JPH05127695A - Signal generation device - Google Patents

Abstract

PURPOSE:To enable assignment for other processes without using the processing ability of a signal processor when a repetitive waveform is outputted by the speech signal generation device which digitally composes a speech signal. CONSTITUTION:A signal processor 1 stores a dual-port RAM 3 with a series of sample data of one cycle of the repetitive waveform and sends command to a sampling frequency setting part 9 and a variable cutoff frequency LPF 13. A memory control part 5 performs control so that the sample data series is outputted repeatedly from the dual-port RAM 3. A multiplexer 7 switches the data from the signal processor 1 and dual-port RAM 3 and outputs the data to a D/A converter 11. A speech output part 15 is connected ahead of the D/A converter 11 and the speech signal is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal generator, and more particularly to a signal generator for synthesizing digital signals representing signals including periodic signals.

[0002]

2. Description of the Related Art As a conventional signal generator of this type, an audio signal generator for generating an audio signal will be described.
In FIG. 7, the signal processor 31 synthesizes each sample data string of a signal to be generated by calculation. Each synthesized sample data string is
It is transferred to the D / A converter 33. The D / A converter 33 converts the sample data, which is a digital amount, into an analog amount, such as voltage and current, which is amplified by the audio output unit 35 to an appropriate level and output as audio.

[0003]

The speech waveform has periodicity, especially in the speech portion. In addition to the voice waveform, there are many signals having such periodicity.

However, in such a conventional voice signal generator, the sample data string to be output is all synthesized by the signal processor irrespective of its nature. Therefore, in the case of repetitive waveforms, the signal processor repeatedly performs the same operation,
The sample data string was calculated and output one by one. Therefore, there is a drawback that the processing capacity of the signal processor is consumed and cannot be applied to other processing.

The present invention has been made in order to solve the above-mentioned problems, and when a repetitive waveform is output, it can be assigned to other processing without spending the processing capacity of the signal processor. The purpose is to do so.

[0006]

To achieve this object, a signal generator according to the present invention comprises a signal processing means for synthesizing a digital signal representing a signal including a periodic signal, and a digital signal synthesized by the signal processing means. Storage means for storing signals, a D / A converter for converting a digital signal stored in the storage means into an analog signal, the signal processing means, the storage means and the D / A converter A control means for controlling the operation is provided.

Further, the signal generator of the present invention determines the period of the periodic waveform region detected by the periodic waveform region detecting means for detecting the periodic waveform region from the signal including the periodic signal and the period of the signal of the periodic waveform region detected by the periodic waveform region detecting means. It may be provided with a cycle detecting means for detecting.

[0008]

In the signal generator of the present invention having the above-mentioned structure, for the periodic signal, the signal processing means calculates and synthesizes a sample data string for one cycle of the periodic waveform and stores it in the storage means. .. The control means repeatedly outputs a sample data string for one cycle from the storage means to the D / A converter to generate an audio signal.

Further, in the signal generator of the present invention,
The periodic waveform region detecting means detects the periodic waveform region from the signal including the periodic signal, and the period detecting means detects the period of the signal in the periodic waveform region. The control means replaces the signal corresponding to the entire periodic waveform region with a signal corresponding to only one cycle detected by the cycle detection means, which is combined by calculation by the signal processing means and stored in the storage means. A sample data string for a period is output to the D / A converter to generate an audio signal.

[0010]

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

FIG. 2 is a block diagram showing a signal generator embodying the present invention. In this embodiment, the signal processor is the signal processor 1, the storage is the dual port RAM 3, the D / A converter is the D / A converter 11, and the like.
The control means are the signal processor 1 and the memory control unit 5.
, Multiplexer 7, and sampling frequency setting unit 9
And the variable cutoff frequency LPF 13, and the audio output unit 15 is connected to the end of the variable cutoff frequency LPF 13.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG.

First, it is determined whether the signal waveform to be generated is a repetitive waveform (S1). For non-repetitive waveforms,
The signal processor 1 commands the multiplexer 7 to select the data from the signal processor 1 (S2). Therefore, the data string synthesized by the signal processor 1 is directly output to the D / A converter 11 (S3), amplified by the audio output unit 15 to an appropriate level, and output as audio. S until all signal sequences are output
3 is repeated (S4). This case is the same as the prior art. When the signal waveform to be generated in S1 is a repetitive waveform, the signal processor 1 outputs the repetitive waveform before the sample data string x ₁ , x ₂ , ..., X for one cycle shown in FIG. _{Compose n} by calculation (S
5). In addition, the memory control unit 5 includes a dual port RAM.
A command is issued to 3 to store the combined sample data string for one period (S6).

As a result, as shown in FIG. 4B, the sample data string for one cycle is stored in the dual port RAM 3. To repeatedly output this sample data string, the sampling frequency must be an integral multiple of the repetition frequency. Therefore, the signal processor 1 issues a sampling frequency setting command to the sampling frequency setting unit 7 so as to satisfy the above condition.
In response to this, a command for an appropriate cutoff frequency is issued to the variable cutoff frequency LPF 13 for preventing aliasing of the D / A converter 11 (S7).

Further, the signal processor 1 issues a command to the multiplexer 7 to select the data from the dual port RAM 3 (S8). After the above settings, the signal processor 1 issues a command to the memory control unit 5 so that the dual port RAM 3 repeatedly outputs the sample data string shown in FIG. 4B (S).
9).

The memory controller 5 is a dual port RAM.
3 is generated while incrementing the read address, and the read address is reset every cycle, so that the sample data string for one cycle is repeated and D
Output to the / A converter 11. The sound output unit 15 amplifies the sound to an appropriate level and outputs the sound. Meanwhile, as shown in FIG. 4C, the signal processor 1
Since it is not necessary to combine the sample data strings, it is possible to execute other processing. In the above embodiment, the signal processor 1 may be a microprocessor as long as the processing speed is sufficiently high, and the dual port RAM 3 may be a normal RAM with a control circuit added.

FIG. 3 is a block diagram showing another embodiment of the present invention.

In this embodiment, the periodic waveform area detecting means is
A zero-cross detection unit 21, a zero-cross memory 25,
It is composed of a periodicity judging section 27, and the cycle detecting means is composed of a zero-cross detecting section 21 and a cycle measuring section 23.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG. In FIG. 3, the time of the point (zero cross point) where the value of the input data string crosses 0 is obtained by the zero cross detection unit 21 (S20). The input data string from a certain zero-cross point to the next zero-cross point is stored in the zero-cross memory 25 (S21). An input data string for two cycles is stored in the zero-cross memory 25, and the periodicity judgment unit 27 determines whether or not there is periodicity by comparing the data string of one cycle before and the data string of the current cycle. A determination is made (S22). The greater the periodicity in S22, the smaller the total sum of absolute values of the differences between data strings (or the sum of squared differences). Therefore, if the sum total of the absolute values of the differences in the data strings is equal to or less than the predetermined reference value, the periodicity determination unit 27 determines that there is periodicity (S2
3).

In S23, if the sum total of the absolute values of the differences in the data strings exceeds the predetermined reference value, the periodicity determination unit 2
7 determines that there is no periodicity, S20 to S23 are repeated, and the detection of the periodic waveform region is continued. When it is determined in S23 that there is periodicity, the period measuring unit 23 measures the period by counting the time difference between the zero cross points (S24). The periodicity determining unit 27 determines whether the cycle is the same as the previous cycle (S2).
5). When the periodicity determination unit 27 determines that the period is the same as the previous period, the periodicity determination unit 27 increments the value of the period counter that indicates how many periods the period continues (S26). If it is determined that the cycle is different from that before, the periodicity judgment unit 27
Outputs the previous cycle and the value of the cycle counter, and resets the value of the cycle counter (S27).

As described above, the periodic waveform region and the period are detected for the input data string. Further, the signal generation of the detected periodic waveform is performed in exactly the same way as in the first embodiment. Although the determination of the periodicity in the time domain is shown in the second embodiment, it may be performed in the frequency domain.

[0022]

As is clear from the above description, when the signal generator of the present invention outputs repetitive waveforms, the processing capacity of the signal processor is not consumed,
It can be assigned to another process.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a block diagram showing a first embodiment of the present invention.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4A is a diagram showing a data string for one cycle of a repetitive waveform to be generated. (B) is a diagram showing that a data string for one cycle of the repetitive waveform is stored in the dual port RAM 3. (C) is a figure which shows that the signal processor 1 is performing another process, while outputting a repeating waveform.

FIG. 5 is a flowchart of the first embodiment of the present invention.

FIG. 6 is a flowchart of a second embodiment of the present invention.

FIG. 7 is a block diagram of a conventional signal generator.

[Explanation of symbols]

 1 Signal Processor 3 Dual Port RAM 5 Memory Control Section 7 Multiplexer 9 Sampling Frequency Setting Section 11 D / A Converter 13 Variable Cutoff Frequency LPF 21 Zero Cross Detection Section 23 Cycle Measurement Section 25 Zero Cross Memory 27 Periodicity Determination Section

Claims (2)

[Claims] 1. A signal processing means for synthesizing a digital signal representing a signal including a periodic signal, a storage means for storing the digital signal synthesized by the signal processing means, and a digital signal stored in the storage means. Has a D / A converter for converting the signal into an analog signal, the signal processing means, the storage means, and a control means for controlling the operation of the D / A converter, and the control means should generate the signal. If the signal is a periodic waveform,
A signal generating device, characterized in that the digital signal for one cycle stored in the storage means is repeatedly output to the D / A converter. 2. The signal generator according to claim 1, wherein a periodic waveform area detecting unit that detects a periodic waveform area from a signal including the periodic signal, and a periodic waveform area detected by the periodic waveform area detecting unit. Cycle control means for detecting the cycle of the signal, wherein the control means replaces the signal corresponding to the entire cyclic waveform region with a signal corresponding to only one cycle detected by the cycle detection means. The signal generating device is characterized in that it is controlled to be stored in the storage means.