JP2897377B2 - Waveform signal forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform signal forming apparatus capable of reproducing a musical tone waveform with a smaller storage capacity when reproducing a musical tone waveform based on waveform sample data.

[Prior art]

In electronic musical instruments and the like, sampled musical tones of a natural musical instrument are stored in a memory as waveform sample data, and the data is read out from the memory and reproduced during performance.
PCM type is also used. In the PCM method, a linear prediction method of storing initial data and differential data and reproducing waveform sample data is used in order to reduce a capacity for storing waveform sample data. As an apparatus for reproducing waveform sample data by a linear prediction method, an apparatus disclosed in Japanese Patent Application Laid-Open No. 61-90198 is conventionally known. In this apparatus, a plurality of serially connected delay circuits store sequentially input waveform sample data while delaying them, and a predetermined linear prediction coefficient is added to the waveform sample data stored in each delay circuit by a multiplication circuit. In addition to the multiplication, the sequentially input difference data is also multiplied by a predetermined linear prediction coefficient, and the multiplication results are added together by an adder circuit to reproduce the compressed waveform sample data. On the other hand, as a method for similarly reducing the capacity for storing waveform sample data, a linear interpolation method for reproducing waveform data between sampling timings is also used, and as an apparatus for reproducing waveform data by such a linear interpolation method, Conventionally, the one disclosed in JP-B-59-17838 is known. In this device, while reading waveform sample data sequentially from the waveform memory, multiply the read multiple waveform sample data by a predetermined linear interpolation coefficient, add each multiplication result, and reproduce the waveform data corresponding to the predetermined phase value doing.

[Problems to be solved by the invention]

However, in the conventional apparatus, in order to compress the waveform sample data using the linear prediction method and to further reduce the storage area using the linear interpolation method, a plurality of apparatuses are required in the apparatus supporting the linear prediction method. In addition to storing waveform sample data, a plurality of waveform sample data must be stored even in a device that supports the linear interpolation method. Can not be measured. The present invention has been made to address the above problems,
It is an object of the present invention to provide a waveform signal forming apparatus capable of preventing an increase in hardware by activating a storage area when reducing the capacity of a waveform memory using a linear prediction method and a linear interpolation method. What you want to do.

[Means for Solving the Problems]

In order to achieve the above object, a structural feature of the present invention is that difference data obtained by compressing waveform sample data by a predetermined operation is stored, and the difference data before compression is stored using the stored difference data. In a waveform signal forming apparatus for sequentially reproducing waveform sample data, a difference data memory storing difference data, and a waveform sample data storage means for storing a plurality of waveform sample data restored based on the difference data in time series An accumulating means for accumulating a phase increment value corresponding to a pitch of a musical tone to be generated at a predetermined timing, and a differential data memory by using higher-order data of the accumulated value accumulated by the accumulating means. Read control means for generating an address and sequentially reading the differential data stored in the differential data memory according to the generated address; and read control means. Therefore, the pre-compression waveform sample data is restored by a predetermined operation using the read difference data and the plurality of waveform sample data stored in the waveform sample data storage means, and the restored waveform sample data is converted into the waveform sample data. A predetermined interpolation operation is performed by using a restoration means for sequentially storing the data in the storage means, and a plurality of waveform sample data stored in the waveform sample data storage means and data lower than the accumulated value accumulated by the accumulation means. And interpolating means for deriving waveform sample data corresponding to the predetermined phase value.

Actions and effects of the present invention

In the present invention configured as described above, when a phase increment value corresponding to the pitch of a musical tone generated is given to the accumulating means, the accumulating means accumulates the phase increment value at every predetermined timing. Then, the read control means generates an address for the difference data memory using the higher-order data of the accumulated value, and sequentially reads the difference data stored in the difference data memory in accordance with the generated address. Read.
The restoration means restores the pre-compressed waveform sample data by a predetermined operation using the read difference data and the plurality of waveform sample data stored in the waveform sample data storage means. The sample data is sequentially stored in the waveform sample data storage means. Thus, the waveform sample data storage unit stores a plurality of waveform sample data restored on the basis of the difference data stored in the difference data memory in a time-series manner. On the other hand, the interpolation means performs a predetermined interpolation operation using a plurality of waveform sample data stored in the waveform sample data storage means and lower-order data of the accumulated value accumulated by the accumulation means. Derive waveform sample data corresponding to the phase value of As described above, according to the present invention, the waveform sample data storage means for storing the plurality of time-series waveform sample data and the plurality of waveform sample data restores the waveform sample data based on the difference data. And are commonly used for both calculations for interpolating waveform sample data. Therefore, the hardware configuration can be omitted, and the time until the final waveform sample data is reproduced by both operations can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an electronic musical instrument equipped with a waveform signal forming apparatus according to the present invention and capable of simultaneously producing a plurality of musical tones from a plurality of sounding channels. The electronic musical instrument includes a keyboard unit 10 including a plurality of key switches provided for each key of a keyboard, and an operation panel 20 including a plurality of tone color selection switches for selecting tone colors and the like. The keyboard 10 and the operation panel 20 are connected to a control signal generator 30. The control signal generation unit 30 detects a key depression operation of each key on the keyboard unit 10 and an operation state of a tone color etc. selection switch on the operation panel 20, and a key code signal KC corresponding to the depressed key, a key depression key Touch signal T representing speed or keypress pressure
D, a key-on signal KON indicating a key pressed state, a timbre signal TC indicating a selected timbre, and the like. The key-on signal KON is input to the timing signal generation circuit 40. The timing signal generation circuit 40 generates a tone corresponding to each key press as shown in FIG. A signal KONP, a key-off pulse signal KOFP indicating a key-off timing,
Various timing signals such as a clock signal CLK representing the operation timing of the waveform data are generated. The key code signal KC is generated by a frequency number generation circuit (hereinafter, referred to as
This is called an F number generation circuit. ) 50 and the parameter data generation circuit 60, and the F number generation circuit 50 generates a phase increment value corresponding to the key depression pitch based on the key code signal KC.
Outputs FN. The in-phase increment value FN is input to the accumulator 70,
The accumulator 70 clears the accumulated value up to that time when the key-on pulse signal KONP representing the key press timing is input from the timing signal generation circuit 40, and thereafter, the clock signal CLK also output by the timing signal generation circuit 40. The phase increment value FN is accumulated for each input timing of. The phase increment value FN is a numerical value less than "1", and the accumulator 70 sequentially accumulates the phase increment value FN, and normally converts the decimal place data FRAC to a linear interpolation coefficient generation circuit (hereinafter, referred to as an FIR coefficient generation circuit). ), And outputs the note clock pulse NCL of the read control circuit 80 when the accumulated value is counted up to the place of "1". The read control circuit 80 designates a read address AD of the differential data memory 100, counts up the start address SA output from the parameter data generation circuit 60 at each input timing of the note clock pulse NCL, and sets the read address AD. I do. However, when the number of times of input of the note clock pulse NCL exceeds a predetermined value, the read address AD is counted up again from an address SA1 which is a predetermined address after the start address SA. In the present embodiment, the tone waveform corresponding to the attack portion immediately after the tone is reproduced only once, and the tone waveform of the sustain portion subsequent to the tone waveform is repeatedly played back.
The amount of data stored in 0 is reduced. The start address SA is a start address of a data group stored corresponding to each tone in the difference data memory 100, and the parameter data generation circuit 60 is selected according to the tone color signal TC input from the control signal generation unit 30. The start address SA corresponding to the selected tone is output. In the present embodiment, waveform sample data is compressed by a linear prediction method in order to reproduce waveform data, and difference data relating to such data compression is stored in the difference data memory 100. Since the linear prediction method is publicly known, the detailed description is omitted. In this embodiment, the waveform sample data at the sampling timing n is represented by F (n), and the waveform sample data F (n−4), F (n) -3), F
(N-2), waveform sample data F based on F (n-1)
D (n) represents difference data for predicting (n),
In addition, linear prediction coefficients (hereinafter, referred to as LPC coefficients) are x1 to x
Assuming that 5, the difference data D (n) is D (n) = [F (n) − ｛x4 · F (n−4) + x3 · F (n−3) + x2 · F (n−2) + x1 F (n-1)}] / x5, and the predicted waveform sample data F (n) is: F (n) = x4.F (n-4) + x3.F (n-3) + x2 F (n-2) + x1F (n-1) + x5D (n) The LPC coefficients x1 to x5 are embedded in the difference data of the difference data memory 100 except for the initial data, and are sequentially reproduced by the read control circuit 80, and are switched every predetermined interval to be reproduced by the linear prediction method. Used for Specifically, the most significant bit of the difference data is used as an LPC coefficient area, and the read control circuit 80
Each time the difference data D0 (n) is read from 0, only the most significant bit is stored in a separate area.
Convert to LPC coefficient. Further, the data excluding only the most significant bit is output to the linear prediction / interpolation circuit 110 as difference data D (n). As shown in FIG. 3, the linear prediction / interpolation circuit 110 includes delay circuits 110a1 to 110a4, which are connected in series and hold input data by a note clock pulse NCL and output stored data, and each delay circuit 110a1. ~ 1
Multipliers 110b1-1 to multiply the output of 10a4 by multiplication coefficients x1 to x4
10b4 and a multiplier 110b that multiplies input data by a multiplication coefficient x5
5, an adder 110c1 for adding the multiplication results of the multipliers 110b1 to b5 to input the addition result to the delay circuit 110a1, and a multiplier 110b6 to multiply the output of each delay circuit 110a1 to 110a4 by a multiplication coefficient y1 to y4. 110b9, and an adder 110c2 that adds the multiplication results of the multipliers 110b6 to 110b9 and outputs the added data. The linear prediction / interpolation circuit 110 includes a difference data memory 1
The LPC coefficient output from the read control circuit 80 together with the difference data D (n) read from the 00 and the FIR coefficient generation circuit 90
Output linear interpolation coefficient (hereinafter referred to as FIR coefficient)
And LPC coefficient initial data x1 (0) to x5 (0) output from the parameter data generation circuit 60, and are selectively input to the LPC coefficient output from the read control circuit 80 by a selector (not shown). ) Is input, and the compressed data is restored by the linear prediction method and linear interpolation is performed based on the restored waveform sample data. Note that the difference data D (n)
Is input to the multiplier 110b5, and the LPC coefficient is
The FIR coefficient is input as a multiplication coefficient in 10b5, and the FIR coefficient is input as a multiplication coefficient in each of the multipliers 110b6 to 110b9. The FIR coefficient generating circuit 90 for generating the FIR coefficient includes a decimal place data FRAC (0 ≦ FRAC ≦
1), the waveform sample data F (I), F (I +
1), the waveform sample data F (I + 1 + FRAC) is calculated from F (I + 2), F (I + 3) by linear interpolation. In this embodiment, each calculation coefficient y1 is used to perform the same calculation by the cubic interpolation method. As ~ y4, Is calculated and output. The waveform data obtained by the linear prediction / interpolation circuit 110 is input to a multiplier 120, and the multiplier 120 multiplies the waveform data by the envelope data ED output from the envelope generator 130 to generate sound waveform data. Mixer 140
Output to Here, envelope setting data EDT (representing the attack level AL, the attack rate AR, the decay level DL, and the decay rate DR) output from the parameter data generation circuit 60 based on the touch signal TD is input to the envelope generator 130. At the same time, the key-on pulse signal KONP and the key-off pulse signal KOFP generated by the timing signal generation circuit 40 based on the key-on signal KON are input. Is output to the multiplier 120, and the envelope data ED indicating the release portion of the tone waveform is output to the multiplier 120 from the input timing of the key-off pulse signal KOFP. The mixer 140 sums the tone waveform data of each channel, which is the output of the multiplier 120, and outputs the sum to the D / A converter 150, where the D / A
The converter 150 converts the digital tone waveform data into an analog value and converts the converted tone waveform signal into a sound system.
Output to 160. The sound system 160 includes an amplifier, a speaker, and the like, amplifies an input musical sound waveform signal, and reproduces the musical sound signal from the speaker. Next, the operation of the present embodiment configured as described above will be described. It is assumed that a player turns on a power switch (not shown) on the operation panel 20 and selects a musical instrument sound by using a tone color etc. selection switch on the operation panel 20, and then starts playing on the keyboard of the keyboard unit 10. After turning on the power switch, the control signal generation unit 30 detects whether or not various switches are operated on the operation panel 20. Tone signal TC indicating operation
Is output to the parameter data generation circuit 60. On the other hand, when the player starts playing by pressing any key on the keyboard section 10, the control signal generating section 30 determines a channel to be sounded, and displays a key representing the key pressed at a predetermined time-division timing. The code signal KC is output to the F number generation circuit 50 and the parameter data generation circuit 60, and the key-on signal KON indicating that the key is being pressed is output to the timing signal generation circuit 40. The F-number generation circuit 50 receives the input key code signal
The phase increment value FN corresponding to KC is output to the accumulator 70, and the accumulator
When the key-on pulse signal KONP output from the timing signal generation circuit 40 is input, 70 clears the accumulated value up to that time in the sounding channel, and the timing signal generation circuit
The phase increment value FN is accumulated for each tone generation channel at the timing of inputting the predetermined clock signal CLK output by 40. The parameter data generation circuit 60 outputs the key-on pulse signal KO
When the NP is input, the start address SA is output to the read control circuit 80 corresponding to the tone channel and the tone color, and the LPC coefficient initial data x1 (0) to x5 corresponding to the tone color
(0) is output to the linear prediction / interpolation circuit 110. In the linear prediction / interpolation circuit 110, the key-on pulse signal KON
When P is input, LPC coefficient initial data x1 (0) output from the parameter data generation circuit 60 by a selector (not shown)
To x5 (0), and thereafter, select LPC coefficients x1 to x5 extracted from the difference data for each predetermined section. That is, when the LPC coefficients x1 to x5 are not output from the read control circuit 80, the LPC coefficient initial data x1 (0) to x5 (0)
Is selected, and when the LPC coefficients x1 to x5 are output from the read control circuit 80, the same LPC coefficients x1 to x5 are selected. When the key-on pulse signal KONP is output, the start address SA is output as the read address AD for the difference data memory 100, and the difference data memory 100 outputs the first difference data D (0) stored at the start address. Therefore, the LPC coefficient initial data x5 in the multiplier 110b5
(0) is multiplied by the difference data D (0), and the adder 110c1 adds the multiplication result (in this case, the outputs of the multipliers 110b1 to 110b4 are “0”), and the waveform sample data F is added.
(0) is output. This calculation is performed every time the clock signal CLK is output. However, until the note clock pulse NCL is output from the accumulator 70, the delay circuits 110a1 to 110a
Since the stored data in 4 is not changed, the waveform sample data F (0) is repeatedly calculated. On the other hand, when the key-on pulse signal KONP is output, the accumulator 70 accumulates the phase increment value FN at each input timing of the clock signal CLK, and outputs the decimal place data FRAC to the FIR coefficient generation circuit 9.
Output to 0. When the decimal place data FRAC is input to the FIR coefficient generation circuit 90, the FIR coefficient generation circuit 90
The IR coefficients y1 to y4 are output to the linear prediction / interpolation circuit 110. Therefore, in the linear prediction / interpolation circuit 110 to which the same FIR coefficients y1 to y4 are input, the multipliers 110b6 to b9 convert the respective coefficients y1 to y4 into the delay circuit 11
The output values of 0a1 to 110a4 are multiplied, and the adder 110c2 adds the multiplication results to obtain the waveform data at each time point by interpolation. The same waveform data is input to a multiplier 120, and the multiplier 120 multiplies the envelope data output by the envelope generator 130. This envelope data is generated by the envelope generator 130 based on the envelope setting data EDT output by the parameter data generation circuit 60 in response to the touch signal TD.
Is generated from the input of the key-on pulse signal KONP,
It comprises an attack portion immediately after a key is pressed, a relatively stable sustain portion following the attack portion, and a release portion after the key is released, and gives a predetermined envelope to the waveform data. On the other hand, when the accumulated value in the accumulator 70 is counted up to the place of “1”, the accumulator 70 outputs the note clock pulse.
Outputs NCL. As a result, the read address AD output from the read control circuit 80 is added by “1”, and the difference data stored at the next address is input from the difference data memory 100 to the linear prediction / interpolation circuit 110. In the linear prediction / interpolation circuit 110, the waveform sample data F (0) output from the adder 110c1 at the time when the note clock pulse NCL is output is taken into the delay circuit 110a1. Then, when the next clock signal CLK is output, the waveform sample data F (1) is calculated, and thereafter, the waveform sample data is sequentially obtained and each of the delay circuits 110a1 to 110a-a is calculated.
3 is stored in the delay circuit 110a2.
~ A4. Also in the linear interpolation, the waveform data is calculated based on the waveform sample data stored in each of the delay circuits 110a1 to 110a4 and the FIR coefficients y1 to y4. In this way, the waveform data is sequentially calculated, and the multiplier 12
After the envelope is given at 0, the waveform data of each sounding channel is added by the mixer 140. Then, when the waveform data of all the sounding channels is added, the D / A converter 150
Input to the sound system and converted to analog values
Music tone is reproduced from 160. In this embodiment, the plurality of delay circuits are constituted by a plurality of registers, but may be constituted by a single shift register. In this case, the number of channels may be multiplied by the number of stages of the delay circuit. Further, a single multiplier may be used, and the output of the shift register may be selected and used in a time division manner. The FIR coefficient generating circuit is configured to calculate the FIR coefficient by calculation, but may be configured by a memory in which the decimal place data FRAC is used as an address input and the FIR coefficient is referred to. The linear prediction method and the linear interpolation method are not limited to those in the above embodiment, but may be multiplication coefficients obtained by other arithmetic methods.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electronic musical instrument to which a waveform signal forming apparatus according to an embodiment of the present invention is applied, FIG. 2 is a timing chart of timing signals in the electronic musical instrument, and FIG. FIG. Description of symbols 110a1 to 110a4 ... delay circuit, 110b1 to 110b5 ... multiplier
110c1 ... Adder, 110b6 to 110b9 ... Multiplier, 110c2 ...
Adder.

Claims (1)

(57) [Claims] 1. A waveform signal forming apparatus for storing difference data obtained by compressing waveform sample data, and sequentially reproducing the waveform sample data before compression using the stored difference data. A stored difference data memory; a waveform sample data storage means for storing a plurality of waveform sample data restored based on the difference data in time series; and a phase increment value corresponding to a pitch of a generated musical tone is determined. Accumulating means for accumulating at each timing of: generating an address for the differential data memory using data higher in the accumulated value accumulated by the accumulating means; and generating the same differential data according to the generated address. Read control means for sequentially reading the difference data stored in the memory; difference data read by the read control means; Using a plurality of waveform sample data stored in the pull data storage means to restore the pre-compressed waveform sample data by a predetermined calculation and sequentially store the restored waveform sample data in the waveform sample data storage means Means, a predetermined phase value by a predetermined interpolation operation using a plurality of waveform sample data stored in the waveform sample data storage means and data lower than the accumulated value accumulated by the accumulation means. A waveform signal forming apparatus comprising: an interpolation unit for deriving corresponding waveform sample data.