JP2970396B2 - Waveform processing device - Google Patents

Abstract

PURPOSE:To provide the waveform processor which can easily specify a compression rate or expansion rate when the time base of a musical tone signal waveform is compressed or expanded without varying the pitch of the musical tone. CONSTITUTION:The waveform processor performs a time stretching process for compressing or expanding the time base of the musical tone signal waveform without varying the pitch of the musical sound on an automatic playing device using a sequencer 1, etc., and is provided with a before-conversion tempo specifying means which specifies the original tempo of the musical tone signal waveform an after-conversion tempo specifying means which specifies a desired tempo after the conversion of the musical tone signal waveform, an arithmetic means which calculates the ratio of the tempo specified by the before-conversion tempo specifying means and the tempo specified by the after-conversion tempo specifying means, and a time stretch waveform generating means which performs stretches the time of the musical tone signal waveform according to the ratio calculated by the arithmetic means and generates the musical tone signal waveform of the tempo specified by the after-conversion tempo specifying means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform processing apparatus, and more particularly, to a waveform processing apparatus for converting a tone signal into a time axis.

[0002]

2. Description of the Related Art An electronic musical instrument such as a synthesizer generally has a sound source such as a waveform memory type sound source, an FM sound source, and a physical model sound source, and generates a musical tone signal by electric means. On the other hand, an electronic musical instrument called a sampler records an audio signal such as a natural sound input from the outside as it is, reads a recorded audio signal by pressing a key on a keyboard, etc., and converts it into a tone signal. Pronounce.

An audio signal recorded on a sampler is usually reproduced within the same time as the recording when the pitch is the same (pitch). However, depending on the case, there is a case where it is desired to reproduce in a shorter time or a longer time than the recording time. If the playback speed is simply made faster or slower, the playback time will be shorter or longer than the recording time, and the pitch of the audio signal will be different from that at the time of recording.

Therefore, even if the reproduction time is changed from the recording time, it is necessary to convert the audio signal so that the reproduction can be performed without changing the pitch at the time of recording. The conversion is performed by time-stretching the audio signal at the time of recording to generate an audio signal for reproduction. Time stretching is processing for compressing or expanding the time axis without changing the pitch by thinning out or interpolating the audio signal.

[0005] It is known that the time stretch circuit sequentially samples a target audio signal at a predetermined frequency, writes it into a random access memory (RAM), and reads it out of the RAM at a frequency different from that at the time of writing. . By changing the ratio between the write and read clock frequencies, the reproduction time of the audio signal can be shortened or lengthened. To shorten the playback time, audio signals are thinned out, and to increase the playback time, interpolation of the audio signals is performed.

To perform time stretching, it is necessary to input a recording time and a reproduction time to a circuit. The time stretch circuit determines the frequency of writing to and reading from the RAM by calculating the ratio of the recording time to the reproduction time. Even if the recording time and the reproduction time are not known, the time stretching can be performed as long as the ratio between the recording time and the reproduction time is known.

[0007]

In the conventional time stretching circuit, it is possible to compress or expand the time axis of the audio signal at the time of recording by designating the recording time and the reproduction time.

On the other hand, in an automatic performance device using a sequencer or the like, the performance speed can be increased or decreased without changing the pitch by specifying the tempo by the operator. The tempo is represented, for example, by the number of quarter notes struck in one minute.

The automatic performance device stores therein automatic performance data, and changes the reading speed of the automatic performance data according to a specified tempo. Even if you change the reading speed,
Since the information such as the note number (pitch information) included in the automatic performance data does not change, the pitch does not change. Once the automatic performance data is created, time stretching can be performed by specifying a tempo using an automatic performance device.

[0010] Consider a case where simultaneous performance is performed using both a sampler and an automatic performance device. The sampler performs time stretching by designating a recording time and a reproduction time, while the automatic performance device performs time stretching by designating a tempo.

Therefore, in order to perform the simultaneous performance, it is necessary to match the reproduction time of the sampler with the tempo at which the automatic performance device performs the automatic performance. After designating the tempo at which the automatic performance is performed to the automatic performance device, the player must calculate the relationship between the recording time and the reproduction time of the sampler that matches the tempo. Simultaneous performance of sampler and automatic performance device,
The procedure for adjusting the performance timing is complicated.

An object of the present invention is to provide a waveform processing apparatus capable of easily designating a compression ratio or an expansion ratio when compressing or expanding the time axis of a musical tone signal waveform without changing the pitch of the musical tone. It is to be.

[0013]

SUMMARY OF THE INVENTION A waveform processing apparatus according to the present invention compresses or expands the time axis of a musical tone signal waveform without changing the pitch of the musical tone using a tempo which is the number of beats in a predetermined time. A pre-conversion tempo designating unit for designating an original tempo of a tone signal waveform, and a post-conversion tempo designating unit for designating a desired tempo after the tone signal waveform is transformed. Calculating means for calculating the ratio between the tempo specified by the pre-conversion tempo specifying means and the tempo specified by the post-conversion tempo specifying means; and the time of the tone signal waveform according to the ratio calculated by the calculating means. Time stretching waveform generating means for performing stretching and generating a tone signal waveform having a tempo designated by the converted tempo designating means.

[0014]

The compression or expansion of the time axis performed without changing the pitch of the musical tone is performed by designating the pre-conversion tempo and the post-conversion tempo. By designating a desired tempo with respect to a tone signal waveform having a predetermined tempo, the tone signal waveform can be converted to a tone signal waveform having a desired tempo. Even if the tempo of the musical tone changes, the pitch of the musical tone does not change.

[0015]

FIG. 1 shows a performance system of a sequencer and a sampler using a time stretching circuit according to an embodiment of the present invention.

The operator gives an instruction to start or stop automatic performance by operating a switch of the sequencer 1. The sequencer 1 starts supplying automatic performance data such as note-on, note-off, note number (pitch information) stored therein to the sampler 2 according to a start instruction, and supplies automatic performance data according to a stop instruction. Stop.

The operator can specify the tempo of the automatic performance to the sequencer 1. When a tempo is designated, the sequencer 1 reads out the automatic performance data at a speed corresponding to the tempo and supplies it to the sampler 2. The sequencer 1 has a clock generator therein, and reads out automatic performance data at a period according to a tempo designated by an operator.

The sampler 2 has a sampling waveform 3 inside. The sampling waveform 3 is a tone amplitude waveform recorded by sampling and recording an analog signal of a tone input from the outside at a predetermined sampling frequency or by directly writing a digitally encoded signal.

FIG. 2 shows a sampling waveform stored in the sampler. For example, waveform A
And waveform B are sampled and recorded. FIG.
2A shows a waveform A (tone signal), and FIG. 2B shows a waveform B (tone signal). Waveforms A and B are recorded signals when a drum is played live at a tempo of 120, for example.
These are waveforms for two bars of different performances. It is assumed that the waveform A is set to note number = C3 and the waveform B is set to note number = D3 by the sampler.

In the sampler 2 shown in FIG. 1, when a note-on signal is supplied from the sequencer 1, a sampling waveform corresponding to a note number supplied together with the note-on signal is read out and reproduced. For example, note number =
When C3 is supplied, the sampling waveform A is read,
If note number = D3 is supplied, sampling waveform B
Is read. The read waveform is output as a tone signal.

The waveform A does not necessarily have to be a tone signal having a pitch of C3, but may be a tone signal containing a plurality of different pitches and timbres. For example, the waveform A includes tone signals of different timbres such as a bass drum and a snare drum.

When the note number = C3 is supplied from the sequencer, the two-bar drum performance of the waveform A is output as a tone signal, and when the note-off signal is supplied, the sampler 2 stops reading the sampling waveform.

Since the sampling waveforms A and B are recorded at a speed of tempo = 120,
If the operator designates tempo = 120 for sequencer 1, the speed at which sequencer 1 outputs automatic performance data and the tempo of sampling waveforms A and B become the same. The sampling waveforms A and B are reproduced at a speed that matches the tempo of the automatic performance data.

In the sampler 2, a sampling waveform 3 including the waveforms A and B described above is recorded at a tempo of 120, for example. The time stretch circuit 4 can change the reproduction tempo of the sampling waveform 3. To specify a tempo for the time stretch circuit, the value of the tempo is specified by a numerical value. For example, a numerical value is set using an up / down switch, a numeric keypad, a rotary volume, or the like. Instead of specifying a numerical value, an interval of one beat may be specified by tapping or the like.

For example, a case will be described in which a sampling waveform 3 recorded at tempo = 120 is played at tempo = 100, for example. The operator sets tempo =
100 is specified, and tempo = 100 is also specified in the time stretch circuit 4 in the same manner. The time stretching circuit 4 time-stretches a sampling waveform recorded at tempo = 120 to a sampling waveform at tempo = 100. The time stretching circuit 4 performs time stretching by thinning out or interpolating the signal waveform so as not to change the pitch in the sampling waveform. The time stretching may be a real-time process, that is, performing compression and decompression on the time axis while reproducing a waveform, or a non-real-time process, that is, performing a time-axis compression and decompression once and recording a new waveform, and then performing the subsequent processing. May be played back from

There are various time stretching methods, which are well-known and will not be described in detail here. Sequencer 1 supplies automatic performance data to sampler 2 at tempo = 100. Sampler 2
Can receive a note-on signal from the sequencer 1 and output a time-stretched tempo = 100 waveform as a tone signal.

FIG. 3 shows the automatic performance data supplied to the sampler and the reproduced waveform read and reproduced by the sampler. Automatic performance data is supplied from a sequencer to a sampler. The sampler reads and reproduces a sampling waveform according to the supplied automatic performance data.

FIG. 3A shows a reproduction waveform of the sampler designated to tempo = 120. The sequencer supplies the automatic performance data to the sampler at tempo = 120.
As shown in FIG. 2, a waveform A and a waveform B recorded at a tempo of 120 are recorded in the sampler in advance. Since the tempos of the waveforms A and B are the same as the tempo of the automatic performance data, the sampler can reproduce the recorded waveform as it is.

At time t11, note number = C3
Is supplied to the sampler. When the note-on signal is supplied, the sampler obtains a note number = C
The reproduction of the waveform A set to 3 is started. Since the waveform A has a length of two measures, the sampler ends the reproduction of the waveform A at time t12. Here, when the loop reproduction is set for the waveform A, when the reproduction of the waveform A ends, the sampler starts reproduction from the beginning of the waveform A again and repeats the reproduction of the waveform A. The waveform A is repeatedly reproduced until a note-off signal is supplied.

At time t13, at the same time when the waveform A has been reproduced twice, a note-off signal of note number = C3 is supplied from the sequencer. When the note-off signal is supplied, the sampler stops reproducing the waveform A corresponding to note number = C3.

At time t13, when the note-on signal of note number = D3 is supplied following the supply of the note-off signal, the sampler starts reproducing the waveform B set to note number = D3.

At time t14, after reproducing the two measures of the waveform B, the sequencer supplies a note-off signal of note number = D3. When the note-off signal is supplied, the sampler stops reproducing the waveform B.

At time t14, when the note-on signal of note number = C3 is supplied following the supply of the note-off signal, the sampler starts reproducing the waveform A again.
As described above, when the waveforms A and B have the same tempo as the automatic performance data, the sequencer and the sampler can perform the synchronous performance without performing any special processing.

FIG. 3B shows a reproduction waveform of the sampler designated with the tempo = 100. The sequencer supplies automatic performance data to the sampler at a tempo of 100.
The automatic performance data of tempo = 100 is the same as the automatic performance data of FIG. 3A, but is supplied to the sampler at a lower speed (longer time interval) than tempo = 120.

The sampler has a tempo = 12 shown in FIG.
Since the waveform A and the waveform B recorded at 0 are recorded,
The time stretching circuit performs time stretching of the waveforms A and B from tempo = 120 to tempo = 100. The sampler reproduces the time-stretched waveform.

At time t21, note number = C3
Is supplied, and at time t23, a note-off signal is supplied. As the speed at which the automatic performance data is supplied is reduced, the tempo of the playback waveform of the time-stretched sampler is also reduced. Since the waveform of the reproduced waveform is interpolated by the time stretch circuit, only the tempo is reduced without changing the pitch of the musical sound.

As a result, during the period from the note-on signal of note number = C3 to the supply of the note-off signal,
Waveform A is reproduced twice as in the case of tempo = 120. If there is no time stretch circuit, waveform A
However, during the third repetition, the note-off signal is supplied during the third repetition, and it is interrupted.

As described above, the time stretch circuit time-stretches the sampling waveform, so that the sampler can reproduce the sampling waveform suited to the supply speed of the automatic performance data. The sampler does not need to record the sampling waveforms of both tempo = 100 and tempo = 120 in advance, and the time stretch circuit can generate the sampling waveform of the desired tempo from the sampling waveform of tempo = 120. . The present invention can also be applied to a case where a plurality of waveforms having different tempos are provided as original waveforms and are reproduced at the same tempo.

FIG. 4A shows an original waveform in which a musical tone played in accordance with a predetermined tempo TMP1 (eg, 120) is recorded. The original waveform is a signal waveform in which a drum performance of, for example, two measures is recorded as described above, but the performance time (recording time) may be unknown.

As a method of recording a tone signal of a predetermined tempo TMP1, a method of recording a performance performed in accordance with a metronome or the like can be considered. At this time, it is necessary to set the metronome to a predetermined tempo TMP1.

As another method, there is a method of recording a musical tone played without using a metronome, and automatically extracting the tempo TMP1 by performing signal processing on the recorded waveform. For example, when a drum performance is recorded, it is possible to detect only a musical tone of a certain drum tone (for example, bass drum) and calculate a tempo.

Also, when the recorded waveform is reproduced, a metronome is sounded, and the tempo of the metronome is obtained by listening to the ear and adjusting the metronome tempo so that the tempo of the metronome coincides with the tempo of the waveform. Good.

FIG. 4B shows a reproduced waveform at tempo = 100 generated by performing time stretching on the original waveform recorded at a predetermined tempo TMP1. FIG.
9 is a flowchart showing a process in which the time stretching circuit performs time stretching on an original waveform of a predetermined tempo TMP1 (for example, 120). The time stretch circuit normally performs the basic processing in the main routine, but when the time stretch is instructed, the next step P
The processing is started from 1.

In step P1, the range of the original waveform to be time-stretched is specified, for example, in bar units. The specification of the range may be the whole or a part of the recorded original waveform.

In step P2, a desired tempo TMP2 (for example, 100) of a reproduced waveform generated by time stretching is designated. In step P3, the time stretching ratio RT is calculated by the following equation.

RT = TMP1 / TMP2 TMP1 is the tempo of the original waveform before time stretching, and is a value known in advance by, for example, recording using a metronome. TMP2 is the tempo of the reproduced waveform after time stretching, and is the value specified by the operator in step P2.

In step P4, time stretching is performed on the original waveform in the range specified in step P1 at the calculated rate RT. When the time stretching process ends, a reproduction waveform of the specified tempo TMP2 is generated. The generated reproduced waveform is recorded in a storage area different from the original waveform. It is not always necessary to record the reproduced waveform, and the original waveform may be time-stretched in real time to output a tone signal to the sampler.

When the time stretching is performed, the processing ends, and the process returns to the main routine. The sampler outputs a tone signal based on the time-stretched reproduction signal.

FIG. 5A shows an original waveform in which a musical tone played with an unknown tempo is recorded. When performing without using the metronome, the tempo of the performance is unknown. If the tempo of the original waveform is unknown,
The time stretching cannot be performed by the processing method of (1). In such a case, the recording time TW1 of the original waveform is calculated, and time stretching is performed based on the recording time TW1. The recording time TW1 can be calculated from the sampling frequency at which the original waveform was recorded and the number of samples.

FIG. 5B shows a reproduced waveform generated by performing time stretching on the original waveform recorded with the tempo unknown. The playback waveform is tempo = 1
00 is specified.

FIGS. 7 and 8 show two different processing methods for performing time stretching on an original waveform whose tempo is unknown. FIG. 7 is a flowchart showing a process of performing time stretching on an original waveform whose tempo is unknown. When the time stretch circuit is instructed, the time stretch circuit
The processing from step Q1 is started.

In step Q1, the range of the original waveform for which time stretching is to be performed is specified, for example, in bar units. The specification of the range may be the whole or a part of the recorded original waveform.

In step Q2, the required time TW1 in the specified range is calculated by the following equation. TW1 = number of samplings / sampling frequency The sampling frequency is the frequency when the original waveform is sampled and recorded. The sampling number is a number sampled in the range of the original waveform specified in step Q1. The time actually required for the reproduction may be measured and obtained.

In step Q3, the number of beats NNT1 included in the range of the original waveform specified in step Q1 is determined and specified. The number of beats corresponds to, for example, the number of quarter notes included in the specified range. In other words, it indicates how many quarter notes the specified range corresponds to.
The number of bars may be calculated instead of the number of quarter notes. To determine the number of beats, for example, there is a method of analyzing original waveform data or a method in which an operator actually listens to a musical tone of the original waveform to make a determination.

In step Q4, a desired tempo TMP2 (for example, 100) of a reproduced waveform generated by time stretching is designated. In step Q5, the tempo TMP1 of the original waveform is calculated by the following equation.

TMP1 = NNT1 × 60 / TW1 NNT1 is the number of beats of the original waveform obtained in step Q3. TW1 is the required time TW1 [s] of the original waveform calculated in step Q2.

In step Q6, the time stretching ratio RT is calculated by the following equation. RT = TMP1 / TMP2 TMP1 is the tempo of the original waveform before time stretching calculated in step Q5. TMP2 is executed in step Q4
Is the tempo of the reproduced waveform after the time stretching specified by the operator.

In step Q7, a time stretching process is performed on the original waveform in the range specified in step Q1 at the rate RT calculated in step Q6. When the time stretching process is completed, the specified tempo TMP2
Is generated, and the process ends. The sampler outputs a tone signal based on the time-stretched reproduced waveform.

FIG. 8 is a flowchart showing another processing method for performing time stretching on the original waveform whose tempo is unknown. When the time stretch circuit is instructed, the time stretch circuit starts processing from step R1.

Steps R1 to R4 are the same as the processing in the flowchart of FIG. Step R1
Use to specify the range of the original waveform for which you want to perform time stretching,
The required time TW1 in the range specified in step R2 is calculated, the number of beats NNT1 of the original waveform is specified in step R3, and the desired tempo TMP2 of the reproduced waveform is specified in step R4.

In step R5, the required time TW2 [s] of the reproduced waveform after time stretching is calculated by the following equation. TW2 = NNT1 × 60 / TMP2 NNT1 is the number of beats of the original waveform obtained in step R3, and is the same as the number of beats of the reproduced waveform after time stretching. TMP2 is the tempo of the reproduced waveform specified by the operator in step R4.

In step Q6, the time stretching ratio RT is calculated by the following equation. RT = TW2 / TW1 TW2 is the required time of the reproduced waveform after the time stretching calculated in step R5. TW1 is equal to step R2
Is the time required for the original waveform before the time stretching calculated in step (1).

In step R7, time stretching is performed on the original waveform in the range specified in step R1 at the rate RT calculated in step Q6. When the time stretching process is completed, the specified tempo TMP2
Is generated, and the process ends. The sampler outputs a tone signal based on the time-stretched reproduced waveform.

The processing method of time-stretching the original waveform has been described above. However, in order to inform the operator how much the time-stretched reproduction waveform generated by time-stretching has been performed, the time required for reproducing the reproduction waveform is required. May be displayed on the display device. In this case, it is sufficient that the required time TW2 of the reproduced waveform has already been calculated in the process, but if it has not been calculated yet, it is necessary to calculate it by a similar process.

FIG. 9 shows a process of performing waveform retarding and accelerand by applying the above-described technique. Ritaldand indicates that the performance is gradually slowed down, and Acceleland indicates that it is gradually accelerated.
The time stretch circuit can realize ritardando and accelerand by performing time stretch processing.

FIG. 9A shows an original waveform recorded at a constant tempo. A case where the retard processing is performed on the original waveform will be described. First, a range L0 of a waveform to be subjected to ritardand processing is designated. Next, the designated waveform range L0 is divided into a plurality of regions. For example,
When divided into five regions, the waveform range L0 becomes five regions L
1, L2, L3, L4, L5. The ritardand will gradually slow down the tempo in five steps. The tempo changes smoothly as the number of divisions increases.

FIG. 9B shows the tempo of the waveform obtained by performing the ritardando process on the original waveform of FIG. 9A. It is assumed that the original waveform has a constant tempo and has a tempo value tmp0. The waveform of the ritardando is initially set to the tempo t
mp0, and then gradually changes in five regions L1 to L5. The operator needs to specify a tempo width DT that changes in one area.

A constant tempo tm before the waveform range L0
The reproduction is performed at p0, and the tempo is slightly slowed down in the area L1, and the reproduction is performed at the tempo tmp1. The tempo tmp1 is later than the tempo tmp0 by the change width DT as in the following equation.

Tmp1 = tmp0-DT Similarly, in the area L2, the tempo (tm
p2), and in the areas L3, L4, and L5, the tempos tmp3, tmp4, and tmp5 become slower by DT in order.

FIG. 10 shows the original waveform before performing the ritardando process and the retardand waveform after performing the ritardando process. FIG. 10A shows an original waveform before the ritardand processing. The original waveform is divided into five regions L1, L2, L3, L4,
Divide into L5 and slow down the tempo in 5 steps. Since all five areas L1 to L5 have the same tempo (tmp0),
Have the same time span.

FIG. 10 (B) shows the waveform after the ritardando processing. Due to the retardation process, the tempo gradually decreases from the area L1 to the area L5. Five areas L1 to L
The time width corresponding to 5 gradually changes long.

FIG. 11 is a flowchart showing processing for generating ritardand and accelerando. The time stretch circuit can realize ritardando and accelerand by performing time stretch processing.

In step V1, a range L0 of a waveform to be subjected to ritardando or accelerando is designated.
In step V2, the tempo change width DT is specified. In practice, it is preferable that the tempo changes gradually and smoothly, but here, the tempo is changed in fine steps at regular intervals. Here, a stepwise change width DT of one step is designated.

At step V3, the waveform range L0 designated at step V1 is divided into a plurality of regions. For example, when the region is divided into five regions L1 to L5, in the case of ritardando, the tempo gradually decreases in five stages.

At step V4, the tempo of each divided area is calculated. The tempo of each area is calculated from the initial tempo tmp0 of the waveform and the tempo change width DT specified in step V2. For example, the tempo tmp1 of the area L1 is
tmp1 = tmp0−DT, and the tempo tm of the area 2
p2 is tmp2 = tmp0−2 × DT. If the change width DT is a positive value, it becomes a ritardand, and if the change width DT is a negative value, it becomes an accelerand.

In step V5, the ratio of the time stretch for each divided area is calculated. For example, the ratio RT1 of the area L1 is RT1 = tmp0 / tmp1, and the area L1
The ratio RT2 of 2 is RT2 = tmp0 / tmp2.

In step V6, the time division processing is performed on the divided area L1 at the corresponding ratio RT1. Step V
At 7, it is checked whether or not the time stretch processing has been completed for all the divided areas. If the processing has not been completed for all the divided areas, the processing of the time stretch for the next divided areas L2 to L5 is repeated in step V6. After the processing of all the areas L1 to L5 is completed, step V
Proceed to 8.

At step V8, it is checked whether or not the area after the area L0 specified at step V1 is at a tempo. Attempo is an instruction to return to the original speed. If the tempo is the atempo, after the area L0, the processing is terminated without performing the time stretch, leaving the tempo tmp0 of the original waveform. On the other hand, if not at the atempo, the process proceeds to step V9.

In step V9, time stretching processing is performed on the area after the area L0 at the same rate RT5 as that of the last divided area L5. The area after the area L0 is the tempo tmp0
Is converted to tempo tmp5. FIG. 12 shows a method for performing time stretching by synchronizing the original waveform with the MIDI clock.

FIG. 12A shows a signal waveform of a MIDI clock. The sequencer 1 shown in FIG. 1 reads out the automatic performance data in synchronization with the MIDI clock and supplies it to the sampler 2. The MIDI clock is, for example, a MIDI signal generated at intervals of a 96th note.

FIG. 12B is a waveform diagram showing an original waveform. The original waveform is stored as the sampling waveform 3 in the sampler 2 of FIG. FIG. 12C shows that the original waveform is M
This is a reproduced waveform generated by performing time stretching processing in synchronization with the IDI clock. When performing time stretching on the original waveform, time stretching is performed so as to match the MIDI clock interval. That is, the tempo of the original waveform is converted to match the tempo of the MIDI clock.

Note that the unit of the time stretch area need not be the area between the minimum clocks of the MIDI clock, and the time stretch may be performed in a wider area.

FIG. 13 is a flowchart showing a process for performing time stretching by synchronizing the original waveform with the MIDI clock. The process starts from step W1. In step W1, a clock tempo TMPC is obtained from the MIDI clock interval. The tempo is represented by the number of quarter notes struck per minute.

In step W2, the time stretching ratio RT is calculated by the following equation. RT = TMP1 / TMPC TMP1 is a previously known tempo of the original waveform before time stretching. TMPC is the tempo of the MIDI clock calculated in step W1.

At step W3, time stretching is performed on the original waveform at the rate RT calculated at step W2. When the time stretching process ends, a reproduction waveform of the tempo TMPC is generated, and the process ends. The sampler outputs a tone signal based on the time-stretched reproduced waveform.

It should be noted that the present invention is not limited to the MIDI signal, and may be controlled so as to synchronize with the tempo of another periodic signal. As described above, when performing using a sequencer and a sampler, the performance speed can be specified by specifying the tempo for both the sequencer and the sampler, making it easy to specify the time stretch ratio. is there.

By connecting a time stretch circuit to the sampler and time stretching the original waveform of the sampler at a desired tempo, the sampler can easily perform synchronous reproduction with an automatic performance device such as a sequencer.

Even if the tempo of the original waveform stored in the sampler is not known in advance, time stretching can be performed by obtaining the required time and the number of beats of the original waveform.

Further, the time stretching circuit can perform a time stretching process to make the original waveform into a ritardand or an accelerrand, or to synchronize with the MIDI clock.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like are possible.

[0091]

By designating a desired tempo for a tone signal waveform having a predetermined tempo, a tone signal waveform having a desired tempo can be generated. Since the tempo represents the performance speed of a musical sound, the performance speed can be easily converted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a performance system of a sequencer and a sampler using a time stretch circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a sampling waveform stored in a sampler.

FIG. 3 shows automatic performance data supplied to a sampler and a reproduced waveform read and reproduced by the sampler. FIG.
FIG. 3A is a waveform diagram showing a reproduction waveform of a sampler designated to tempo = 120, and FIG.
FIG. 7 is a waveform diagram showing a reproduction waveform of the sampler designated by “1”.

FIG. 4A is a waveform diagram of an original waveform in which a musical tone played according to a predetermined tempo TMP1 is recorded, and FIG. 4B is a waveform diagram of the original waveform recorded at a predetermined tempo TMP1. FIG. 9 is a waveform diagram of a reproduced waveform at a tempo of 100 generated by performing time stretching by using the following formula.

FIG. 5A is a waveform chart showing an original waveform in which a musical tone played with an unknown tempo is recorded.
(B) is a waveform diagram showing a reproduced waveform generated by performing time stretching on an original waveform recorded with the tempo unknown.

FIG. 6 is a flowchart showing a process in which a time stretching circuit performs time stretching on an original waveform at a predetermined tempo.

FIG. 7 is a flowchart illustrating a process of performing time stretching on an original waveform whose tempo is unknown.

FIG. 8 is a flowchart illustrating a processing method for performing time stretching on another original waveform whose tempo is unknown.

FIG. 9 shows a process for generating ritardand and accelerando. FIG. 9A is a waveform diagram showing an original waveform recorded at a constant tempo, and FIG. 9B shows a tempo of a waveform obtained by performing the ritardando process on the original waveform of FIG. 9A. It is a conceptual diagram.

FIG. 10 shows an original waveform before the ritardund processing and a ritardund waveform after the ritardund processing. FIG. 10A is a waveform diagram of an original waveform before the retard processing, and FIG. 10B is a waveform diagram showing a waveform after the retard processing.

FIG. 11 is a flowchart showing processing for generating ritardand and accelerand.

FIG. 12 shows a method of performing time stretching by synchronizing an original waveform with a MIDI clock. FIG.
FIG. 12 is a waveform diagram showing a signal waveform of a DI clock, and FIG.
FIG. 12B is a waveform chart showing an original waveform, and FIG. 12C is a waveform chart of a reproduced waveform generated by performing a time stretching process in synchronization with the MIDI clock.

FIG. 13 is a flowchart showing a process of performing time stretching by synchronizing an original waveform with a MIDI clock.

[Explanation of symbols]

1 sequencer, 2 sampler, 3 sampling waveform, 4 time stretch circuit

Claims (5)

(57) [Claims] 1. A waveform processing apparatus for performing a time stretching process for compressing or expanding the time axis of a tone signal waveform without changing the pitch of a tone using a tempo which is the number of beats in a predetermined time. A pre-conversion tempo specifying means for specifying an original tempo of the tone signal waveform, a post-conversion tempo specifying means for specifying a desired tempo after the conversion of the tone signal waveform, and a tempo specified by the pre-conversion tempo specifying means. Calculating means for calculating a ratio of the tempo designated by the converted tempo designating means; and performing time stretching of the tone signal waveform in accordance with the ratio calculated by the calculating means, and specifying by the converted tempo designating means. A time-stretched waveform generating means for generating a musical tone signal waveform having a predetermined tempo. 2. The waveform processing apparatus according to claim 1, wherein the pre-conversion tempo specifying means determines a tempo according to a required time and a beat number of the tone signal waveform, and then specifies the tempo. 3. A waveform processing apparatus for performing a time stretching process for compressing or expanding a time axis of a tone signal waveform without changing a pitch of the tone, wherein the time-stretching processing is performed before designating a required time of the tone signal waveform. Required time designating means, beat number designating means for designating the number of beats of the musical tone signal waveform, converted tempo designating means for designating the tempo which is the number of beats at a predetermined time for the converted tone signal waveform, Means for calculating the required time of the converted tone signal waveform in accordance with the number of beats specified by the means and the tempo specified by the converted tempo specifying means; A ratio calculating means for calculating a ratio between the designated required time and the required time calculated by the converted required time calculating means; A time stretching waveform generating means for performing time stretching of the sound signal waveform and generating a tone signal waveform having a tempo designated by the converted tempo designating means. 4. A sound signal of ritardando or accelerando by a time stretching process for compressing or expanding the time axis of a tone signal waveform without changing the pitch of the tone using a tempo which is the number of beats in a predetermined time. A waveform processing apparatus for generating a waveform, wherein a pre-conversion tempo designating means for designating the original tempo of the tone signal waveform, a displacement designating means for designating the degree to which the tempo of the tone signal waveform is changed, and ritardando or acceleland Range specifying means for specifying a range of a tone signal waveform; dividing means for dividing the range specified by the range specifying means into a plurality of regions; tempo specified by the pre-conversion tempo specifying means and the displacement specifying means After conversion to calculate the tempo of each area divided by the dividing means according to the specified degree A ratio calculating unit that calculates a ratio between a tempo specified by the pre-conversion tempo specifying unit and a tempo of each area calculated by the post-conversion tempo calculating unit; A waveform generating means for performing time stretching on a plurality of areas divided by the dividing means in accordance with a ratio of each area to generate a ritardand or acceleland tone signal waveform. 5. A waveform processing apparatus for performing a time stretching process for compressing or expanding the time axis of a tone signal waveform without changing the pitch of a tone using a tempo which is the number of beats in a predetermined time. Periodic signal generating means for generating a periodic signal having an interval corresponding to a tempo; pre-conversion tempo specifying means for specifying an original tempo of a tone signal waveform; and a cycle for specifying a tempo according to a time interval of the periodic signal Signal tempo designating means; computing means for computing a ratio between a tempo designated by the pre-conversion tempo designating means and a tempo designated by the periodic signal tempo designating means; Time stretch waveform generation for performing time stretching of a tone signal waveform and generating a tone signal waveform having a tempo designated by the periodic signal tempo designating means. Waveform processing apparatus having a stage.