JPH0423800B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention outputs different pitches in response to the pitch of an input signal, and is useful for special effect generation devices in the record, broadcasting, and movie industries, or for sound sources with different pitches. The present invention relates to a pitch conversion device that can be used as a pitch correction device and as an accompaniment pitch conversion device in a so-called karaoke machine.

Structure of a conventional example and its problems FIG. 1 shows a conventional example in which a digital memory 1 is used and the write clock f ₀ and the read clock f _v are different. The analog input signal _S0 input to the input terminal 2 is converted into a digital signal S1 via a low-pass filter (hereinafter referred to as "LPF") 3 and an analog-to-digital converter (hereinafter referred to as "ADC") ₄ . Ru. This digital signal S ₁ is synchronized with the write clock f ₀ to the digital memory (e.g.
After being written into the RAM) 1, it is read out in synchronization with the read clock _fv and outputs a digital signal _S2 . This digital signal _S2 is sent to a digital-to-analog converter (hereinafter referred to as "DAC") 5 and an LPF.
6 and is outputted to the output terminal 7 as an analog signal _S3 . The pitch P in this case is determined by the following formula.

P=f _v /f _p ... However, the above conventional example has the following problems.

B. When the pitch is changed significantly, the sound quality of high-frequency instruments such as cymbals and low-frequency instruments such as basses is greatly degraded.

(b) Since the purpose is to convert the pitch of the entire band, the frequency of the sampling clock, that is, the writing clock f to the digital memory 1, must be made very large, which increases the capacity of the digital memory 1, which increases costs. .

OBJECT OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional device, and is capable of manufacturing at a low cost and of high sound quality, and the range of the high sound quality is greater than the limit range of the conventional device. It is an object of the present invention to provide a pitch converting device which can arbitrarily change the pitch to be higher or lower than the pitch of the pitch.

Structure of the Invention In order to achieve the above object, the pitch conversion device of the present invention includes a branching means for branching an input signal into two channels, and a pitch conversion device for converting the frequency of the input signal of one channel of the outlet of the branching means. means, a first equalizer means for extracting a signal in a frequency band of 3KHz or less from the output of the pitch conversion means, a time delay means for delaying the input signal of the other channel, and an output signal of the time delay means.
The configuration includes second equalizer means for extracting a signal in a predetermined frequency band of 3KHz or more, and addition means for adding the output signal of the first equalizer means and the output signal of the second equalizer means.

Further, the pitch conversion device of the present invention converts the input signal into two
A branching means for branching into channels, a pitch converting means for converting the frequency of an input signal of one channel among the outputs of the branching means, and a signal in a frequency band of 3KHz or less is extracted from the output of the pitch converting means. a first filter means; a second filter means for extracting a signal in a frequency band of 3KHz or more from the output of the other channel; an output signal of the first filter means; and an output signal of the second filter means. This configuration includes an adding means for adding the.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The present invention realizes that the frequency band in which humans perceive pitch is only the middle range, and the low range (for example, 150Hz or less).
In the high frequency range (for example, 3KHz or higher), the ability to perceive pitch decreases, and even if the pitch change shown in the formula above is performed for a signal in that frequency band, the percentage of people who perceive that the pitch has changed This is an application of the results of a psychological experiment showing that the

That is, the present invention does not perform pitch conversion on all frequency bands of an input signal, but only performs pitch conversion on bands where changes in pitch are easily perceived. The concept of the present invention will be explained using FIGS. 2 to 7.

FIG. 2 is an explanatory diagram showing the frequency characteristics of a cymbal as an example of a high-range musical instrument, with the horizontal axis representing the frequency and the vertical axis representing the voltage level. In this way, the cymbal outputs the waveform B ₁ around the frequency f ₁ .

FIG. 3 is an explanatory diagram of the case where the pitch of a cymbal is converted, and frequency bands A ₁ and A ₂ indicate the frequency bands where the deterioration of sound quality is large and is a problem in practice. In this way, the band exists both when the pitch is raised and when it is lowered.

FIG. 4 is an explanatory diagram of the frequency characteristics of a bass as an example of a low-frequency instrument, and the bass outputs waveform _B2 .

FIG. 5 is an explanatory diagram when the pitch of the bass is changed, and the frequency bands that are a problem in practice are indicated by A ₃ and A ₄ .

FIGS. 6 and 7 are explanatory diagrams showing the basic idea of the present invention. In other words, the entire band is A ₅ ~ _{A 7}
Pitch conversion is performed only on the band _A5 of frequencies _f7 to _f8 where the pitch shown in Figure 6 is perceived, and the band below frequency _f9 where it is difficult to perceive the pitch shown in Figure 7. A ₆ and a band A ₇ having a frequency f ₁₀ or higher do not perform pitch conversion. The frequencies _f7 to _f10 are
Although it varies depending on the characteristics of the input signal, we have confirmed through psychological experiments that when using normal music as an input signal, f ₇ and f ₉ should be set around 150Hz, and f ₈ and f ₁₀ should be set around 3KHz. .

FIG. 8 is a circuit block diagram of the pitch converter according to the first embodiment of the present invention, in which the same components as those shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. The analog input signal S ₀ input to the input terminal 2 is converted into a digital signal S ₁ via the LPF 3 and ADC 4 . This digital signal S ₁ is inputted via branching means 14 to a digital memory 8 whose write and read clocks are f ₀ and output as a digital signal S ₂ . In this case, since the addresses are different for writing and reading, the digital memory 8 has a time delay function. Also write the other clock to f ₀
The signal is input to the digital memory 1 whose read clock is _fv , and is output as a digital signal _S3 . This digital memory 1 has a pitch conversion function. The digital signal S ₂ is a DAC
5 and LPF 6 into an analog signal _S4 . This analog signal S ₄ is converted into an analog signal via a band emissive filter (hereinafter referred to as "BEF") 11 that passes band A ₆ which is below 150 Hz and band A ₇ which is above 3 KHz as shown in FIG. Output as _S5 . said digital signal
S ₃ is converted into an analog signal S ₆ via DAC 9 and LPF 10. This analog signal S ₆ is the sixth
Band A ₅ which is above 150KHz and below 3KHz as shown in the figure
A band pass filter (hereinafter referred to as “BPF”) that passes
) 12 as an analog signal _S7 . The analog signals S ₅ and S ₇ are sent to adder 1
3 and an output signal _S8 is output to the output terminal 7. The time delay function of the digital memory 8 corrects the time delay that occurs to obtain the pitch conversion function of the digital memory 1, and converts the analog signal.
This is to prevent a time lag between _S5 and _S7 . Incidentally, the digital memories 1 and 8 use the same memory through time-sharing processing in practice. For parallel processing, of course, separate memory is required.

FIG. 9 is a circuit block diagram of the pitch converter according to the second embodiment. In this example, frequency components of 3KHz or higher are passed from the output signal _S9 of the DAC5, targeting only quality deterioration in the high frequency range.
An analog signal S ₁₁ is obtained via the HPF 15, and an output signal S ₁₂ is outputted to the output terminal 7 via the adder 13.

FIG. 10 is a circuit block diagram of the pitch converter according to the third embodiment. In this embodiment, the time delay caused by the pitch converting function is ignored, and only the quality deterioration in the high range is targeted, and two channels are branched. for one channel of the outputs of the means 14;
Signal S13 is obtained by passing through HPF15 which passes frequency components of 3KHz or higher, and LPF3,
Contained in the output signal S14 of the pitch conversion means composed of ADC4, digital memory 1, and DAC9
A signal S15 is obtained by passing a frequency component of 3KHz or less through an LPF 10, and the signal S1 is
3 and S15 are added via the adder 13, and the output terminal 7 is made to output the output signal S16. In this case, if the time delay is not a practical problem, it will function satisfactorily.

Next, cost reduction will be explained. The write clock _f0 to digital memory 1 is ADC4.
sampling clock. The upper limit of the reproduction band is 1/2 of the sampling clock frequency, and if the normal upper limit is 20 KHz, the frequency of the sampling clock _f0 is 40 KHz. Assuming that the time delay required for pitch conversion is T, the relationship between the required memory capacity M and the frequency f ₀ of the write clock f ₀ is as follows.
It is calculated using the formula below.

T=1/f ₀ ·M ... Since the present invention lowers the upper limit of the reproduction band, the relationship between the memory capacity M' of the digital memory 1 and the frequency f _p ' of the write clock f ₀ is expressed by the following formula. Desired.

T=1/f ₀ ′・M′...For example, if the upper limit of the playback band is lowered from 20KHz to 3KHz, then substituting the above equation into the above equation, we get, which can be seen from the above equation. As such, it can be realized with 3/20 the memory capacity, making it possible to significantly reduce costs.

In each of the above embodiments, examples using digital memories 1 and 8 have been described, but the present invention can also be realized using analog memories.

Effects of the Invention As explained above, according to the present invention, high sound quality can be produced at low cost, and furthermore, the pitch of the output signal can be reliably raised or lowered only in a band where the pitch of the output signal is easily perceived relative to the pitch of the input signal. , and can be changed arbitrarily.

[Brief explanation of drawings]

Figure 1 is a circuit block diagram of a conventional pitch conversion device, Figure 2 is an explanatory diagram of the cymbal frequency characteristics, Figure 3 is an explanatory diagram of the sound quality deterioration band when changing the pitch of the cymbal, and Figure 4 is the bass frequency. An explanatory diagram of the characteristics. Fig. 5 is an explanatory diagram of the sound quality deterioration band during bass pitch conversion. Fig. 6 is an explanatory diagram of the band pass filter characteristics of the present invention. Fig. 7 is an explanatory diagram of the band eluminate filter characteristics of the present invention. The explanatory drawings and FIGS. 8 to 10 are circuit block diagrams of a pitch converter according to an embodiment of the present invention. 1, 8...Digital memory, 3, 6, 10
...LPF, 4...ADC, 5, 9...DAC, 11
... BEF, 13 ... adder, 14 ... branching means,
12,15...HPF.

Claims (1)

[Scope of Claims] 1. Branching means for branching an input signal into two channels; pitch converting means for converting the frequency of the input signal of one channel among the outputs of the branching means;
a first equalizer means for extracting a signal in a frequency band of 3KHz or less from the output of the pitch conversion means;
A time delay means for delaying the input signal of the other channel, and 3K from the output signal of this time delay means.
A pitch conversion device comprising: second equalizer means for extracting a signal in a predetermined frequency band of Hz or higher; and addition means for adding the output signal of the first equalizer means and the output signal of the second equalizer means. 2 150Hz or more 3KHz as the first equalizer means
150 as a second equalizer means using a bandpass filter that extracts signals in the following frequency bands.
2. The pitch conversion device according to claim 1, wherein the pitch conversion device is configured to use a band elminate filter that excludes signals in a frequency band of Hz or more and 3KHz or less. 3. Claims in which the pitch conversion means is constituted by an analog-to-digital converter, a digital memory whose writing clock frequency and reading clock frequency are different, a digital-to-analog converter, and a digital memory control signal generating means. The pitch conversion device according to item 1. 4. The pitch converter according to claim 1, wherein the time delay means includes an analog-to-digital converter, a digital memory whose writing clock frequency and reading clock frequency are the same, and a digital-to-analog converter. . 5. The pitch conversion device according to claim 1, wherein the pitch conversion means and the time delay means are constructed using analog memories. 6 Branching means for branching the input signal into two channels; pitch converting means for converting the frequency of the input signal of one channel of the output of this branching means; and a frequency band of 3 KHz or less from the output of this pitch converting means. a first filter means for extracting a signal in a frequency band of 3KHz or more from the output of the other channel;
and addition means for adding the output signal of the filter means. 7. The pitch conversion means is constituted by an analog-to-digital converter, a digital memory whose writing clock frequency and reading clock frequency are different, a digital-to-analog converter, and a digital memory control signal generating means. The pitch conversion device according to scope 6. 8. The pitch conversion device according to claim 6, wherein the pitch conversion means is configured using an analog memory.