JPH01273267A - Audio signal reproducing device for video tape recorder - Google Patents

Abstract

PURPOSE:To always listen to a sound with an excellent sound quality from a video tape without any troublesome operation when PCM audio signals are recorded on the video tape by automatically selecting the signal to be outputted by an audio signal reproducing means corresponding to the record system of the audio signals. CONSTITUTION:When PCM audio signals are recorded on a video tape 12, the signals are read by means of a magnetic head 42 for PCM audio signal and demodulated by performing de-interleave, error correction, and error compensation at a demodulator circuit 44 for PCM audio signal. The demodulated digital signals are supplied to the contact 52b of a changeover switch 52 through an A/D converter 45 and LPF 46 and reproduced from a sound output circuit 53 through the contact 52c of the switch 52. Since the frequency of error compensation performed at the circuit 44 is small and the number of compensation flags never exceeds a prescribed number when the audio signals are demodulated, excellent sounds can be outputted from the circuit 53. When no PCM audio signal is recorded on the tape 12, on the other hand, the circuit 44 cannot make normal demodulation and continuously performs error correction.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an audio signal reproducing device for a video tape recorder that reproduces audio from a signal recorded on a video tape using a PCM modulation method or other modulation method. be.

[Conventional technology]

Some conventional audio signal reproducing devices for video tape recorders are equipped with a linear audio signal reproducing means for reproducing an audio signal from a linear audio signal recorded on a videotape without being modulated. Furthermore, in order to improve the sound quality of reproduced audio, some devices are equipped with FM audio signal reproducing means for reproducing audio signals from FM audio signals recorded using the FM modulation method. Furthermore, in order to obtain even better sound quality, some devices are provided with PCM audio signal reproducing means for reproducing audio signals from PCM audio signals recorded using the PCM modulation method.

The audio signal reproducing device of the video tape recorder, which is equipped with a plurality of audio signal reproducing means for reproducing audio signals from audio signals recorded on video tapes using these various methods, is provided with a manual switching means, and each The signal output from the audio signal reproducing means can be selectively switched.

That is, when reproducing an audio signal, first, the switching means is operated while listening to the reproduced audio. Then, it is determined by which method the audio signal is recorded depending on whether the reproduced sound is normal or not, and the signal to be output from the audio signal reproducing means corresponding to the recorded method is selected. It had become.

[Problem to be solved by the invention]

However, in the above-mentioned conventional audio signal reproducing device for a video tape recorder, when a PCM audio signal is not recorded on the video tape, the switching means switches from PCM to PCM.
When the audio signal reproducing means is set to select the output signal, very large noise is generated. This noise is not only harsh and unpleasant, but can also damage the speaker.

On the other hand, when a PCM audio signal is recorded on a videotape, if the switching means is set to select the signal output from another audio signal reproduction means, the reproduced audio can be played back with better sound quality. Even though you can listen to music, you end up having to settle for somewhat inferior sound quality.

Further, it is troublesome to operate the switching means every time the format in which the audio signal is recorded is changed, and there is a problem in that the operability is poor.

[Means to solve the problem]

In order to solve the above-mentioned problems, an audio signal reproducing device for a video tape recorder according to the present invention includes a PCM audio signal reproducing means for reproducing an audio signal from a PCM audio signal recorded on a videotape using a PCM modulation method; at least one non-PCM audio signal reproducing means for reproducing an audio signal from a signal recorded on a videotape using a method different from a modulation method;
In an audio signal reproducing device for a video tape recorder, the audio signal reproducing device for a video tape recorder includes switching means for selectively switching between a signal output from the audio signal reproducing means and a signal output from the non-PCM audio signal reproducing means. a detection means for detecting whether or not a PCM audio signal is recorded on a videotape based on an error correction flag;
The switching means is controlled so that when it is detected that the audio signal is recorded on a video tape, the signal output from the PCM audio signal reproduction means is selected, and the detection means also controls whether the PCM audio signal is recorded on a video tape or not. The present invention is characterized by comprising a switching control means for controlling the switching means so that the signal output from the non-PCM audio signal reproduction means is selected when it is detected that the non-PCM audio signal is not recorded on the tape.

[For production]

With the above configuration, the detection means detects whether or not a PCM audio signal is recorded on the videotape based on the error correction flag output from the PCM audio signal reproduction means.

When a PCM audio signal is recorded on the videotape, the switching control means selects the signal output from the PCM audio signal reproduction means.
Control the switching means.

Therefore, when a PCM audio signal is recorded on a videotape, the user can always listen to the reproduced audio with good sound quality without any troublesome operations.

On the other hand, if no PCM audio signal is recorded on the videotape, the switching control means controls the switching means so that a signal output from another audio signal reproduction means is selected. Therefore, very loud noise will not be generated that will cause harshness or discomfort, and damage to the speaker will also be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

For example, as shown in FIG. 1, the audio signal reproducing device 11 of the video tape recorder includes a linear audio signal reproducing device that reproduces an audio signal from a linear audio signal that is a non-PCM audio signal recorded on a video tape 12 without being modulated. means 21, FM audio signal reproducing means 31 for reproducing an audio signal from an FM audio signal which is a non-PCM audio signal recorded by an FM modulation method, and an FM audio signal reproducing means 31 for reproducing an audio signal from a PCM audio signal recorded by a PCM modulation method. A PCM audio signal reproducing means 41 is provided.

The linear audio signal reproducing means 21 includes a linear audio signal magnetic head 22 for extracting the linear audio signal recorded on the video tape 12, and a linear audio signal for amplifying the signal extracted by the linear audio signal magnetic head 22. A preamplifier 23 is also provided. The output of the linear audio signal preamplifier 23 is connected to the contact 51 of the changeover switch 51.
connected to a.

Further, the FM audio signal reproducing means 31 is an FM audio signal reproducing means for extracting an FM audio signal recorded on the video tape 12.
An audio signal magnetic head 32, an FM audio signal preamplifier 33 that amplifies the signal extracted by the FM audio signal magnetic head 32, and an FM audio signal preamplifier 33 that demodulates the signal output from the FM audio signal preamplifier 33. A demodulation circuit 34 is also provided.

The output of the FM audio signal demodulation circuit 34 is connected to the contact 51b of the changeover switch 51. Also, F
A switching control signal is output from the M audio signal demodulation circuit 34, and this switching control signal causes the neutral contact 51c of the changeover switch 51 to switch between the contacts 51a and 51b.
It is designed to be electrically conductive with one of the following.

On the other hand, the PCM audio signal reproducing means 41 includes a PCM audio signal magnetic helad 42 for extracting the PCM audio signal recorded on the video tape 12,
A PCM audio signal preamplifier 43 that amplifies the signal extracted by the audio signal magnetic head 42
, a PCM audio signal demodulation circuit 44 that performs demodulation, that is, decreep, error correction, and error correction on the signal output from the PCM audio signal preamplifier 43; and a PCM audio signal demodulation circuit 44.
A D/A converter 45 that converts the digital signal demodulated by the D/A converter 45 into an analog signal;
A low-pass filter 46 is provided to cut off frequency components of 24 kHz or higher in the signal output from the low-pass filter 46.

The neutral contact 51c of the changeover switch 51 and the output of the low-pass filter 46 in the PCM audio signal reproducing means 41 are connected to the changeover switch 5, respectively.
It is connected to the second contact 52a and the second contact 52b.

A neutral contact 52c of the changeover switch 52 is connected to the audio output circuit 53.

The changeover switch 52 is operated by the linear audio signal reproducing means 2 under the control of a changeover control means 64, which will be described later.
1 or the signal output from the FM audio signal reproducing means 31 and the signal output from the PCM audio signal reproducing means 41 and inputting the same to the audio output circuit 53.

Further, the PCM audio signal demodulation circuit 44 in the PCM audio signal reproduction means 41 outputs an error correction flag and inputs it to the detection means 63 when an error correction operation of the PCM audio signal is performed. It has become.

The detection means 63 includes, for example, a counter circuit 61 and a gate pulse generation circuit 62, as shown in FIG. As shown in FIG. 3, the counter circuit 61 controls the PCM audio signal demodulation circuit 44 during the time t during which the gate pulse is inputted from the gate pulse generation circuit 62.
The number of error correction flags inputted from the controller is counted, and whether or not a PCM audio signal is recorded on the videotape 12 is detected based on whether the number of error correction flags reaches a predetermined number N or more. It has become.

The counter circuit 61 of the detection means 63 is connected to the switching control means 64. This switching control means 64 is
When the detection means 63 detects that a PCM audio signal is recorded on the videotape 12,
By setting the switching control signal to low level, P
A changeover switch 52 is configured so that the signal output from the CM audio signal reproduction means 41 is input to the audio output circuit 53.
control. The switching control means 64 also detects that the PCM audio signal is detected by the detection means 63 on the video tape 12.
When it is detected that the FM audio signal is not recorded, the signal output from the linear audio signal reproducing means 21 or the FM audio signal reproducing means 31 is input to the audio output circuit 53 by setting the switching control signal to a high level. The changeover switch 52 is controlled in this manner.

In the above configuration, when a PCM audio signal is recorded on the video tape 12, this PCM audio signal is extracted by the PCM audio signal magnetic head 42, and is taken out by the PCM audio signal preamplifier 4.
After being amplified by PCM audio signal demodulation circuit 44, the signal is subjected to deinterleaving, error correction, and error correction, and then demodulated. The demodulated digital signal is
The signal is converted into an analog signal by the D/A converter 45, frequency components of 24 kHz or higher are cut off by the low-pass filter 46, and the signal reaches the contact 52b of the changeover switch 52.

When a PCM audio signal is recorded on the video tape 12, the frequency of error correction performed by the PCM audio signal demodulation circuit 44 is low. Therefore, during the time t during which the gate pulse is input from the gate pulse generation circuit 62 to the counter circuit 61, the number of error correction flags output from the PCM audio signal demodulation circuit 44 exceeds the predetermined number N. It won't happen. Therefore, the switching control means 64 controls the changeover switch 52 using a low-level switching control signal to bring the contact 52b and the neutral contact 52c into conduction. Therefore, the signal output from the PCM audio signal reproducing means 41 is input to the audio output circuit 53, so that audio with good quality is reproduced.

On the other hand, if no PCM audio signal is recorded on the videotape 12, the PCM audio signal demodulation circuit 44 cannot perform normal demodulation because a regular PCM audio signal is not input, and errors continue to occur. Corrections will be made. Therefore, the PCM audio signal demodulation circuit 44 reaches its error correction capability limit, and further error correction is performed continuously.

In this case, in the counter circuit 61, the number of error correction flags input from the PCM audio signal demodulation circuit 44 regularly exceeds the predetermined number N during the time t during which the gate pulse is input. Therefore, the switching control means 64 controls the switching switch 52 using a high-level switching control signal to switch between the contact 52a and the neutral contact 52c.
The noise output from the PCM audio signal reproducing means 41 is prevented from being input to the audio output circuit 53. The switching control signal is maintained at a high level until the number of error correction flags input from the PCM audio signal demodulation circuit 44 does not reach a predetermined number N during the time t during which the gate pulse is input. Ru.

By the way, as mentioned above, no PCM audio signal is recorded on the video tape 12, but if an FM audio signal is recorded, this FM audio signal is extracted by the FM audio signal magnetic head 32, and the FM audio signal is recorded on the video tape 12. After being amplified by the signal preamplifier 33, it is demodulated by the FM audio signal demodulation circuit 34 and reaches the contact 51b of the changeover switch 51. Also, at this time, a switching control signal is output from the FM audio signal demodulation circuit 34, and this switching control signal causes the neutral contact 51c of the changeover switch 51 to change to the contact 51b.
connected to.

Here, the contact 52a of the changeover switch 52 to which the neutral contact 51C of the changeover switch 51 is connected becomes electrically conductive with the neutral contact 52c because no PCM audio signal is recorded on the video tape 12, as described above. ing. Therefore, FM audio signal demodulation circuit 3
The signal output from 4 is the contact 5 of the changeover switch 51.
1b, the signal is input to the audio output circuit 53 via the neutral contact 51c, the contact 52a of the changeover switch 52, and the neutral contact 52c.

In addition, when only a linear audio signal is recorded on the video tape 12, this linear audio signal is taken out by the linear audio signal magnetic head 22, and after being amplified by the linear audio signal preamplifier 23, the changeover switch 51 The signal is input from the contact 51a to the audio output circuit 53 via the neutral contact 51c, the contact 52a1 of the changeover switch 52, and the neutral contact 52c.

In this way, the changeover switch 51 and the changeover switch 52 can be switched according to the recording method of the audio signal recorded on the video tape 12 without any troublesome operation, so that the playback audio can always be played back with good sound quality. You can hear the sound without the noise being so loud that it becomes harsh or unpleasant.
Furthermore, damage to the speaker is also prevented.

〔Effect of the invention〕

As described above, the audio signal reproducing device for a video tape recorder according to the present invention includes a PCM audio signal reproducing means for reproducing an audio signal from a PCM audio signal recorded on a videotape using a PCM modulation method, and a PCM modulation method. at least one non-PCM for reproducing audio signals from signals recorded on videotape by different methods;
An audio signal reproducing device for a video tape recorder comprising an audio signal reproducing means and a switching means for selectively switching between a signal output from the PCM audio signal reproducing means and a signal output from the non-PCM audio signal reproducing means. Based on the error correction flag output from the audio signal reproducing means, P
a detection means for detecting whether or not a CM audio signal is recorded; and a signal output from the PCM audio signal reproduction means when the detection means detects that a PCM audio signal is recorded on a videotape. The switching means is controlled so that the PCM audio signal is selected, while the signal output from the non-PCM audio signal reproduction means is selected when the detection means detects that the PCM audio signal is not recorded on the videotape. and switching control means for controlling the switching means.

As a result, the switching means automatically selects the signal output by the audio signal reproducing means that corresponds to the audio signal recording method, so that the PCM is recorded on the video tape.
If an audio signal is recorded on the video tape, you can always listen to the playback sound in good quality without any troublesome operations. This has the effect of not generating extremely loud noise that is harsh on the ears or causing discomfort, and also prevents damage to the speaker.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a block diagram showing the configuration of an audio signal reproducing device for a video tape recorder, and FIG. 2 is a detailed configuration of the detection means. FIG. 3 is a timing chart showing the operations of the detection means and the switching control means. 11 is an audio signal reproducing device of a video tape recorder, 12 is a video tape, 21 is a linear audio signal reproducing means (non-PCM audio signal reproducing means), and 31 is an F
M audio signal reproducing means (non-PCM audio signal reproducing means), 41 is PCM audio signal reproducing means, 52
63 is a detection means, and 64 is a switching control means.

Claims (1)

[Claims] 1.P recorded on videotape using PCM modulation method
PCM audio signal reproducing means for reproducing an audio signal from a CM audio signal; at least one non-PCM audio signal reproducing means for reproducing an audio signal from a signal recorded on a videotape using a method different from the PCM modulation method; In an audio signal reproducing apparatus for a video tape recorder, the audio signal reproducing apparatus for a video tape recorder includes a switching means for selectively switching between a signal output from an audio signal reproducing means and a signal output from a non-PCM audio signal reproducing means.
a detection means for detecting whether or not a PCM audio signal is recorded on the videotape based on an error correction flag output from the M audio signal reproduction means; The switching means is controlled so that the signal output from the PCM audio signal reproduction means is selected when it is detected that the PCM audio signal is not recorded on the video tape, while the detection means detects that the PCM audio signal is not recorded on the video tape. 1. An audio signal reproducing apparatus for a video tape recorder, comprising: switching control means for controlling the switching means so that the signal output from the non-PCM audio signal reproducing means is selected when the non-PCM audio signal reproducing means is selected.