JPH03219462A - Sound speed converter - Google Patents

Abstract

PURPOSE:To listen to sound at desired reproducing speed without generating the discontinuity of a waveform and the omission of data by multiplying a memory content by a window function, and superimposing and adding a sound waveform so as to increase a correlation function and to reduce deviation from a targeted companding ratio. CONSTITUTION:An input signal is written on a buffer 12 via an A/D converter 11. A speed control circuit 13 controls a demultiplexer 14 corresponding to a speed conversion ratio, and sends write data to memories 15, 16 and the multiplexer. The deviation between the targeted companding ratio of the control circuit 13 is monitored with a companding ratio detector 21. A weight function generator 22 varies a weight coefficient value corresponding to the quantity of deviation. A correlator 17 calculates the correlation coefficient of the contents of the memories 15, 16, and multiplies them by the output of the weight function generator 22 with a multiplier 23, and supplies a result to the control circuit 13, a window function generator 18, and an adder 24. A multiplexer 25 performs weighting with multipliers 19, 20, and selects output so as to increase the correlation function, and to decrease the deviation from the targeted companding ratio, and outputs a result via a D/A converter 26.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a voice rate conversion device that changes only the duration of the voice without changing its fundamental frequency.

2. Description of the Related Art Conventionally, audio speed conversion devices have been used to listen to audio signals recorded on a tape recorder or the like quickly or slowly.

Hereinafter, a conventional voice speed conversion device as described above will be explained with reference to the drawings.

FIG. 3 shows the configuration of a conventional voice speed conversion device. In FIG. 3, 31 is an A/D converter, 32 is a buffer, 33 is a speed control circuit, 34 is a data read circuit, 35 is a muting circuit, and 36 is a D/A converter.

The operation of the voice speed conversion device configured as described above will be described below.

First, the input signal is converted into a digital signal by the A/D converter 31 and written to the buffer 32. Next, the speed control circuit 33 controls the data reading circuit 34 according to the speed conversion ratio to read data from the buffer 32. Depending on this data reading method, the playback speed can be varied in various ways. To increase the playback speed, data to be read out in blocks is thinned out. If the playback speed is to be slowed down, the data read out in blocks is repeated. A muting circuit 35 applies muting to discontinuous portions between each block, and a D/A converter 36 converts the signal into an analog signal and outputs the signal.

Figure 4 is a schematic diagram of a conventional speed conversion algorithm.
Figures (a), (b), and (c) show cases where the speed conversion ratio is 1.0.5.2, respectively. Here, it is assumed that the speed conversion ratio α is defined by the following equation.

Problems to be Solved by the Invention However, with the above configuration, when increasing the speed, the intelligibility of consonants etc. deteriorates due to thinning of data, and discontinuous points of the waveform are muted. Another problem was that only unnatural sounds could be obtained.

Furthermore, the method using the pitch period cannot be applied and is not suitable when music or noise is superimposed, since it is difficult to extract the pitch.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a voice speed conversion device capable of outputting natural-looking voice without waveform discontinuity or data loss.

Means for Solving the Problems To achieve this object, the voice speed conversion device of the present invention includes: a first memory for storing voice; a second memory for storing voice subsequent to the contents of the first memory; a correlator that calculates a correlation function between the contents of the first memory and the contents of the second memory; a window function generator that outputs a window function; a first multiplier that multiplies the output; a second multiplier that multiplies the content of the second memory by the output of the window function generator; and a companding ratio detector that detects a deviation from a target companding ratio. , a weighting function generator that outputs a weighting coefficient based on the output of the companding ratio detector, and a third weighting function generator that multiplies the output of the correlator by the output of the weighting function generator.
and the first multiplier based on the output of the third multiplier.
and an adder that adds the output of the multiplier and the output of the second multiplier at the position of the weighted correlation value.

Effect: With this configuration, the contents of the memory are multiplied by a window function, and the audio waveform is superimposed and added in such a way that the value of the correlation function becomes large and the deviation from the target companding ratio is reduced, thereby eliminating waveform discontinuities. It is possible to listen to audio at a desired playback speed without causing data loss or loss of data.

Embodiment The present invention is an audio system that can output natural-looking audio without discontinuities in waveform amplitude and phase and without data loss, and that can be realized with simple hardware. A speed conversion device is provided.

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

FIG. 1 shows a configuration diagram of a voice speed conversion device in an embodiment of the present invention. In Figure 1, 11 is A/
D converter, 12 is a buffer, 13 is a speed control circuit, 14
is a demultiplexer, 15 is the first memory, 16 is the second memory
17 is a correlator, 18 is a window function generator, 19 is a first multiplier, 20 is a second multiplier, 21 is a companding ratio detector, 22 is a weighting function generator, 23 is a third multiplier, 24
is an adder, 25 is a multiplexer, and 26 is a D/A converter.

The operation of the voice speed conversion device configured as described above will be described below.

First, the input signal is converted into a digital signal by the A/D converter 11 and written to the buffer 12. Next, the speed control circuit 13 controls the demultiplexer 14 according to the speed conversion ratio.
and transfers the data in the buffer 12 to the first memory 15.
, to be output to the second memory 16 or the multiplexer 25. The companding ratio detector 21 calculates the number of data D□1 input to the demultiplexer 14 and the number of data output from the multiplexer 25. ut detects the companding ratio currently being processed, monitors the deviation from the target companding ratio set in the speed control circuit 13, and outputs the information to the weighting function generator 22.

The weighting function generator 22 outputs an output according to the amount of deviation from the target companding ratio obtained from the companding ratio detector 21 so that the companding ratio of the audio data currently being processed does not deviate greatly from the target companding ratio. Change the weighting coefficient value. A correlator 17 calculates a correlation function between the contents of the first memory 15 and the contents of the second memory 16 . The third multiplier 23 multiplies the output of the correlator 17 and the output of the weighting function generator 22, and outputs the information to the speed control circuit 13, window function generator 18, and adder 24. Then, the window function generator 18 outputs a window function to the first multiplier 19 and the second multiplier 20 based on the information from the third multiplier 23 . Next, the first multiplier 19 multiplies the contents of the first memory 15 and the output of the window function generator 18, and the second multiplier 20 multiplies the contents of the second memory 16 and the output of the window function generator 1.
Multiply with the output of 8. Based on the information from the third multiplier 23, the adder 24 shifts the output of the first multiplier 19 and the output of the second multiplier 20 to a position where the weighted correlation value is large. Addition is performed and output to multiplexer 25. Finally, the multiplexer 25 selects the output of the adder 24 and the output of the demultiplexer 14 and outputs it to the D/A converter 26, where it is converted into an analog signal.

FIG. 2 is a schematic diagram of waveforms processed by the speech rate conversion device in this embodiment of the present invention, and (a), (b), (
C) shows the case where the speed conversion ratio α is 1.0.5.2. As is clear from FIG. 2, if the addition is continued in a portion where the correlation is high, the speed may be converted to a companding ratio different from the target companding ratio. Therefore, the companding ratio detector 21 detects the companding ratio in the middle of processing, and in order to reduce the deviation from the target value, the output of the correlator 17 is assigned a weighting coefficient which is the output of the weighting function generator 22. Multiplying determines the point for addition based on the combined result.

As described above, according to this embodiment, the window function output from the window function generator 18 is applied to the contents of the first memory 15 and the second memory 16 by the first multiplier 19 and the second multiplier. By performing multiplication using a multiplier 20 and adding the outputs of the respective multipliers using an adder 24, a highly natural sound without discontinuity in waveform amplitude and without data loss is output. I can do it.

Furthermore, a correlator 17 calculates a correlation function between the contents of the first memo January 5 and the contents of the second memory 16, and correlates the output of the first multiplier 19 and the output of the second multiplier 20. Since the addition is performed by shifting to a position where the value of the function becomes large, discontinuity in the phase of the waveform can be reduced. In addition, the companding ratio detector 21
Detects the companding ratio during processing and monitors the deviation from the target value.
The weighting coefficient output from the weighting function generator 22 is changed according to the amount of deviation. As a result, weighting and addition are performed by shifting to a position where the deviation from the target companding ratio is small and the correlation value is large. therefore,
It is possible to obtain high-quality processed audio in which the phase of the added waveform is less likely to be discontinuous at a desired playback speed.

Effects of the Invention The present invention multiplies the contents of a first memory and the contents of a second memory by a window function output from a window function generator using a first multiplier and a second multiplier, and adds the results. By adding the outputs of the respective multipliers in the multiplier, it is possible to output a sound rich in naturalness without discontinuities in waveform amplitude and without data loss. Further, a correlator calculates a correlation function between the contents of the first memory and the contents of the second memory, and a companding ratio detector calculates the amount of deviation between the companding ratio being processed and the target companding ratio. The weighting coefficients of the weighting function generator are changed accordingly. That is, since the addition is performed while shifting the weighted correlation value between the output of the first multiplier and the output of the second multiplier to a position where it becomes large, the deviation from the target companding ratio can be reduced. In addition, weighting of parts with large correlations can be added. Therefore, it is possible to realize an excellent audio speed conversion device that can output high-quality audio without phase discontinuity in the waveform at a desired playback speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a voice speed conversion device according to a first embodiment of the present invention, FIG. 2 is a schematic diagram of processing waveforms by the voice speed conversion device according to a first embodiment of the present invention,
The figure is a block diagram of a conventional voice speed converter, and FIG. 4 is a schematic diagram of waveforms processed by the conventional voice speed converter. 11... A/Dim device, 12... Old buffer, 13... Speed control circuit, 14... Demultiplexer, 15... First memory, 16
...Second memory, 17...Correlator,
18... Window function generator, 19... First
multiplier, 20... second multiplier, 21...
... Companding ratio detector, 22 ... Weight function generator, 23 ... Third multiplier, 24 ... Adder, 25 ...・Multiplexer, 26...
...D/A converter.

Claims (1)

[Claims] a first memory for storing audio, a second memory for storing audio following the contents of the first memory, and a correlator for calculating a correlation function between the contents of the first memory and the contents of the second memory. , a window function generator that outputs a window function, and the first
A first step of multiplying the memory contents of by the output of the window function generator.
a second multiplier that multiplies the contents of the second memory by the output of the window function generator; a companding ratio detector that detects a deviation from a target companding ratio; a weighting function generator that outputs a weighting coefficient based on the output of the detector; a third multiplier that multiplies the output of the correlator by the output of the weighting function generator; and based on the output of the third multiplier. A voice speed conversion device comprising: an adder that adds the output of the first multiplier and the output of the second multiplier at a position of a weighted correlation value.