JPH05342763A - Variable speed reproducer of digital voice signal - Google Patents

Abstract

PURPOSE:To provide a variable speed reproducer for a digital voice signal which enables reproduction to such an extent as to allow hearing naturally without increase in noise even when a reproduction is performed at a speed lower than the normal reproduction speed. CONSTITUTION:This apparatus includes a reproduction means 1, a operation means 2. a timing control means 3 and a signal processing means 4. When a reproduction speed ratio L is set by the operation means 2, the reproduction means 1 reproduces a digital voice signal at a reproduction speed corresponding to the reproduction speed ratio L. The timing control means 3 generates timing signals A, C and (a) according to the reproduction speed ratio L set. The signal processing means 4 interpolates a digital voice signal D reproduced from the reproduction means 1 based on the timing signals A and (a) from the timing control means 3 thereby generating a digital voice signal E.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed reproducing apparatus for a digital audio signal, which is applied to a digital recorder such as a digital tape recorder or a digital disk recorder and is suitable for reproducing at a speed other than a normal reproducing speed.

[0002]

2. Description of the Related Art Digital recorders such as digital tape recorders and digital disk recorders digitize and record audio signals. Further, since the digital recorder does not deteriorate even if the signal is copied between recording media, it is effective when used for editing audio signals such as music and broadcasting programs.

By the way, when the digital recorder is used for editing a voice signal, it is convenient for the digital recorder to have a variable speed reproduction function for reproducing at a speed different from the normal reproduction speed. This variable speed reproduction function is used, for example, when reproducing an audio signal recorded on a recording medium at a speed lower than a normal reproduction speed when accurately determining an edit point.

On the other hand, conventionally, there are known several kinds of techniques for reproducing an audio signal at a speed other than the normal reproduction speed. For example, Japanese Unexamined Patent Publication No. 220220/1990 discloses a variable speed reproducing device having a function of interpolating a digital audio signal when reproducing at a special speed. The variable speed reproducing device described here is a variable speed reproducing device which is particularly useful when reproducing at a reproducing speed higher than the normal reproducing speed, and a technique for thinning data is described.

As a related technique, Japanese Patent Publication No. 63-
Japanese Patent Publication No. 29346 discloses a technique of interpolating and reproducing data of a digital audio signal.

[0006]

However, in the conventional variable speed reproducing apparatus for digital audio signals, noise is increased or sounds unnatural when reproduced at a speed slower than the normal reproducing speed. There was a problem.

The reason for this is that when the data is reproduced at a reproduction speed slower than the normal reproduction speed, the time between two adjacent data of the digital audio signal is extended, and therefore the change in the value of the two data remains unchanged. It is in the place where it is output.

Therefore, the present invention has been made in view of the above circumstances, and even when reproduced at a reproduction speed slower than the normal reproduction speed, a digital audio which can be reproduced so as to be heard naturally without increasing noise. It is an object of the present invention to provide a variable speed reproduction device for signals.

[0009]

In order to achieve the above object, the invention according to claim 1 is a reproducing means for reproducing a digital audio signal from a recording medium at a speed slower than a normal reproducing speed, and a reproducing means of this reproducing means. Based on the operation means for setting the reproduction speed, the timing control means for generating a timing signal according to the reproduction speed set by the operation means, and the reproduction means based on the timing signal from the timing control means. In a variable speed reproduction device for a digital audio signal, which has a signal processing means for performing signal processing on the reproduced digital audio signal and generating an audio reproduction signal,
The signal processing means is characterized in that, based on the timing signal from the timing control means, the digital audio signal reproduced from the reproducing means is interpolated to generate an audio reproduction signal.

According to a second aspect of the invention, in the first aspect of the invention, the signal processing means corresponds to the interpolation of the digital audio signal reproduced from the reproducing means with a sampling cycle at a normal reproduction speed. Is performed so that the data exists.

[0011]

According to the first aspect of the present invention, the signal processing means interpolates the digital audio signal reproduced by the reproducing means to generate an audio reproduction signal. As a result, even when the reproducing means reproduces the digital audio signal at a speed slower than the normal reproducing speed, the noise can be reproduced without being increased in noise.

According to the second aspect of the invention, the signal processing means performs the interpolation of the digital audio signal reproduced by the reproducing means such that the data exists corresponding to the sampling cycle at the normal reproduction speed. In this way, because interpolation is performed as if playing at the normal playback speed,
Even if the time interval between two adjacent data is extended in the data of the digital audio signal, the data exists between the two data, and the reproduction means digitally reproduces the data at a speed slower than the normal reproduction speed. Even when the audio signal is played back, the noise does not increase, and the audio signal can be played back naturally.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of a variable speed reproducing apparatus for digital audio signals according to the present invention.

The present apparatus shown in the figure is a reproducing means 1 for reproducing a digital audio signal recorded on a recording medium (not shown).
An operation means 2 for setting the reproduction speed and the like of the reproduction means 1, a timing control means 3 for controlling the operation timing of the reproduction means 1 and a signal processing means 4 which will be described later, and a reproduction signal B from the reproduction means 1. , D for processing D,
And is configured.

The reproducing means 1 comprises a reproducing mechanism 6, R
The AM 7 and the latch 8 are provided.

The reproducing mechanism 6 reproduces a digital audio signal from a recording medium such as a magnetic tape or a disk (not shown).

The RAM 7 temporarily stores the reproduced digital audio signal from the reproduction mechanism 6. The reading / writing of the signal to / from the RAM 7 is performed based on the output of the extended clock signal C from the frequency dividing unit 12.

The latch 8 holds one sample of the digital audio signal stored in the RAM 7 and outputs it as an output of the reproducing means 1 to the signal processing means 4. Latch 8
The timing control of is performed based on the output of the extended clock signal C from the frequency dividing unit 12.

The operating means 2 includes an operating section 9 and a CPU 1.
It has 0.

The operation unit 9 is for setting a reproduction speed ratio L which is a ratio to the normal reproduction speed when reproducing at a reproduction speed different from the normal reproduction speed.

The CPU 10 controls the entire apparatus based on the setting state of the operation unit 9. For example, the frequency division ratio m corresponding to the reproduction speed ratio L set by the operation unit 9 is set for the frequency division unit 12 described later.

The timing control means 3 comprises a basic clock generating section 11, a frequency dividing section 12, a counter 13 and the like. Based on the setting state of the operating means 2, the basic clock signal A as a timing signal and the extended clock signal. C and the cycle ratio signal (a) are generated to control the operation timing of the reproducing means 1 and the signal processing means 4.

The basic clock generating section 11 generates a constant basic clock signal A regardless of the setting state of the operating means 2.

The frequency division unit 12 divides the basic clock signal A from the basic clock generation unit 11 to generate an extended clock signal C.
Is output, and the frequency division ratio m is set by the CPU 10 of the operating means 2.

The counter 13 includes a basic clock generator 11
Of the basic clock signal A and the extended clock signal C from the frequency dividing unit 12 to obtain a period ratio a between the basic clock A and the extended clock C, and the period ratio signal (a) is sent to the signal processing means 4. It is output.

The signal processing means 4 is composed of a DSP 14 including a high-speed arithmetic unit and a program memory in which a processing operation program of this unit is stored, and performs interpolation processing on the digital audio signal D reproduced from the reproducing means 1. The processing result is output to the output terminal 5 as a digital audio signal E.

Here, the interpolation processing performed by the signal processing means 4 will be described in more detail with reference to FIG.

FIG. 2 shows the processing operation of the signal processing means 4 as a signal flow. In the figure, X _m represents the signal value of the digital audio signal D input from the reproducing means 1, and Y _k represents the signal value of the digital audio signal E interpolated by the signal processing means 4.

As shown in FIG. 3, which will be described later, the DSP 14 of the signal processing means 4 has a pair of adjacent signal values X sequentially input in synchronization with the generation timing of the extended clock signal C.
Based on the cycle ratio a of the basic clock A and the extended clock C, the digital audio signal D of _m-1 , X _m is interpolated according to the following interpolation formula (1), and the signal values Y ₁ , Y ₂ , Y ₃ of The digital audio signal E is sequentially output in synchronization with the timing of the basic clock signal A.

Y _k = a · k · (X _m −X _m−1 ) + X _m−1 (1)

Here, a indicates the cycle ratio of the basic clock signal A and the extended clock signal C as described above. For example, if the cycle of the basic clock A is T _a and the cycle of the extended clock C is T _c , the cycle ratio a is a = T _a / T _c . However, k is k = 1, 2, 3, ... In the range of a · k <1.
Is sequentially changed, and interpolation is performed by the maximum number of times k. For example, if the cycle ratio a is 300%, the value of a · k is a ·
It changes to k = 1/3, 2/3, 3/3.

Next, referring to FIG. 3 for the operation of this embodiment,
A case where the set value of the reproduction speed ratio L is 300% will be described as an example.

FIG. 3 is a timing chart showing the operation of the embodiment of the present invention shown in FIG. In the figure, A indicates a basic clock signal generated by the basic clock generating section 11 as described above, B indicates a digital audio signal when reproduced from the reproduction means 1 at a normal reproduction speed, and the vertical axis thereof. It shows the signal value. From the figure, digital audio signal B
However, it can be seen that the value changes each time the basic clock signal A is generated. Further, in the figure, C indicates the extended clock signal generated by the frequency dividing unit 12 as described above, and in the configuration shown in FIG. 1, the reproduction speed ratio L of the operation unit 9 is 300%.
When the value of is set, the set frequency division ratio M for the frequency division unit 12 becomes 1/3, and the clock whose time is tripled with respect to the clock signal A when reproduced at the normal reproduction speed. It shows the state. Further, D represents a digital audio signal when reproduced from the reproducing means 1 at a reproduction speed different from usual, and the vertical axis thereof represents a signal value. As shown in the figure, the signal value of the digital audio signal D changes every time the extended clock signal C is generated, and the signal value of the digital audio signal D changes when it is reproduced at a normal reproduction speed. It is extended to 300% of the time as compared with the digital audio signal B. Further, E indicates a digital audio signal interpolated by the signal processing means 4.

First, the operator operates the operating section 9 of the operating means 2 to set the reproduction speed ratio L. Here, 300% is set as described above. Then, the CPU 10 of the operating means 2 reproduces the reproducing mechanism 6 of the reproducing means 1 based on the reproducing speed ratio information (l) set by the operating section 9.
On the other hand, the reproduction speed is set, and the frequency division ratio M (1/3) is set for the frequency division unit 12 of the timing control means 3.

The counter 13 compares the outputs of the frequency divider 12 and the basic clock generator 11 to obtain the cycle ratio a, and outputs the signal to the DSP 14 of the signal processing means 4.

The DSP 14 of the signal processing means 4 is based on the basic clock signal A supplied from the basic clock generator 11 and the cycle ratio signal (a) supplied from the counter 13, and the digital audio signal D supplied from the latch 8. From
The interpolated digital audio signal E is generated by the procedure described above and is output to the output terminal 5.

According to the above-described embodiment, even if the digital audio signal D reproduced by the reproducing means 1 is reproduced at a speed slower than the normal reproducing speed, the signal processing means 4 causes the timing control means 3 to operate. On the basis of the above, the basic clock signal A is interpolated as if a digital audio signal exists, and the digital audio signal E which is reproduced at the normal reproduction speed is generated, so that it is slower than the normal reproduction speed. Even when played back at the playback speed, the noise does not increase and it can be played back naturally.

Therefore, although not shown, the characteristics of the filter and the like connected to the output terminal 5 and thereafter shown in FIG. 1 need not be changed according to the speed.

The interpolated digital audio signal E output from the output terminal 5 can be used as it is as a recording signal of another digital audio signal recording device without converting the clock of the digital audio signal. ..

The present invention is not limited to the above embodiment,
Various modifications can be implemented. For example, in the present embodiment, the case where the reproduction speed ratio L set by the operation means 2 is an integral multiple compared with the normal reproduction speed ratio is shown, but the reproduction speed ratio set by the operation means 2 is shown. Needless to say, can be any value.

[0042]

According to the invention described in claim 1 described above in detail, since the digital audio signal reproduced from the reproducing means by the signal processing means is interpolated to generate the audio reproduction signal, the normal reproduction is performed. It is possible to provide a variable speed reproducing device for a digital audio signal which can be reproduced so as to be heard naturally without increasing noise even when reproduced at a reproducing speed lower than the speed.

According to the second aspect of the present invention, the digital audio signal reproduced from the reproducing means by the signal processing means is interpolated so that the data exists corresponding to the sampling cycle at the normal reproducing speed. Therefore, even if the playback speed is slower than the normal playback speed, interpolation is performed as if the playback speed was normal.
It is possible to provide a variable speed playback device for a digital audio signal that can be played back naturally without increasing noise.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a variable speed reproducing apparatus for a digital audio signal of the present invention.

FIG. 2 is a signal flow showing the operation of the timing control means of this embodiment.

FIG. 3 is a timing chart showing the operation of this embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 reproduction means 2 operation means 3 timing control means 4 signal processing means A basic clock signal (timing signal) C extended clock signal (timing signal) a period ratio signal (timing signal)

Claims (2)

[Claims] 1. A reproducing means for reproducing a digital audio signal from a recording medium at a speed slower than a normal reproducing speed, an operating means for setting a reproducing speed of the reproducing means, and an operating means for setting the reproducing speed. A timing control means for generating a timing signal according to the reproduction speed, and a signal for performing signal processing on the digital audio signal reproduced by the reproduction means on the basis of the timing signal from the timing control means to generate an audio reproduction signal. In the variable speed reproduction device for a digital audio signal, the signal processing means interpolates the digital audio signal reproduced by the reproduction means based on the timing signal from the timing control means to reproduce the audio. A variable speed reproducing device for a digital audio signal, which is characterized by generating a signal. 2. The signal processing means performs interpolation of the digital audio signal reproduced from the reproducing means such that data exists corresponding to a sampling cycle at a normal reproduction speed. 1. A variable speed playback device for digital audio signals according to 1.