JPH0519767A - Musical tone synthesis device - Google Patents

Abstract

PURPOSE:To provide the musical tone synthesis device of simple circuit constitution by solving the problem point that waveform data needs to be read out twice so as to calculate one waveform to be outputted when pitch control is performed by interpolating the waveform, and also reducing an arithmetic load. CONSTITUTION:This musical sound synthesis device consists of an address generator 51 which outputs an address consisting of an address integer part Ai and an address decimal part Af corresponding to the pitch of a musical instrument to be outputted, a waveform memory 11 stored with data to be read out according to the address integer part Ai, a decoder 12 which divides the data outputted from the waveform memory 11 into waveform data P and difference data A, a multiplier 56 which multiplies the difference data D by the address decimal part Af, and an adder 57 which adds the multiplication output and waveform data P together. In this constitution, the data are read out of the waveform memory only once to find an interpolation value for the musical tone waveform corresponding to the pitch of the musical instrument to be outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a musical tone synthesizer for pitch control in a so-called electronic musical instrument by interpolating a waveform.

[0002]

2. Description of the Related Art In recent musical tone synthesizers, as a method for obtaining a musical tone waveform of a pitch to be output, a method of only skipping the waveform data stored in a waveform memory or a method of skipping after reading the waveform data is performed. , There is a method of obtaining by interpolating between waveform data.

As a conventional musical sound synthesizer, for example, Japanese Patent Publication No. 56-52317 and Japanese Patent Publication No. 53-30015.
It is shown in the publication.

FIG. 3 shows the configuration of a conventional tone synthesizer.
The explanation will be given. Here, an example is shown in which the waveform data stored in the waveform memory is linearly interpolated in order to obtain a musical tone waveform having a desired pitch.

In FIG. 3, 31 is an address integer part Ai.
Is an address generator that outputs an address formed from the address fractional part Af. An adder 32 increments the address integer part Ai by 1. Waveform memories 33 and 34 store the same waveform data.
Reference numeral 35 is a subtractor, which performs subtraction between the waveform data output from the waveform memories 33 and 34. 36 is a multiplier, and subtractor 3
The output of 5 is multiplied by the address fractional part Af. 37
Is an adder that adds the waveform data output from the waveform memory 33 and the output from the multiplier 36.

The operation of the tone synthesizer having the above arrangement will be described below.

First, when the pitch information of the musical instrument to be output is input to the address generator 31, the address formed by the address integer part Ai and the address decimal part Af is output.
Here, the pitch information input to the address generator 31 is
It is determined based on the pitch of the musical instrument to be output, the pitch F [Hz], 1 stored in the waveform memory
When the number of samples of the periodic waveform is WS [sample] and the predetermined timing, that is, the sampling frequency is Fs [Hz], the pitch information S is represented by (Equation 1).

[0008]

[Equation 1]

Here, the configuration of the address generator 31 is shown in FIG.
Shown in. In FIG. 4, 41 is an adder and 42 is a register. The register 42 stores an address, which has 20 bits. Further, when the number of samples WS of one cycle waveform stored in the waveform memory is 1024,
As shown in FIG. 5, the address integer part Ai has 10 bits, and thus the address fraction part Af has 10 bits.

The operation of the address integer part Ai when the sampling frequency Fs is 32 KHz will be described below.

When the pitch information S is "1", the pitch information "1" is added to the contents of the register 42 for each sampling frequency by the adder 41. Therefore, the address integer part Ai is from address 0 to 1023. Stored waveform data 1024
The points will be read from the waveform memory 33. Since the address integer part Ai has 10 bits, the value of the address integer part Ai starts again from the address 0 when the value exceeds the address 1023, so that 1024 points of the waveform data stored in the waveform memory 33 are repeatedly output. It will be. The pitch output at this time is 31.25 Hz because it is obtained by transforming (Equation 1).

Similarly, when the pitch information S is "2",
A sound with a pitch of 62.5 Hz is obtained. When the pitch information S is "1" and "2", there is a one-octave relationship, and in order to form another pitch within the one-octave,
The pitch information S will take a decimal value. The pitch information S has an integer part of 2 bits and a decimal part of 10 bits.
If takes a value of 1-2, then 31.25Hz-62.5
It is possible to form sounds with pitches in the octave of Hz.

When the pitch information S is "1.5", the waveform data output from the waveform memory 33 as the waveform data of the first point is the address obtained by rounding the address 1 or the address 1.5. If the waveform data stored in 2 is output, the output waveform will be distorted. Therefore, the distortion can be reduced by calculating the waveform data corresponding to the address 1.5. The operation of linearly interpolating such an operation will be described below. In the waveform memory 34, the number of samples of one cycle waveform is 1024,
It is the same as the waveform memory 33.

The waveform data of the waveform memory 33 is sent out corresponding to the address integer part Ai, while the waveform of the waveform memory 34 corresponding to the address integer part (Ai + 1) incremented by 1 in the adder 32. Data is sent out. One word of the data stored in the waveform memories 33 and 34 has 16 bits. The subtracter 35 obtains the difference between the waveform data output from the waveform memories 33 and 34. Output of subtractor 35 (16 bits)
And the address fraction part Af (10 bits)
Is multiplied by. The output (16 bits) of the multiplier 36 is added to the waveform data (16 bits) output from the waveform memory 33 in the adder 57. The output (16 bits) of the adder 37 is used as a tone wave interpolation value.

The waveform memories 33 and 34 may be one memory, and the waveform data may be read twice from one memory.

[0016]

However, the above-mentioned conventional configuration has a problem that it is necessary to read out two waveform data in order to obtain one interpolation value corresponding to the pitch of the musical instrument to be output. Was there.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems, and to provide a musical tone synthesizer having a reduced circuit load and a simpler circuit configuration.

[0018]

In order to achieve this object, the tone synthesizer of the present invention outputs an address formed of an address integer part and an address decimal part corresponding to the pitch of a musical instrument to be output. An address generator, a waveform memory in which data read out based on an address integer part is stored, a decoder for dividing data output from the waveform memory into waveform data and difference data, and difference data and an address fractional part. It is composed of a multiplier for multiplication and an adder for adding the multiplication result and the waveform data.

[0019]

According to the present invention, the address integer part and the address decimal part are output according to the pitch of the musical instrument desired to be output by the address generator, but the data read based on the address integer part is The decoder divides the waveform data and the difference data, then multiplies the decimal address and the difference data, and adds the multiplication result and the waveform data to obtain a tone waveform interpolation value.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the construction of a musical sound synthesizing apparatus according to an embodiment of the present invention. In FIG. 1, 11 is a waveform memory, 12 is a decoder, 13 is a multiplier, and 14 is an adder. Incidentally, 31 is an address generator, which has the same configuration as the conventional example.

The operation of the musical tone synthesizing apparatus of this embodiment having the above configuration will be described below.

The operation of the address generator 31 is similar to that of the conventional example. When the pitch information (12 bits) of the musical instrument to be output to the address generator 31 is entered, the address integer part Ai (10
Bit) and the address fractional part Af (10 bits) are divided and output, and the address integer part Ai is the waveform memory 11
Then, the address fraction part Af is sent to the multiplier 13.

When the address integer part Ai is input to the waveform memory 11, the corresponding data in the waveform memory is sent from the waveform memory 11. Each word of data stored in the waveform memory 11 is composed of a combination of waveform data and difference data of adjacent waveform data as shown in FIG.

Generally, as the number of bits of waveform data,
As can be seen from the standards of digital audio related technologies such as digital audio tape recorders and compact disc players, 16 bits are often used, and 16 bits have been described in the description of the conventional example. The number of bits of 16 bits does not always correspond to human hearing, and it is because one data of the semiconductor memory used as the waveform memory, that is, a unit forming a word is a power of two. It is also possible to reduce the number. Further, assuming that the number of bits used for waveform data is Np and the number of bits used for difference data between adjacent waveform data is Nd, it can be expected that the relationship for a tone signal is Np> Nd. Therefore,
For example, as shown in FIG. 2, it is possible to allocate waveform data of 10 bits and difference data of 6 bits in the structure of 1 word of 16 bits.

The data output from the waveform memory 11 (1
The 6-bit data is input to the decoder 12 to be divided into waveform data P (10-bit) and difference data Δ (6 bits).

When the difference data Δ (6 bits) and the address fractional part Af (10 bits) are input to the multiplier 13,
Although the multiplication of Δ and Af is performed, the obtained multiplication result is added to the waveform data P (10 bits), so only the integral part 6 bits of the multiplication result need be validated. Therefore,
The multiplier 13 only needs to have a calculation accuracy of about 6 × 7 bits. Then, the output (6 bits) of the multiplier 13 and the waveform data P (10 bits) are added by the adder 14. The output (10 bits) of the adder 14 is an interpolation value according to the pitch of the musical instrument desired to be output.

Although the bits of 1 word of the waveform data and the difference data are combined here as 10 bits and 6 bits, they may be combined as 9 bits and 7 bits, for example.

As described above, according to the present embodiment, one word is formed by combining one word of data in the waveform memory with 10 bits of waveform data and 6 bits of difference data between adjacent waveform data. Bits can be used efficiently.

In addition, the calculation accuracy of the multiplier is set to the difference data (6
Since it can be set according to the number of bits), the configuration of the multiplier can be simplified.

[0031]

As described above, according to the present invention, an address generator for outputting an address formed from an address integer part and an address decimal part corresponding to a pitch of an instrument to be output, and a read based on the address integer part. Stored in the waveform memory, a decoder that divides the data output from the waveform memory into waveform data and difference data, a multiplier that multiplies the difference data and the address fractional part, and the multiplication result and the waveform data. 1 by adding an adder for adding
It is possible to obtain the musical tone waveform interpolation value corresponding to the pitch of the musical instrument to be output by reading the data from one waveform memory only once, reduce the calculation load, and simplify the circuit configuration. It has an excellent effect in its practical use.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a musical sound synthesizer in one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a bit configuration of one word of waveform data stored in a waveform memory according to the embodiment.

FIG. 3 is a block diagram showing the configuration of a conventional musical sound synthesizer.

FIG. 4 is a block diagram showing a configuration of an address generator in the conventional example.

FIG. 5 is a schematic diagram showing a bit configuration of an address in the conventional example.

[Explanation of symbols]

11 Waveform memory 12 decoder 13 Multiplier 14 adder 31 Address generator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiro Nakanishi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (2)

[Claims] 1. An address generator for outputting an address formed of an address integer part and an address decimal part corresponding to a pitch of an instrument to be output, and data sent out corresponding to the address integer part are stored. Waveform memory, a decoder that divides the data output from the waveform memory into waveform data and difference data, a multiplier that multiplies the difference data and the address fractional part, an output of the multiplier and the waveform A tone synthesizer comprising an adder for adding data and data. 2. The musical tone synthesizing apparatus according to claim 1, wherein one word of the data stored in the waveform memory is stored by combining the waveform data and the difference data of adjacent waveform data.