JPH0799474B2 - Waveform signal processor - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a waveform signal processing device that digitally processes an input waveform signal and outputs the processed signal.

[Background of the Invention]

BACKGROUND ART Conventionally, various electronic musical instruments having a sampling function of inputting an acoustic signal from the outside, digitally recording the acoustic signal, reading the recorded waveform signal as a sound source signal, and outputting it as each scale tone signal have been developed.

In this kind of electronic musical instrument, an acoustic signal is generally sampled as it is, converted into a digital signal and recorded, and since the input waveform signal has a peculiar envelope, it is previously stored as a scale sound signal. Even if the digitally recorded waveform signal is read at a predetermined speed and converted to an analog signal and then an envelope is added with a voltage control amplifier (VCA), etc., the original envelope and the envelope added later are superimposed. It was difficult to perform sufficient envelope control.

In addition, even when a specific section of the waveform signal as described above is repeated to generate a continuous read sound or the like, if the waveform signal originally has an attenuated envelope, for example, the level at the joint of the waveform is There is a disadvantage that the difference appears as a noticeable amount and noise such as a click sound is output, and when the loop function is to be implemented, there is a problem that it can be performed only in a short section.

[Object of the Invention]

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a waveform signal processing device capable of obtaining a normalized waveform signal by removing the envelope of the input waveform signal with a simple configuration.

[Main points of the invention]

In order to achieve the above object, the present invention provides a waveform storage means for digitally storing an input waveform signal, a division means for dividing the waveform signal stored in the waveform storage means into a plurality of blocks, and a plurality of division means by the division means. From the waveform signal divided into blocks, the address where the absolute value of the waveform signal takes the maximum value in each block and the maximum value are detected, and the absolute value of the waveform signal detected in each block becomes the maximum. Envelope signal calculating means for calculating the envelope signal by interpolating the maximum value of each block by digital operation processing from the address taking the value and the maximum value, and the envelope signal calculated by the envelope signal calculating means. According to the above, the waveform signal stored in the waveform storage means is normalized to remove the envelope of the input waveform. Envelope normalization means that, the main point by comprising a.

[Structure of Invention]

FIG. 1 shows the configuration of the present invention. Reference numeral 1 is a waveform storage means for storing a waveform signal, and the waveform signal can be input and set in advance from the outside.

Then, the waveform signal stored in the waveform storage means 1 is read out by the block reading means 2 as each means for each block, with the predetermined width of the address as a block.

The waveform signal read by the block reading means 2 is supplied to the maximum absolute value detecting means 3 to detect the address having the maximum absolute value in the block and the maximum value.
It is given to the maximum value / address storage means 4. Therefore, the maximum value / address storage means 4 sequentially stores the maximum value of all blocks and the address having the maximum value.

The output of the maximum value / address storage means 4 is interpolated envelope value calculation means 6 together with the sample value of the waveform read from the waveform storage means 1 by the waveform reading means 5.
Are supplied to the envelope normalizing means 7 to calculate the interpolation envelope value. This maximum absolute value detection means 3,
The maximum value / address storage means 4, the waveform reading means 5, and the interpolation envelope value calculation means 6 constitute an envelope signal calculation means.

The envelope normalizing means 7 has a predetermined value to remove the original envelope of the waveform signal from the sample value supplied from the waveform reading means 5 and the interpolation envelope value supplied from the interpolation envelope value calculating means 6. Perform a calculation to obtain a normalized sample value.

Then, this sample value is sent to the waveform writing means 8 and is again supplied to the waveform storing means 1, so that the stored contents can be rewritten.

In this way, the waveform signal having an envelope is converted into an envelope waveform signal having a substantially constant value by removing the envelope according to the interpolation envelope value calculated by the interpolation envelope value calculation means 6. . That is, a normalized waveform signal is obtained by the series of processes.

The configuration and features of the present invention will be understood concretely by the embodiments described in detail below.

〔Example〕

Hereinafter, an embodiment in which the present invention is configured by using a CPU such as a microprocessor will be described in detail.

FIG. 2 shows its circuit configuration. An acoustic signal input through the microphone 11 is sampled by the waveform input circuit 12 at an appropriate sampling frequency, converted into a digital signal, and supplied to the CPU 13.

The CPU 13 sends this input waveform signal to the waveform memory read / write circuit 14 and finally stores it in the waveform memory 15.
Therefore, the waveform signal having the envelope of the input sound is digitally stored in the waveform memory 15.

Further, the CPU 13 normalizes the waveform signal stored in the waveform memory 15 to remove the envelope. The working register 16 used at that time includes an address register (ad register), a dt register, a block register (bl register), an ev register, and a madj / mdtj register. Data and addresses, which will be described later, are stored in these registers.

Also, this CPU 13 is connected to the keyboard 17,
In addition to the CPU 13 performing various processes based on the key operation of the keyboard 17, the waveform signal normalized from the waveform memory 15 at a predetermined speed corresponding to each scale according to the operation of the performance keys provided on the keyboard 17. The waveform memory read / write circuit 14 is controlled so as to read.

Then, the digital signal read from the waveform memory 15 is supplied to the D / A converter 18 via the waveform memory read / write circuit 14, converted into an analog signal, and the voltage controlled amplifier (VCA) 19 Applied to.

To this VCA19, the envelope signal calculated and output by the CPU 13 by soft processing is supplied after being converted into an analog signal by the D / A converter 20, the amplifier is determined, and as a result, from the VCA19, A waveform signal having an envelope designated by the CPU 13 is output, and the output of this VCA 19 is converted into an acoustic output by the sound system 21.

Next, the operation of this embodiment will be described with reference to the flow chart of FIG. First, this series of processing is performed by an address where the absolute value of the sample value in the block has the maximum value, a routine A for obtaining the maximum value, and a routine for normalizing the stored contents of the waveform memory 15 from the result of this routine A. It consists of B and.

First, in step A1 in routine A, the block register (bl register) in the working register 16 is initialized. That is, 1 is set to specify the first block. In addition, the block means each of the areas when the waveform memory 15 is divided by a predetermined address width BS.

Next, in step A2, the address register (ad register) is initialized. That is, the content of the ad register is used as data for designating the start address of the waveform memory 15. Then, in step A3, the address having the maximum value among the absolute values of the sample values and the contents of the register (madj / mdtj register) storing the maximum value are initialized.

That is, when the first block of the waveform memory 15 is j = 1 and the last block is j = N, the contents of the madj / mdtj register are set to zero in the range of j = 1 to N, and
Of the virtual block j = 0, which is one before the first block j = 1
The contents of the mado / mdto register, the address of the waveform memory 15
Width of each block from the top register of (block size B
S) is subtracted and the maximum value is set to zero. Similarly, the virtual block j one after the final block j = N
= N + 1 mad _{N + 1} / mdt _{N + 1} register contents, block size from the final address of waveform memory 15
Set to the value with BS added, and set the maximum value to zero.

Then, following the above series of initialization processing,
The maximum value of each block is detected in the processing after A4. First, at step A4, the sample value of the waveform memory 15 designated by the content of the ad register is read and the absolute value is obtained.

Then, at the next step A5, it is detected whether or not the absolute value is larger than the maximum value mad _{bl of the} current block which has already been recorded. If YES, the process proceeds to step A6 and madj / md
Rewrite the value of the tj register.

Then proceed to step A7. Also, when it is determined to be ON in step A5, the operation proceeds to step A7 following step A5. At step A7, the value of the ad register is incremented.

Then, in step A8, it is judged whether the value of the ad register is the final address of the block (that is, it is determined whether or not the value of the ad register matches the value of bl × BS), and if NO. Return to step A4 again,
Then, the processes of steps A4 to A8 are executed. In this way, the maximum value of the block and its address are obtained.

FIG. 4 shows the relationship between the sample address of each block and its maximum value, and the values shown in the figure are stored in the madj / mdtj register (j = bl). In addition, the waveform shown by the dotted line in the figure is obtained by rewriting so that the sample point having a negative value takes a positive value by taking the absolute value of each sample value as described above.

When the processing of the block is completed, step A8
Then, make a YES decision and proceed to the next step A9. Step A
At 9, the value of the bl register is incremented. At the next step A10, that block is the last block (j =
N), the process returns to the main flow if YES, and returns to step A4 if NO to start the process for the next block.

In this way, the address at which the absolute value of the sample value of each block (j = 1 to N) takes the maximum value and the maximum value are
It is stored and set in the madj / mdtj register.

Then, the normalization processing of the waveform memory 15 of the routine B is executed next.

First, in step B1, in the working register 16
Set the content of the ad register to the address that specifies the start address of the waveform memory 15. It also sets the contents of the bl register to a value of 1 that specifies the start address.

Next, in step B, the waveform sample value at the address designated by the ad register is read from the waveform memory 15 and set in the dt register in the working register 16.

Next, in step B3, the interpolation envelope value is calculated and ev
Input to the register. That is, as shown in FIG. 4, the interpolation envelope value ev is obtained from the maximum value (mdt _j-1 ) of the previous block, the maximum value (mdt _j ) of the block, and the address (ad) at that time.

That is, the calculation formula is as follows.

Note that if j = bl, it corresponds to the values shown in FIG.

Then, in step B4, the waveform is normalized using the interpolation envelope value ev at the address point obtained as described above. That is, specifically, the following calculation is performed.

Dt = MV × dt / ev Note that MV is a level value to be normalized, and is 700 in hexadecimal display in the embodiment. That is, the interpolation envelope value ev is an approximation of the envelope of the original waveform and causes an error, and depending on the input waveform, a normal value that exceeds the value of MV can occur, so the maximum value of the waveform is , For example
In the case of 12-bit two's complement representation, a value smaller than 7FF (hexadecimal representation) must be taken.

Then, the normalized sample value Dt is input and set to the address of the waveform memory 15. Then, in step B5, the content of the ad register is incremented.

At the next step B6, the contents of the ad register and mad _bl
The ad register is mad when the size of the register is judged.
_When the value of the bl register is exceeded, the process proceeds to step B7 and the bl register is incremented.

Then proceed to step B8. Also, when it is judged to be ON in step B6, the process directly goes to step B8. Then, at step B8, it is judged whether the normalization processing has been completed up to the last sample value of the waveform.
Return to B2.

In this way, steps B2 to B8 are repeatedly executed to complete the normalization processing of all sample points. FIG. 5 (B) shows the waveform thus normalized, and the envelope as shown in FIG. 5 (A) (shown by a chain line).
The input waveform signal with is removed from the envelope by the execution of routines A and B and has a substantially constant value (corresponding to MV).
Is converted into a waveform signal having an envelope (indicated by a chain line).

Therefore, according to the present embodiment, even if the waveform sample value re-stored in the waveform memory 15 is read and the envelope is added to it by the VCA 19, the envelope originally possessed by the input waveform signal is removed. Effective envelope control is possible.

Further, even if a part of the waveform stored in the waveform memory 15 is read out by looping, the noise is not generated, such as unnecessary clicking noise, because the envelope is kept substantially constant.

Although the contents of the waveform memory 15 are rewritten to the normalized waveform signal in the above embodiment, they may be written to another waveform memory.

Further, in the above embodiment, the interpolation envelope value is obtained according to the above-described calculation formula, and the sample value of the waveform is divided by this interpolation envelope value to obtain the normalized sample value. You may ask for it. The point is to remove the envelope originally possessed by the input waveform signal.

〔The invention's effect〕

As described in detail above, since the envelope of the input waveform signal is removed with a simple configuration to obtain a normalized sample value of the waveform as described above, in obtaining the sound source waveform signal of the electronic musical instrument,
It will be very effective.

[Brief description of drawings]

The drawings show the present invention, and FIG. 1 shows the configuration of the present invention.
FIG. 2 is a circuit configuration diagram of an embodiment of the present invention, FIG. 3 is a flow chart showing the operation of the embodiment, and FIG. 4 is an explanatory view of a concrete operation of calculating an interpolation envelope value, and FIG. The figure is a waveform diagram showing an input waveform signal and a normalized waveform signal. 1 ... Waveform storage means, 3 ... Maximum absolute value detection means, 4 ...
... maximum value / address storage means, 6 ... interpolation envelope value calculation means, 7 ... envelope normalization means, 13 ... CP
U, 15 ... Waveform memory, 16 ... Working register.

Claims (2)

[Claims] 1. A waveform storage means for digitally storing an input waveform signal, a dividing means for dividing the waveform signal stored in the waveform storage means into a plurality of blocks, and a waveform divided into a plurality of blocks by the dividing means. The address at which the absolute value of the waveform signal takes the maximum value in each block from the signal and the maximum value is detected, and the address at which the absolute value of the waveform signal detected in each block takes the maximum value and the maximum And an envelope signal calculation means for calculating the envelope signal by interpolating the maximum value of each block by digital calculation processing from the value, and stored in the waveform storage means according to the envelope signal calculated by the envelope signal calculation means. Envelope normalization procedure for removing the envelope of the envelope of the input waveform by normalizing the generated waveform signal. When the waveform signal processing apparatus characterized by comprising a. 2. The envelope signal calculating means calculates the envelope value ev by the interpolation as follows: ev = mdt _bl-1 − (mad _bl-1 −ad) × {(mdt _bl −mdt _bl-1 ) / (Mad _bl −mad _bl-1 )} where bl is the block number, mdt is the maximum value of the block, mad is the address that takes the maximum value, and ad is the address of the sample value of the waveform signal. Yes, the envelope normalization means calculates a sampled value Dt of the normalized waveform signal according to the following equation: Dt = MV × dt / ev where dt is a sampled value of the waveform signal before normalization, and MV is a normalized value The waveform signal processing device according to claim 1, wherein the waveform signal processing device shows the respective level values to be converted.