JPS6117529Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing device for recording/reproducing video signals and audio signals.

As the recording density of VTRs and the like increases, the running speed of the magnetic recording medium decreases, resulting in a problem in that the quality of recording/reproducing audio signals becomes extremely poor. In order to solve this problem, a method has been proposed in which a video head is used to record and reproduce audio signals.

Frequency multiplexing is known as one such method. This method amplitude modulates the audio signal at a frequency that is above the low conversion frequency band of the chroma signal (for example, 688KHz ± 500KHz) and that has little mutual influence on the lower sideband of the FM wave of the luminance signal. Alternatively, it is frequency modulated and multiplexed recorded.

In this method, it is not possible to record a new audio signal on a recording medium on which audio has already been recorded (so-called dubbing).

On the other hand, a time-minute multiplexing method is known as another method. This method records a time-axis compressed audio signal or an audio signal that has been sampled at a predetermined synchronization and pulse-modulated (PCM, PAM, PWM, etc.) by inserting it into the horizontal or vertical blanking period of the video signal. It is something to do.

The present invention uses the above-mentioned time division multiplexing method to enable overlapping recording (after-recording) of an audio signal after recording a video signal.

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

FIG. 1 is a block circuit diagram of a VTR showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part of FIG.

In FIG. 1, a switch circuit 2 is used to switch the VTR between a normal recording mode and an audio recording mode in which only audio signals are recorded, with the fixed contact 2a side being the recording mode and the fixed contact 2b side being the audio recording mode. It's summery. Note that this switch circuit 2 may be switched by manual operation.

During normal recording, a video signal a shown in FIG. 2A is transmitted from terminal 1 to fixed contact 2a of switch circuit 2,
The fixed contact 4 of the switch 4 passes through the movable contact 2c and the low-pass filter 3 for band limitation of FM modulation.
supplied to a. The output of the low-pass filter 3 is also supplied to a sync separation circuit 12, from which a horizontal sync signal b shown in FIG. 2B is formed.
This horizontal synchronizing signal b is supplied to each of the timing circuit 14 and sample hold circuit 13.

On the other hand, the audio signal c shown in FIG. 2C is supplied from a terminal 10 to a sample-and-hold circuit 13 via a low-pass filter 11 for band limitation during sampling. Therefore, the sample hold circuit 13
As shown in FIG. 2D, a signal d obtained by sampling and holding the audio signal c every horizontal period is obtained from the output of the . This signal d is supplied to the fixed contact Pb of the switch circuit 4.

In the timing circuit 14, a timing signal e shown in FIG. 2e is generated based on the horizontal synchronization signal b. This timing signal e is a pulse of a predetermined width located in the back porch portion of the horizontal synchronization signal.
This timing signal e is supplied to the switch circuit 4 as a control signal, so when the signal e is low level, the movable contact 4c of the switch circuit 4 is connected to the fixed contact 4a, and when the signal e is high level, the movable contact 4c is connected to the fixed contact 4a. 4c is connected to the fixed contact 4b. Therefore, as shown in FIG. Obtained from contact terminals.

This composite signal f is subjected to frequency modulation in an FM modulator 5, and then to a recording amplifier 6 and a switch circuit 7.
The signal is then supplied to the video head 8 through which normal recording (video signal and audio signal) is performed. Note that during normal recording, the switch circuit 7 is supplied with a high-level signal REC as a control signal via the OR circuit 15, and the movable contact 7c is connected to the fixed contact 7a. Note that during normal recording, only the video signal a may be recorded and the audio signal c may not be recorded.

During playback, the switch 24 is closed in conjunction with the playback button, so the movable contact 7c of the switch circuit 7
is connected to the fixed contact 7b. Therefore, the reproduction signal from the video head 8 is supplied to the reproduction amplifier 16 via the switch circuit 7. The output of the playback amplifier 16 is demodulated by the FM demodulator 17, and a playback video signal h is led out from the terminal 21. Furthermore, the reproduced video signal h is transmitted to the synchronization separation and delay circuit 1.
8, from which a timing signal e' similar to that shown in FIG. 2E is generated. The reproduced video signal h is also supplied to a sample and hold circuit 19, where the video signal h is sampled and held using the timing signal e' as a sampling pulse.
The output of the sample hold circuit 19 is smoothed by a low pass filter 20 and then outputted to the outside from a terminal 22 as a reproduced audio signal i.

Next, the audio recording mode will be explained. In this mode, only the audio signal is superimposed on the magnetic tape that has already been recorded, allowing you to record audio signals that were not recorded during the video signal, or to record audio signals that have already been recorded. It is now possible to rewrite to another audio signal.

In the audio recording mode, the movable contact 2c of the switch circuit 2 is connected to the fixed contact 2b. Also, when the switch 24 is opened, the switch circuit 7
The timing signal e (FIG. 2E) output from the timing circuit 14 is supplied as a control signal via the OR circuit 15. Therefore, the movable contact 7c of the switch circuit 7 is closed when the signal e is at a high level.
a, and when the level is low, it is connected to contact 7b. That is, the VTR is in a recording state when the signal e is at a high level (audio part), and is in a reproducing state when the signal e is at a low level.

The audio signal c to be recorded is transmitted from the terminal 10 to the fixed contact 4b of the switch circuit 4 via the low-pass filter 11 and the sample-hold circuit 13, as described above.
supplied to Furthermore, when the signal e is at a low level, the playback signal from the video head 8 is transmitted to the playback amplifier 1.
6. The audio signal is supplied to the sync separation circuit 12 via the FM demodulator 17, the switch circuit 2, and the low-pass filter 3, and the audio signal is sampled and held based on the horizontal sync signal b obtained from the separation circuit 12. , a timing signal e is formed in the timing circuit 14.

Therefore, when the timing signal e is at a high level,
The movable contact 4a of the switch circuit 4 is connected to the fixed contact 4b, whereby the pulse amplitude modulated audio signal is transmitted from the switch circuit 4 via the FM modulator 5 and the recording amplifier 6 to the fixed contact 7a of the switch circuit 7.
supplied to Since the movable contact 7c of the switch circuit 7 is connected to the fixed contact 7a when the signal e is at a high level, the recording current for only the audio signal shown in FIG. 2G is supplied from the switch circuit 7 to the video head. As a result, a new audio signal is recorded over the audio recording portion of the magnetic tape that has already been recorded. Note that if the audio signal has already been recorded, the previous audio signal will be erased by this overlapping recording.

Note that when the signal e is at a low level and the movable contact 4c of the switch circuit 4 is connected to the fixed contact 4a, the reproduced video signal is supplied to the switch circuit 7 via the FM modulator 5 and the recording amplifier 6; Since the switch circuit 7 is on the side of the contact 7b,
There is no inconvenience that the playback video signal is recorded.

In the above embodiment, the audio signal is time-divisionally inserted into the horizontal sampling period, but the audio signal may be PCM-modulated and time-compressed before being inserted into the vertical sampling period. In this case, the S/N ratio will not deteriorate when overlapping recording is performed. Furthermore, PWM modulated audio signals may be time-division multiplexed and recorded. Further, PWM and PAM may be used in combination. According to the experiment,
Regarding S/N due to overlapping recording of audio signals,
It was observed that PCM was good, PAM was slightly degraded, and PMW was significantly degraded.

As described above, the present invention records audio signals and video signals by time-division multiplexing, so even if the tape speed is low, audio recording/reproduction can be performed with high quality. Furthermore, by synchronizing with the reproduced video signal, a new audio signal is superimposed on the audio recording portion of the magnetic recording medium, so even with a simple circuit configuration, after-recording of the audio signal can be easily and accurately performed. can.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a VTR showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part of FIG. 1. In addition, in the symbols used in the drawings, 4...
...Switch circuit, 5...FM modulator, 7...Switch circuit, 8...Video head, 13...Sample hold circuit, 17...FM demodulator, 19...
This is a sample and hold circuit.

Claims (1)

[Scope of utility model registration request] At least one horizontal blanking section of the video signal
In a magnetic recording/reproducing device configured to insert a sampled audio signal into a part to form a composite signal of video and audio, and record the composite signal on a magnetic recording medium by angle modulating the composite signal, During recording, the audio signal is multiplexed with the video signal using a sampling pulse synchronized with the horizontal synchronization signal of the video signal to be recorded, and when rewriting only the audio signal to the recorded composite signal, the audio signal is reproduced from the magnetic recording medium. 1. A magnetic recording and reproducing apparatus characterized in that a new audio signal is intermittently recorded on the magnetic recording medium using a sampling pulse synchronized with a horizontal synchronizing signal.