JPH05191783A - Video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain an excellent reproduction video signal by operating an AGC circuit in a reproduction system accurately in the video signal recording and reproducing, device in which a PCM audio signal subject to time division multiplex is recorded and reproduced for a blanking period of a video signal. CONSTITUTION:When a PCM audio signal is subject to time division multiplex for a blanking period of a recording video signal and reproduced/recorded, an AGC circuit 32 outputs a reproduction signal itself for a PCM audio signal area and generates a control voltage by detecting a level of a reproduced FM signal for a video signal area. Then the gain is automatically adjusted so that the signal level at the output is constant. Furthermore, a pre-stage of the AGC circuit is provided with a clip circuit 14 controlled by a PCM area signal and the reproduction signal at the PCM audio signal area is clipped to a prescribed level so as not to give effect onto the AGC circuit and the clipped signal is inputted to the AGC circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention modulates a video signal by FM,
The present invention relates to a video signal recording / reproducing device configured to record and reproduce a digital audio signal (hereinafter referred to as a PCM audio signal) by time-division multiplexing in a blanking period of an FM video signal.

[0002]

2. Description of the Related Art FIG. 8 shows a video signal (F
M video signal) A magnetic recording / reproducing apparatus (hereinafter referred to as V, which is an example of a conventional video signal recording / reproducing apparatus for time-divisionally multiplexing and recording and reproducing a PCM audio signal in a part of a vertical blanking period.
It is a block diagram showing TR). In the figure, 1
Is a pre-emphasis circuit that emphasizes the high frequency component of the input video signal, 2 is an FM modulator that FM-modulates the video signal, and 3 is a PCM encoder, which is a shuffling process and an error correction code is added to the input audio signal. Etc., the time axis compression processing is performed to insert the digital audio signal of one field period into the vertical blanking period of the FM video signal which is the output of the FM modulator 2, and the digital audio signal is digitally modulated and output. 4, 5 are switches, 6 is the above switches 4, 5
Adder for adding the outputs of 7 and 7 are recording amplifiers, 8a and 8b
Is a rotary head, and 9 is a magnetic tape.

Reference numerals 12a and 12b denote head amplifiers for amplifying reproduction signals from the rotary heads 8a and 8b, and 13
Is a head switching circuit for switching the outputs from the head amplifiers 12a and 12b based on a head switching signal, 14
Is a reproduction equalizer for compensating the frequency characteristic of the reproduced FM video signal, and 15 is an automatic gain for automatically adjusting the gain so that the output level of the reproduced signal from each of the rotary heads 8a and 8b becomes a constant level value at the output. An adjusting circuit (hereinafter referred to as an AGC circuit), 16 is an FM demodulator, 17 is a dropout detection circuit that detects a dropout of a reproduced FM signal, and outputs a dropout detection signal, and 18 is the pre-emphasis circuit 1. A de-emphasis circuit having an inverse characteristic, 19 is a reproduced video signal for performing a time axis correction on the reproduced video signal and a dropout compensation process using the dropout detection signal output from the dropout detection circuit 17 Processing circuit, 20 is a PC inserted in the vertical blanking period for the above-mentioned one-field period
It is a PCM decoder that detects an M audio signal and performs error correction, deshuffling processing, error correction processing, and the like to restore and output the original audio signal.

FIG. 9 is a top view of a rotary head used in a VTR. 10 is a rotary drum in which rotary heads 8a and 8b are mounted at an interval of 180 °, and 11
Reference numerals a and 11b are guide pins for winding the magnetic tape 9 around the rotary drum 10.

Next, the operation will be described. In the block diagram of FIG. 8, the video signal is input to the pre-emphasis circuit 1, and the high frequency component of the video signal is emphasized to enhance the FM modulator 2.
And the FM modulator 2 FM-modulates the video signal. On the other hand, the audio signal is input to the PCM encoder 3,
After performing shuffling processing, adding error correction code, etc.,
In order to insert the digital audio signal of one field period into the vertical blanking period of the FM video signal which is the output of the FM modulator 2, time axis compression processing is performed, digital modulation is performed, and the signal is output.

Thereafter, the PCM audio signal output from the PCM encoder 3 in the one field period is FM.
The video signal is inserted into the vertical blanking period of the video signal at the timing shown in FIG. 11, for example, and is output to the recording amplifier 7. In addition, the switches 4 and 5 use the FM video signal and the PCM.
A voice signal is switched and added by the adder 6 to create a recording signal. Then, the recording amplifier 7 amplifies the FM video signal and the PCM audio signal, which are the recording signals, and records them on the magnetic tape 9 by the rotary heads 8a and 8b.

At this time, the magnetic tape 9 is strongly wound around the rotary drum 10 by 180 ° as shown in FIG. 9, and is recorded on the magnetic tape 9 even if the recording current is constantly flowing to the rotary heads 8a and 8b. It is only during the period when the rotary head is in contact with the magnetic tape 9. Therefore, the recording pattern on the magnetic tape 9 is divided into two areas a and b as shown in FIG. 12, and the recording signal of one field is recorded on one track. In the figure, a indicates a track recorded by the rotary head 8a, and b indicates a track recorded by the rotary head 8b. Further, since the PCM audio signal is time-division multiplexed and recorded in the vertical blanking period of the FM video signal, the portion where the PCM audio signal is recorded is the shaded portion.

Next, the operation during reproduction will be described. The reproduced FM video signal reproduced by the rotary heads 8a and 8b and the PCM audio signal mixed at the time of recording are supplied to the head amplifier 12
a and 12b are amplified respectively. The reproduction signals output from the head amplifiers 12a and 12b are selected by the head switching circuit 13 from reproduction signals from the rotary head that is in contact with the magnetic tape 9 as shown in FIG. Then, the reproduction signal is switched to one reproduction signal (FIG. 13C). The reproduction signal from the head switching circuit 13 is reproduced by the reproduction equalizer 14
And is sent to the PCM decoder 20. P
The CM decoder 20 detects the PCM audio signal in the one field period inserted in the vertical blanking period of the reproduced signal, and performs error correction, deshuffling processing,
Error correction processing is performed to restore the original audio signal and output it.

In general, when an FM signal is recorded and reproduced by an electromagnetic conversion system using a tape and a head, the lower sideband is emphasized and the upper sideband is suppressed so that the modulation index changes and at the same time the sideband unbalance occurs. Therefore, the reproduced FM video signal corresponding to the rising portion (FIG. 14A) of the video signal in which the high-frequency component is emphasized by the pre-emphasis circuit 1 is largely constricted as shown in FIG. 14B. Therefore, in the reproduction equalizer 14, for example, the lower sideband is suppressed and the upper sideband is emphasized to compensate the frequency characteristic of the reproduced FM video signal. As a result, the output from the reproduction equalizer 14 is as shown in FIG. The number of bunches is reduced. Then, the output of the reproduction equalizer 14 is input to the AGC circuit 15 which automatically adjusts the gain and controls so that the output level of the output reproduction signal becomes an appropriate constant level value. The AGC circuit 15 outputs the reproduction signals output from the rotary heads 8a and 8b with a constant output level, and the output is sent to the FM demodulator 16 and the dropout detection circuit 17. The FM demodulator 16 FM demodulates the reproduced signal from the AGC circuit 15. Further, the dropout detection circuit 17 compares the reproduced FM signal with a predetermined comparison reference value, determines that the reproduction signal level is a dropout when the reproduction signal level is lower than the comparison reference value, and outputs a dropout detection signal.

After that, the output of the FM demodulator 16 is
It is input to the emphasis circuit 18, and the de-emphasis circuit 18 attenuates the high frequency component emphasized at the time of recording, and the output thereof is input to the reproduced video signal processing circuit 19. The reproduction video signal processing circuit 19 separates the synchronization signal from the reproduction video signal and performs time axis correction on the reproduction video signal based on the synchronization signal, and the dropout detection circuit 1 described above.
A dropout compensation process using the dropout detection signal from 7 is performed to obtain a reproduced video signal.

By the way, the dropout detection circuit 1
In 7, the reproduced FM signal is compared with a predetermined comparison reference value,
Since the dropout detection signal indicating the dropout is output, if the output level of the reproduction signal output from the rotary heads 8a and 8b is different for each head due to the characteristics of the head and tape, reproduction of one head is performed. The comparison reference value for dropout detection is the optimum level value for the signal output level, but it may not be the optimum level for the reproduction signal output of the other head. Also, F
If the output level of the reproduction signal at the circuit inputs of the M demodulator 16 and the dropout detection circuit 17 is excessive, distortion occurs and the operation of the circuit breaks down. Therefore,
Even if the output level of the reproduction signal from the rotary heads 8a and 8b differs depending on the characteristics of the head and the tape as in the case of performing the compatible reproduction, the output level of the reproduction signal does not vary between the heads and is always a proper constant value. The gain is automatically adjusted by the AGC circuit 15 so as to obtain the level value.

The operation of the AGC circuit 15 will be described here. The AGC circuit 15 is configured, for example, as shown in FIG. 10. In the figure, 21 is a detector that detects the output level value of the reproduction signal and outputs a control voltage, 22 is a rectifier circuit, 23 is an integrator, 24 Is a control voltage generator that generates and outputs a control voltage, and the detector 21 is composed of the rectifier circuit 22, the integrator 23, and the control voltage generator 24. Reference numeral 25 is a variable gain amplifier whose gain is controlled by the control voltage which is the detection result of the detector 21.

The operation of the AGC circuit 15 is such that the detector 21 outputs the output signal V to detect the level value of the reproduction signal.
It begins with rectifying _OUT . First, the output signal V _OUT which is a reproduction signal is input to the rectifier circuit 22 in the detector 21 and rectified. Then, this rectified output is the integrator 2
3, the DC component V _D is extracted, and the control voltage generator 24 detects the change from the DC component V _D and generates and outputs a control voltage for controlling the gain of the variable gain amplifier 25. .. Here, the control voltage is AG
It is generated as a voltage value for adjusting the gain of the variable gain amplifier 25 so that the output level value of the reproduction signal is always a constant level value at the output of the C circuit 15. The control voltage obtained as a result of detection by the detector 21 is the gain variable amplifier 25.
Then, the gain of the amplifier is automatically adjusted by the control voltage so that the output level of the output of the AGC circuit 15 is always an appropriate constant level value.

[0014]

In the conventional video signal recording / reproducing apparatus as described above, at the time of recording, the PCM audio signal is time-division multiplexed and recorded in the vertical blanking period of the FM-modulated video signal, At the time of reproduction, the reproduced FM video signal and the mixed PCM audio signal are reproduced as a reproduction signal as they are and input to the reproduction equalizer 14 and the AGC circuit 15. On the other hand, the PCM voice signal has a pulse waveform,
The signal band has wideband signal components as shown in FIG.

By the way, the frequency characteristic of the reproduction output in the magnetic recording / reproducing is generally as shown in FIG. 16, and the output level of the reproducing signal is lowered in the high range due to the loss in the recording / reproducing and the low range in the FM video signal. The reproduction output at becomes higher than that at high frequencies. Therefore, FIG.
The output level of the reproduction signal of the PCM audio signal having a frequency component lower than the FM video signal band as shown in FIG.
As shown in 3, compared to the output level of the FM video signal,
It will be output at a large level value.

On the other hand, the AGC circuit 15 outputs a control voltage from the result of rectifying and integrating the level values of the reproduction signal in all periods as shown in FIG.
When the gain is automatically adjusted so that the level value of the output of the GC circuit 15 becomes a constant level, the AGC circuit operates even in the PCM audio signal area where the output level is high. Also, in the AGC circuit, as shown in FIG. 17, the response characteristics differ depending on whether the response gain due to the control voltage is high or low. Therefore, when the output level of the reproduction signal greatly differs between the video signal area and the PCM audio signal area, the response of the AGC circuit is changed due to the change of the level value of the reproduction signal near the boundary between the PCM audio signal area and the video signal area. Due to the influence of the characteristics, the operation of automatically adjusting the gain in the video signal area is not normally performed.
There is a problem that a reproduced FM video signal that always has an appropriate constant level value cannot be obtained at the output of the GC circuit, and a good reproduced video signal cannot be obtained.

Further, the reproduction signal having the PCM audio signal as shown in FIG. 13C inserted therein is output from the head switching circuit 13 or the reproduction equalizer 14 as shown in FIG.
There is a configuration in which the reproduced FM video signal and the PCM audio signal are separated as shown in (c), and then the reproduced FM video signal after the separation is input to the AGC circuit 15 and processed. At this time, the PCM audio signal area period in the reproduced FM video signal (FIG. 18C) after separating the PCM audio signal becomes a non-signal portion. Also in this case, similarly to the above, in the AGC circuit having the configuration as shown in FIG. 10, the AGC circuit operates even in the PCM audio signal area which is a non-signal portion, and therefore, in the video signal area due to the response characteristic of the AGC circuit and the like. The operation of automatically adjusting the gain is not normally performed, and it is impossible to obtain a reproduced FM video signal that always has an appropriate constant level value at the output of the AGC circuit, so that a good reproduced video signal cannot be obtained. there were.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to normally perform the operation of the AGC circuit in the video signal area, and to reproduce the output which always has a constant level value. An object of the present invention is to obtain a video signal recording / reproducing apparatus which can obtain an FM video signal and can obtain a good reproduced video signal even when compatible reproduction is performed.

[0019]

A video signal recording / reproducing apparatus according to the present invention includes a PCM area signal generator for generating a control signal indicating a PCM audio signal area in a reproduced signal during reproduction, and the PCM area signal generator. An AGC circuit for automatically adjusting the gain so that the output level of the reproduction signal always becomes a constant level value only in the video signal area other than the PCM audio signal area in the reproduction signal based on the PCM area signal which is the output of The level value of the reproduced FM video signal of the reproduced signal at the output of the AGC circuit is always kept at a constant level.

Further, the video signal recording / reproducing apparatus according to the present invention keeps the output level of the PCM area signal generator and the PCM area signal generator for generating the control signal indicating the PCM audio signal area in the reproduction signal always constant. In the preceding stage of the AGC circuit for automatically adjusting the gain, the output level of the reproduction signal in the PCM audio signal area of the reproduction signal is set to a predetermined level based on the PCM area signal output from the PCM area signal generator. A clip circuit for clipping is provided so that the output level value of the reproduced signal at the output of the AGC circuit is always a constant level.

[0021]

The video signal recording / reproducing apparatus of the present invention is a PC
On the basis of the PCM area signal indicating the M audio signal area, the gain is adjusted so that the output level of the reproduced FM video signal at the output operates in the video signal area excluding the PCM audio signal area. Since the AGC circuit for automatically adjusting is provided so that the level value of the reproduced FM video signal in the reproduced signal at the output of the AGC circuit is always a constant level, the AGC in the video signal area is set.
The circuit can be operated normally, and a good reproduced video signal can be obtained even when compatible reproduction is performed.

Further, the video signal recording / reproducing apparatus according to the present invention is characterized in that in the clip circuit provided in the preceding stage of the AGC circuit,
Based on the PCM area signal indicating the PCM audio signal area, the output level of the reproduced signal in the PCM audio signal area in the reproduced signal is clipped to a predetermined level, and the output level value of the reproduced signal at the output of the AGC circuit is always a constant level. As a result, the operation of the AGC circuit in the video signal area can be normally performed, and a good reproduced video signal can be obtained even when compatible reproduction is performed.

[0023]

EXAMPLES Example 1. Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a VTR according to the first embodiment of the present invention. In FIG. 1, recording systems 1-9
Since the reproducing systems 12 to 14 and 16 to 19 are exactly the same as those of the conventional apparatus, detailed description thereof will be omitted.

Reference numeral 30 denotes a PCM decoder, which detects a PCM voice signal in one field period inserted in the vertical blanking period of the reproduction signal, and performs error correction, deshuffling processing, error correction processing, etc., on the original voice signal. Restore and output. Reference numeral 31 is a PCM area signal generator for generating a PCM area signal indicating a PCM audio signal area of a reproduction signal in the PCM decoder 30, and 32 is the PCM.
Based on the PCM area signal generated from the area signal generator 31, the input signal is output as it is for the reproduction signal in the PCM audio signal area, and the gain is set for the video signal area other than the PCM audio signal area. It is an AGC circuit that automatically adjusts and controls so that the level value of the output signal is output at a constant level value.

FIG. 2 is a diagram showing an example of the configuration of the AGC circuit in FIG. In FIG. 2, reference numeral 33 denotes a PCM area signal output from the PCM area signal generator 31, which generates and outputs a predetermined control voltage in the PCM audio signal area, and an output level value of the reproduction signal in the video signal area. A detector that detects and outputs a control voltage from the detection result, 34 is a rectifier circuit, 35 is an integrator, and 36 is the PCM.
The detector 33 is a control voltage generator that is controlled based on the PCM region signal from the region signal generator 31 and generates and outputs a control voltage. The detector 33 is the rectifier circuit 34, the integrator 35,
It is composed of a control voltage generator 36. Reference numeral 37 is a variable gain amplifier which controls the gain by the control voltage which is the detection result of the detector 33. In the PCM audio signal area, the input reproduced signal is output as it is (gain is 0).
The control voltage from the detector 33 in the PCM audio signal area is set to a value (such as dB).

Next, the operation will be described. During recording, the input video signal is input to the pre-emphasis circuit 1, emphasizes the high frequency component of the video signal and outputs it to the FM modulator 2. The FM modulator 2 FM-modulates the video signal. ..
On the other hand, the audio signal is input to the PCM encoder 3, subjected to shuffling processing, addition of error correction code, etc., and then the digital audio signal for one field period is converted to the FM modulator 2 described above.
Of the FM video signal, which is the output of the above, is subjected to time-axis compression processing for insertion in the vertical blanking period, digitally modulated, and output.

Thereafter, the PCM audio signal output from the PCM encoder 3 in the one field period is FM.
The recording amplifier 7 is inserted in the vertical blanking period of the modulated video signal at a timing as shown in FIG.
Is output to. The switches 4 and 5 switch between the FM video signal and the PCM audio signal, and the adder 6 adds them.
A recording signal is generated. Then, the recording amplifier 7 amplifies the FM video signal and the PCM audio signal, which are the recording signals, and records them on the magnetic tape 9 by the rotary heads 8a and 8b. At this time, the magnetic tape 9 is strongly wound around the rotary drum 10 by 180 ° as shown in FIG.
Even if a recording current flows through a and 8b, the magnetic tape 9 is recorded only during the period when the rotary head is in contact with the magnetic tape 9. Therefore, the recording pattern on the magnetic tape 9 is divided into two areas a and b as shown in FIG. 12, and the recording signal of one field is recorded on one track. In the figure, a is a rotary head 8a.
Shows a track recorded by, and b is the rotary head 8b.
Shows a track recorded by. Also, PCM
Since the audio signal is time-division multiplexed and recorded during the vertical blanking period of the FM video signal, the portion where the PCM audio signal is recorded is the shaded portion. The recording operation up to this point is the same as in the conventional example.

Next, the operation during reproduction will be described. The reproduced FM video signal reproduced from the rotary heads 8a and 8b and the PCM audio signal mixed at the time of recording are supplied to the head amplifier 12
It is amplified by a and 12b. Then, the head amplifier 1
The reproduced signals which are the outputs of 2a and 12b are the reproduced signals from the rotary head which is in contact with the magnetic tape 9 in the head switching circuit 13 as shown in FIGS. 3 (a), 3 (b) and 3 (c). One reproduction signal (FIG. 3C) is selected and switched based on the head switching signal.
The reproduction signal from the head switching circuit 13 is sent to the reproduction equalizer 14 and the PCM decoder 3
Sent to 0. The PCM decoder 30 detects the PCM audio signal of one field period inserted in the vertical blanking period of the reproduced signal and performs error correction, deshuffling processing, error correction processing, etc. to restore the original audio signal and output it. .. On the other hand, the reproduction equalizer 14 compensates the frequency characteristic of the reproduction FM video signal of the input reproduction signal and sends it to the AGC circuit 32.

Here, at the time of recording, the PCM audio signal is time-divisionally multiplexed and recorded during the vertical blanking period of the FM-modulated video signal, and at the time of reproduction, the reproduced FM video signal and the mixed PCM audio signal are recorded. Play as it is as a playback signal,
Through the reproduction equalizer 14. On the other hand, the PCM audio signal has a pulse waveform and has a wideband signal component as shown in FIG. The frequency characteristic of the reproduction output in magnetic recording / reproduction is generally as shown in FIG.
In the high range, the output level of the reproduction signal is lowered due to the loss of recording and reproduction, and the reproduction output in the low range is larger than that in the high range. Therefore, as shown in FIG. 3, the output level of the reproduction signal of the PCM audio signal having a frequency component lower than the FM video signal band as shown in FIG. 15 is higher than the output level of the reproduction signal of the FM video signal. It will be output at the level value.

Therefore, in the AGC circuit 32, when the level value of the reproduction signal in all the periods is detected and the control voltage is output, and the gain of the AGC circuit is adjusted accordingly, the reproduction is performed in the video signal area and the PCM audio signal area. If the output levels of the signals are significantly different, the AGC circuit will operate even in the PCM audio signal region where the output level is high.
The operation will not be performed normally due to the response characteristics of the circuit (see FIG. 17).

Therefore, in the AGC circuit 32,
Based on the PCM area signal indicating the PCM audio signal area, P
The input signal is output as it is for the reproduction signal in the CM audio signal area, and the gain value is automatically adjusted for the video signal area other than the PCM audio signal area so that the level value of the output signal is always constant. The output is controlled by the level value.
Here, the PCM area signal generated by the PCM area signal generator 31 in the PCM decoder 30 is sent to the AGC circuit 32. The PCM area signal generator 31 is
In the PCM decoder 30, the end timing of the PCM audio signal area of the reproduction signal is detected, and the start time of the next PCM audio signal area is predicted from the above detection result to generate the PCM area signal indicating the PCM audio signal area. is doing.

In the PCM domain signal generator 31, for example, in the PCM audio signal domain as shown in FIG.
h, generate a Low pulse in the video signal area, and
Send to C circuit 32. In the AGC circuit 32,
The PCM domain signal pulse is sent to a control voltage generator 36 in the detector 33, which controls the generation of the control voltage based on the PCM domain signal. That is, in the video signal region period in which the pulse is Low, the reproduction signal is supplied to the rectification circuit 3
4 is rectified and integrated by the integrator 35 to extract the DC component V _D , and the control voltage generator 36 outputs the value V _D of this DC component.
Generates a control voltage and outputs it to the variable gain amplifier 37. Then, in the variable gain amplifier 37, the gain is automatically adjusted by the control voltage so that the output level of the reproduced FM video signal at the output of the AGC circuit 32 becomes an appropriate constant level value.

On the other hand, the control voltage generator 36 in the detector 33 is switched so as to generate and output a constant control voltage V _r during the PCM audio signal region period in which the pulse from the PCM region signal generator 31 is High. Then, the control voltage V _r is output to the variable gain amplifier 37. The control voltage V _r is set to such a value that the gain thereof becomes 0 dB in the variable gain amplifier 37, for example. Therefore, since the constant control voltage V _r is sent to the variable gain amplifier 37, the gain of the AGC circuit 32 remains 0 dB regardless of the level value of the reproduced signal in the PCM audio signal region period. It will not change. And AG
The reproduction signal input to the AGC circuit 32 is output from the C circuit 32 at the same level value.

From the above, the reproduction signal output from the AGC circuit 32 becomes a signal that is the same as the input reproduction signal in the PCM audio signal area, as shown in FIG. In the video signal area, the level value of the reproduced FM video signal is detected, and the control voltage is generated from the detection result to control the gain.
The level value of the reproduced FM video signal becomes a signal adjusted to a constant level value. Then, the AGC circuit 3 sets the level value of the reproduced FM video signal to a constant level signal without the influence of the output level of the reproduced signal in the PCM audio signal area.
2 will be performed.

The output of the AGC circuit 32 is then input to the FM demodulator 16 and FM demodulated. And Di
The emphasis circuit 18 attenuates the high frequency component emphasized by the pre-emphasis circuit 1 in the recording circuit, and inputs it to the reproduction signal processing circuit 19. The output of the AGC circuit 32 is also input to the dropout detection circuit 17, which detects a dropout from the reproduced signal and outputs a dropout detection signal indicating the dropout. The reproduction signal processing circuit 19 separates the sync signal from the reproduction video signal,
Based on this synchronization signal, a process for correcting the reproduced video signal on the time axis and a dropout compensation process using the dropout detection signal from the dropout detection circuit 17 are performed to output a good reproduced video signal.

In the first embodiment, the PCM area signal generator 31 outputs Low and PCM in the video signal area.
Although the case where a high-level pulse is generated in the audio signal region has been described, an inverted pulse of the pulse in the first embodiment may be generated, and based on the PCM region signal output from the PCM region signal generator 31, In the AGC circuit 32, the input reproduction signal is output as it is in the PCM audio signal area, and in the other video signal area, the level value of the reproduction FM video signal is detected and a control voltage is generated to automatically adjust the gain. If the control is performed so that the level value of the reproduced FM video signal is always a constant level value, the same effect as that of the above-described embodiment is obtained.

In the first embodiment, the AGC circuit 32
In the PCM audio signal area, the input signal is output as it is, that is, in the PCM audio signal area, a constant control voltage is set so that the gain of the variable gain amplifier 37 is fixed to 0 dB, and the signal is output from the detector 33. Although the case has been described, the gain fixed by the variable gain amplifier 37 in the PCM audio signal region is not limited to this, and even if the control voltage value V _r is set so that the gain becomes higher than that, it becomes lower than that. Such a control voltage value may be set, and the same effect as that of the above embodiment can be obtained.

In the first embodiment, the configuration of the AGC circuit 32 is such that the PCM area signal is the detector 3 in the AGC circuit 32.
3, the predetermined control voltage V _r is output in the PCM audio signal area, the input signal is output as it is in the variable gain amplifier 37, and the level value of the reproduced FM video signal is detected in the video signal area to detect the control voltage. To automatically adjust the gain,
The case has been described where the level value of the reproduced FM video signal is controlled to always be a constant level value.
The configuration of the AGC circuit controlled by the area signal is not limited to this. The configuration of the AGC circuit is based on the PCM area signal, and in the video signal area, the gain is automatically adjusted by detecting the level value of the reproduced FM video signal. The level value of the reproduced FM video signal is always output as a constant signal,
In the audio signal area, for example, if the configuration is such that the operation of the AGC circuit is stopped and the reproduced signal is output as it is, or the amplifier is controlled to switch to a fixed gain,
The same effect as that of the above embodiment is obtained.

Further, in the above-mentioned first embodiment, when the reproduction is performed as shown in FIG.
The case where the PCM audio signal mixed with the reproduced FM video signal shown in (c) is directly processed as a reproduction signal has been described. For example, at the output of the head switching circuit 13 or the reproduction equalizer 14, the FM video signal and the PCM in the reproduction signal are described. Even when the audio signal is configured to be separated as shown in FIG. 4C, the PCM is used as in the above embodiment.
With the configuration in which the AGC circuit 32 is controlled based on the PCM area signal output from the area signal generator 31, the same effect as that of the above-described embodiment is obtained.

In the first embodiment, the end timing of the PCM audio signal area in the reproduced signal is detected by the PCM area signal generator 31, and the start time of the next PCM audio signal area is predicted from the detection result. P depending on configuration
The case where a CM area signal is generated has been described.
The method of generating the M region signal is not limited to this, and may be generated from the timing of the head switching signal, for example.

In the first embodiment, the PCM audio signal is switched by the switch 4 during the vertical blanking period of the FM video signal.
Although the case of switching and recording in 5 has been described, the present invention is not limited to this, and for example, the PCM audio signal may be divided and switched and inserted in the horizontal blanking period. Further, in a VTR for recording / reproducing by dividing a video signal of one field into a plurality of segments as shown in FIG. 5 (FIG. 5 shows a case of two segment division), each segment blanking period and vertical blanking are performed. Even when the PCM audio signal of one field is divided and inserted in the period and the recording / reproduction is performed, the reproduction F in the reproduction signal is reproduced at the time of reproduction.
Identifying a region of the PCM audio signal mixed with the M video signal and generating a control signal indicating the PCM audio signal region,
As long as the operation of the AGC circuit 32 is controlled on the basis of the control signal, a recording format for recording a PCM audio signal during the segment blanking period may be used, and the same effect as that of the first embodiment can be obtained.

In the first embodiment, the magnetic tape is 18
Although the case of recording in one field and one track by winding 0 ° is shown, the winding angle and the recording format are not limited to this. It may be recorded.

In the first embodiment, the case where the FM-modulated video signal is recorded on the magnetic tape by the rotary head and is applied to the magnetic recording / reproducing apparatus (VTR) is described. Any device can be used as long as it is a device for time-division-multiplexing a signal with a digital audio signal and recording / reproducing, for example, a video signal recording / reproducing device for FM-modulating a video signal and recording / reproducing it on a disk-shaped recording medium, or a laser disk (LD) Also in other video signal recording / reproducing apparatus such as a magneto-optical disk, the same effect as that of the above-described embodiment can be obtained.

Example 2. FIG. 6 is a block diagram of a VTR according to the second embodiment of the present invention. In the figure, the recording systems 1-9 and the reproduction systems 12-19 are exactly the same as those of the above-mentioned conventional apparatus, so a detailed description will be given. Omit it.

Reference numeral 30 denotes a PCM which detects the PCM voice signal of one field period inserted in the vertical blanking period of the reproduced signal and performs error correction, deshuffling processing, error correction processing and the like to restore and output the original voice signal. A decoder, 31 identifies a PCM audio signal area in the reproduced signal in the PCM decoder 30, and generates a PCM area signal indicating the PCM audio signal area, and 40 indicates from the PCM area signal generator 31. This is a clipping circuit that clips the signal output in the PCM audio signal region in the reproduction signal output from the reproduction equalizer 14 to a predetermined level value based on the output PCM region signal.

Next, the operation will be described. During recording, the input video signal is input to the pre-emphasis circuit 1, the pre-emphasis circuit 1 emphasizes the high frequency component of the video signal and outputs it to the FM modulator 2, and the FM modulator 2 outputs the video. FM modulate the signal. On the other hand, the audio signal is input to the PCM encoder 3 and subjected to shuffling processing, addition of error correction code, etc., and then the digital audio signal of one field period is output to the vertical block of the FM video signal output from the FM modulator 2. It is subjected to time-axis compression processing for insertion in the ranking period, digitally modulated, and output.

Thereafter, the PCM audio signal output from the PCM encoder 3 in the one field period is FM.
The recording amplifier 7 is inserted in the vertical blanking period of the modulated video signal at a timing as shown in FIG.
Is output to. The switches 4 and 5 switch between the FM video signal and the PCM audio signal, and the adder 6 adds them.
A recording signal is generated. Then, the recording amplifier 7 amplifies the FM video signal and the PCM audio signal, which are the recording signals, and records them on the magnetic tape 9 by the rotary heads 8a and 8b. At this time, the magnetic tape 9 is strongly wound around the rotary drum 10 by 180 ° as shown in FIG.
Even if a recording current flows through a and 8b, the magnetic tape 9 is recorded only during the period when the rotary head is in contact with the magnetic tape 9. Therefore, the recording pattern on the magnetic tape 9 is divided into two areas a and b as shown in FIG. 12, and the recording signal of one field is recorded on one track. In the figure, a is a rotary head 8a.
Shows a track recorded by, and b is the rotary head 8b.
Shows a track recorded by. Also, PCM
Since the audio signal is time-division multiplexed and recorded during the vertical blanking period of the FM video signal, the portion where the PCM audio signal is recorded is the shaded portion. The recording operation up to this point is the same as in the conventional example.

At the time of reproduction, the rotary heads 8a and 8b respectively reproduce from the magnetic tape 9 a PCM audio signal mixed with the reproduced FM video signal at the time of recording as a reproduction signal, and the head amplifiers 12a and 12b amplify the reproduced PCM audio signal. The reproduced signals output from the head amplifiers 12a and 12b are reproduced by the head switching circuit 13 as shown in FIGS.
As shown in (c), the reproduction signal from the rotary head that is in contact with the magnetic tape 9 is selected and switched based on the head switching signal, and one reproduction signal (FIG. 7C) is obtained. The reproduction signal from the head switching circuit 13 is sent to the reproduction equalizer 14 and the PCM decoder 30. In the PCM decoder 30, the PCM of one field period inserted in the vertical blanking period of the reproduction signal
The voice signal is detected, and error correction, deshuffling processing, error correction processing and the like are performed to restore the original voice signal and output it. On the other hand, the reproduction equalizer 14 compensates the frequency characteristic of the reproduction FM video signal of the input reproduction signal, and its output is P indicating the area of the PCM audio signal in the reproduction signal.
It is input to the clipping circuit 40 controlled by the CM area signal.

By the way, at the time of recording, the PCM audio signal is time-divisionally multiplexed and recorded in the vertical blanking period of the FM-modulated video signal, and at the time of reproduction, the reproduced FM video signal and the mixed PCM audio signal are unchanged. It is reproduced as a reproduction signal and passed through the reproduction equalizer 14. On the other hand, the PCM audio signal has a pulse waveform and has a wideband signal component as shown in FIG. The frequency characteristics of the reproduction output in magnetic recording and reproduction are generally as shown in FIG. 16, and the output level of the reproduction signal decreases in the high range due to recording and reproduction loss, and the reproduction output in the low range is high. It will be large in comparison. Therefore, FIG.
As shown in FIG. 7, the output level of the reproduction signal of the PCM audio signal having a frequency component lower than the FM video signal band is output at a level value higher than the output level of the reproduction signal of the FM video signal area. Will be done.

AGC circuit 1 in the latter stage of the clipping circuit 40
As shown in FIG. 10, a detector 5 detects the level value of the reproduction signal in all the periods in the detector 21, generates and outputs a control voltage, and adjusts the gain of the variable gain amplifier 25 by the control voltage. Has been done. Therefore, when a reproduced signal whose output level is greatly different between the video signal area output from the reproduction equalizer 14 and the PCM audio signal area is directly input to the AGC circuit 15, even in the PCM audio signal area where the output level is high, The circuit 15 will operate, and the response characteristics of the circuit (see FIG. 17)
The operation of the AGC circuit 15 will not be performed normally.

Therefore, the reproduction signal is input to the clipping circuit 40 before being input to the AGC circuit 15, and the output level of the reproduction signal in the PCM audio signal area is set to a level value that does not affect the operation of the AGC circuit 15 in the subsequent stage. Then, for example, the level value is clipped to a level value that is almost the same level as the reproduction signal level in the video signal area. The clip circuit 40 has P
The PCM area signal generated by the PCM area signal generator 31 in the CM decoder 30 is sent. Note that the PCM area signal generator 31 has a configuration in which the end timing of the PCM audio signal area of the reproduction signal is detected in the PCM decoder 30 and the start time of the next PCM audio signal area is predicted from the detection result. A PCM area signal indicating the PCM audio signal area is generated.

In the PCM domain signal generator 31, for example, in the PCM voice signal domain as shown in FIG.
h, a low pulse is generated in the video signal area and sent to the clipping circuit 40. In the clip circuit 40, during the video signal area period in which the pulse is Low, the input reproduction signal is output as it is to the AGC circuit 15,
In the PCM audio signal region in which the pulse is High, the reproduction signal in the PCM audio signal region having a high reproduction signal output level is clipped to a predetermined level value because it has a low frequency component.

At this time, the level value of the clip in the clip circuit 40 is PC level as shown in FIG.
The output level of the reproduction signal in the M audio signal area is the AG of the latter stage.
A level that does not affect the operation of the C circuit 15 is set, for example, a level value V _pp that is substantially the same level as the reproduction signal level in the video signal area.

Therefore, the reproduction signal output from the clipping circuit 40 is as shown in FIG. 7 (e), and then input to the AGC circuit 15. The AGC circuit 1
5 is configured as shown in FIG. 10 and includes a rotary head 8a,
Even if the reproduction signal output level value from 8b varies depending on the characteristics of the head and tape, the AGC circuit 15 automatically adjusts the gain so that the output level is always a constant level value. The detector 21 in the AGC circuit 15, rectifies the input reproduced signal V _OUT, takes out the DC component V _D by integrating its output, which generates a control voltage output from the DC component V _D. This control voltage is the variable gain amplifier 25.
In the variable gain amplifier 25, the gain of the amplifier is automatically adjusted by the control voltage from the detector 21 so that the output level of the AGC circuit 15 is always an appropriate constant level value. Clip circuit 4 above
The reproduction signal output from 0 (FIG. 7 (e)) is such that the level value of the reproduction signal in the PCM audio signal area is almost the same as the level value of the reproduction FM signal in the video signal area, and the operation of the AGC circuit 15 is performed. The reproduction signal output from the AGC circuit 15 is adjusted so that the level value of the reproduction signal is constant during all periods, as shown in FIG. 7 (f). Signal will be output.

The reproduced signal whose output level has been adjusted to a constant level value by the AGC circuit 15 is then sent to the FM demodulator 16 for FM demodulation. The FM demodulator 1
The output from 6 is input to the de-emphasis circuit 17, and the de-emphasis circuit 17 attenuates the high frequency component emphasized by the pre-emphasis circuit 1 in the recording circuit and sends it to the reproduction signal processing circuit 19. .. In addition, the above AGC
The output of the circuit 15 is also sent to the dropout detection circuit 17, which detects the dropout from the reproduction signal and outputs a dropout detection signal indicating the dropout. Then, the reproduction signal processing circuit 19 separates the synchronization signal from the reproduction video signal and performs time axis correction on the reproduction video signal based on the synchronization signal, and the dropout detection signal output from the dropout detection circuit 17. By performing a dropout compensation process or the like using, a good reproduced video signal is obtained.

In the second embodiment, the PCM area signal generator 31 outputs Low and PCM in the video signal area.
Although the case where a high-level pulse is generated in the audio signal region has been described, an inverted pulse of the pulse in the above embodiment may be generated, and a clip is generated based on the PCM region signal output from the PCM region signal generator 31. In the circuit 40, the input reproduction signal is output as it is in the video signal area, and the reproduction signal level is set to A in the PCM audio signal area.
If the configuration is such that a predetermined level value that does not affect the operation of the GC circuit 15 is clipped and output, and then the output of the clipping circuit 40 is input to the AGC circuit 15, the same effect as that of the above-described embodiment is obtained. ..

In the second embodiment, the clip circuit 4
As shown in FIG. 7E, the clip level value in the PCM audio signal area at 0 is a video signal whose output level in the PCM audio signal area does not affect the operation of the AGC circuit 15 in the subsequent stage. Although the case has been described where the level value V _pp that is almost the same level as the reproduced signal level in the area is set, the level value to be clipped is not limited to the level value V _pp as shown in FIG. The output level of the reproduced signal at the AGC circuit 1 at the latter stage
If the level value does not affect the operation of No. 5, the same effect as that of the above embodiment is obtained.

In the second embodiment, the end timing of the PCM audio signal area in the reproduced signal is detected by the PCM area signal generator 31, and the start time of the next PCM audio signal area is predicted from the detection result. P depending on configuration
The case where a CM area signal is generated has been described.
The method of generating the M region signal is not limited to this, and may be generated from the timing of the head switching signal, for example.

In the second embodiment, the PCM audio signal is switched by the switch 4 during the vertical blanking period of the FM video signal.
Although the case of switching and recording in 5 has been described, the present invention is not limited to this, and for example, the PCM audio signal may be divided and switched and inserted in the horizontal blanking period. Further, in a VTR for recording / reproducing by dividing a video signal of one field into a plurality of segments as shown in FIG. 5 (FIG. 5 shows a case of two segment division), each segment blanking period and vertical blanking are performed. Even when the PCM audio signal of one field is divided and inserted in the period and the recording / reproduction is performed, the reproduction F in the reproduction signal is reproduced at the time of reproduction.
Identifying a region of the PCM audio signal mixed with the M video signal and generating a control signal indicating the PCM audio signal region,
As long as the operation of the clip circuit is controlled on the basis of the control signal, a recording format for recording the PCM audio signal during the segment blanking period may be used, and the same effect as in the second embodiment can be obtained.

In the second embodiment, the magnetic tape is 18
Although the case of recording in one field and one track by winding 0 ° is shown, the winding angle and the recording format are not limited to this. It may be recorded.

In the second embodiment, the clipping circuit 4
Although 0 has been described as being inserted between the reproduction equalizer 14 and the AGC circuit 15, it may be inserted in the preceding stage of the reproduction equalizer 14, and if it is located in the preceding stage of the AGC circuit, it is possible to use the above-mentioned embodiment. Has the same effect.

In the second embodiment, the case where the FM-modulated video signal is applied to the magnetic recording / reproducing apparatus (VTR) which records and reproduces on the magnetic tape by the rotary head has been described. Any device can be used as long as it is a device for time-division-multiplexing a signal with a digital audio signal and recording / reproducing, for example, a video signal recording / reproducing device for FM-modulating a video signal and recording / reproducing it on a disk-shaped recording medium, or a laser disk (LD) Also in other video signal recording / reproducing apparatus such as a magneto-optical disk, the same effect as that of the above-described embodiment can be obtained.

[0063]

As described above, according to the present invention, the PCM
The audio signal is time-division multiplexed in the blanking period of the FM video signal, recorded and reproduced, and reproduced in the video signal area excluding the PCM audio signal area in the reproduced signal based on the PCM area signal indicating the PCM audio signal area during reproduction. An AGC circuit that automatically adjusts the gain so that the output level of the signal always becomes a constant level value is provided so that the level value of the reproduced FM video signal of the reproduced signal at the output of the AGC circuit becomes always a constant level. Therefore, the operation of the AGC circuit in the video signal area can be normally performed, and an excellent reproduced video signal can be obtained.

As described above, according to the present invention, P
The CM audio signal is time-division multiplexed in the blanking period of the FM video signal and recorded / reproduced. At the time of reproduction, in the clip circuit provided in the preceding stage of the AGC circuit, based on the PCM area signal indicating the PCM audio signal area, Since the output level of the reproduction signal in the PCM audio signal area is clipped to a predetermined level so that the output level value of the reproduction signal in the previous period in the output of the AGC circuit is always a constant level, There is an effect that the operation of the AGC circuit can be normally performed and a good reproduced video signal can be obtained.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration example of an AGC circuit in FIG.

FIG. 3 is a waveform diagram for explaining the operation of the PCM region signal generator and AGC circuit according to the first embodiment of the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the AGC circuit when the FM video signal of the reproduction signal and the PCM audio signal are separated and processed in the first embodiment of the present invention.

FIG. 5 is a diagram showing an example of a case where a PCM audio signal is time-division multiplexed in each segment blanking period of an FM video signal in a VTR of 2-segment recording.

FIG. 6 is a block diagram showing a magnetic recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 7 is a waveform diagram for explaining operations of the PCM region signal generator, the clipping circuit, and the AGC circuit in FIG.

FIG. 8 is a block diagram showing an example of a conventional magnetic recording / reproducing apparatus.

FIG. 9 is a view of the rotary drum as viewed from above.

FIG. 10 is a block diagram showing a configuration example of an AGC circuit in a conventional magnetic recording / reproducing apparatus.

FIG. 11 is a diagram showing an example of a case where a PCM audio signal is time-division multiplexed during a blanking period of an FM video signal.

FIG. 12 is a diagram showing an example of a recording pattern on a magnetic tape.

FIG. 13 is a diagram for explaining the operation of the head switching circuit.

FIG. 14 is a diagram for explaining the operation of the reproduction equalizer.

FIG. 15 is a characteristic diagram showing an FM video signal band and a PCM audio signal band during reproduction.

FIG. 16 is a characteristic diagram showing an example of frequency characteristics of reproduction output of a reproduction signal in magnetic recording.

FIG. 17 is a characteristic diagram for explaining response characteristics of the AGC circuit.

FIG. 18 is a waveform diagram showing waveforms when an FM video signal and a PCM audio signal of a reproduction signal are separated and processed.

[Explanation of symbols]

 15, 32 AGC circuit 21, 33 Detector 22, 34 Rectifier circuit 23, 35 Integrator 24, 36 Control voltage generator 25, 37 Variable gain amplifier 31 PCM region signal generator 40 Clip circuit

[Procedure amendment]

[Submission date] May 21, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0055

[Correction method] Change

[Correction content]

The reproduced signal whose output level has been adjusted to a constant level value by the AGC circuit 15 is then sent to the FM demodulator 16 for FM demodulation. The FM demodulator 1
The output from 6 is inputted to the de-emphasis circuit 18, the de-emphasis circuit 18 attenuates the high frequency components are emphasized by the pre-emphasis circuit 1 in the recording circuit, and sends to the reproduction signal processing circuit 19 .. In addition, the above AGC
The output of the circuit 15 is also sent to the dropout detection circuit 17, which detects the dropout from the reproduction signal and outputs a dropout detection signal indicating the dropout. Then, the reproduction signal processing circuit 19 separates the synchronization signal from the reproduction video signal and performs time axis correction on the reproduction video signal based on the synchronization signal, and the dropout detection signal output from the dropout detection circuit 17. By performing a dropout compensation process or the like using, a good reproduced video signal is obtained.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

FIG. 2 is a block diagram illustrating a configuration example of an AGC circuit according to the first exemplary embodiment .

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

FIG. 7 is a waveform diagram for explaining operations of a PCM region signal generator, a clipping circuit, and an AGC circuit in the twelfth embodiment .

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

[Procedure Amendment 8]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 17

[Correction method] Change

[Correction content]

FIG. 17

Claims (2)

[Claims] 1. A video signal recording / reproducing apparatus for FM-modulating a video signal and time-division multiplexing and recording / reproducing a digital audio signal in the blanking period of the FM-modulated recording video signal. Other than the digital audio signal area in the reproduced signal based on the output signal from the area signal generating means for determining the area of the digital audio signal in The video signal recording / reproducing apparatus comprising: an automatic gain adjusting means for automatically adjusting the gain so that the level value of the reproduced signal becomes constant and is output during the period. 2. A video signal recording / reproducing apparatus for FM-modulating a video signal and time-division multiplexing and recording / reproducing a digital audio signal in the blanking period of the FM-modulated recording video signal. The area signal generating means for discriminating the area of the digital audio signal and generating a control signal indicating the area of the digital audio signal, and the gain are automatically adjusted so that the output level value of the reproduction signal becomes constant and is output. The output level of the reproduction signal in the area of the digital audio signal in the reproduction signal is clipped to a predetermined level based on the output signal from the area signal generating means in the automatic gain adjusting means and the preceding stage of the automatic gain adjusting means. A video signal recording / reproducing apparatus comprising: a clipping unit.