JPS6248310B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video tape recorder for recording and reproducing audio multiplexed television signals.

In television audio multiplexing, in addition to the conventional main channel, a subchannel that is FM modulated using 31.5kHz as a subcarrier frequency is provided, and two audio signals are transmitted through these channels. Current broadcasting uses stereo and dual audio, such as in two languages.

In stereo, a sum signal of left and right audio is transmitted through the main channel, a difference signal is transmitted through the subchannel, and the left and right audio are separated by a matrix circuit on the receiving side. On the other hand, in dual audio, the first audio is transmitted on the main channel, the second audio is transmitted on the sub channel, and these audios are extracted as is. Further, in the case of dual audio, a switch circuit or the like is required to take out the first audio and the second audio separately.

That is, on the receiving side, it is necessary to switch circuits such as inserting and removing a matrix circuit or inserting and removing a switch circuit for stereo and dual audio.

Therefore, on the transmitting side, approximately 55.125kHz (3.5
_H : _H is horizontal frequency) 982.5Hz in stereo,
During dual audio, a control signal AM modulated at 922.5 Hz is superimposed, this is detected on the receiving side, and the above-mentioned circuits etc. are automatically switched.

By the way, when recording such an audio multiplexed television signal on a video tape recorder, two audio tracks are provided, and in stereo, the left and right audio are recorded separately on each track, and the left and right audio are recorded separately on each track. Regarding audio, first and second audio are recorded on respective tracks.

However, in this case, the above-mentioned control signal is not recorded. For this reason, when playing back video tape recorders, the user has to manually switch a switch depending on the content of the playback signal, which requires complicated operations. Furthermore, depending on the content, it may be difficult to make a judgment, and there is also a risk that playback may be performed without realizing that the switching position is incorrect.

Therefore, consideration has been given to recording a signal corresponding to the above-mentioned control signal during recording, and detecting this during playback to perform automatic switching. In that case, for example, it is conceivable to use a track other than the audio track to record the control signal, but this method is not preferable from the point of view of compatibility, and the control signal of the audio signal cannot be recorded on the audio track. considered desirable.

In view of these points, the present invention is designed to enable recording of the above-mentioned control signals with a simple configuration. An embodiment of the present invention will be described below with reference to the drawings.

First, the recording system will be explained. In the figure, a signal received by a tuner 1 is supplied to a video detection circuit 3 through a VIF circuit 2, and the detected video signal is supplied to a rotating magnetic head 6 through a recording circuit 4 and a recording side contact R of a recording/playback switch 5. and recorded on tape T.

Further, the signal from the detection circuit 3 is supplied to the FM detection circuit 12 through the SIF circuit 11, and the detected signal is supplied to the low-pass filter 13 to extract the main channel signal S _M. Furthermore, the detection circuit 1
The signal from 2 is supplied to the FM detection circuit 15 through the bandpass filter 14 of 16 kHz or more, and the detected signal is supplied to the low-pass filter 17 through the muting circuit 16, and the sub-channel signal S _S is extracted. These main channel signal S _M and sub-channel signal S _S are supplied to the matrix circuit 18.

Furthermore, the signal from the bandpass filter 14 is
The signal from this band pass filter 19 is supplied to a 55.125 kHz band pass filter 19.
982.5Hz or
The 922.5 Hz control signal is demodulated, and these signals are supplied to narrowband bandpass filters 21 and 22 to detect a stereo control signal C _S and a dual audio control signal C _B . These control signals C _S ,
C _B is supplied to the switch signal forming circuit 23, and three types of switch signals, stereo, dual audio, and monaural, are formed. This signal is matrix circuit 1
8 switching control terminals. Further, the output of the bandpass filter 19 is supplied to the control terminal of the muting circuit 16, and when there is no control signal, the sub-channel signal S _S is muted.

Then, from the matrix circuit 18, the left and right audio signals are output in stereo mode, the first and second audio signals are output in dual audio mode, and the main channel signal is output in monaural mode. 1st
and taken out to the second output end. The first of these
The signals from the and second output terminals are supplied to mixing circuits 24 and 25, respectively.

Further, a signal from a pulse generator 31 for detecting the rotational phase of the rotary head 6, for example, is supplied to a 1/2 frequency divider circuit 32 to form a 15 Hz signal. This signal is supplied to the low-pass filter 33 and converted into a sine wave, and this signal is supplied to the movable contact of the changeover switch 34. This switch 34 is provided with three fixed contacts: stereo S, dual audio B, and monaural M. A signal from the switch signal forming circuit 23 is supplied to the switching control terminal of the switch 34. Then, during stereo, the signal from the contact S is supplied to the mixing circuit 24, during dual audio, the signal from the contact B is supplied to the mixing circuit 25, and during monaural, the contact M is grounded.

The signals from the mixing circuits 24 and 25 are then supplied to the magnetic heads 28 and 29 through the recording side contacts R of the recording/reproduction changeover switches 26 and 27, and are recorded on the first and second tracks of the tape T.

Therefore, in the recording system, the video signal is recorded on the rotary head 6, and the audio signal is recorded on the head 2.
It is recorded on the first and second tracks at 8 and 29. In this case, in stereo, left and right audio signals are recorded on the first and second tracks, and a 15 Hz signal is superimposed and recorded on the first track. Also, in the case of double audio, the first and second audio signals are recorded on the first and second tracks, and the 15
A Hz signal is superimposed and recorded on the second track. Furthermore, when monaural, the main channel audio signal is the first
and recorded on the second track.

Next, the reproduction system will be explained. In the figure, a signal from a rotating head 6 is taken out through a reproducing contact P of a switch 5, and this signal is supplied to a mixing circuit 8 through a reproducing circuit 7.

Further, signals from the heads 28 and 29 are taken out through the playback side contacts P of the switches 26 and 27, respectively, and these signals are sent to the matrix circuit 4 through high-pass filters 41 and 42 of 20 Hz or higher, respectively.
3. At the same time, switches 26 and 27
The signals are supplied to 15 Hz band pass filters 44 and 45, respectively, and the 15 Hz signals recorded in a superimposed manner on the first and second tracks are extracted. That is, during stereo, the control signal C _'S is detected from the bandpass filter 44, and during dual audio, the control signal _C'B is detected from the bandpass filter 45.
These control signals C' _S and C' _B are supplied to a switch signal forming circuit 46 to form three types of switch signals: stereo, dual audio, and monaural. This signal is supplied to the switching control terminal of the matrix circuit 43.

Then, from the matrix circuit 43, the sum signal of the left and right audio from the heads 28 and 29 is output to the first output terminal in the stereo mode, and the difference signal is output to the second output terminal. One audio is output from the first output terminal, the second audio from the head 29 is output from the second output terminal, and when monaural, the output from the head 28,
A mixed signal of audio from 29 is taken out at a first output. The main channel signal S′ _M from the first output terminal of this matrix circuit 43 is sent to the mixing circuit 47.
The sub-channel signal S _'S from the second output terminal is also supplied to the mixing circuit 47 through the 31.5 kHz FM modulation circuit 48. Note that the signal from the switch signal forming circuit 46 is supplied to the FM modulation circuit 48, so that the degree of modulation during dual audio is made shallower than during stereo.

Furthermore, a 982.5 Hz oscillator 51 and a 922.5 Hz oscillator 52 are provided, and these signals are supplied to the stereo contact S and the dual audio contact B of the changeover switch 53. Furthermore, the monaural contact M of the switch 53 is grounded. A signal from the switch signal forming circuit 46 is supplied to the switching control terminal of the switch 53.

The signal from this switch 53 is transmitted to the AM modulation circuit 5.
4. Also, a 55.125kHz signal from the oscillator 55 is supplied to the modulator 54, and this signal is AM at 982.5Hz for stereo and 922.5Hz for dual audio.
Modulated and suppressed when monaural. The signal from this modulator 54 is supplied to a mixing circuit 47. Furthermore, the signal from this mixing circuit 47 is FM modulated by an FM modulation circuit 49 and supplied to the mixing circuit 8.

The signal from this mixing circuit 8 is transmitted to the RF circuit 9.
The signal is supplied to the television and is used as a signal for the first channel or the second channel of the television, and this signal is taken out to the output terminal 10.

Therefore, in the reproduction system, the rotary head 6 reproduces the video signal, the audio signals reproduced by the heads 28 and 29 are matrixed as necessary, and the control signal is further mixed into the video signal. This mixed signal is converted into a first or second channel signal and extracted. In this case, the 15Hz signal superimposed on the first and second tracks is detected, and the matrix circuit 4
3rd prize will be automatically switched.

In this way, the audio multiplexed television signal is recorded and played back.According to the present invention, the pilot signal is
Since the signals are superimposed and recorded on different tracks of the first and second audio tracks, it is possible to detect this signal and automatically switch circuits during playback.

By using a sine wave outside the audio band (20 to 10,000 Hz) as the pilot signal as described above, it does not affect the audio signal, and the detection is free from disturbances such as the audio signal and pulse generator output. becomes stable.

Also, the circuit configuration is extremely simple.

Furthermore, since control signals are recorded only on the audio track, compatibility with other devices is also good.

[Brief explanation of the drawing]

The figure is a system diagram of an example of the present invention. 23 is a switch signal forming circuit, 24 and 25 are mixing circuits, 31 is a pulse generator, 33 is a low-pass filter, and 34 is a changeover switch.

Claims (1)

[Claims] 1. When recording an audio multiplexed television signal on a video tape recorder, multiplexed audio signals are recorded on each of a plurality of tracks, and a pilot signal is assigned to each of the plurality of tracks according to each mode of audio multiplexing. A videotape recorder that allows superimposed recording on different tracks.