JPH0263238B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time axis expansion device for lowering the pitch of musical sounds such as voices without changing their waveforms.

Such devices are already known, and an example is shown in FIG. 11 is a charge transfer element such as a BBD, 12 is a sweep generator that generates a transfer clock, and 13 is a low-pass filter that cuts off a transfer clock component. Here, 12
The sweep generator generates a pulse train whose period increases linearly with time, as shown in FIG. In this case, the read speed at the time of reading the signal written in the No. 11 BBD is lower than the speed at the time of writing, so the pitch decreases. The rate of change is uniquely determined by the slope of the straight line in FIG. However, in reality, the period of the transfer clock cannot be increased indefinitely because there are limitations on the sampling rate, transfer rate, number of delay stages, delay time for input, etc. Therefore, when the transfer clock period reaches a certain value, the sweep is restarted from the minimum set value, and so on. The state of the operation at this time is shown in FIG. This example shows a case where the slope of the transfer clock is adjusted to halve the adjustment pitch. The input signal during the period T of the repetitive operation is composed of two parts, as shown in Fig. 3a, and as shown in Fig. 3a, but in the output b after time axis expansion, for example, the signal occupies the section T. Information about the storage part is missing from the output. Similarly, half of the input information is missing. It is known that by appropriately setting system constants, it is possible to prevent a decline in intelligibility due to missing information, but when this system is used for music etc., minute information may be lost. He is said to be unwell. In the case of the above system, it can be seen that when the pitch conversion ratio is close to 1, the slope of the periodic change shown in FIG. 2 becomes small, so that the period T of the repetitive operation becomes large, and becomes small as it approaches 0. It is also understood from FIG. 3 that if this period T and pitch conversion ratio are given, a write segment to the charge transfer element etc. is defined.

SUMMARY OF THE INVENTION An object of the present invention is to provide a time axis expansion device that has a simple configuration and is free from missing information. For example, the following can be done to eliminate missing information.
In other words, as can be seen from Figure 3, if the segmentation of the time axis is shifted by about half from T in the figure, the waveform portion that will be discarded will be as shown in the figure.
Therefore, if we add these two series together, there will be no missing information. However, this method requires two signal processing systems, making it large-scale.

The present invention will be explained based on an embodiment shown in FIG. 41 is an input terminal, 42 is for example
A delay element such as BBD, 43 a timing control circuit that controls the timing of the entire system, 4
4 and 45 are the same delay elements such as BBD, 46 and 4
7 is an electronic switch, 48 is an output terminal, and 49
is a mixer. This embodiment shows a case where the pitch is halved by a fixed cutting section. Half of this fixed cut-out section is assumed to be τ as shown in FIG. In this case, the input signal is a sequence of segments of width τ (,
, etc.). In addition, Fig. 5 shows the 4th
The states of signals at corresponding symbols (a to h) in the figure are shown. Figure 5a shows the state of segmentation. On the other hand, the signal passing through BBD42 is the fifth
As shown in Fig. b, the waveform C which is outputted with a delay of time τ and is added through the mixer 49 has the information of the original segment waveform that is successive to each segment, as shown in Fig. 3c. The signal i in Figure 4 is
In this case, the BBD transfer clock is set to cause a delay of τ. This signal i is generated by a timing control circuit 43 along with other control signals d, e, f, and g. 44 and 45 are BBDs having the same number of stages, and their inputs are also the same, and the output of the mixer is applied thereto. Here each BBD
As shown in Figure 5 d and e, the transfer clocks d and e are outputted alternately every period 2τ when the frequency is ω and when the frequency is 2ω. is becoming the opposite. The electronic switches 46 and 47 at the output of each BBD are opened and closed in opposite phases to each other at the timing shown in FIG. 5(f). Note that this electronic switch is turned on at H level. Now, the electronic switch 46 is off while the input a is, and the BBD
45 is in the reading state and BBD44 is
It enters a writing state at a frequency of 2ω and writes the +, + segments in Figure 5c.
After that, in Figure 5 a, this time BBD4
5 is in the write state, and the BBD 44 is read at the frequency ω. In this case, the read frequency is half that of writing, so the pitch is also half, but on the other hand, the data written immediately before +, +
If only the first half + of both segments are read, the reading for that time is interrupted. then again
BBD 45 is for reading and 44 is for writing.
In this way, a time-extended waveform shown in FIG. 5h appears at the output 48 in FIG. 4. Comparing this waveform of h with the original waveform of a, at a...
In h, the column becomes +, +, +, . . . , and the time axis is expanded twice, and at the same time, there are no missing segments in the original segment. If the waveform in Fig. 5a is input as is instead of the waveform in Fig. 5c, the output h will be a column,
,... only segments appear and half of the information is missing.

Conventional echo devices obtain an echo effect by adding the raw signal and the delayed signal without any loss of information, but this does not have a time expansion function, and the delay feeling of the audio signal itself is Since this is a music effect, the effect is usually not noticeable unless the delay time is 100 msec or more.

The purpose of the present invention is to realize a time axis expansion device with a simple configuration and excellent sound quality without missing information.
In order to avoid the feeling of delay in the audio signal, it is desirable to set the delay time τ to about 10 to 20 msec.

As described above, according to the present invention, the time axis can be extended with a simple configuration and without losing original information, so the output sound quality is excellent and thick without losing the subtle timbre of the original sound. A time axis expansion device can be realized.

In this example, an example was explained in which the pitch was halved with a fixed segment length, but the pitch could be reduced to 1/2.
When changing the ratio between . Furthermore, as described as a conventional example, in the system using a sweep generator, the segments change according to the rate at which the pitch changes, so in that case, it is better to change the delay time accordingly. Further, when the pitch ratio is set to 1/3, information loss can be prevented by adding a delay element series and inputting a mixture of a plurality of delay data. Furthermore, here we assumed a charge transfer device (CTD) such as a BBD or CCD as a delay element or memory element, but it is also possible to use a shift register or RAM to handle digital signals.

[Brief explanation of the drawing]

Figure 1 shows an example of the conventional method, Figures 2 and 3
FIG. 4 is a block diagram showing an embodiment of the present invention, and FIG. 5 is a waveform diagram of each part to explain its operation. 42... Delay element, 43... Timing control circuit, 44, 45... BBD.

Claims (1)

[Claims] 1. In a device configured to divide an audio input signal into segments with an appropriate time width and write them into a signal transfer element or a storage element, and extend the time axis by making the reading speed slower than the writing speed, Adding and mixing the input signal with its raw signal and a signal delayed within the time width of the segment;
A time axis expansion device characterized in that the data is sequentially inputted to a plurality of the transfer elements or storage elements in which writing and reading are sequentially repeated, and sequentially outputted.