JPH05174312A - Sound recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent an output of nuisance noise by generating a mute signal prior to the changeover from an FM audio signal to a normal audio signal and muting at the output stage. CONSTITUTION:In a sound recording/reproducing device consisting of the FM audio having two rotary heads and the normal audio based on a fixed head, a hold detecting circuit 8 detecting the existence of a reproducing FM signal to hold the demodulated signal and mute circuits 23, 24 generating the mute signal in a detecting circuit 9 having the time constant different from that of the hold detecting circuit 8 are provided. The demodulated signal of the FM audio and the reproduced signal of the normal audio are changed over by an output switch control signal which is delayed than the timing of this mute signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice recording / reproducing apparatus having FM audio and normal audio in a VTR.

[0002]

2. Description of the Related Art Conventionally, an audio recording / reproducing apparatus of this type is shown in FIG.
There is one shown in. That is, as shown in FIG.
The audio recording / reproducing apparatus includes amplifiers 3 and 4 for respectively amplifying input signals of channels CH1 and CH2 input from two rotary heads, a switch 5 for switching between them, and a band-pass filter for L channel (ch) ( BPF) 6, bandpass filter (BPF) 7 for R channel (ch), and hold detection circuit 8
A normal detection circuit 9, demodulators 10 and 11, a mono-multi circuit 12, hold circuits 13 and 14, peak noise reduction (PNR) circuits 15 and 16, output switches (SW) 17 and 18, It also has an amplifier 19 for amplifying the output from the fixed head.

In the above structure, the channels CH1 and CH input from the two rotary heads during reproduction
The input signal 2 is input from the amplifiers 3 and 4 and the switch 5 to the BPF 6 for the L channel and the BPF 7 for the R channel, respectively. It is assumed that the reproduced FM signal is missing in the middle of this output as the waveform shown in FIG. First, the hold detection circuit 8 obtains the hold detection output shown in FIG. 4B in synchronization with the reproduced FM signal, whereby the L-channel signal output from the demodulator 10 is held by the hold circuit 13, and R output from the demodulator 11 through the BPF 7 for R channel
The channel signal is held by the next hold circuit 14 to form the hold waveform shown in FIG.

At the same time, the BPF 6 for the L channel
The output of the mono-multi circuit 1 through the normal detection circuit 9.
The normal detection mono-multi output shown in FIG. 7C is obtained by the time constants input to the input terminal 2 and set by the attack time T1 and the recovery time T2. On the other hand, the output from the fixed head goes through the amplifier 19 to the output switch 17,
18 has been entered. In the output switches 17 and 18, the FM audio signal and the normal audio signal are switched by the normal detection mono-multi output, and noise due to the offset generated at the time of switching is generated as in the waveform of the L channel output shown in FIG. It is output to the L channel output and the R channel output, respectively.

[0005]

However, in the above-mentioned conventional example, when the portion such as the tracking deviation or the scratch on the tape is reproduced and the FM audio signal is switched to the normal audio signal, an offensive noise due to the offset of both is output. There was a problem. Therefore, the present invention has been made in consideration of the above circumstances, and an object of the present invention is to generate a mute signal before switching from an FM audio signal to a normal audio signal, and to mute at an output stage without causing annoyance. An object of the present invention is to provide an audio recording / reproducing device that prevents noise from being output.

[0006]

In order to achieve the above object, a voice recording / reproducing apparatus according to the present invention comprises an FM audio having two rotary heads and a normal audio having a fixed head. The FM audio recording / reproducing apparatus is provided with means for detecting the presence / absence of a reproduced FM signal and holding a demodulation signal, and means for generating a mute signal by a detection circuit having a time constant different from this means.
An output switch control signal delayed from the timing of the mute signal is used to switch between the FM audio demodulation signal and the normal audio reproduction signal.

[0007]

In the present invention having the above construction, the reproduction F
Detecting that the M signal is missing, a mute signal is generated, an output switch control signal delayed from this mute signal is generated, and this output switch control signal is used to generate an FM audio signal and a normal signal.
Noise is prevented from being output by switching the audio signal and muting by the mute signal.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of an audio recording / reproducing apparatus according to the present invention. Note that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIG. As shown in the figure, the audio recording / reproducing apparatus of the present embodiment has amplifiers 3 and 4 for respectively amplifying input signals of channels CH1 and CH2 input from two rotary heads, and a switch 5 for switching between them. BPF6 for L channel,
A BPF 7 for the R channel, a hold detection circuit 8 that detects the presence or absence of a reproduced FM signal and holds a demodulation signal, a normal detection circuit 9 having a time constant different from that of the hold detection circuit 8, demodulators 10 and 11, Mono-multi circuit 12
, Hold circuits 13 and 14, peak noise reduction (PNR) circuits 15 and 16, and output switch (S
W) 17, 18 and an amplifier 19 for amplifying the output from the fixed head. Further, the audio recording / reproducing apparatus according to the present embodiment has a delay circuit 20, a mute mono-multi circuit 21, and an output switch control circuit 22.
And mute circuits 23 and 24.

Next, the operation of this embodiment will be described.
Channel C input from two rotary heads during playback
The input signals of H1 and channel CH2 are input from amplifiers 3 and 4 and switch 5 to BPF 6 for L channel, respectively.
And to the BPF 7 for the R channel. It is assumed that the reproduced FM signal is missing in the middle of this output as shown by the waveform shown in FIG. With such a waveform, the presence / absence of a reproduced FM signal is first detected by the hold detection circuit 8 to obtain the hold detection output waveform shown in FIG. As a result, the L-channel signal output from the demodulator 10 is held by the hold circuit 13, and the R-channel signal output from the demodulator 11 through the R-channel BPF 7 is held by the next hold circuit 14. The hold waveform shown in FIG.

At the same time, the BPF 6 for the L channel
Is output to the normal detection circuit 9. Unlike the time constant of the hold detection circuit 8, the normal detection circuit 9 is set with the attack time T1 as shown in FIG. Further, after this, the mono-multi circuit 12 provides a time difference of T2 at the rising edge and then restores the FM audio. The output of the mono-multi circuit 12 is delayed by T3 after passing through the delay circuit 20, and the waveform shown in FIG.
On the other hand, the reproduced FM signal is output from the hold circuits 13 and 14 to PN.
It is input to the output switches 17 and 18 via the R circuits 15 and 16.

The normal audio output from the fixed head is input to the output switches 17 and 18 via the amplifier 19. The reproduced FM audio signal and the reproduced normal audio signal are switched at the timing of the waveform of the output switch control circuit 22 shown in FIG. That is, when the output switch control (SWCTL) signal is "H", the reproduced FM audio signal is output, and when "L", the reproduced normal audio signal is output. At the time of this switching, DC offsets of both are generated in a considerable amount, so that switching noise as shown in FIG.

The mute signal for preventing this is further converted by the mute mono-multi circuit 21 into a signal having a certain pulse width as shown in FIG. Sent out,
During the period of this pulse width, the output signals of the output switches 17 and 18 are muted and output as L channel and R channel outputs, respectively (shown in FIG. 6H as L channel output). Therefore, the timing at this time is delayed by T3 when the output switch is switched by T3 compared to the rising edge of the mute signal, so that the switching noise is not necessarily output but muted, and no offensive noise is output.

[0013]

As described above, according to the audio recording / reproducing apparatus of the present invention, a portion such as a tracking shift or a scratch on the tape is reproduced, and this occurs when the FM audio signal is switched to the normal audio signal. It is possible to prevent annoying noise from being output.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an audio recording / reproducing apparatus according to the present invention.

FIGS. 2A to 2H are timing charts of respective parts in FIG.

FIG. 3 is a block diagram showing an embodiment of a conventional audio recording / reproducing apparatus.

4 (A) to (E) are timing charts of respective parts of FIG.

[Explanation of symbols]

 5 switch 6 BPF for L channel 7 BPF for R channel 8 Hold detection circuit 9 Normal detection circuit 12 Mono-multi circuit 13 Hold circuit 14 Hold circuit 17 Output switch 18 Output switch 20 Delay circuit 21 Mute mono-multi circuit 22 Output switch control Circuit 23 mute circuit 24 mute circuit

Claims (1)

[Claims] 1. An audio recording / reproducing apparatus comprising an FM audio having two rotary heads and a normal audio having a fixed head, and a means for detecting the presence or absence of a reproduced FM signal and holding a demodulation signal, and this means. A detection circuit having different time constants is provided with a means for generating a mute signal, and the output switch control signal delayed from the timing of the mute signal switches between the FM audio demodulation signal and the normal audio reproduction signal. An audio recording / reproducing apparatus characterized by the above.