied from a waveform generator as input and controls the amplitude of the waveform data using envelope data, and includes an envelope generator, a multiplier, and a shifter, and the envelope generator has a mantissa and an exponent. The lower code that forms the mantissa part and the waveform data are input to the multiplier, and when inputting, the upper code of the lower code that forms the mantissa part is input to the multiplier. Add 1 as an additional bit to
An envelope control device for applying an attenuation envelope by adding the output of the multiplier to the shifter and shifting the shifter in accordance with an upper code forming the exponent part.