JPH03292676A - Vtr - Google Patents

Abstract

PURPOSE:To record a signal in a correct format by performing switching between stereo recording and monaural recording in accordance with the detection output indicating whether a plug is inserted in a jack or not. CONSTITUTION:In a monaural/stereo detecting circuit 30, a switch contact MC of an input jack 1R of the right channel is connected to the base of a transistor TR 31, and a collector output Sw is supplied to switch circuits 13 and 17 for monaural/stereo switching and a video recording circuit 23 as the control signal. It is detected by a detecting circuit 30 whether a plug is inserted in the jack 1R or not, and switching between stereo recording and monaural recording of an audio signal is performed by the detection signal Sw. Thus, the signal is always automatically recorded in the correct format, and the degradation in quality of reproduced pictures due to appearance of the noise in edge parts of reproduced pictures is prevented at the time of reproducing because the carrier component of an FM signal S(L-R) is not recorded at the time of monaural recording.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a VTR.

[Summary of the invention]

The present invention improves the characteristics of, for example, 8 mm video by detecting the audio input mode and switching between monaural recording and stereo recording.

[Conventional technology]

For example, in the case of 8 mm video, the audio signal starts with a standard for recording and playing back in monaural, and later a standard for recording and playing back in stereo has been added.

Therefore, in the case of 8 mm video, in order to ensure compatibility with monaural and stereo machines, the signals recorded and reproduced on the magnetic tape have a formant as shown in FIG.

That is, Figure A shows the signal format in monaural mode, which includes an FM luminance signal sy that is FM-modulated by a luminance signal, an FM sound audio signal S color that is FM-modulated by a monaural audio signal M, and a low-frequency carrier color signal. The SC and a tracking servo pilot signal SP are frequency multiplexed.

In addition, Figure B shows the signal format in stereo,
The audio signals of the left and right channels are placed at the frequency position of the FM signal SM in monaural mode, and the sum signal of H (L+R) is used to
As the M-modulated FM signal S (L+R) arrives,
On the upper side of the FM signal SM in monaural mode, there is an FM signal 5 (L-R
) is located.

Therefore, compatibility can be achieved between monaural and stereo devices.

Since 8 mm video is recorded and reproduced in the format described above, the audio input circuit of the recording system is configured as shown in FIG. 5, for example.

That is, in the same figure, (IL) and (IR) indicate the input jacks for the external microphone or line input of the left and right channels, and in these jacks (IL) and (IR), HC is the hot side contact, and CC is the hot side contact. cold side contact,
MC is a switch contact. Furthermore, (10) is an audio signal recording circuit.

Then, when the left and right channel input plugs PLGL and PLGR are inserted into the jacks (IL) and (IR), the contact IC and contact hole of the jack (IR) are separated, so the audio signals from the plugs PLGL and PLGR are removed. ,R
is supplied to the recording circuit (10) through the contacts HC and HC of the jacks (IL) and (IR), and the audio signals are
is recorded in stereo in the format shown in FIG. 4B.

Also, if only the plug (3L) is inserted into the jack (IL), the audio signal from the plug PLGL will be
L) to the recording circuit (1) as the left channel audio signal.
0) and the contact H of the jack (IR)
C and contact MC are in contact as shown in the figure, so the right channel audio signal R is recorded as the audio signal R from the jack (IL) to the jack (IR) through the contacts MC and IC (10).
supplied to

Therefore, in this case, since L=R, the FM signal 5
(LR) becomes only the carrier component, and the audio signal of the plug PLGL is recorded in the format shown in FIG. 4C.

If this format is used, it is equivalent to the monaural format shown in FIG. Therefore, when the audio signal M is monaural, monaural recording can be performed through the plug PLGL.

[The third problem to be solved by the invention is that in the case of the above-mentioned audio input circuit, during monaural recording, the monaural audio signal M and the FM audio signal S
It is equivalent to monaural recording in terms of color, but the FM signal 5 (L
-R) carrier components are recorded.

If this carrier component is recorded, during reproduction, this carrier component may appear as noise at the edge portions of the reproduced image, degrading the reproduced image quality.

Also, when playing back 8mm video, which distinguishes between stereo recording and monaural recording based on the presence or absence of FM signal 5 (L-R), even though it is not stereo, FM signal 5 (IJR) is detected. , s (LR), the left and right channel audio signals are demodulated and matrixed.
The S/N of the audio signal supplied to the monitor receiver is reduced. Or, the mode display shows stereo even though the audio is monaural.

Furthermore, even though the recording is monaural, the FM luminance signal SY cannot be extended to the low frequency side because of the FM signal 5 (LR).

This invention attempts to solve these problems.

(Means for solving the problem) Therefore, in this invention, the jack (IL), (
One jack of the IR) is used for both stereo and monaural purposes, and it detects whether an input plug is inserted into the other jack, and the detection output is used to connect the former or the former shown in Figure 4 A or B. It is designed so that recording can be performed using

[Effect]

Plug PLG for input jacks (IL), (IR)
L.

Audio signals are recorded in the correct format according to the state of the PLGR.

〔Example〕

In Fig. 1, (30) indicates a monaural/stereo detection circuit, the switch contact of the right channel input jack (IR) is connected to the base of the transistor (31), and its collector output Sw is a monaural/stereo detection circuit. The signal is supplied as a control signal to the stereo switching switch circuits (13), (17) and the video recording circuit (23).

In addition, the hot side contact IC of the jack (IL) and (IR)
Resistors (2L) and (2R) are connected between and ground.

When recording in stereo, the jack (IL), (I
Insert the plugs PLGL and PLGR into R).

Then, the contacts IC and MC of the jack (IR) are separated, so the transistor (30) is turned off and Sw=
“0”, and as a result, the switch circuit (13), (1
7) is connected to the state shown in the figure.

Then, the left and right channel audio signals from the plugs PLGL and PLGR are connected to the jack (IL), (I
R) → Capacitor (3L), (3R) → AGC amplifier (
The matrix circuit (12) is supplied through the signal lines IIL) and (IIR) to output the sum signal (L+R) and the difference signal (
LR) is formed, and the signal (L+R) is supplied to the FM modulation circuit (15L) through the switch circuit (13) and the noise reduction circuit (14L) to generate the FM signal S(
L+R).

In addition, the signal 5 (L-R
) is transmitted to FM through the noise reduction circuit (14R).
FM signal 5 (L-R) is supplied to the modulation circuit (15R)
is converted to

Then, the FM signals S(L+R) and 5(LR) are supplied to the addition circuit (16), and the addition signal is sent to the switch circuit (
17) to the adder circuit (24).

Further, a video signal from an image sensor, for example a COD (21), is supplied to a video signal processing circuit (22), where a luminance signal Y and red and blue color difference signals are extracted. 23), the FM luminance signal sy, carrier color signal SC, and pilot signal sp are extracted, and these signals are supplied to an adder circuit (24).

Therefore, a recording signal in stereo format is taken out from the adder circuit (24) as shown in FIG. 4B.

This recording signal is transmitted to a pair of rotating magnetic heads (25
), (25), one field of which is diagonal one.
It is recorded on magnetic tape (26) to become the magnetic track of the book.

On the other hand, during monaural recording, plug PLGL is inserted into the jack (IL).

Then, the contacts HC and MC of the jack (IR) come into contact, so the transistor (30) turns on and Sw=
becomes “1”, which causes the switch circuit (13), (1
7) is connected in the opposite state as shown in the figure.

Then, the monaural audio signal M from the plug PLGL is
The FM modulation circuit (
15L) and is converted into an FM signal SM, and this signal SM is supplied to the adder circuit (2) via the switch circuit (17).
4).

Further, at this time, the recording circuit (23) is controlled by the signal Sw, and the occupied band of the FM luminance signal sy is expanded to the frequency position of the FM signal 5 (LR) during stereo recording.

Therefore, as shown in FIG. 4A, a recording signal in monaural format is taken out from the adder circuit (24), and this recording signal is sent to the tape (26) by heads (25), (25) in the same way as in stereo. ) is recorded.

Note that at this time, the switch circuit (17) is switched to a state opposite to that shown in the figure by the signal Sw, so that the FM signal 5 (LR) or its carrier component is not recorded.

Furthermore, the reproduction system may be the same as the conventional one.

Thus, according to the present invention, the stereo audio signal R
Alternatively, it is possible to record a monaural audio signal M. In this case, in particular, according to the present invention, when recording monaural, the FM signal M
Since the (LR) carrier component is not recorded, during reproduction, noise does not appear at the edge portions of the reproduced image and degrade the reproduced image quality.

Also, when playing back 8mm video, which distinguishes between stereo recording and monaural recording based on the presence or absence of FM signal 5 (L-R), FM signals S (L+R), 5 (
Since the audio signals of the left and right channels from L-R are not demodulated and matrixed, the S/N of the audio signal supplied to the monitor receiver will not deteriorate, or the mode display will not be displayed even though the audio is monaural. is never stereo.

Furthermore, during monaural recording, the FM luminance signal SY is
The band can be expanded to the M signal 5 (L-R) band.

Moreover, the detection circuit (30) detects whether or not the plug PLGR is inserted into the jack (IR), and the detection signal Sw switches between stereo recording and monaural recording of the audio signal. There is no need to be aware of monaural recording and monaural recording, and recording can always be automatically performed in the correct format.

FIG. 2 shows a case where the line output jack is used for both stereo and monaural output.

That is, in the figure, (40) indicates an 8 mm video audio signal reproducing circuit, and during stereo reproduction, the terminal TL
, TR outputs left and right channel audio signals, and during monaural playback, a monaural audio signal M is output to terminals TL and TR.

Also, (4L) and (4R) indicate the line output jacks for the left and right channels, and these jacks (4L) and (4R) indicate the line output jacks for the left and right channels.
R) is the jack (IL), (IR) contact point) 1c,
It has contacts HC, CC, and MC similar to CC and MC.

Then, connect the detection circuit (30
) is connected, and its output signal Sw is supplied to the switch circuit (51) as its control signal.

When supplying the output signals of terminals TL and TR to a stereo input device, use jacks (4L) and (4R).
) into each input plug (not shown).

Then, the contact IC of the jack (4R) and the anus are separated and S
Since w=“0”, the switch circuit (51) is connected to the state shown in the figure, and therefore the audio signal L (or M) at the terminal TL is connected to the switch circuit (51) and the capacitor (
6L) and is output to the jack (4L).

Furthermore, the audio signal R (or M) at the terminal TR is output to the jack (4R) through the capacitor (6L).

Therefore, stereo audio signals from terminals TL and TR can be supplied to stereo input devices connected to jacks (4L) and (4R).

On the other hand, when supplying the output signals of the terminals TL and TH to a monaural input device, the input plug (not shown) is inserted into the jack (4L).

Then, the contact point HC of the jack (4R) and the anus touch and the S
Since w = "1", the switch circuit (51) is connected in the opposite state to that shown in the figure, and therefore, the audio signals R (or M) at terminals TL and TR are added in the adder circuit (52). The signal (L+R) is converted into a switch circuit (
51) and is output to the jack (4L).

Therefore, a monaural input device connected to the jack (4L) receives stereo audio signals from terminals TL and TR.
, R can be added to provide a monaural signal (L+R).

FIG. 3 shows a case where the line input jack and line output jack are used together.

That is, the output of the switch (71) is connected to the switch circuit (7
2), (73), and (74) as their control signals. Further, (84) is a muting transistor, which is turned on only during muting and turned off during recording and reproduction.

When the jack (7) is used as an input jack, the switch (71) is turned off.

Then, the output of the switch (71) causes the switch B
(72) is connected to the state shown in the figure, and the switch circuits (73) and (74) are turned off, so the transistor (82) is turned off, and the transistor (82) side is viewed from the jack (7). The impedance is the input impedance mainly determined by the resistor (86).

Therefore, the audio signal from the jack (7) is supplied to the audio circuit (81) through the switch circuit (72),
Furthermore, it is supplied to a recording system (not shown) and recorded.

On the other hand, when using the jack (7) as an output jack, the switch (71) is turned on.

Then, the output of the switch (71) causes the switch circuit (
72) is connected in the opposite state to that shown in the figure, and the switch circuits (73) and (74) are turned on, so the transistor (82) becomes an emitter follower state, and the transistor (82) is connected from the jack (7) to the transistor (82). The impedance viewed from the side is the output impedance mainly determined by the resistors (83) and (85).

Therefore, the audio signal from the reproduction system (not shown) is transmitted from the audio circuit (81) to the transistor (82) to the resistor (83).
) → jack (7) through the signal line of the resistor (85)
) is output.

Also in this circuit, when there are jacks (7) for two channels, switching between stereo and monaural can be performed by the detection circuit (30).

〔Effect of the invention〕

According to this invention, during monaural recording, FM signal 5 (L-
Since the carrier component of R) is not recorded, during reproduction, noise does not appear at the edge portions of the reproduced image and degrade the reproduced image quality.

Also, when playing back 8mm video, which distinguishes between stereo recording and monaural recording based on the presence or absence of FM signal 5 (L-R), FM signals S (L+R), 5 (
Since the audio signals of the left and right channels are not demodulated and matrixed from the left and right channels (L-R), the S/N of the audio signal supplied to the monitor receiver does not deteriorate. Or, even though the audio is monaural, the mode display does not change to stereo.

Furthermore, during monaural recording, the FM luminance signal SY is
The band can be expanded to the M signal 5 (L-R) band.

Moreover, the detection circuit (30) detects whether or not the plug PLGR is inserted into the jack (IR), and the detection signal Sw switches between stereo recording and monaural recording of the audio signal. There is no need to be aware of monaural recording and monaural recording, and recording can always be automatically performed in the correct format.

[Brief explanation of drawings]

FIGS. 2 and 3 are system diagrams of an example of the present invention, and FIGS. 4 and 5 are diagrams for explaining the same. (IL), (IR) are input jacks, (10) is audio signal recording circuit, (12) is matrix circuit, (15L)
, (15R) is an FM modulation circuit, (21) is an image sensor, (
22) is a video signal processing circuit, (23) is a video signal recording circuit, (25) is a rotating magnetic head, (30) is a detection circuit,
(4L) and (4R) are output junks, and (40) is an audio signal reproducing circuit. P lap number

Claims (1)

[Claims] An audio circuit for recording or reproducing stereo audio signals and monaural audio signals, first and second jacks, and a detection circuit for detecting whether a plug is inserted into the second jack. According to the detection output of the detection circuit, when the plug is inserted into the second jack, the audio circuit is set to stereo mode and the stereo audio signal is accessed to the first and second jacks. . A VTR, wherein when the plug is not inserted into the second jack, the audio circuit is set to a monaural mode and the monaural audio signal is accessed to the first jack.