JPH0652476B2 - Waveform generator for electronic musical instruments - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a waveform generator of an electronic musical instrument using a harmonic overtone synthesis method based on Fourier series.

[Conventional technology]

Conventionally, in the waveform calculation using the harmonic overtone synthesizing method based on the Fourier series, the frequency direction data is calculated by the number of overtones, and the sum is set as 1 word of the sample point in the time direction.
The procedure is to calculate the number of words equal to or more than (overtone number).

The formula showing the specific calculation procedure is Expanding equation (1), Here, m: number of words m2n n: number of overtones h _n : harmonic coefficient of n overtones S _{(m, n)} : sine table memory value corresponding to m words / n overtones W _m : m word value And the calculation amount becomes m × n times.

FIG. 3 is a general explanatory diagram of this type of overtone synthesis system.

That is, in the frequency direction and the coordinate of the amplitude, double from the basic, 3
.., n times harmonic overtone values are shown, and the time change of the waveform is processed by the waveform generator by the sample values 1 word, 2 words, 3 words ... m words in the time axis direction.

[Problems to be solved by the invention]

The values of m and n are determined by the number of overtones contained in the desired musical tone signal and the sampling theorem, and generally m = 256, n = 1.
A sound quality of about 28 will be satisfactory.

The calculation amount at this time is 256 × 128 = 32768 times, and it takes time to realize this at the current element speed, so parallel processing is required.

In order to speed up this processing time, by proposing Japanese Patent Publication No. 52-10373, a technique is disclosed in which the number of harmonic overtones in the frequency direction is divided into a plurality of groups, and each group is operated in parallel to reduce the operation time to a plurality of times. is doing.

However, in the parallel operation of this method, it is necessary to add the number of divisions before the accumulator. For example, when the harmonic overtones are divided into high order, middle order, and low order, and the multiplication values of these and the sine table memory are S _A , S _B , and S _C , respectively, S _A + S _B + S _C is obtained. There is no choice but to take the form of accumulating later.

On the other hand, the present inventor divides the number of words in the time direction into a plurality of groups in parallel processing and performs a parallel operation, the accumulator only accumulates up to the nth order in the word, and the word is selected by the selector. I focused on the fact that it can be done and is greatly simplified.

An object of the present invention is to provide a waveform generator for an electronic musical instrument in which the number of words in the time direction is divided into a plurality of groups for parallel calculation.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention uses a harmonic overtone synthesizing method based on Fourier series, has harmonic overtones up to the n-th order in the frequency direction, and shows sampling points in the time direction.
A waveform generator of an electronic musical instrument for generating a waveform of a plurality of words, a means for instructing to divide the m words into a plurality of groups, a harmonic coefficient memory for storing a harmonic coefficient corresponding to each harmonic order, A sine function memory is included, and in accordance with an instruction from the division instruction means, the harmonic coefficients up to the nth order of the words divided into the plurality of groups are multiplied by a sine function,
A plurality of word waveform data generators for accumulating the multiplication results and sequentially outputting an output waveform for each word, and means for selecting and synthesizing the word waveforms from the plurality of word waveform data generators are provided. It is characterized by.

[Work]

Since m words are divided into a plurality of words and input in parallel to the plurality of word generators to calculate the harmonic overtones up to the nth order of the words in parallel, a high-speed operation becomes possible and only by selecting the word. Since it can be processed, there is an advantage that the configuration is simplified.

〔Example〕

FIG. 1 is an explanatory diagram of the configuration of the embodiment of the present invention. In the figure, the word generators 100 and 200 are devices having the same function, and the word control circuit 2 selects an even word by branching the word input into two and inputting “H” to the word control terminal 1. An even word is sequentially generated in the generator 3, while an odd word is selected by the word control circuit 12 by inputting "L" to the word control terminal 11, and the address generator 13 sequentially generates the odd word. The configuration of the word generator 100 will be continuously described below.

The sign table memory 5 is read according to the address of the even word generated by the address generator 3. On the other hand, the system clock is input to the counter 4, and the timing control circuit 6
The harmonic coefficient memory 7 is read according to the timing. Then, the multiplier 8 multiplies the sine table memory value by the address and the harmonic coefficient memory value from the sine table memory 5.

Here, the sine table memory value multiplied by the harmonic coefficient in the word generator 100 is an element of an even row of the sine table memory values S _{(1,1) to} S _{(m, n)} shown in the equation (1). And the harmonic coefficient memory values correspond to h ₁ to h _n . The accumulator 9 repeats addition of the harmonic overtones n times. The result is an even word value of W ₂ , W _4, ...
Sequentially stored in 10.

On the other hand, even the word generator 200 device has an address generator 1
In the same manner as the word generator 100, the odd word values W ₁ , W _3, ... Are generated and sequentially stored in the latch 20 in accordance with the sequential generation of the addresses of the 3 odd words.

The even word output value from the word generator 100 is input to the A terminal of the select circuit 21, and the odd word output value from the word generator 200 is input to the B terminal of the select circuit 21. By inputting control information to the select terminal S of the select circuit 21, input A and B information are output alternately.

FIGS. 2 (a) to 2 (e) are explanatory views showing the operation time of one word of the present invention in comparison with the conventional example.

The figure (a) shows that the calculation time of 1 word W ₁ by the conventional method is T
Then, in the present invention, the odd-numbered word output W ₁ of FIG.
Although the operation time T of the even word output W ₂ in FIG. 7C is the same, the parallel operation and the sequential selection by the select circuit 21 correspond to the select terminal input signal in FIG. The output word information of the select circuit shown in FIG. 7E is equivalently obtained.

In the above, the group is divided into an odd word and an even word, but it is also possible to carry out parallel operation by multi-division and re-align and output by the select circuit by adding a flag to the input word and dividing it into a plurality.

〔The invention's effect〕

As described above, according to the present invention, similar high-speed processing can be obtained by dividing the word in the time direction instead of the conventional division of the overtone group in the frequency direction. Moreover, its composition is significantly reduced. That is, addition between harmonic overtone groups divided by the conventional method is performed by an adder and accumulated to obtain word information. In that case, the operation procedure is set in advance,
In order to control this at high speed, a combination of many gates is required.

On the other hand, in the present invention, only one accumulator is needed in the word, and the word order is controlled by the selector order as described above, and since this control is simple, external control by the CPU or the like is sufficient. The configuration is greatly simplified.

The selector circuit usually has 1/4 to 1/5 the number of gates as compared with an adder having the same function, and has a great advantage that external control can be used.

Since the reduction of the adder and the number of gates is very effective for simplifying the LSI, the application of the present invention enables high-speed processing.
It has great advantages in satisfying both miniaturization of LSI and improving performance and reducing cost.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the structure of an embodiment of the present invention, FIG. 2 is a diagram for explaining the word operation time, and FIG. 3 is a diagram for explaining the harmonic overtone synthesis method. In the figure, 1, 2, 11, and 12 are words. Control terminal, 3,13
Is an address generator, 4 is a counter, 5 is a sine table memory, 6 is a timing control circuit, 7 is a harmonic coefficient memory, 8 is a multiplier, 9 is an accumulator, 10 and 20 are latches, 21 is a select circuit, 100 and 200 are word generators.

Claims (1)

[Claims] 1. A waveform generation for an electronic musical instrument using a harmonic series synthesis method based on a Fourier series, having harmonic harmonics up to the nth order in the frequency direction and generating a waveform of m words indicating sample points in the time direction. And a means for instructing the m words to be divided into a plurality of groups, and a harmonic coefficient memory and a sine function memory for storing the harmonic coefficients corresponding to each harmonic order. And multiplying the harmonic coefficients up to the nth order of the words divided into the plurality of groups with a sine function,
A plurality of word waveform data generators for accumulating the multiplication results and sequentially outputting an output waveform for each word, and means for selecting and synthesizing the word waveforms from the plurality of word waveform data generators are provided. Waveform generator for electronic musical instruments characterized by.