JPS6315795B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color video signal recording method and a recording/reproducing method, and in particular, when recording a SECAM method color video signal on a recording medium and reproducing it, the present invention relates to a color video signal recording method and a recording/reproducing method. By blocking the transmission output of the carrier color signal transmission system with a pulse generated using a delay by a filter, the S/N of the color video signal to be recorded and reproduced can be improved with a circuit configuration that does not require adjustment. The purpose of the present invention is to provide a method capable of stabilizing the synchronization of a monitor television receiver.

FIG. 1 shows a block system diagram of an example of a conventional color video signal recording and reproducing system. First, to explain the operation during recording, the input terminal 1
The SECAM color video signal is branched into two, one being supplied to a low pass filter 2 and the other being supplied to a band filter 3. The low-pass filter 2 separates the luminance signal from the SECAM color video signal, and passes this luminance signal through the pre-emphasis circuit 4.
FM modulator 5. The FM modulator 5 frequency-modulates a carrier wave of a predetermined frequency with the luminance signal, and supplies the frequency-modulated luminance signal to the recording amplifier 7 after removing unnecessary low-frequency components using the high-pass filter 6 .

On the other hand, the band filter 3 separates a carrier color signal obtained by frequency-modulating two carrier waves of a predetermined frequency alternately with a line-sequential color difference signal from the SECAM color video signal, and converts this carrier color signal into an equalizer circuit 8 with predetermined characteristics. and a limiter 9, respectively, to the 1/4 countdown circuit 10. The 1/4 countdown circuit 10 steps down the frequency of the carrier color signal to 1/4 so that the bandwidth is 1/4 of the input carrier color signal, and
A low-pass filter 11 removes unnecessary high-frequency components, and an equalizer circuit 12 corrects the level attenuation of the upper and lower sidebands due to the frequency downshift. The signals are supplied to the recording amplifier 7 through the respective channels.

Here, the carrier color signal of the SECAM system is not transmitted in the front porch T ₂ within the horizontal blanking period T ₁ shown in FIG. 2, and in the period T ₃ consisting of the horizontal sync pulse width and a part of the back porch, 3
Among the vertical blanking periods shown in FIGS. A to D, horizontal scanning line numbers 624 to 6, 16 to 22,
It is not transmitted during each period of 311-319 and 329-335. For this reason, if a highly sensitive limiter is used as the limiter 9 or a flip-flop is used as the 1/4 countdown circuit 10, noise will occur during the above-mentioned period when the carrier color signal is not transmitted.

In other words, if a highly sensitive limiter 9 is used, the output signal of the bandpass filter 3 will contain high-frequency components of the luminance signal in addition to the carrier color signal, and this will be at the same level as the carrier color signal. Even the noise is emphasized as noise. Furthermore, playback noise becomes a problem during playback and dubbing recording. Also,
When a flip-flop is used as the 1/4 countdown circuit 10, the blanking period becomes a pulse with a long period, and if the level of the high frequency component of the luminance signal extracted from the band filter 3 is at a level sufficient to operate the flip-flop,
An unnecessary noise component having the same level as the carrier color signal is generated in the output of the flip-flop.

When these noise components pass through the equalizer circuit 12 or the equalizer circuit 31 shown in FIG. 1 of the reproduction system described later, the carrier color signal is attenuated and the noise components are emphasized. Therefore, during recording, the recording amplifier 7 multiplexes the frequency-modulated luminance signal from the band filter 6 and the low-frequency conversion carrier color signal from the equalizer circuit 12, which occupies a lower area than the band, and sends this multiplexed signal to the rotating head. When recording on a magnetic tape (not shown) by 18,
The frequency modulated luminance signal in the portion of the multiplexed signal where the noise component is superimposed is attenuated.

Therefore, conventionally, during recording, a luminance signal as shown in FIG. 4A from the low-pass filter 2 is supplied to the synchronization signal separation circuit 14 through the changeover switch 13 shown in FIG. 1 connected to the contact R side. Separate and extract the horizontal synchronization signal shown in Figure 4B to create a monostable multivibrator (hereinafter referred to as "monomulti").
15. The monomulti 15 is triggered by the trailing edge (or even the leading edge) of the horizontal sync signal and produces a pulse of width α ₁ at the beginning of the front porch of the next incoming horizontal sync signal. FIG. 4C shows the charge/discharge waveform of the capacitor of the monomulti 15, and FIG. 4D shows the output pulse of the monomulti 15.

The output pulse of monomulti 15 is the output pulse of monomulti 16.
is applied to trigger it at its trailing edge. As a result, the charging/discharging waveform of the capacitor of the monomulti 16 becomes as shown in FIG. 4E, and the monomulti 1
6 outputs a pulse as shown in FIG. 4F having a width α ₂ approximately equal to the period of the sum of T ₂ and T ₃ shown in FIG.
The output pulse of this monomulti 16 is applied as a noise gate pulse to the switch circuit 17 in FIG. The switch circuit 17 AC-grounds the output signal of the 1/4 countdown circuit 10 during the width α ₂ of the output pulse of the monomulti 16 shown in FIG. 4F, and transmits this output signal to the low-pass filter 11. cut off. Thereby, noise components within the horizontal blanking period can be removed.

Next, to explain the operation during reproduction, the multiplexed signal reproduced by the rotary head 19 is supplied to a high-pass filter 21 and a low-pass filter 22 via a preamplifier 20, respectively. A high-pass filter 21 separates a frequency modulated luminance signal from the reproduced multiplexed signal and supplies it to an FM demodulator 24 via a limiter 23 for removing amplitude fluctuations. FM demodulator 2
4 performs FM demodulation, a reproduced luminance signal is extracted, and is supplied to an amplifier 26 through a low-pass filter 25.

On the other hand, the low-pass filter 22 separates a low-pass converted carrier color signal from the reproduced multiplexed signal, and supplies this to a quadrupling circuit 29 through an equalizer circuit 27 and a limiter 28, respectively. The quadrupling circuit 29 multiplies the frequency of the reproduced low-pass converted carrier color signal by four to obtain a reproduced carrier color signal having the same bandwidth and the same band as the original carrier color signal. This reproduced carrier color signal is passed through the band filter 3.
0 and the equalizer circuit 31, are supplied to the amplifier 26, where they are multiplexed with the reproduced luminance signal and outputted to the output terminal 33 as a reproduced SECAM system color video signal.

Here, the noise component generated during the non-transmission period of the carrier color signal passes through the equalizer circuit 31 and is input to the amplifier 2.
When multiplexed with the reproduced luminance signal in step 6, the multiplexed position becomes the synchronization signal part of the reproduced luminance signal, which induces malfunction in the synchronization separation circuit of the monitor television receiver, causing screen shake, synchronization flow, etc. This will cause an unstable synchronization state.

Therefore, in FIG. 1, the FM demodulator 24 is connected through the changeover switch 13 connected to the contact P side during playback.
The reproduced luminance signals are supplied to a synchronization signal separation circuit 14 to separate horizontal synchronization signals. This horizontal synchronizing signal passes through the monomultis 15 and 16, respectively, as during recording, and is converted into a pulse as shown in FIG. 4F.
Transmission of the reproduced carrier color signal or noise component supplied to the switch circuit 32 and supplied from the quadrupling circuit 29 to the high-pass filter 30 is interrupted for the period α ₂ .
This makes it possible to prevent horizontal synchronization from becoming unstable due to the noise component.

However, in the above conventional method, the carrier color signal non-transmission period within the horizontal blanking period is T ₂ ,
As shown in T ₃ , it is only about 7μsec, so
The trailing edge of the pulse width α ₁ of the output pulse of the monomulti 15 must be within the period T ₂ (actually within 1 μsec), and the trailing edge of the pulse width α ₂ of the output pulse of the monomulti 16 must also be horizontally synchronized. Within the carrier color signal non-transmission period of the back porch after the pulse (actually
However, as mentioned above, the delay time caused by the monomulti 15, 16 is large, so even if the deviation is about 1%, it will not be within the above period.
The disadvantage is that the adjustment of the time constants (adjustment of pulse widths α ₁ and α ₂ ) of No. 6 is required to be extremely precise and strict.

The present invention eliminates the above drawbacks, and the fifth
Each embodiment will be described with reference to the drawings below.

FIG. 5 shows a block system diagram of an embodiment of the system of the present invention. In the figure, the same components as those in FIG. 1 are given the same numbers, and their explanations will be omitted. First, to explain the operation during recording, the SECAM color video signal input to input terminal 1 in Fig. 5 is
The signal is supplied to a low-pass filter 34, and also to a low-pass filter 36 through a changeover switch 35 connected to the contact R side during recording. low pass filter 3
4 and 36 each separate the luminance signal from the SECAM color video signal, but the low-pass filter 34 has a steep slope characteristic in order to separate the luminance signal with high accuracy, and its envelope delay time is designed to be a small value of about 1.5 μsec to 1.2 μsec in the low range (the envelope delay time of the low pass filter 25, which will be described later, is also designed to have a similar value). On the other hand, the low-pass filter 36 takes into consideration the starting position of the noise gate in the horizontal blanking period, which will be described later, and its envelope delay time is
It is designed to have an extremely small value of about 0.2 μsec to 0.3 μsec. Therefore, the luminance signal from the low-pass filter 34 will be delayed by about 1 μsec relative to the luminance signal from the low-pass filter 36.

The luminance signal extracted from the low-pass filter 36 is supplied to a synchronization signal separation circuit 37, where the composite synchronization signal is separated. Therefore, the synchronization signal separation circuit 37 inputs the luminance signal from the low-pass filter 36 near the vertical blanking period shown in FIG. Separate and output. These composite synchronization signals are fed to monomulti 38 and trigger it on its leading edge (designated B1 in FIG. 6B).
As a result, the charge/discharge waveform of the capacitor of the monomulti 38 becomes as shown in _FIG . fall behind.

Here, the constant time α ₃ is selected to be a value between 0.5H and 1H (H is the horizontal scanning period of 64 μsec), so the charging and discharging waveform of the monomulti 38 capacitor is as shown in Figure 6C. , the equalization pulse and the vertical synchronization pulse do not exceed the threshold level during the incoming period, so the output of the monomulti 38 remains at a high level, and the output pulse eventually becomes as shown in FIG.

Note that if the monomulti 38 is triggered by the trailing edge of the composite synchronization signal (shown as B2 in FIG. 6B),
Since the output pulse falls immediately after the starting position of the vertical synchronization pulse shown as C1 in FIG. 6A, it is not possible to trigger at the trailing edge.

The pulse shown in FIG. 6D taken out from the monomulti 38 in this way is supplied to the monomulti 39 whose time constant is selected to be larger than the monomulti 38, and the pulse shown in FIG. Trigger this. As a result, the charging/discharging waveform of the capacitor of the monomulti 39 becomes as shown in FIG. Reset on trailing edge of output pulse. Therefore, the output pulse of the monomulti 39 is the sixth
As shown in Figure F, the pulses are at a high level for more than 1H before and after the vertical synchronization pulse. Note that the period α ₄ shown in FIG. 6F is selected to be larger than the pulse width α ₃ .

The pulse shown in FIG. 6F taken out from the monomulti 39 passes through the mixing circuit 40 to the switch circuit
1, and during the high level period, the output terminal of the equalizer circuit 12 is AC grounded. As a result, noise components in the vertical synchronizing pulse and the non-transmission period of 1H period or more before and after the vertical synchronizing pulse are removed from the low frequency conversion carrier color signal supplied from the equalizer circuit 12 to the recording amplifier 7.

In this way, it is possible to remove noise components that are transmitted in the carrier color signal non-transmission period near the vertical blanking period in the low-pass conversion carrier color signal transmission system. Furthermore, the time constant of the monomulti 38 is determined so that the pulse width α ₃ is between 0.5H and 1H, but 0.5H is 32 μsec, and it is extremely difficult to insert the pulse width α ₃ between these values. It is easy, and the time constant can be roughly adjusted. Similarly, since the time constant of the monomulti 39 only needs to satisfy the condition that α ₄ is larger than the pulse width α ₃ , its adjustment may be rough. In other words, this means that even if the time constants of the monomultis 38 and 39 change, the output will only change by a few microseconds at most.
This means that no adjustment is required.

Next, the removal of noise components within the horizontal blanking period in the low frequency conversion carrier color signal transmission system during recording will be explained. As shown in FIG. 7B, the luminance signal taken out from the low-pass filter 34 is delayed by a fixed time τ ₁ from the luminance signal in the SECAM color video signal input to input terminal 1 (shown in FIG. 7A). This luminance signal is supplied to a synchronizing signal separation circuit 44 through a changeover switch 43 connected to the recording contact R side, where the horizontal synchronizing signal is separated. This horizontal synchronizing signal has a waveform as shown in _FIG .

On the other hand, as shown in FIG. 7C, the luminance signal taken out from the low-pass filter 36 has a delay of about 1 μsec smaller than the output luminance signal of the low-pass filter 34 (shown in FIG. 7B) as described above. I have received
A synchronization signal separation circuit 37 separates the composite synchronization signal. A horizontal synchronizing signal as shown in FIG. 7E extracted from the synchronizing signal separation circuit 37 is supplied to the mixing circuit 40. The mixing circuit 40 is shown in FIG. 7E.
The horizontal synchronization signal shown in Figure F and the delay circuit 4 shown in Figure F.
The horizontal synchronizing signals from 5 and 5 are mixed to output a pulse as shown in G in the same figure, and this is sent to the switch circuit 4.
1, and the output terminal of the equalizer circuit 12 is grounded AC during the high level period.

Here, the frequency modulated luminance signal supplied to the recording amplifier 7 is frequency modulated with the delayed luminance signal shown in FIG. 7B, and the timing must match with the low frequency conversion carrier color signal. The output terminal of the equalizer circuit 12 is approximately equal to the horizontal synchronizing pulse.
During the period from 1 μsec before to about 0.7 μsec after the horizontal synchronizing pulse, that is, during the non-transmission period of the low-frequency conversion carrier color signal within the horizontal blanking period, it is grounded AC-wise, so that the noise component can be removed. can.

The position and width of the noise gate pulse shown in FIG. 7G within this horizontal blanking period are determined by the respective delay times of the low-pass filters 34, 36 and the delay circuit 45, and these delay times are approximately 1.5 μsec or less. Since it is an extremely small value, its variation hardly poses a problem, so it is possible to completely eliminate adjustment.

Next, the operation during playback will be explained. During playback, the changeover switches 35 and 43 are connected to the contact P side, and the reproduced brightness signal from the FM demodulator 24 is supplied to the low-pass filter 36 through the changeover switch 35, and the low-pass filter 25 transmits the signal for about 1 μsec.
The reproduced luminance signal, which has been further delayed, is supplied to a synchronization signal separation circuit 44 through a changeover switch 43. As a result, noise components generated in the carrier color signal transmission system during the horizontal blanking period and near the vertical blanking period, when the carrier color signal is not originally transmitted, are removed by the switch circuit 42 by the same operation as during recording. .

Note that the pulse for removing noise components near the vertical blanking period during reproduction (equivalent to the pulse shown in Fig. 6F) is generated in synchronization with the reproduction composite synchronization signal, so it can be used as a simple magnetic recording/reproducing device. This has the advantage that even if the time axis fluctuation of the reproduced signal is large, the fluctuation is synchronized with the time axis fluctuation.

FIG. 8 shows a block system diagram of the main parts of another embodiment of the system of the present invention. In the figure, the same components as those in FIG. 5 are given the same numbers, and their explanations will be omitted. In this embodiment, a delay circuit 46 for delaying the output composite synchronization signal of the synchronization signal separation circuit 37 is provided in place of the circuit section shown in FIG. It is. As a result, pulses as shown in FIG. 7G can be obtained from the mixing circuit 40. This embodiment can simplify the circuit configuration compared to the embodiment shown in FIG.

Note that the method of the present invention utilizes the delay time of the low-pass filter when recording and reproducing by cutting off the output of the carrier color signal transmission system during the carrier color signal non-transmission period within the horizontal blanking period. This is for adjustment, and the noise gate in the vicinity of the vertical blanking period may or may not be performed.

As described above, the color video signal recording method according to the present invention uses a second filter having a delay time smaller than the delay time caused by the first filter for separating the luminance signal to be recorded from the SECAM method color video signal. The luminance signal is separated from the color video signal by a filter, the horizontal synchronization signal is separated and extracted from the luminance signal from the second filter, and the horizontal synchronization signal is extracted from the luminance signal from the second filter.
Alternatively, the horizontal synchronizing signal from the second filter is delayed by delay circuit means such that its trailing edge approximately corresponds to the end position of the carrier color signal non-transmission period within the horizontal blanking period, and the luminance passing through the second filter is The output of the low frequency conversion carrier color signal transmission system is cut off for a certain period of time within the horizontal blanking period and recorded using the pulse obtained by mixing the horizontal synchronization signal separated from the signal and the output of the main stage of the delay circuit. Therefore, the circuit can be made without adjustment, and the S/N of the recorded color video signal can be improved.

Further, according to the color video signal recording and reproducing method of the present invention, the same signal processing as that during recording is performed during reproduction, and the output of the reproduction carrier color signal transmission system is interrupted for a certain period of time within the horizontal blanking period. Because it is reproduced, it is possible to improve the S/N of the reproduced color video signal, stabilize the horizontal and vertical synchronization of monitor television receivers, and eliminate the need for circuit adjustments. It is something that you have.

[Brief explanation of the drawing]

Fig. 1 is a block system diagram showing an example of a conventional system, Fig. 2 is a diagram showing waveforms near the horizontal blanking period of a SECAM color video signal, and Figs. 4A to 4F are time charts for explaining the operation of FIG. 1, and FIG. 5 is a block system diagram showing an embodiment of the method of the present invention.
6A to 6F are time charts for explaining the noise gate operation near the vertical blanking period in FIG. 5, respectively, and FIGS. 7A to G are time charts for explaining the noise gate operation in the horizontal blanking period in FIG. 5, respectively. FIG. 8 is a block system diagram showing the main parts of another embodiment of the system of the present invention. 1...SECAM color video signal input terminal,
2, 34, 36...low-pass filter for luminance signal separation;
3...Band filter for carrier color signal separation, 5...FM modulator, 10...1/4 countdown circuit, 14,3
7, 44...Synchronization signal separation circuit, 15, 16, 3
8, 39... Monostable multivibrator (mono multi), 22... Low-pass filter for low-pass conversion carrier color signal separation, 24... FM demodulator, 25... Low-pass filter for reproduced luminance signal separation, 29... 4-multiplying circuit, 33... Playback SECAM method color video signal output terminal, 40...
Mixing circuit, 45, 46...delay circuit.

Claims (1)

[Claims] 1. A luminance signal and a carrier chrominance signal are separated from a SECAM color video signal, the luminance signal is frequency modulated, and the carrier chrominance signal is transmitted to a lower band than the frequency modulated luminance signal. In the method of sequentially forming and recording tracks on a recording medium by multiplexing the frequency-modulated luminance signal after conversion, the above-mentioned
separating the luminance signal from the SECAM color video signal with a second filter having a delay time smaller than the delay time of the first filter for separating the luminance signal to be recorded from the SECAM color video signal; The horizontal synchronizing signal separated from the luminance signal from the first or second filter is processed by delay circuit means so that the trailing edge thereof is at the end of the carrier color signal non-transmission period within the horizontal blanking period of the luminance signal that has passed through the first filter. The horizontal synchronizing signal separated from the luminance signal that has passed through the second filter and the output horizontal synchronizing signal of the delay circuit means are delayed so as to approximately correspond to the position of the second filter, and the output horizontal synchronizing signal is mixed. A color video signal recording method characterized in that the output of a color signal transmission system is cut off for a certain period of time within the horizontal blanking period and recorded. 2 A luminance signal and a carrier color signal are separated from a SECAM color video signal, the luminance signal is frequency modulated, and the carrier color signal is converted to a lower band than the frequency modulated luminance signal and then frequency modulated. tracks are sequentially formed and recorded on a recording medium, and during playback, the reproduced frequency-modulated luminance signal and low-frequency conversion carrier chrominance signal are restored to their original bands, and then both signals are In a method of multiplexing to obtain a reproduced color video signal, a second filter having a delay time smaller than a delay time of the first filter is used to separate the luminance signal to be recorded from the SECAM color video signal. A luminance signal is separated from the SECAM color video signal, and the horizontal synchronization signal separated from the luminance signal from the first or second filter is processed by a first delay circuit means, the trailing edge of which is the luminance signal that has passed through the first filter. a horizontal synchronizing signal delayed so as to substantially correspond to the end position of the carrier color signal non-transmission period within the horizontal blanking period of the signal and separated from the luminance signal passed through the second filter; and the first delay circuit means. The output of the low frequency conversion carrier chrominance signal transmission system is cut off for a certain period of time within the horizontal blanking period and recorded using the pulses obtained by mixing the output horizontal synchronizing signal of A reproduced luminance signal to be used as the final output is extracted from the output signal of the FM demodulator that performs frequency demodulation by a third filter, and
The reproduced luminance signal is extracted from the output signal of the FM demodulator by a fourth filter having a delay time smaller than the delay time by the filter, and the horizontal synchronization signal is separated from the reproduced luminance signal from the third or fourth filter. the signal is delayed by the second delay circuit means such that its trailing edge substantially corresponds to the end position of the carrier color signal non-transmission period within the horizontal blanking period of the reproduced luminance signal passed through the third filter; The output of the reproduction carrier chrominance signal transmission system is subjected to the horizontal blanking by a pulse obtained by mixing the horizontal synchronization signal separated from the luminance signal passed through the fourth filter and the output horizontal synchronization signal of the second delay circuit means. A color video signal recording and reproducing method characterized by shutting off and reproducing for a certain period of time. 3. Claim 2, characterized in that the first and second delay circuit means share the same circuit, and the second and fourth filters share the same circuit, respectively. Color video signal recording and playback method.