JPH09269774A - Musical sound generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the load on a CPU in a software sound source. SOLUTION: Musical sound waveform data corresponding to a MIDI signal to be inputted are arithmetically generated by using waveform data and tone data stored in a hard disk device 13. The generated musical sound waveform data are outputted to a codec 19 and in the codec 19, the multiplying of envelopes and the multiplying of pan coefficients are executed and the waveform data are subjected to a D/A conversion every one sampling cycle to be outputted from a sound system 20 to the outside as a musical sound signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a musical tone generating device which generates a musical tone by calculation by a calculation processing device.

[0002]

2. Description of the Related Art Conventional tone generators are usually MIDI.
(Musical Instrument Digital Interface), a performance input section for inputting performance information from a keyboard or a sequencer, a sound source section for generating musical tone waveforms, a central processing unit (CPU) for controlling the sound source section in accordance with the input performance information And so on. Here, the CPU executes sound source driver processing such as channel assignment and parameter conversion in accordance with the input performance information, and supplies the converted parameters and the sound generation start instruction (note-on) to the channels assigned by the sound source unit. . Further, the tone generator generates a tone waveform based on the supplied parameters, and hardware such as an electronic circuit is employed as the tone generator. Therefore, the musical tone generating device becomes a dedicated device for generating musical tones, and it is necessary to prepare a dedicated musical tone generating device when generating musical tones.

Further, when a musical tone is generated in a general-purpose processing device such as a personal computer, a dedicated sound source device is added to the outside of the device, or a sound source chip for generating a musical tone waveform and a waveform for storing waveform data. R
OM, A / D conversion circuit, D / A conversion circuit, FI
A musical tone has been generated by connecting an expansion board, on which several IC chips are mounted, such as an encoding / decoding circuit (CODEC) chip including an FO buffer and an interface circuit, to the main body.

Furthermore, recently, the operation of the hardware sound source is replaced with a sound source process (software sound source) by a computer program, and the CPU executes the performance process and the sound source process, that is, a so-called software sound source. Is proposed. Here, the performance process is a process corresponding to the sound source driver process described above, and is a process of creating control information for controlling a generated musical tone based on input performance information such as MIDI. is there. The sound source processing is processing for generating waveform data of musical sounds based on the control information created in the performance processing. According to this tone generation method,
Without using a special tone generator or sound source board, C
In addition to the PU and software, it is possible to generate musical tones simply by providing a DA conversion chip.

In order to generate a musical tone, a sampling period, that is, a DAC (Digital Analog Converter) is used.
It is necessary to supply the DAC with the waveform samples calculated and generated at each conversion timing in
The calculation amount in U is very large. That is, the CPU has to execute a process of generating musical tone control information from the input performance information such as a MIDI event and a waveform generating process in order to arithmetically generate a musical tone.

For example, in the case of a waveform memory type sound source,
In this waveform generation process, the LFO is generated for each sound generation channel based on the tone control information generated from the performance information.
(Low Frequency Oscillator), filter EG, volume EG, and other waveform calculations are performed, waveform data is read from the corresponding waveform memory (waveform table), interpolation calculation is performed on the read waveform data, and the result is obtained. The waveform data is multiplied by various EG waveform samples to generate waveform data for the sound channel,
This is repeatedly executed for all sound generation channels to accumulate waveform sample data for each sound generation channel, thereby generating musical tone waveform data corresponding to one sampling timing.

[0007]

The above-described method of connecting the sound source board has a problem that the number of IC chips mounted on the sound source board is large and the cost for generating a musical sound is high. . In addition, the waveform data is the waveform R
It was stored in the OM, and the degree of freedom of the generated musical sound was poor. Further, the software sound source described above does not require special hardware to generate a musical tone, but it is necessary to generate waveform data to be output every DAC cycle by calculation, so that the tone waveform data is generated. There is a problem that the load of the CPU for calculating and generating is very large.

Therefore, an object of the present invention is to provide a musical tone generating apparatus which has a degree of freedom and has a comparatively small processing load on the CPU.

[0009]

In order to achieve the above object, a musical tone generating apparatus of the present invention generates musical tone waveform data by calculation by a calculation processing unit, and encodes and decodes the generated musical tone waveform data. In a tone generating apparatus for converting the signal into an analog signal by a digital-to-analog converter provided in an encoding circuit and outputting it to the outside, the encoding / decoding circuit performs a level multiplication process and a pan for the tone waveform data arithmetically generated by the arithmetic processing unit. It has means for executing coefficient multiplication processing. The encoding / decoding circuit includes at least one of an envelope generator and a pan coefficient generator.

In the musical tone generating apparatus of the present invention, since the musical tone is generated by the arithmetic processing, no special hardware for the sound source is required, and the volume control calculation for the musical tone generated by the calculation is performed by the code. Decoding circuit (COD
Since it is executed by hardware in EC), the CPU load for musical tone generation does not become too large.
Further, even in the conventional soft sound source, the CODEC for the D / A conversion is required, so that the provision of the hardware for the volume control operation in the CODEC does not cause an extra cost increase.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the musical tone generating apparatus of the present invention. In the figure, 10 is a central processing unit (CPU) that executes the generation of tone waveform samples and various application programs, 11 is a ROM that stores preset tone color data, and 12 is a program and data that are executed. A RAM used as a waveform table, various buffer areas and work areas, 13 is a hard disk device in which various waveform data, tone color data and various application programs are stored, and 14 is a CD storing various data and programs. -CD driving ROM
-ROM device, 15 is a MIDI interface for transmitting and receiving performance data and control signals to and from an externally connected performance device such as a MIDI keyboard, and 16 and 1
Reference numerals 7 are a keyboard and a display device, which are commonly used in personal computers.

Reference numeral 18 is a DMA control circuit (Direct Memory Access Controller) for reading the waveform sample data from the sample buffer area in the RAM 12 without passing through the CPU 10 and transferring it to the encoding / decoding circuit 19. In addition,
The DMA control circuit 18 can be omitted when the transfer rate of the bus is high. Reference numeral 19 denotes a coding / decoding circuit (CODEC) which executes a multiplication process of an amplitude envelope and a pan coefficient on the waveform sample data, converts the obtained musical tone waveform data into an analog musical tone signal, and outputs the analog musical tone signal to the sound system 20. ), And the details thereof will be described later. Reference numeral 20 is a sound system that amplifies the tone signal output from the CODEC 19 and externally outputs the signal. Reference numeral 21 interrupts the CPU 10 at predetermined time intervals, and
A timer that supplies a sampling clock to the DEC 19. Each of these constituent elements is connected to each other via a bus. The above configuration is equivalent to that of an ordinary personal computer or workstation, and the tone generation method of the present invention can be executed on them.

FIG. 2 shows the internal structure of the CODEC 19. In the figure, 30 is an interface circuit connected to the bus for exchanging various signals and data, 31 is an analog digital signal obtained by sampling a stereo external audio signal input from external input terminals LLINE and RLINE at a predetermined sampling frequency. Convert A
An A / D conversion circuit 32 is a first-in-first-out (FIFO) buffer for left and right channels for storing stereo external input data output from the A / D conversion circuit 31. The data stored in the FIFO buffer 32 is read by the CPU 10 through the interface circuit 30 and a predetermined process is performed.

Reference numeral 33 is a FIFO buffer for storing the waveform data calculated and generated by the CPU 10. In this example, the CPU 10 is configured to arithmetically generate musical tone waveform samples for 32 channels, and the FIFO buffer 33 is configured to be able to store 32 channels of musical tone waveform data.

Reference numeral 34 has a register for storing EG control data corresponding to each channel, generates a volume envelope signal AEG on the basis of the EG control data of each sounding channel supplied from the CPU 10, and outputs the AEG.
Volume parameter vol supplied from CPU10
Envelope generator EG, 35 that multiplies with and outputs volume control data is also CP for each channel.
A pan coefficient generator having a register for storing pan control data supplied from U10 and generating a pan coefficient based on the pan control data pan. Reference numeral 36 is a multiplier for multiplying the waveform data of each sound output channel output from the FIFO buffer 33 by volume control data corresponding to the sound output channel output from the EG 34. 37 is sequentially output from the multiplier 36. Is a pan multiplier for multiplying the tone waveform data corresponding to each channel by the pan coefficient corresponding to the channel output from the pan coefficient generator 35.

Reference numeral 38 denotes a channel accumulator for sequentially adding and summing the musical tone waveform data of 32 tone generation channels output from the pan multiplier 37 for each sampling period. As shown, by inputting the output of the A / D converter 31 to the channel accumulator 38,
It is possible to mix the external input signal and the calculated musical tone waveform signal. 39 is the channel accumulator 3
8 is an effect circuit for performing effect processing such as reverb on the musical tone waveform data output from 8. In addition,
This effect circuit 39 can be omitted in some cases. Reference numeral 40 denotes a digital-analog converter that performs digital-analog conversion on the tone waveform sample signal output from the effect circuit 39 for each DAC cycle and outputs the converted signal as LOUT and ROUT to the sound system 20. Thus, in the present invention, CODE
Volume control and accumulation processing are executed at C19.

Next, the software sound source in the musical tone generating apparatus of the present invention will be described. FIG. 3 is a diagram for explaining the temporal flow of processing in this software sound source. The soft sound source of the present invention generates musical tone waveform data at a sampling frequency (rate) of 25.6 kHz, for example, and the musical tone waveform data generation process is performed every 128 samples (one frame) time, for example.
Then, when there is a performance input in a time slot corresponding to a certain frame (FL), calculation processing of musical tone waveform data corresponding to the performance input is performed in the next frame, and the musical tone waveform data 25. A tone signal is formed by reading out one sample every 6 kHz cycle. Therefore, there is a time lag of about 2 frames from the input of the performance until the actual sound of the musical tone is generated (or until the musical tone is muted).
Since it is a sample (5 milliseconds), the time lag is slight. The number of samples in one frame can be set arbitrarily, but if the number of samples is increased, the sound is delayed, and if it is decreased, the time margin is reduced and the response becomes worse when the amount of calculation is temporarily increased. Sometimes.

Further, in the present invention, the so-called table look-up tone generation is performed to generate a tone based on the waveform sample stored in the waveform table read from the hard disk device 13 onto the RAM 12.

FIG. 4 shows the RAM 1 when the soft sound source operates.
3 is a diagram illustrating a storage area set to 2. FIG. FIG. 3A shows an input buffer, which is a buffer for storing the contents of the performance input and its generation time when the performance input is received from the MIDI interface 15. The contents of this buffer is the MID described later.
It is read in the I process and the corresponding process is executed.

FIG. 3B shows the sample buffer WB. This sample buffer WB is provided for 32 channels, and the buffer for each channel is 1
Waveform data storage area for 28 samples (SDi1-S
Di128). Waveform data generation operation is 1
128 frames of one frame time are calculated for each channel, and the procedure is repeated for a maximum of 32 channels (for the sounding channels). The waveform of 128 samples of each channel generated in this way The sample buffer WB stores the data.

FIG. 1C shows a tone color data register.
This tone color data register is a register that stores tone color data that determines the musical tone waveform generated in each MIDI channel (performance part). As this tone color data, a waveform table that is a material for each tone range of each tone color is specified. Waveform designation data, EG control data, pan control data, etc. are stored.

FIG. 3D shows a tone generator register. The sound source register stores data for determining a tone waveform generated in each sound generation channel for each sound generation channel. As this data, note number, either 1
Waveform designation addresses (attack start address AS, attack end address AE, loop start address LS, loop end address LE) indicating the addresses of two waveform tables, note-on data, and the like are stored.

Next, the operation of the soft tone generator of the present invention will be described with reference to the flow chart. FIG. 5A is a flowchart showing the main routine. When the program is started, first, initial settings such as securing a register area are executed (S1), and thereafter, the process waits in S2 and S3 until there is any start factor (trigger). When the activation factor occurs, the activation factor is determined in S4 and the corresponding processing operation is executed. The activation factors are (1) when MIDI data is written in the input buffer, (2) an interrupt from the timer 21 generated at each time corresponding to one frame, (3) other panel or window screen There are four types of factors, the occurrence of the switch event of (1) and the input of the end command (4).
MIDI processing (S5), sound source processing (S6), other processing (S7), and end processing (S8) are executed.

The ending process S8 is a process of saving the setting data, clearing the register, and the like, and the operation is finished after this process is finished. Other processing S7 is processing corresponding to various panel inputs and command inputs. Sound source processing (S6)
3 is a process that is executed by detecting that the read reproduction in FIG. 3 has progressed to the next frame due to an interrupt or the like generated by counting 128 sample clocks from the timer 21.

FIG. 5B is a flowchart of the MIDI interrupt process executed as the highest priority interrupt process. This interrupt processing is performed from the MIDI interface 15 to MIDI.
It is activated when data is received, and the M
Importing IDI data (S10), the received MID
The reception time data together with the I data are written in the input buffer shown in FIG. 4 (A) (S11).

The MIDI process (S5) is started when it is detected that MIDI data is written in the input buffer, and a process corresponding to the written MIDI data is performed. FIG. 6 is a diagram showing an operation in a note-on event process which is one of the MIDI processes. This processing is executed when the note-on event data is written in the input buffer. First, note number of the note-on event data, velocity data, tone color of each part, generation time are NN and V, respectively.
It is stored in the EL, t, and TM registers (S20). next,
Of the 32 channel sound channels, a sound channel for generating the note-on tone is assigned, and this sound channel number is stored in i (S2).
1). The EG control data of the tone color data TP (t) related to the note-on is processed according to VEL (S22).
Next, the processed EG control data and pan control data, together with the data indicating the note-on, are stored in the CODEC 19
Write to the channel register (S23). continue,
The tone color data TP (t) and the F number FN other than the EG control data and the pan control data are written in the tone generator register of the i-th channel together with the note-on (S24).

FIG. 7 is a flow chart showing the sound source processing S6 started in a cycle corresponding to one frame time. This sound source processing operation is a processing for generating one frame (128 samples) of musical tone waveform data for 32 sounding channels, but is forcibly ended when the occupable time of the CPU 10 has passed even during the calculation. Because
The lower the channel in the calculation order, the higher the possibility that the channel will be terminated. Therefore, the calculation order of the 32 sound generation channels is first determined so that the calculation is performed from the channel with the higher priority (the channel that is difficult to be muted) first (S3).
0). Next, 1 is set to the pointer i indicating the calculation order (S31). Subsequently, a waveform data calculation preparation process (S32) is executed in which an address is set in the tone generator register of the i-th sound generation channel, which is the first in the calculation order, so that the data of the channel can be read. Next, the waveform reading from the designated waveform table and the interpolation processing (S33) are executed.

The waveform reading and interpolation processing (S33) will be described with reference to FIG. In this process, the waveform data of the tone generation channels in the calculation order designated by i are collectively calculated for one frame (128 samples). First, the sample number counter s is set to 1 (S4
0). Next, the F number FN is added to the address of the immediately preceding calculation (the address generated last in the waveform reading in the previous frame of this processing channel) to update the address (S41). At this time, an address composed of an integer part and a fractional part is usually generated, so that two samples including this address (the sample specified by the integer part address and the address specified by the waveform specification data t of the RAM 12 are included). The waveform data of the sample designated by the address of the integer part + 1 is read (S42). The data of these two samples is linearly interpolated by the value of the fractional part, and the value is set in the ID register (S43). Next, the contents of the ID register are set in the waveform data storage area SDi (s) of the corresponding channel of the sample buffer WB (S44). This operation is repeatedly executed from s = 1 to s = 128 (S45, S46), and when the process of 128 times is completed, the process returns to the sound source process (FIG. 7).

After the waveform reading and interpolation processing S33 is completed, it is determined whether the waveform data calculation for all channels is completed (S34). If not completed, i is incremented to i + 1 (S36), and the waveform data calculation preparation process (S36) is performed for the next priority sounding channel.
32) The subsequent processing is executed. When the waveform data calculation for all channels is completed, the reproduction of the generated waveform data is reserved for reproduction in the reproduction unit (DMA control circuit 18) (S35). This reproduction reservation is performed by notifying the DMA control circuit 18 of the storage address of the sample buffer WB in the RAM 12.

In this way, the sample buffer WB (SDi1 to SDi12
8, i = 1 to 32), interpolation samples for one frame time are stored for each tone generation channel. The CODEC 19 performs volume control and accumulation processing on this interpolation sample to generate musical tone waveform data.

The interpolated samples stored in the sample buffer WB are coded by the DMA control circuit 18 into the CODE.
It is transferred to the FIFO buffer 33 in C19. That is, when the FIFO buffer 33 in the CODEC 19 becomes empty, a DMA transfer request signal is output to the DMA control circuit 18, and the DMA control circuit 18 makes a sample reserved for reproduction in step S35 (FIG. 7). The interpolated sample data is read from the buffer WB and transferred to the FIFO buffer 33.

The interpolated samples of each tone generation channel stored in the FIFO buffer 33 are sequentially read out at each sampling timing and input to the level multiplier 36. On the other hand, in the envelope generator 34,
Based on the EG control data and the volume parameter written in the register in step S23 (FIG. 6), volume control data corresponding to each sound generation channel is sequentially generated in a time division manner. In the level multiplier 36, the FIF
The interpolation sample of each sound generation channel at the sampling timing output from the O buffer 33 is multiplied by the volume control data output from the envelope generator 34.

In the pan coefficient generator 35,
The pan control data written in the register in step S23 (FIG. 6) causes the pan coefficient corresponding to each sounding channel to be generated in a time division manner. The pan coefficient is multiplied by the volume sampled waveform sample data output from the level multiplier 36 in the pan multiplier 37, and the waveform sample data of each sound generation channel where the sound image is localized is output in a time division manner.

The channel accumulator 38 has a storage area corresponding to each sampling timing, and the musical tone waveform sample data of each sounding channel output from the pan multiplier 37 in a time division manner at each sampling timing. It is cumulatively added to the storage area of the sampling timing of the channel accumulator 38. That is, the waveform data of all sound generation channels at the sampling timing is added to each storage area of the channel accumulator 38. As described above, the A / D conversion circuit 3
By simultaneously adding the output signals from 1 in the channel accumulator 38, mixing with the input analog signal can be performed.

The output from the channel accumulator 38 is
Depending on the case, effect processing such as reverb is performed in the effect circuit 39, and is input to the D / A conversion circuit 40 at each sampling timing, converted into an analog musical tone signal, and output signals LOUT of the left and right channels.
And ROUT are output to the sound system 20.

In the above embodiment, the COD
The envelope generator 34 provided in the EC 19
The volume control data and the pan coefficient are generated by the pan coefficient generator 35. However, when the processing capacity of the CPU 10 is large, the volume control data and the pan coefficient can be generated by the calculation by the CPU 10. In this case, the envelope generator 3
4 and a pan coefficient generator 35 may be replaced with a FIFO buffer for storing volume control data and pan coefficient similar to the FIFO buffer 33, and the calculated volume control data and pan coefficient may be stored.

[0037]

According to the tone generating apparatus of the present invention, the tone generation itself is performed by software, and the volume control calculation for the tone generated by the calculation is performed by the hardware in the CODEC. The amount of calculation required is reduced and the load on the CPU can be reduced.
Further, it becomes possible to generate a musical tone by requiring less hardware than the conventional sound source board. Furthermore, since musical tones can be generated using various waveform data and tone color data stored in the hard disk, the degree of freedom in generating musical tones can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a musical sound generating device of the present invention.

FIG. 2 is a diagram illustrating a configuration of a CODEC according to the present invention.

FIG. 3 is a diagram for explaining a temporal flow of processing in the present invention.

FIG. 4 is a diagram for explaining each storage area in the present invention.

FIG. 5 is a flowchart of processing according to the present invention.

FIG. 6 is a flowchart of note-on event processing according to the present invention.

FIG. 7 is a flowchart of sound source processing according to the present invention.

FIG. 8 is a flowchart of waveform reading and interpolation processing according to the present invention.

[Explanation of symbols]

10 CPU, 11 ROM, 12 RAM, 13 hard disk device, 14 CD-ROM device, 15 M
IDI interface, 16 keyboard, 17 display device, 18 DMA control circuit, 19 encoding / decoding circuit (CODEC), 20 sound system, 3
0 interface circuit, 31, A / D conversion circuit, 3
2, 33 FIFO buffer, 34 envelope generator, 35 pan coefficient generator, 36, 37 multiplier, 38 channel accumulator, 39 effect circuit, 4
0 D / A conversion circuit

Claims (2)

[Claims] 1. A musical tone waveform data is generated by calculation by a calculation processing device, and the calculated musical tone waveform data is converted into an analog signal by a digital-analog converter provided in an encoding / decoding circuit and output to an external device. In the musical tone generating apparatus, the encoding / decoding circuit has means for executing level multiplication processing and pan coefficient multiplication processing for the musical tone waveform data arithmetically generated by the arithmetic processing apparatus. 2. The musical tone generating apparatus according to claim 1, wherein the encoding / decoding circuit includes at least one of an envelope generator and a pan coefficient generator.