JPH0217996B2 - - Google Patents

Description

[Detailed Description of the Invention] When recording a color video signal such as an NTSC signal on a VTR, the characteristics of the signal distribution of this NTSC signal are used. In other words, as shown in FIG. The color signal C is distributed on the side.
Utilizing the fact that it is distributed on the high frequency side centered on the 3.58MHz subcarrier, the luminance signal Y is FM modulated as shown in Figure 2, and the color signal C is low frequency converted and superimposed on this luminance signal Y. A recording method (Y/C separation recording using a color heterodyne method) is widely adopted.

However, this Y/C separation recording method first
Another drawback is that both the luminance signal Y and the chrominance signal C cannot be recorded in a wide band.

In other words, the luminance signal Y is extracted through a low-pass filter, but considering sufficient separation from the color signal C, the band of the luminance signal Y that can be extracted is at most
Up to about 3.0MHz. Also, if you try to convert the chrominance signal C to low frequency while keeping it wideband, you will have to increase the low frequency conversion frequency, but this will also increase the FM carrier frequency for the luminance signal Y, which will result in an increase in triangular noise. Luminance signal Y
The S/N of the signal deteriorates. For these reasons, wideband expansion of the color signal C is also limited.

Second, in this recording method using Y/C separation,
As shown in Fig. 2, a part of the FM luminance signal Y-FM overlaps with a part of the low-frequency conversion color signal _C.
Interference between Y/C, that is, cross color occurs.

Third, image quality deterioration occurs due to changes in brightness level. That is, since the FM carrier frequency is used as the AC bias frequency of the low frequency conversion color signal C _C , when the brightness level changes and the FM carrier frequency changes, this AC bias frequency changes. However, in AC bias recording, as shown in Figure 3, the magnetization level and therefore the reproduction output level depend on the bias frequency, so when the luminance level changes, the signal level of the low-frequency converted color signal C _C changes, and the differential As the gain (DG) increases, the image quality deteriorates.

As described above, the conventional Y/C separation recording method has various drawbacks. Therefore, the present invention eliminates these drawbacks by adopting a special signal recording method, and also makes it possible to eliminate the drawbacks that occur when the signals are recorded at high density.

Next, the present invention will be explained with reference to FIG. 4 and subsequent figures. The example shown in FIG. 4 is a case where an NTSC composite color video signal is used as the information signal to be recorded, and numeral 10 indicates a VTR recording apparatus according to the present invention, and numeral 20 indicates a reproducing apparatus thereof.

The composite color video signal S _I (its frequency characteristics are shown in FIG. 5A) supplied to the terminal 1 is passed through the first low-pass filter 2 and the first bypass filter 3.
and the signal band is divided into two. As shown in FIG. 5B, the first low-pass filter 2 extracts a low-frequency signal _SL containing a signal indicating a luminance component from the composite color video signal _SI . This low frequency signal S _L
There is no need to specifically select the band of about 3MHz as in the past; it is arbitrary. In the example shown in Figure 5, 3MHz is selected as in the past.

On the other hand, as shown in FIG. 5C, the first high-pass filter 3 extracts a high-frequency signal S _H containing color signal components from the composite color video signal S _I. Therefore, this high frequency signal S _H includes both a color signal component (carrier color signal) and a high frequency luminance signal component. and,
The cutoff frequency of the band of this high frequency signal S _H is selected so that the high frequency components of the low frequency signal S _L partially overlap. Therefore, the bandwidth W _R of the high-frequency signal S _H divided by the first high-pass filter 3 is wider than that of the conventional one.

The composite color video signal S _I is further processed by a synchronization separation circuit 4.
The horizontal synchronizing pulse P _H is separated from the composite color video signal S I supplied to the burst gate circuit 6, which is supplied to the burst flag pulse generator 5 to form _the burst flag pulse F _B. The burst signal S _B is extracted. This burst signal S _B is down-converted to 1/2 frequency by a downshifter 7, and is also supplied to a low-pass filter 8, where its fundamental wave component is extracted. This fundamental wave component burst signal S _BL is combined with the low frequency signal S _L in the synthesizer 9 as a first reference signal for time axis correction. In this case, the horizontal synchronizing pulse P _H portion of the low-frequency signal S _L divided by the low-pass filter 2 is as shown in FIG. 6A, so the first reference signal S _BL is as shown in FIG. 6B. This means that it is inserted on the back porch side of the horizontal synchronizing pulse P _H in the same way as the normal burst signal S _B.

Note that lowering the frequency of the burst signal to 1/2 as the first reference signal S _BL is because the band of the low-frequency signal S _L is
This is because it is limited to 3.0MHz.

The low frequency signal S _L into which the first reference signal S _BL has been inserted is angularly modulated, for example, FM modulated, by the modulator 11, then amplified by a recording amplifier (not shown), and then sent to the rotating recording head H _RL . and recorded on tape 12.

On the other hand, the high frequency signal S _H including the color signal C is converted to a low frequency signal by the frequency converter 13 . In this example, a frequency that is 1/3 of the subcarrier frequency (approximately 1.2 MHz) is selected as the low frequency conversion frequency, and therefore, in this case, the bandwidth of the high frequency signal S _H can be expanded to approximately 1.0 MHz.

Frequency converted high frequency signal S _HC is low frequency signal S _L
Similarly, a second reference signal for time axis correction is inserted. In this case, the burst signal S _B is used as the high frequency signal S _H.
(FIG. 7A), the horizontal synchronizing pulse P _H is used as the second reference signal in this example. Therefore, the sync-separated horizontal sync pulse
After being delayed for a certain period of time by the delay element 14, P _H is supplied to the combiner 15 and combined with the high frequency signal P _HC . In this case, as shown in FIG. 7B, the second reference signal P _HH is inserted at the same position as the horizontal synchronization pulse of the composite color video signal S _I.

This high frequency signal S _HC with the second reference signal P _HH inserted
is angularly modulated, for example, FM modulated, by the modulator 16, amplified by a recording amplifier (not shown), and then recorded by the recording head _HRH onto a recording track different from the above-mentioned low frequency signal recording track. be done.

Signal recording is performed using a high-density recording method, and the azimuth angles of the recording heads H _RL and H _RH are different from each other.
Recorded without guard band (see Figure 8).

In this way, the composite color video signal to be recorded is appropriately band-divided, and one of the band-divided signals, that is, the low-frequency signal S _L , is used as the first reference signal.
S _BL is inserted and FM modulated and recorded on the first track, and the other signal, that is, the high frequency signal S _H is FM modulated by inserting the second reference signal P _HH after low frequency conversion.
The data is recorded on a track (second track) different from the first track.

Next, the playback device 20 will be explained.

FM low frequency signal S _L − recorded on the first track
FM is reproduced by a reproduction head _HPL , amplified by a reproduction amplifier (not shown), and then demodulated by an FM demodulator 21. Demodulated low frequency signal S _L
is fed to a second low-pass filter 22 to limit the band in a desired manner. The specific content to be restricted will be described later.

FM high frequency signal S _H − recorded on the second track
FM is similarly reproduced by the reproduction head _HPH , amplified by a reproduction amplifier (not shown), and then demodulated by the FM demodulator 24. After passing through the demodulated variable delay line for time axis adjustment, the frequency converter 25 converts the signal to a signal centered on the subcarrier frequency of 3.58 MHz, and then the second high-pass filter 26 converts the signal as expected. Bandwidth is limited.

That is, the second low-pass filter 22 has a frequency band characteristic narrower than that of the first low-pass filter 2, as shown by the broken line in FIG. 5B. In this example, the cutoff frequency f _c is
2.7MHz is selected. On the other hand, the band characteristic of the second high-pass filter 26 is also selected to be narrower than that of the first high-pass filter 3, and as shown by the broken line in FIG. It is chosen to be equal to the cutoff frequency f _c of filter 22. Therefore,
The above-described first high-pass filter 3 has its bandwidth W _R determined so that at least a signal near the cut-off frequency f _c is included.

If the frequency characteristics of the second low-pass filter 22 and the second high-pass filter 26 are selected as described above, the overall frequency characteristic including both becomes flat as shown by the solid line in FIG.

If the frequency characteristics of the first low-pass filter 2 and the first high-pass filter 3 are selected to have sufficiently wide band characteristics compared to the frequency characteristics of the second low-pass filter 22 and the second high-pass filter 26, respectively, Second low pass filter 22
The low frequency signal S _LO passed through the second high pass filter 26 and the high frequency signal S _HO passed through the second high pass filter 26 were obtained by directly supplying the composite color video signal S _I supplied to the terminal 1 to these filters 22 and 26. It has the same frequency characteristics as the signal.

FIG. 10 shows an example of the second high-pass filter 26, and in order to make its cut-off frequency match the cut-off frequency f _c of the second low-pass filter 22, a low-pass filter 30 having the same characteristics as this filter 22 is used. Then, as shown in the figure, an inverter 31 and a delay element 32 are provided,
If the frequency-reconverted high-frequency signal S _H is supplied to the low-pass filter 30 and the delay element 32 and synthesized by the synthesizer 33 as shown in the figure, the cut-off frequency is equal to the cut-off frequency f _c of the second low-pass filter 22. A second high pass filter 26 can be configured.

The low-frequency signal S _LO output from the second low-pass filter 22 and the high-frequency signal S _HO output from the second high-pass filter 26 are subjected to time axis correction in time axis adjustment circuits 40 and 50, respectively. , the two are combined in a combiner 35 and a composite color video signal S _O is reproduced.

Next, the necessity of the time axis adjustment circuits 40 and 50 and their circuit configuration will be explained. In other words, each of the FM-modulated low-frequency and high-frequency signals S _L −
Since FM and S _H -FM are recorded at high density as shown in Figure 8, there is a slight tracking deviation during playback, as shown in Figure 11, and the position is shifted by L from the normal track. Head _HPL ,
Assuming that the H _PH is reproducing, the reproducing head H _PL will reproduce the low frequency signal l ₁ later than during normal tracking.
The reproducing _{head HPH} reproduces the high frequency signal S _H -FM which is _l2 earlier.

Therefore, due to this tracking deviation, a time axis error occurs between the reproduced low frequency signal S _L -FM and high frequency signal S _H -FM. When the relative speed between the tape 12 and the playback heads H _PL , H _PH is V,
The time axis error Δt between each track is Δt=l ₁ +l ₂ /V.

Therefore, this time axis error Δt must be corrected.

Furthermore, as mentioned above, by band-dividing the composite color video signal S _I , the luminance signal is distributed across the low-frequency signal S _L and the high-frequency signal S _H , but these signals
Since S _L and S _H pass through separate signal transmission systems, their delay times are slightly different. Further, when the recording head and the reproducing head are different, a difference in the mechanical position of each head also causes a shift on the time axis. Therefore, even when no tracking deviation occurs, it is necessary to adjust the time axes so that the delay times of each channel accurately match.

For this reason, each channel is provided with time axis adjustment circuits 40 and 50.

The example shown in Fig. 4 is a case where the time axis of the low frequency signal S _L is fixed and the time axis of the high frequency signal S _H is adjusted.
This is the case where 1 is used. 42 is a clock oscillator, 43 is a driver, and its output is CCD41
This clock frequency and CCD41
A predetermined delay time determined by the number of bits (for example,
1H) is given to the low frequency signal _SLO .

The clock frequency of the CCD 51 is changed according to the time axis error. Therefore, the first and second reference signals S _BL and P _HH , which serve as time axis references, inserted into the low-frequency and high-frequency signals S _L and S _H are detected.

First, the low frequency signal delayed by CCD41
S _LO is supplied to the synchronization separation circuit 44 to separate the horizontal synchronization pulse P _H (FIG. 6C), and this horizontal synchronization pulse P _H operates the first mono multivibrator 45 to generate the horizontal synchronization pulse P _H For example, 0.5 of the first reference signal _SBL inserted into the back pouch side of
A first multi-output M ₁ (D in the figure) having a pulse width corresponding to the position of the cycle is formed, and the second mono-multivibrator 46 is actuated by this first multi-output M ₁ to generate the first multi-vibrator 46 . 2nd multi-output with a pulse width of 1 cycle of the 1st reference signal S _BL
M ₂ (E in the same figure) is formed.

The first gate circuit 47 is operated by this second multi-output _M2 , and the first reference signal _SBL is output for one cycle from the predetermined cycle _.
is extracted (Figure F), and this extracted signal
S' _BL is supplied to a first comparison pulse forming circuit 48 to form a first comparison pulse φ _L corresponding to the zero-crossing point of signal S' _BL .

A second reference signal P _HH is also detected by similar means to form a second comparison pulse φ _H . Therefore, although a detailed explanation thereof will be omitted, 54 is a separation circuit for the second reference signal _PHH (FIG. 7C), and 55 and 56 are the third
and a fourth mono-multi vibrator, which respectively output third and fourth mono-multi outputs M ₃ and M ₄ shown in FIGS. 7D and E. Further, 57 is a second gate circuit, from which one cycle of signal S' _B (FIG. 7F) constituting the burst signal S _B is extracted, and a second comparison pulse forming circuit 58 generates a comparison pulse φ _H (G in the same figure) is formed.

When there is no difference in delay time in both channels and tracking is performed correctly, the time T _L from the horizontal synchronizing pulse P _H until the first comparison pulse φ _L is obtained (Fig. 6G) and the second It is equal to the time T _H (FIG. 7G) from the reference signal P _HH until the second comparison pulse φ _H is obtained. Therefore, by comparing the phases of the first and second comparison pulses φ _L and φ _H , it is possible to know the amount of time axis correction on the high frequency signal S _H side.

Therefore, these first and second comparison pulses φ _L and φ _H are supplied to the phase comparison circuit 60, and the variable oscillator (VCO) 52 is controlled by the phase comparison output. The clock output of VCO52 is driver 5
3 to the CCD 51.

Therefore, the delay time is controlled by the CCD 51 in accordance with the phase comparison output, and the high frequency signal that has passed through the CCD 51 is on the time axis of the low frequency signal S _LO that has passed through the CCD 41.
The time axes, that is, the delay times, are controlled so that the time axes of _SHO coincide.

Note that the low frequency signal S _LO and the high frequency signal S _HO whose time bases have been adjusted are supplied to wave removers (trap circuits) 61 and 62, respectively, before being supplied to the synthesizer 35.
First and second reference signals S _BL , P _HH are trapped, respectively.

By the way, although the embodiment shown in FIG. 4 has been described using a composite color video signal as the video signal input to terminal 1, it is also possible to input these signals even when the luminance signal and color signal exist independently. It can be used as a video signal. FIG. 12 shows an example of a circuit system used in that case. however,
In this example, the configuration is such that both the luminance signal Y and the color signal C can be used even when they are separated or when they are frequency multiplexed like a composite color video signal.

In this example, the luminance signal S _Y is supplied to a terminal 70Y provided between the synthesizer 9 and the modulator 11. As this luminance signal S _Y, for example, a luminance signal before being combined with the color signal _SC formed by a television camera is used. Therefore, as shown in FIG. 13, this luminance signal S _Y is a wider band signal than the luminance signal Y obtained by dividing the composite color video signal S _I.

Further, the color signal S _C is supplied to a terminal 70C provided between the first high-pass filter 3 and the frequency converter 13. This color signal _SC also uses a signal before being frequency multiplexed with the luminance signal _SY , and therefore this color signal _SC does not include the luminance signal _SY at all.

When recording the luminance signal S _Y and the color signal _SC , unlike the embodiment shown in FIG. 4, the horizontal synchronizing pulse P _H itself is used as the reference signal for time axis adjustment on the luminance signal S _Y side. Therefore, the phase comparison is performed based on the horizontal synchronizing pulse P _H and the second reference signal P _HH inserted into the color signal _SC , as will be described later.

The luminance signal S _Y and the color signal S _C supplied to the terminals 70Y and 70C are respectively subjected to the same signal processing as described above and then recorded on different tracks by the recording heads H _RL and H _RH, respectively.

The reproducing device 20 also has a configuration similar to that described above, but since this embodiment has a dual-purpose configuration, the second low-pass filter 22 is a pair of low-pass filters whose frequency characteristics are selected as shown in FIG. Filters 73 and 74 are provided, and when the luminance signal S _Y and color signal S _C are used as input video signals, the low-pass filter 73 with a wide band of about 4.5 MHz is selected and the composite color video signal S _I is used. In this case, the low pass filter 74 having the frequency characteristics used in the embodiment of FIG. 4 is selected. 75 is its selection switch.

Selection switch 75 is automatically selected based on the mode discrimination output supplied to terminal 76. In this example, in order to determine whether the recorded signal is a composite color video signal S _I supplied to terminal 1 or a video signal in which the luminance signal S _Y and color signal S _C are separated, the composite color video signal S _I is The first reference signal S _BL inserted only into the divided low-frequency side signal S _L is also used as its mode discrimination output, and when this first reference signal S _BL is detected by the synchronization separation circuit 44, The selection switch 75 is switched to the low-pass filter 74 side by the output of the first reference signal _SBL .

Note that the time axis adjustment in the above case is as follows. That is, the horizontal synchronizing pulse _PH itself included in the luminance signal _SY is used as the first reference signal, and comparison pulses φ _L are obtained from this and the second reference signal P _HH inserted into the chrominance signal _SC . , φ _H is formed
A phase comparison output that controls VCO 52 is formed.
Therefore, the circuit system for forming comparison pulses φ _L and φ _H is slightly different from that shown in FIG.

The reason why the reference signal for time axis adjustment differs depending on the signal to be recorded is because the required time axis adjustment accuracy differs.

In other words, when the luminance signal Y exists across the low frequency signal S _L and the high frequency signal S _H as in the case of a composite color video signal, the time axis error allowed between each channel is extremely small. According to the applicant's experiments, it is necessary to suppress the time axis error to about 10 to 20 nanoseconds. Therefore, when handling composite color video signals, it is necessary to control the VCO 52 using the pseudo color burst signal S _BL and the burst signal S _B.

On the other hand, when dealing with a signal that does not include a luminance signal in the high-frequency signal S _H , the time axis error between channels does not need to be exactly the same; The error was found to be acceptable. In other words, this is because it has been confirmed that a time axis error of this magnitude does not adversely affect the reproduced image.

Therefore, in this case, comparison of horizontal synchronizing pulses is sufficient.

Of course, the same reference signal may be used for both. In this case, it is necessary to use a dedicated signal for mode discrimination.

As explained above, according to the present invention, all the conventional drawbacks can be completely eliminated. That is, in the present invention, a signal indicating a luminance component and a signal indicating a color component are extracted from an input video signal, these signals are processed and recorded, and after playback, these signals are reprocessed and then synthesized. Even in the case of the first embodiment, the idea is not to separate the luminance signal and the chrominance signal as in the past, but simply to divide the band of the frequency-multiplexed composite color video signal into two. Recording is possible without any restrictions on the bands of luminance and color signals. Therefore, high-quality images can be reproduced because signal processing can be performed in a wide band.

In addition, in this invention, Y/C as shown in FIG.
Since it is not a separate recording method, cross colors naturally do not occur. Furthermore, since the signal indicating the color component is processed and recorded separately from the signal indicating the luminance component, the alternating current bias signal of the signal indicating the color component may fluctuate due to changes in the luminance level. Therefore, there is no deterioration in image quality.

As described above, according to the present invention, a wideband, high-quality video recording device can be provided.

Furthermore, in the present invention, since the playback device 20 is provided with the time axis adjustment circuits 40 and 50, it is possible to absorb differences in delay time between channels and make the time axes of both channels coincide, and also to eliminate tracking deviations. Even when the time axis error occurs due to this tracking deviation, it is possible to absorb the time axis error caused by this tracking deviation.

Then, a low frequency signal S _L is used for adjusting the time axis error.
A reference signal is inserted into the high _- frequency _{signal S} When inserting each synchronization pulse as a reference signal,
Since these are reference signals originally included in the information signal, the reference signal can be easily formed.

Furthermore, although the low-frequency signal S _L includes the horizontal synchronizing pulse P _H as information, when a burst signal is used as a reference signal, this burst signal can be easily separated. Similarly, the high frequency signal S _H includes the burst signal S _B , but if the horizontal synchronizing pulse is used as the reference signal, it becomes easy to separate this horizontal synchronizing pulse.

Furthermore, in the embodiment described above, the time axis adjustment circuit 40
is fixed and the other time axis is adjusted based on the delay time, so the time axis adjustment circuit 40 on the fixed side
This has the effect of simplifying the circuit configuration.

[Brief explanation of drawings]

FIGS. 1 to 3 are diagrams for explaining a conventional example, FIGS. 4 and 12 are system diagrams showing an example of a recording/reproducing apparatus according to the present invention, and FIGS.
1 and 13 are diagrams for explaining the operation, respectively, and FIG. 10 is a system diagram of the high-pass filter. 2, 22 are low pass filters, 3, 26 are high pass filters, 11, 16 are modulators, 21,
24 is a demodulator, 13 and 25 are frequency converters, S _I is a composite color video signal, S _Y is a luminance signal, and S _C is a color signal.

Claims (1)

[Claims] 1. A video signal is separated into a luminance signal indicating a luminance component and a color signal indicating a color component, and the separated luminance signal is subjected to FM modulation after being superimposed with a burst signal having a frequency lower than 3MHz. The separated color signal is then recorded on a first track on the magnetic tape by a first magnetic head, and the separated color signal is processed by a processing means to generate a synchronization signal corresponding to the horizontal synchronization signal of the video signal. is added, and a burst signal having a frequency lower than 3 MHz is superimposed, FM modulated, and recorded on a second track different from the first track on the magnetic tape by a second magnetic head. The burst signals extracted from the reproduced luminance signal and the reproduced chrominance signal respectively reproduced from the first and second tracks and FM demodulated are phase-compared, and the phase comparison results are Based on this, the mutual time axis error of the reproduced luminance signal and the reproduced chrominance signal is adjusted, and the reproduced luminance signal and the reproduced chrominance signal with the time axis error adjusted are synthesized to obtain a reproduced video signal. A video signal recording and reproducing device characterized by: