JPS63241598A - Voice signal correction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention reproduces an audio signal in a first frequency band from a recording medium during normal playback, and during special playback, the speed is different from that during the normal playback. The present invention relates to an audio signal correction method for correcting an audio signal in a second frequency band to a first frequency band in an audio signal reproducing device that reproduces an audio signal in a second frequency band from the recording medium.

<Example> Conventional technology An audio signal in a first frequency band is reproduced from a recording medium during normal playback, and an audio signal in a second frequency band is reproduced from the recording medium at a speed different from that during normal playback during special playback. As a conventional audio signal correction technique for correcting an audio signal in the second frequency band to the first frequency band in an audio signal reproducing device, for example, "Television Technology" (published by Denshi Gijutsu Publishing Co., Ltd.), June 1986, Pages 79 to 84 of the monthly issue are presented, and will be explained below using the drawings. .

FIG. 15 is a block diagram showing an example of a conventional audio signal correction method, and FIG. 16 is a timing chart showing waveforms of each part in FIG. 15. To explain the figure numbers and configurations, (1)
is the magnetic tape on which the audio signal is recorded, (2) is the audio head, (3) is the amplifier, (4) and (5) are the low-pass filters, (
6) is a drive signal generator that generates the clock signal C and mute signal M shown in FIG. 16(a), and (7) is the N-stage B B
D (Bucket Brigade Device
), (8) is a mute circuit, and (9) is an output terminal.

Here, the clock signal C generated from the drive signal generator (6) will be explained. The clock signal C is a geometric progression of a common ratio R that is repeated every period T0. The common ratio R is when the audio signal is input to BBD (7) and BBD
The period ratio of the clock signal C when it is shifted by 8 steps within (7) and output from BBD (7) is set to be a constant time axis expansion ratio within the period T. Also, during the period T, the black/yellow signal is B due to the sampling theorem.
This is the period until the time axis is expanded to twice the frequency of the highest frequency audio signal input to B D (7).

First, when performing normal playback in which the magnetic tape (1) runs at a constant speed, the audio head (2) scans the magnetic tape (1),
The audio signal shown in FIG. 16(b) is reproduced.

Next, when performing fast-forward playback (special playback) in which the magnetic tape (1) runs at a constant speed twice that of normal playback, the audio head (
2) scans the magnetic tape (1), and the audio signal shown in FIG. 16(c), which has twice the frequency of the audio signal shown in FIG. 16(b), is reproduced. However, the audio signal during fast-forward playback, which has a higher frequency than the audio signal during normal playback, is difficult to hear, so it is desirable to convert the frequency of the audio signal during fast-forward playback to the frequency of the audio signal during normal playback. There, the audio signal is amplified by an amplifier (3),
A low pass filter (4) removes aliasing noise due to sampling. The audio signal output from the low-pass filter (4) is sequentially sampled by the clock signal C shown in FIG.
It is shifted by 8 steps within (7) and output from BBD (7). Furthermore, noise is removed from the audio signal output from BBD (7) by a low-pass filter (5). Here, if the period of the clock signal C when the audio signal is input to BBD (7) is smaller than the period of the clock signal C when the audio signal is output from the BBD (7), that is, within the period T1. When the audio signal is subjected to signal processing by the BBD (7), since the period ratio is a constant time axis expansion ratio, the audio signal in FIG. 16(c) is time axis expanded,
The audio signal of the T8 period in FIG. 16(d), which is the same as that in FIG. 16, is outputted from the low-pass filter (5). Furthermore, if the period of the clock signal C when the audio signal is input to the BBD (7) is larger than the period of the clock signal C when the audio signal is output from the BBD (7), that is, from the period T to Over the next period T, the audio signal is B B D
In the case of signal processing according to (7), since the period ratio is not a constant time axis expansion ratio, the audio signal in FIG. 16(c) is time axis compressed, and T r in FIG. 16(d),
The T-period audio signal is output from the low pass filter (5). Therefore, the audio signal shown in FIG. 16(d), which undergoes time axis expansion and time axis compression repeatedly from both, is outputted from the low-pass filter (5). However, period T 1 in Figure 16(d)
．． The audio signal of T- has a higher frequency than the audio signal of FIG. 16(c) and must be removed. Therefore, the audio signal shown in FIG.
The audio signal shown in FIG. 16 (*) in which the preceding and following zero level periods T and the zero level period T6 before and after period 13 are muted is output from the mute circuit (8). As a result, an audio signal having the same frequency as during normal reproduction is outputted from the output terminal (9).

(C) Problems to be Solved by the Invention However, in the above-mentioned conventional technology, the audio signal shown in FIG. Since the information of s was muted and made discontinuous, there were problems such as an increase in noise components and the inability to sufficiently confirm the audio signal.

(d) Means for Solving the Problems The present invention was made to solve the above problems, and it reproduces an audio signal in the first frequency band from a recording medium during normal playback, and during special playback. In an audio signal reproducing device that reproduces an audio signal in a second frequency band from the recording medium at a speed different from that during normal reproduction, after dividing the audio signal in the second frequency band into a plurality of frequency bands. The frequency is converted and added to each band in the first frequency band corresponding to the plurality of frequency bands, and the audio signal in the second frequency band is corrected to the first frequency band.

(*) Effect According to the present invention, an audio signal in a first frequency band is reproduced from a recording medium during normal reproduction, and an audio signal in a second frequency band is reproduced from the recording medium at a speed different from that during normal reproduction during special reproduction. In an audio signal reproducing machine that reproduces an audio signal,
After dividing the audio signal in the second frequency band into a plurality of frequency bands, the first audio signal corresponding to the plurality of frequency bands is
The audio signal in the second frequency band is converted into the audio signal in the first frequency band.
Corrected to the frequency band of

(f) Example The details of the present invention will be specifically explained with reference to the illustrated embodiments.

1 to 13 all relate to the present invention, and FIG.
a frequency-level characteristic diagram showing an audio signal in a frequency band of
Figure 2 is a frequency-level characteristic diagram showing an audio signal in which the second frequency band is divided into multiple frequency bands, and Figure 3 is a frequency-level characteristic diagram showing the audio signal in which the second frequency band is divided into multiple frequency bands.
a frequency-level characteristic diagram showing an audio signal in a frequency band of
Figures 4 to 8 are frequency-level characteristic diagrams showing audio signals obtained by dividing the second frequency band into a plurality of frequency bands;
Figures 1 to 13 show frequencies of audio signals converted from the plurality of frequency bands in Figures 4 to 8 into the first frequency band.
The level characteristic diagram, FIG. 14, is a block diagram showing an embodiment of the audio signal correction method of the present invention. To explain the drawing number and structure of FIG. 14, (10) is a recording medium on which the audio signal is recorded. magnetic tape, (11) is the audio head, (
12) is an amplifier, (13a) (13b)''...(1
3n), (14a) (14b)..."・(14n) is a band filter, (15a) (15b)..."(15
n) is an oscillator, (16a) (16b)... (1
6n) is a balanced modulator, (17) is an adder, and (18) is an output terminal.

First, the audio signal correction method of the present invention will be explained.0 During normal playback, an audio signal in a first frequency band is played back from a recording medium, and during special playback, an audio signal in a second frequency band is reproduced from a recording medium whose speed is different from that during normal playback. In an audio signal reproducing device that reproduces an audio signal in a frequency band, when fast-forward playback (special playback) at double speed is performed from normal playback, the second frequency band is twice that of the first frequency band, as shown in Fig. 1. The audio signal in the frequency band is reproduced from the recording medium. However, it is difficult to hear the audio signal during fast-forward playback, which has a higher frequency than the audio signal during normal playback, and it is desirable to correct the audio signal during fast-forward playback from the second frequency band to the first frequency band. Therefore, as shown in Figure 2, the audio signal in the second frequency band is divided into multiple frequency bands (for example, B, b, c, d, e, etc. at intervals of one octave). The narrower the better, and as shown in FIGS. 9 to 13 corresponding to FIGS. 4 to 8, each audio signal a, b in FIGS. 4 to 8 divided into a plurality of frequency bands. ,c,
d and e are 1 while maintaining each frequency bandwidth on the frequency axis.
Perform so-called heterodyne, which moves the frequency band 72 times, and then convert the audio signal a+ b r c r d
*Add e. From this, as shown in FIG. 3, the second frequency band is corrected to the first frequency band, and a continuous audio signal with no missing syllables or the like is obtained.

Next, the audio signal correction method of the present invention will be explained using FIG. When performing fast-forward playback in which the magnetic tape (10) runs at a constant speed twice that of normal playback, the audio head (11) scans the magnetic tape (10) and plays the first frequency band twice as fast as the first frequency band. The audio signal in the second frequency band is reproduced and amplified by an amplifier (12). This audio signal is passed through bandpass filters (13a) (13b)... (13n)
Each frequency band is extracted, that is, divided into a plurality of frequency bands. Here, the bandpass filter (13a) (
13b)......(13n) The carrier wave for making each frequency band 172 times the audio signal of each frequency band outputted from the oscillator (15a) (15b)...
15n), and the balanced modulator (16a) (1
6b)...=...(16n) causes the oscillator (15
a) (15b)"...(15n) The carrier wave oscillated from bandpass filters (13a) (13b)...(
13n) are balanced modulated using the audio signals of each frequency band. Then, from each balanced modulated signal,
The audio signal of each frequency band, which is 72 times larger, is passed through a bandpass filter (1
4a) (14b)...(14n) and are added by the adder (17). Thereby, the second frequency band is corrected to the first frequency band, and a continuous audio signal of information is output from the output terminal (18).

Although the applicant has described the embodiment of the present invention in terms of double fast forward playback, it goes without saying that the present invention can be applied to n times fast forward playback and 1/n times slow motion playback.

(G) Effects of the Invention According to the present invention, an audio signal in a first frequency band is reproduced from a recording medium during normal reproduction, and a second audio signal is reproduced from the recording medium at a speed different from that during special reproduction during special reproduction. In an audio signal reproducing machine that reproduces audio signals in a frequency band,
After dividing the audio signal in the second frequency band into a plurality of frequency bands, the first audio signal corresponding to the plurality of frequency bands is
Since the frequency is converted and added to each frequency band on the frequency axis and the audio signal in the second frequency band is corrected to the first frequency band, a continuous audio signal without any noise component is generated. It has the effect that can be obtained.

[Brief explanation of drawings]

Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and Figure 13 shows the frequency of the audio signal according to the present invention.
14 is a block diagram showing an embodiment of the audio signal correction method of the present invention, FIG. 15 is a block diagram showing an embodiment of the conventional audio signal correction method, and FIG. 16 is a block diagram showing an embodiment of the audio signal correction method of the present invention.
5 is a timing chart showing waveforms of various parts in the figure. (10)--Magnetic tape, (13a) (13b)=
(13n), (14a) (14b)...(14n
)-band filter, (15a)(15b)・”(15
n)...oscillator, (16a)(16b)...(1
6n)...Balanced modulator, (17)...Adder.

Claims (1)

[Claims] (1) Audio that reproduces an audio signal in a first frequency band from a recording medium during normal playback, and reproduces an audio signal in a second frequency band from the recording medium at a speed different from that during normal playback during special playback. In the signal regenerator, the audio signal in the second frequency band is divided into a plurality of frequency bands, and then frequency-converted and added to each band in the first frequency band corresponding to the plurality of frequency bands; Said second
An audio signal correction method comprising: correcting an audio signal in a frequency band to the first frequency band.