JP3943250B2 - Waveform compression / decompression device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waveform compression / decompression apparatus that compresses or expands a waveform in the time axis direction.
[0002]
[Prior art]
Conventionally, so-called pitch shifters are known that change the pitch of a musical sound or the like by converting the pitch of a signal representing a waveform of the musical sound or the like. However, if the pitch of the signal representing the waveform of a phrase that is long enough to understand the tempo of the musical tone is converted by the pitch shifter, the tempo of the musical tone will also change. Devices that only change height are desired. Conversely, a device that changes the tempo of a musical tone while keeping the pitch of the musical tone is also desired.
As a device that meets these demands, a waveform compression / expansion device has been proposed that compresses or expands a waveform of a musical sound or the like in the time axis direction independently of the pitch.
[0003]
By the way, as a method for compressing or expanding a waveform, a plurality of compression / decompression methods can be considered. There are various types of waveforms that represent sound, such as periodic waveforms, non-periodic waveforms, intermittent waveforms, and continuous waveforms. A compression / decompression method suitable for compression or expansion in the time axis direction is conceivable. In other words, when a certain waveform is compressed and expanded using a method suitable for the type of waveform, the sound quality represented by the compressed and expanded waveform is good, but when a certain waveform is compressed and expanded using a method that is not suitable for the type of waveform. The sound quality represented by the waveform after compression / expansion is poor.
[0004]
[Problems to be solved by the invention]
However, generally, a waveform of a musical sound or the like is a waveform in which various waveforms are mixed. For this reason, no matter which compression / decompression method is adopted, there is a problem that the sound quality of the musical sound or the like represented by the waveform after the compression or expansion of the waveform of the musical sound or the like tends to deteriorate.
In view of the above circumstances, an object of the present invention is to provide a waveform compression / expansion device having good sound quality such as a musical sound represented by a waveform after compression / expansion of a waveform such as a musical sound.
[0005]
[Means for Solving the Problems]
The waveform compression / expansion apparatus according to the present invention that achieves the above-mentioned object is configured to share a plurality of band-divided waveforms obtained by dividing an original waveform into waveform components of a plurality of frequency bands by at least two types of compression / expansion methods. Compressing / decompressing means for generating a plurality of compressed / decompressed waveforms by compressing or expanding all the band-divided waveforms in the time axis direction by the same amount;
And a superimposing unit that generates a compressed / decompressed original waveform in which the original waveform is compressed or expanded in the time axis direction by superimposing a plurality of compressed / decompressed waveforms generated by the compression / decompression unit. .
In many cases, a waveform representing a musical tone or the like in which various waveforms are mixed can generally be separated into waveform types by dividing them into waveform components of a plurality of frequency bands.
According to the waveform compression / expansion apparatus of the present invention, a plurality of band division waveforms obtained by dividing an original waveform into waveform components of a plurality of frequency bands are shared by at least two types of compression / expansion methods, or compressed in the time axis direction. Even if a waveform that represents a musical tone or the like is used as the original waveform, compression is performed by using a compression / decompression method that is suitable for each of the various band-divided waveforms. An expanded waveform can be generated.
[0006]
In general, if one type of compression / decompression method is used to compress and decompress the original waveform, periodic noise called “purple feeling” tends to occur. However, according to the waveform compression / expansion apparatus of the present invention, By selecting each compression / decompression method for compressing / decompressing each band-divided waveform so that the phases of the compressed / decompressed waveforms are different from each other, it is possible to prevent a “plunging feeling”.
In the waveform compression / expansion apparatus according to the present invention, the compression / expansion waveform generation means performs compression / expansion processing on the plurality of band division waveforms with a longer processing period as the band division waveform carrying a waveform component of a lower frequency band, It is desirable to generate a compression / decompression waveform corresponding to the band division waveform.
[0007]
Generally, a waveform component in a lower frequency band is a waveform component that is more important for human hearing. Therefore, a waveform component in a lower frequency band needs to be subjected to advanced compression / decompression processing that requires a longer processing time. In general, the sound quality is maintained even if the processing frequency is reduced for a waveform component in a lower frequency band.
For this reason, a band division waveform carrying a waveform component in a low frequency band is subjected to compression / decompression processing with a longer processing cycle, thereby providing a time margin for performing advanced compression / decompression processing on the waveform component in the low frequency band. And all waveform components can be efficiently compressed and expanded.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, in describing an embodiment of the present invention, an example of a compression / decompression method will be described first, and then an embodiment of a waveform compression / decompression apparatus of the present invention will be described.
Hereinafter, in the description of each compression / decompression method, a waveform before compression / expansion to be compressed / expanded is referred to as an “original waveform”, and a waveform after compression / expansion is referred to as a “compression / decompression waveform”. A case will be described in which a compressed / decompressed waveform having the same pitch as the original waveform and having the original waveform expanded in the time axis direction is generated. In some cases, the waveform and waveform data representing the waveform are used without being distinguished.
[0009]
FIG. 1 is an explanatory diagram of the first compression / decompression method.
In the first compression / decompression method, as will be described in detail below, a clipping start address for dividing the original waveform into one pitch is set on the original waveform, and the original waveform is compressed by about two pitches. Data are alternately read out by the two processing systems at time intervals corresponding to the pitch of the expanded waveform. A processing waveform is generated by each processing system based on the read original waveform, and the generated processing waveforms are superimposed to generate a compression / decompression waveform. When the original waveform is read, the waveform is compressed or expanded in the time axis direction by skipping reading or overlapping reading.
1A shows the original waveform, and the horizontal axis of FIG. 1A indicates the address of the waveform data representing the original waveform and also corresponds to the time axis of the original waveform. . FIG. 1A shows cut start addresses csa1,..., Csa7 that divide the original waveform for each pitch.
[0010]
FIG. 1B shows a time point t arranged on the time axis at a time interval corresponding to the reproduction pitch of the compression / decompression waveform. ₀ , ..., t ₇ Is shown at each time t ₀ , ..., t ₇ The waveform data for about 2 pitches of the original waveform is started to be read. 1B shows position information PP (0),..., PP (7) indicating positions on the original waveform, and each position information PP (0),. The position indicated by PP (7) is ₀ , ..., t ₇ It becomes the object of the reading started in. In addition, the position on the original waveform indicated by each piece of position information PP (0),. ₀ , ..., t ₇ Each arrow F from FIG. 1 (B) to FIG. 1 (A) starting from ₀ , ..., F ₇ Each arrow F is indicated by ₀ , ..., F ₆ Indicates positions on the left side of the drawing relative to the cut-out start addresses csa1,..., Csa7.
[0011]
Here, the intervals between the cut-out start addresses csa1,..., Csa7 shown in FIG. 1 (A) and each time t shown in FIG. ₀ , ..., t ₆ Are equal to each other, and as described above, a compressed / decompressed waveform having the same pitch as the pitch of the original waveform is generated. Further, the positions on the original waveform indicated by the time information PP (1),..., PP (6) indicate positions on the left side of the drawing with respect to the respective cut start addresses csa2,. For this reason, as will be described later, waveform data is read out repeatedly, and as described above, a compressed and expanded waveform in which the original waveform is expanded in the time axis direction is generated.
The triangular waveforms shown by the dotted lines in FIGS. 1C and 1D show the windows for the first processing system and the second processing system, respectively, and FIG. 1C and FIG. A waveform indicated by a solid line in FIG. 1 (D) indicates each processing waveform. FIGS. 1C and 1D show the cut start address, and this cut start address corresponds to the top of the waveform data for two pitches read by each processing system. To do. Each processing waveform is generated by multiplying the window shown in FIGS. 1C and 1D and the waveform data read by each processing system, and these processing waveforms are superimposed. A compression / decompression waveform is generated.
[0012]
Time t ₀ Then, reading of the waveform data by the first processing system is started. As shown in FIGS. 1 (A) and 1 (B), the position information PP (0) indicates the position of the extraction start address csa1, and as shown in FIG. 1 (C), the extraction start address csa1. Waveform data for two pitches is read out.
Time t ₁ Then, reading of the waveform data by the second processing system is started. As shown in FIGS. 1A and 1B, the position information PP (1) indicates the position between the cut start address csa1 and the cut start address csa2. For this reason, this position is included in the reading target, and waveform data for two pitches is read from the cut-out start address csa1 as shown in FIG. As a result, waveform data is redundantly read out.
As above, time t ₂ , ..., t _Five Then, reading of waveform data for two pitches is started from the cut start addresses csa2,..., Csa5.
[0013]
Time t ₆ Then, as shown in FIG. 1C, the first processing system starts reading waveform data for two pitches from the cut-out start address csa5, and performs repeated reading of the waveform data.
As a result of such redundant reading, the original waveform corresponding to time To shown in FIG. 1A is expanded in the time axis direction, and a compressed and expanded waveform corresponding to time Ts shown in FIG. 1D is generated. The Rukoto.
FIG. 2 is an explanatory diagram of the second compression / decompression method.
In the second compression / decompression method, as will be described in detail below, a waveform portion is alternately read out by the two processing systems from the original waveform, and this waveform portion proceeds on the original waveform at a constant speed. The reading start position to be started is the top. Based on the read waveform portion, each processing waveform is generated by each processing system, and the generated processing waveforms are superimposed to generate a compressed / decompressed waveform. The pitch of the compression / decompression waveform is determined according to the reading speed of the waveform portion, and the compression rate or expansion rate of the waveform in the time axis direction is determined according to the progress speed of the reading start position.
[0014]
FIG. 2A shows the original waveform, and the horizontal axis of FIG. 2A indicates the address of the waveform data representing the original waveform, and corresponds to the time axis of the original waveform.
FIG. 2B shows a time point t at which each processing system starts reading the waveform portion. ₀ , ..., t _Five Is shown at each time t ₀ , ..., t _Five Position information PP (0),..., PP (5) indicating the reading start position is shown. In addition, the position on the original waveform indicated by each position information PP (0),. ₀ , ..., t _Five Each arrow F toward FIG. 2 (A) starting from ₀ , ..., F _Five Each arrow F is indicated by ₀ , ..., F _Five Is the time t ₀ , ..., t _Five The position corresponding to the past time is shown.
2 (C) and 2 (D) show waveform portions W alternately read by the first processing system and the second processing system. ₀ , ..., W _Five Each waveform portion starts at each reading start position indicated by each position information PP (0),..., PP (5).
[0015]
FIGS. 2 (E) and 2 (F) show windows for the first processing system and the second processing system, and the waveform portions indicated by these windows and the reference numerals attached to the windows. And each processed waveform is generated. These processing waveforms are superimposed to generate a compressed / decompressed waveform.
Here, each waveform portion W ₀ , ..., W _Five Is the same as the recording speed of the original waveform. For this reason, each waveform portion W after being read by the first processing system and the second processing system shown in FIG. 2 (C) and FIG. 2 (D). ₀ , ..., W _Five The pitch of each waveform portion W before being read from the original waveform ₀ , ..., W _Five Therefore, a compressed / decompressed waveform having the same pitch as that of the original waveform is generated as described above. Further, the progress speed of the reading start position is slower than the recording speed of the original waveform, and as shown in FIGS. 1 (A) and 1 (B), each time t ₁ , ..., t _Five Each reading start position corresponding to is at each time point t. ₁ , ..., t _Five Therefore, it takes a longer time than the recording time of the entire original waveform to read out the entire original waveform. As a result, a compressed / decompressed waveform corresponding to the time Ts shown in FIG. 2F is generated, in which the original waveform corresponding to the time To shown in FIG. 2A is expanded in the time axis direction.
[0016]
FIG. 3 is an explanatory diagram of the third compression / decompression method.
In this third compression / decompression method, as will be described in detail below, a mark address is set that divides the original waveform upward and the original waveform is divided into waveform segments in which the reproduced sound is natural even if the original waveform is reproduced cyclically. Each waveform section is sequentially read out and reproduced to generate a compressed / decompressed waveform. The compression / decompression of the waveform is performed by determining the pitch of the compression / decompression waveform in accordance with the readout speed of the waveform section and skipping or re-reading the waveform section.
FIG. 3A shows the original waveform and the mark address m set on the original waveform. ₁ , ..., m ₇ In FIG. 1A, the horizontal axis indicates the address of waveform data representing the original waveform and corresponds to the time axis of the original waveform.
[0017]
FIG. 3B shows a time point t when reading of each waveform section is started. ₀ , ..., t _Five The position information PP (0),..., PP (4) indicating the position on the original waveform is shown, and the position information PP (0),. t ₀ , ..., t _Five It becomes the object of reading started in Further, the position on the original waveform indicated by each piece of position information PP (0),. ₀ , ..., t _Five Each arrow F toward FIG. 3 (A) starting from ₀ , ..., F _Five Indicated by the arrow F ₀ Is the mark address m ₁ The position of the arrow F ₁ Is the mark address m ₁ And mark address m ₂ The position between is shown. Arrow F ₂ Is the mark address m ₂ And mark address m _Three The position between and the arrow F _Three Is the mark address m _Three And mark address m _Four The position between and the arrow F _Four And arrow F _Five Is the mark address m _Four And mark address m _Five The position between is shown.
[0018]
FIG. 3C shows the read waveform section, and also shows a mark address corresponding to the head of each waveform section.
As shown in FIG. 3A and FIG. ₀ Then, the position information PP (0) is the mark address m. ₁ Since the position of the mark address m is indicated as shown in FIG. ₁ Reading of the waveform section starting from is started. Here, the reading speed of the waveform section is the same as the recording speed of the original waveform. Therefore, the pitch of the waveform section shown in FIG. 3C is the same as the pitch of the original waveform shown in FIG. 3A, and a compression / decompression waveform having the same pitch as the pitch of the original waveform is generated.
Time t ₀ At the time t when the entire waveform section from which reading was started is read ₁ The position information PP (1) is the mark address m ₁ And mark address m ₂ , And this position is included in the read target, and as shown in FIG. ₁ Re-reading of the waveform section starting from is started.
After that, each time t ₂ , T _Three , T _Four Respectively, the mark address m ₂ , M _Three , M _Four Reading of the waveform section starting from is started.
[0019]
Time t _Four At the time t when the entire waveform section from which reading was started is read _Five Then, the position information PP (5) is the mark address m. _Four And mark address m _Five The mark address m is set so that this position is included in the read target. _Four Re-reading of the waveform section starting from is started.
As a result of such re-reading, the original waveform corresponding to time To shown in FIG. 3A is expanded in the time axis direction, and a compressed and expanded waveform corresponding to time Ts shown in FIG. 3C is generated. The Rukoto.
As described above, the decompression operation has been described for the three types of compression / decompression methods. However, if the progress speed of the position information of each method is increased, the original waveform data is skipped and read. As a result, the original waveform is in the time axis direction. Thus, a compressed / decompressed waveform that is compressed in the above manner is generated.
[0020]
As described above, the compression and expansion and the size thereof can be changed by setting the traveling speed of the position information.
In the above description, three types of compression / decompression schemes have been described. However, the compression / decompression scheme referred to in the present invention is not limited to the schemes described above, and may be any scheme that compresses or decompresses a waveform in the time axis direction. Further, the “two types of compression / decompression methods” referred to in the present invention include two types of compression / decompression methods among the three types of compression / decompression methods described above. Two compression / decompression schemes, which employ two compression / decompression schemes and have different time intervals for reading the waveform data portion, are also included.
This is the end of the description of the example of the compression / decompression method, and the embodiment of the present invention will be described below.
[0021]
FIG. 4 is a diagram showing an embodiment of the waveform compression / decompression apparatus of the present invention.
This waveform compression / expansion apparatus 10 compresses or expands a plurality of band division waveforms obtained by dividing an original waveform representing a musical sound or the like into a plurality of frequency band waveform components by the same amount in the time axis direction, thereby compressing and expanding each waveform. Is generated and the compressed and expanded waveforms are overlapped to generate a compressed and expanded original waveform in which the original waveform is compressed and expanded in the time axis direction.
The waveform compression / decompression apparatus 10 includes a CPU 11 and a DSP 12. The DSP 12 is controlled by the CPU 11, and a compression / decompression waveform is generated by the DSP 12 as will be described later.
The waveform compression / decompression apparatus 10 includes a hard disk 13, a ROM 14, a MIDI interface 15, a first RAM 16, and an operator 17. The hard disk 13 stores waveform data of an original waveform representing musical sounds and the like, and a band-divided waveform is generated by the DSP 12 based on this waveform data. The ROM 14 stores a program representing the operations of the CPU 11 and the DSP 12, and the program representing the operation of the DSP 12 is transferred to the DSP 12 by the CPU 11. A MIDI signal is input from the outside via the MIDI interface 15, and the CPU 11 sends information indicating the pitch corresponding to the MIDI signal and the sound generation timing corresponding to the MIDI signal to the DSP 12. The first RAM 16 is used as a working memory of the CPU 11, and the operation element 17 is for the user of the waveform compression / decompression device 10 to instruct the CPU 11 to operate.
[0022]
The waveform compression / decompression apparatus 10 includes a D / A converter 18 and a second RAM 19. The second RAM 19 stores divided waveform data indicating the band-divided waveform, and the DSP 12 generates a compressed / decompressed waveform and a compressed / decompressed original waveform based on the divided waveform data. The D / A converter 18 converts the digital signal representing the compression / decompression original waveform generated by the DSP 12 into an analog signal.
FIG. 5 is a diagram illustrating an example of a band division waveform.
In the present embodiment, the original waveform is divided into waveform components of three frequency bands.
FIG. 5A shows an example of the original waveform. This waveform is a waveform indicating a continuous sound represented by a violin sound or the like.
FIG. 5B shows a first band division waveform carrying a waveform component of the highest frequency band among the three frequency bands. This first band division waveform is an intermittent waveform. It becomes.
FIG. 5C shows a second band division waveform that carries a waveform component in a frequency band having an intermediate frequency among the three frequency bands, and FIG. A third band division waveform carrying a waveform component of the frequency band having the lowest frequency among the frequency bands is shown.
In addition to the waveform shown in FIG. 5A, examples of waveforms that are desirably compressed and expanded by the waveform compression / expansion means of the present invention include not only the above-mentioned single instrument sound but also performance sounds played by a plurality of instruments. There are various musical instruments and waveforms indicating performance sounds of performance forms.
[0023]
FIG. 6 is a diagram showing the frequency band of the waveform component carried by each band division waveform.
In this embodiment, the waveform data representing the original waveform is sampled at the sampling frequency fs, and the original waveform includes a waveform component having a frequency of fs / 2 or less. Frequency band B of the waveform component carried by the first band division waveform ₁ Is a frequency band of fs / 2 or lower and fs / 4 or higher, and the sampling frequency f of the waveform data representing the first band division waveform ₁ Is equal to the sampling frequency fs. Frequency band B of the waveform component carried by the second band division waveform ₂ Is a frequency band of fs / 4 or less, fs / 8 or more, and a sampling frequency f of waveform data representing the second band-divided waveform ₂ Is half the sampling frequency fs. The frequency band of the waveform component carried by the third band division waveform is a frequency band of fs / 8 or less, and the sampling frequency f of the waveform data representing the third band division waveform is _Three Is a quarter of the sampling frequency fs.
[0024]
FIG. 7 is an equivalent circuit diagram for explaining the operation of generating the compression / decompression original waveform by the waveform compression / decompression apparatus 10 shown in FIG.
In this equivalent circuit diagram, three waveform memories 191, 192, and 193 are shown. Here, these waveform memories 191, 192, and 193 are respectively shown in FIG. The divided waveform data representing the three band divided waveforms is stored. Three waveform memories 191, 192, and 193 indicate the role of the second RAM 19 shown in FIG.
Further, this equivalent circuit diagram shows three compression / expansion means 121, 122, 123, and these three compression / expansion means 121, 122, 123 constitute the compression / expansion means referred to in the present invention. Yes. By these compression / expansion means 121, 122, 123, the first, second, and third band division waveforms are respectively compressed or expanded in the time axis direction, and output ao, output bo, and output c are generated, respectively. . As described above, the three waveform memories 191, 192, 193 store the divided waveform data representing the first, second, and third band division waveforms shown in FIG. 5, and the first band division waveform is stored. The second and third band division waveforms are different in waveform type. For this reason, in the present embodiment, the above-described second compression / expansion method is employed in the compression / expansion means 121, and the above-described third compression / expansion method is employed in the compression / expansion means 122, 123. The compression / decompression processing by the respective compression / decompression means 121, 122, 123 is performed at the sampling frequency f. ₁ , F ₂ , F _Three Is performed in a processing cycle corresponding to. In each compression / expansion means 121, 122, 123, pitch information indicating the rate of change of the pitch of each band-divided waveform, companding information indicating the compression / expansion amount of the waveform, timing for starting sound generation, and sound generation are stopped. Reproduction instruction information for instructing timing is input. The pitch information, the companding information and the reproduction instruction information are generated by the CPU 11 and sent to the DSP 12 in accordance with the MIDI signal input via the MIDI interface 15 shown in FIG.
[0025]
Further, in this equivalent circuit diagram, a first low-pass filter 124, a second low-pass filter 125, and addition circuits 126 and 127 are shown, and these constitute superposition means according to the present invention. Yes. Further, the compression / expansion means 121, 122, 123, the low-pass filters 124, 125, and the addition circuits 126, 127 show the function of the DSP 12 shown in FIG.
The second low-pass filter is 125, f _Three / 2 (= fs / 8) is a filter that removes a waveform component having a frequency equal to or higher than that of the second low-pass filter 125, and corresponds to a compression / expansion waveform obtained by compressing and expanding the third band division waveform. When the output c from the compression / decompression means 123 is input, the sampling frequency f _Three (= Fs / 4) to sampling frequency f ₂ The so-called oversampling to (= fs / 2) is performed and the sampling frequency f ₂ An output cf with is generated. Thereafter, the output cf is added by the adding circuit 127 to the output bo from the second compression / expansion means 122 corresponding to the compressed / decompressed waveform obtained by compressing / decompressing the second band division waveform, and the output b is generated.
[0026]
The first low-pass filter 124 is f ₂ / 2 (= fs / 4) is a filter that removes a waveform component having a frequency equal to or higher than that. When the output b is input to the first low-pass filter 124, the sampling frequency f ₂ (= Fs / 2) to sampling frequency f ₁ Oversampling to (= fs) and sampling frequency f ₁ An output bf with is generated. Thereafter, the output bf is added by the adder circuit 126 with the output ao from the first compression / expansion means 121 corresponding to the compression / expansion waveform obtained by compressing / expanding the first band division waveform, and the original waveform is compressed / expanded. An output a corresponding to the original compressed / decompressed waveform is generated.
[0027]
FIG. 8 is a flowchart showing the operation of the waveform compression / decompression apparatus shown in FIG.
This flowchart is a flowchart for causing the DSP 12 shown in FIG. 4 to perform an operation equivalent to the operation described with reference to FIG.
The operation represented by this flowchart is based on the sampling frequency f. ₁ (= Fs) is repeatedly executed, and step S103 described below is performed at the sampling frequency f. _Three (= Fs / 4) is repeatedly executed, and steps S106 to S108 described below are performed at the sampling frequency f. ₂ It is repeatedly executed at (= fs / 2).
When the operation represented by this flowchart is started, first, pitch information P and companding information TR are input from the CPU in step S101.
[0028]
Thereafter, an output c is generated in steps S102 to S104.
First, the process proceeds to step S102, and it is determined whether or not the value of the control variable N that is incremented every time the operation shown in the flowchart is repeated is a multiple of four. If it is determined that the value of the variable N is a multiple of 4, the process proceeds to step S103, where the waveform data indicating the third band division waveform is subjected to the third compression / decompression processing shown in FIG. If it is generated and it is determined that the value of the variable N is not a multiple of 4, the process proceeds to step S104, and the output c becomes the value “0”.
Thereafter, an output b is generated in steps S105 to S109.
First, in step S105, it is determined whether or not the value of the control variable N is a multiple of two. If it is determined that the value of the variable N is a multiple of 2, the process proceeds to step S106, where the output c is subjected to filter processing to generate an output cf. In step S107, the waveform data indicating the second band division waveform is subjected to a third compression / decompression process based on the pitch information P and the companding information TR to generate an output bo. In step S108, the output bo and the output cf are added to generate an output b. If it is determined in step S105 that the value of the variable N is not a multiple of 2, the process proceeds to step S109, and the output b becomes the value “0”.
[0029]
Thereafter, an output a is generated in steps S110 to S112.
First, in step S110, the output b is filtered to generate an output bf. Next, proceeding to step S111, the waveform data indicating the first band division waveform is subjected to the second compression / decompression processing shown in FIG. 2 based on the pitch information P and the companding information TR, and the output ao is obtained. Generated. In step S112, the output ao and the output bf are added to generate the output a.
Thereafter, the process proceeds to step S113, and the output a is output via the D / A converter 18 shown in FIG.
Thereafter, in step S114 to step S116, the value of the control variable N is stepped so as to change cyclically within the range of the value “0” to the value “3”, and the process ends.
[0030]
【The invention's effect】
As described above, according to the waveform compression / expansion device of the present invention, the sound quality of the musical sound or the like represented by the waveform after the waveform of the musical sound or the like is compressed and expanded is good.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a first compression / decompression method.
FIG. 2 is an explanatory diagram of a second compression / decompression method.
FIG. 3 is an explanatory diagram of a third compression / decompression method.
FIG. 4 is a diagram showing an embodiment of a waveform compression / decompression apparatus according to the present invention.
FIG. 5 is a diagram illustrating an example of a band division waveform.
FIG. 6 is a diagram illustrating a frequency band of a waveform component carried by each band division waveform.
FIG. 7 is an equivalent circuit diagram for explaining an operation of generating a compression / decompression original waveform by the waveform compression / decompression apparatus.
FIG. 8 is a flowchart showing the operation of the waveform compression / decompression apparatus.
[Explanation of symbols]
10 Waveform compression / decompression device
11 CPU
12 DSP
13 Hard disk
14 ROM
15 MIDI interface
16 RAM
17 Operator
18 D / A converter
19 RAM
121, 122, 123 Compression / decompression means
124,125 Low-pass filter
126,127 Adder circuit
191,192,193 Waveform memory

Claims (2)

Divide multiple band-divided waveforms in which the original waveform is divided into waveform components in multiple frequency bands using at least two compression / decompression methods, and compress all these band-divided waveforms by the same amount in the time axis direction. Or compression / expansion means for generating a plurality of compression / decompression waveforms by expansion, and
And a superimposing unit that generates a compressed / decompressed original waveform in which the original waveform is compressed or expanded in the time axis direction by superimposing a plurality of compressed / decompressed waveforms generated by the compression / decompression unit. Waveform compression / expansion device. The compression / decompression waveform generation means performs compression / decompression processing corresponding to each band-divided waveform by subjecting the plurality of band-divided waveforms to compression / decompression processing with a longer processing period for a band-divided waveform carrying a waveform component of a lower frequency band. 2. The waveform compression / decompression apparatus according to claim 1, wherein the waveform compression / decompression apparatus generates a waveform.

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