JPH03117989A - Video signal recorder - Google Patents

Abstract

PURPOSE:To use a low-pass filter in simple constitution by limiting the band of a video signal to be recorded by the low-pass filter circuit to limit the band of the video signal to which a digital signal processing is executed. CONSTITUTION:The frequency bands of video signals YIN, PBIN and PRIN to be recorded to a recording medium 20 are limited by second low-pass filter circuits 8A and 8B. In the frequency bands of the video signals YIN and PBIN and PRIN to be recorded to the recording medium 20, the frequency properties of first low-pass filter circuits 40A-40C are set to flat amplitude properties and group delay properties and out of the frequency bands of the video signals YIN, PBIN and PRIN to be recorded to the recording medium 20, the frequency properties are set to smooth attenuating properties by the second low-pass filter circuits 8A and 8B. Thus, the constitution is simplified for the first low- pass filter circuits 40A-40C and the video signals YIN, PBIN and PRIN in the prescribed frequency bands are recorded.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A: Industrial field of application B: Overview of the invention C: Prior art (Figs. 1, 6, and 7) D: Problems to be solved by the invention (Figs. 1, 7, and 7) E: Problems Means to solve (Fig. 1) F action (1st
Figure) G Embodiment (Figures 1 to 5) H Effect of the invention No. 6 A Industrial field of use The present invention relates to a video signal recording device, for example, a video signal recording device that compresses and records a video signal with a wide frequency band. This is suitable for application to tape recorders.

B. Summary of the Invention The present invention provides a low-pass filter circuit for band-limiting the output signal of a digital signal processing circuit in a video signal recording device, by limiting the band of the video signal to be recorded.
A video signal recording device with a simple configuration can be obtained.

C. Prior Art Conventionally, in a video tape recorder designed to record a high-definition television video signal, the video signal is subjected to digital signal processing to compress the band and record it.

That is, in FIG. 1, 1 indicates a video tape recorder as a whole, and video signals consisting of a luminance signal Y, a color difference signal PAIN, and a Pt114 are passed through low-pass filter circuits 2A, 2B, and 2C to an analog-to-digital conversion circuit (A/D). D) Give to 3A, 3B, and 3C.

As shown in FIG. 6, the low-pass filter circuits 2A to 2C are selected so that the amplitude and group delay characteristics are flat in the frequency band below the predetermined cutoff frequencies f and c, and the amplitude characteristics attenuate rapidly outside the band. This effectively avoids deterioration of the video signal and limits the band of the video signal recorded on the video tape recorder 1.

On the other hand, the analog-to-digital conversion circuits 3A to 3C are configured to operate with a clock signal of frequency r+s output from the reference signal generation circuit 4, and at this time, the cutoff frequency flc of the low-pass filter circuits 2A to 2B is set to the clock signal of the frequency r+s output from the reference signal generation circuit 4. It is chosen to be the Nycast frequency of the signal.

Thereby, the video signal can be quantized while effectively avoiding deterioration in high frequencies and occurrence of blurring.

Thus, the band-limited video signals Y0, PIIN, P□ are converted into digital signals via the analog-to-digital conversion circuits 3A to 3C and output to the digital signal processing circuit 5.

The digital signal processing circuit 5 time-base compresses the digital signal based on a predetermined format, and then divides and outputs the signal to digital-to-analog conversion circuits (D/A) 6A and 6B.

After being band-limited by this, the time-base compressed video signal is converted into two video signals with narrow frequency bands and output to digital-to-analog conversion circuits 6A and 6B.

At this time, the digital-to-analog conversion circuits 6A and 6B are
It operates at the repetition frequency of the digital video signal output from the digital signal processing circuit 5 based on a clock signal with a frequency ft output from the reference signal generation circuit 4.

On the other hand, as shown in FIG. 7, low-pass filter circuits 8A and 8B receiving the output signals of digital-to-analog conversion circuits 6A and 6B have cutoff frequencies r! c is the clock frequency f of the digital-to-analog conversion circuits 6A and 6B. Similarly to the low-pass filter circuits 2A to 2B, the Nycast frequency is selected so that the amplitude and group delay characteristics are flat within the band, and the amplitude characteristics are rapidly attenuated outside the band.

This effectively avoids deterioration of the amplitude and phase characteristics of the video signals output from the digital-to-analog conversion circuits 6A and 6B.
It is designed to reliably suppress signal components higher than the Nycast frequency generated at the Nycast frequency.

The signal processing circuits 10A and 10B are configured to perform pre-emphasis processing and the like on the output signals of the low-pass filter circuits 8A and 8B, and output the resulting video signals to the frequency modulation circuits 12A and 12B.

As a result, a recording signal is obtained via the frequency modulation circuits 12A and 12B, and the recording signal is transmitted to the equalizer circuit (BQ
) 14A and 14B, and output to magnetic helads 18A and 18B via amplifier circuits 16A and 16B.

The magnetic heads 18A and 18B each consist of a pair of magnetic heads arranged at an angular interval of 180 degrees, and the magnetic heads 18A and 18B are configured to rotate the magnetic tape a predetermined number of times during a period in which l-field video signals YIN% PIIN, PILIN are input. 20, so that the time-axis compressed video signal can be recorded in segments.

On the other hand, during reproduction, the reproduction signals S IIFA and S, F output from the magnetic heads 18A and 18B
After amplifying ll via amplifier circuits 22A and 22B,
Demodulation is performed by demodulation circuits 26A and 26B via equalizer circuits (EQ) 24A and 24B.

On the other hand, the signal processing circuits 28A and 28B are configured to perform de-emphasis processing, etc. on the output signals of the demodulation circuits 26A and 26B, contrary to the recording process, and pass the signal-processed video signals to the low-pass filter circuit 30A and Give to 30B.

As a result, video signals having the same frequency band as the output signals of the low-pass filter circuits 8A and 8B are input to the low-pass filter circuits 30A and 3OB.

The low-pass filter circuits 30A and 30B are set to have the same frequency characteristics as the low-pass filter circuits 8A and 8B, thereby effectively avoiding deterioration of the amplitude and phase characteristics of the reproduced video signal and eliminating unnecessary high-frequency components. It is designed to suppress the signal.

On the other hand, analog-to-digital conversion circuit (A/D) 3
2A and 32B, the clock frequency ftm is the cutoff frequency rtc of the low-pass filter circuits 30A and 30B.
(that is, a frequency equal to the clock frequency f of the digital-to-analog conversion circuits 6A and 6B), thereby effectively avoiding aliasing and converting the output signals of the low-pass filter circuits 30A and 30B into digital signals. Convert to

Contrary to the digital signal processing circuit 4, the digital signal processing circuit 34 synthesizes the output signals of the analog-to-digital conversion circuits 32A and 32B, expands the time axis, and then separates the signal into a luminance signal and a color difference signal and outputs the signals.

In this way, a video signal having frequency characteristics similar to those of the output signals of the analog digital conversion circuits 3A to 3C can be obtained via the digital signal processing circuit 34.

Digital analog conversion circuits 34A, 34B and 34C
is operated with a clock signal having the same frequency as the clock frequency r+s of the analog-to-digital conversion circuits 3A to 3C, and converts the digital signal output from the digital signal processing circuit 34 into an analog signal.

On the other hand, the low-pass filter circuits 36A, 36B, and 36C have frequency characteristics equivalent to those of the low-pass filter circuits 2A to 2C, thereby effectively avoiding deterioration of the amplitude and phase characteristics of the video signal and converting the analog signal. It is designed to suppress signal components higher than the Nycast frequency that occur when

In this way, by extending the time axis of the reproduced signal and outputting it, the high-density recorded video signal is reproduced and the output luminance signal Y
. . , output color difference signal P,. 1.P. It is designed to obtain u7.

D Problems to be Solved by the Invention By the way, if the number of divisions of the digital signal output from the digital signal processing circuit 5 is increased to achieve high quality segment recording, shortening of the recording wavelength can be effectively avoided.
It is possible to widen the frequency band of video signals that can be recorded.

However, in this case, the low-pass filter circuits 6A, 6B,
In addition to 32A and 32B, the number of low-pass filter circuits increases as the number of divisions increases.

That is, in this type of video tape recorder 1, if the number of input/output signal channels is m and the number of segments is n, the width is widened by the number N expressed by the following formula % () (1) A low-pass filter circuit is required whose phase characteristics and group delay characteristics are flat in the frequency band, and whose amplitude characteristics are rapidly attenuated outside the frequency band.

However, such a low-pass filter circuit, which has flat amplitude and group delay characteristics over a wide frequency band and whose amplitude characteristics attenuate rapidly outside the band, must be constructed by combining many coils, capacitors, etc. Correction of delay characteristics is also required.

Therefore, the low-pass filter circuit has a complicated structure and is complicated to adjust, and accordingly, this type of video tape recorder 1 has a problem in that the overall structure is complicated.

The present invention has been made in consideration of the above points, and aims to propose a video signal recording device whose overall configuration can be simplified.

Means for Solving Problem E To solve this problem, in the present invention, the video signals Y4, P SIN, P□8 inputted via the first low-pass filter circuits 40A, 40B, 40C are digitally Signal processing circuit 3A, 3B, 3C144, 6A, 6B
After converting it into a digital signal and subjecting it to digital signal processing, it is converted into an analog signal and output to the second low-pass filter circuits 8A and 8B.
A.

In the video signal recording device 41 that records the video signal YIN% PaIHs Pa+,l on the recording medium 20 by recording the 8B output signal on the predetermined recording medium 20,
Video signals Y0 and PIIN SP recorded on the recording medium 20
+uN frequency band to the second low-pass filter circuit 8
A, limited by 8B, first low-pass filter circuit 40A
, 40B, 40C are set to flat amplitude characteristics and group delay characteristics within the frequency band of the video signals Y0, Pmtpt, P□ to be recorded on the recording medium 20, and the video signals to be recorded on the recording medium 20. Y4, P□M SP 1 outside the frequency band of □, second low-pass filter circuit 8A, 8
From B, the clock frequency r+s of the digital signal processing circuits 3A, 3B, 3G, 44.6A, and 6B is set to have a gentle attenuation characteristic. , r! 3° is set according to the frequency bands of the first and second low-pass filter circuits 40A, 40B, 40C and 8A, 8B.

Video signal YI, 1, P□8, P recorded on F action recording medium 20
The frequency band of RIM is filtered by a second low-pass filter circuit 8.
A, limited by 8B, first low-pass filter circuit 40A
. Signal YIN, P□N, PIIN
outside the frequency band of the second low-pass filter circuit 8A,
If you set it to a gentler attenuation characteristic than 8B, the brush stroke 1
By simplifying the configuration of the low-pass filter circuits 40A, 40B, and 40C, video signals Y and N of predetermined frequency bands are obtained.

PIIN%P□Work may be recorded.

Furthermore, at this time, the digital signal processing circuit 3A.

Clock frequency f+s of 3B, 3C, 44, 6A, 6B
o, fzs. If set according to the frequency bands of the first and second low-pass filter circuits 40A, 40B, 40G and 8A, 8B, it is possible to prevent distortion and the like from occurring during digital signal processing.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, in this embodiment, low-pass filter circuits 40A-40C are used in place of low-pass filter circuits 2A-2C.

As shown in Figure 2, the low-pass filter circuit 4°A~40
C is selected to have a cutoff frequency f tco approximately 10% higher than that of the low-pass filter circuits 2A-2c, and has amplitude characteristics equivalent to those of the low-pass filter circuits 2A-2C within the frequency band of the low-pass filter circuits 2A-2C. and group delay characteristics, and the attenuation characteristics are set to be gentler than those of the low-pass filter circuits 2A to 2C as the cutoff frequency f Ico is increased.

Therefore, in the low-pass filters 40A to 40C, the attenuation characteristics are made gentler, and as compared to the low-pass filter circuits 2A to 2C, desired frequency characteristics can be obtained with a simpler configuration and simple adjustment work. .

Therefore, as a whole of the video tape recorder 41,
A simple configuration can be obtained.

Furthermore, in this embodiment, a reference signal generation circuit 42 is used in place of the reference signal generation circuit 4, and the frequencies f1m and f output from the reference signal generation circuit 4 are
The frequency rt is 10% higher than the clock signal of
s. and rzs. The analog/digital conversion circuits 3A to 3C convert the clock signal into analog/digital conversion circuits 3A to 3C.

The signal is supplied to the digital signal processing circuit 44 and digital-to-analog conversion circuits 6A to 6C.

Therefore, the analog-to-digital conversion circuits 3A to 3C are configured to convert the video signals output from the low-pass filter circuits 40A to 40C into digital signals at a sampling frequency that is 10% higher than conventional ones, thereby reducing high frequency deterioration and noise. In order to effectively avoid such occurrences, a video signal having a wider frequency band than before is converted into a digital signal.

A digital signal processing circuit 44 used in place of the digital signal processing circuit 4 has a clock frequency f1m. and f
ts. The digital signal processing circuit 4 is set to have a memory with a larger capacity than the digital signal processing circuit 4, which is 10% higher than the conventional one. It is designed to repeat at a repetition period that is 10% shorter than that of the signal processing circuit 4.

Therefore, the digital-to-analog conversion circuits 6A and 6B convert the digital signal whose band has been extended compared to the conventional one into an analog signal using a clock signal having a higher frequency corresponding to the increased band.

As a result, the low-pass filter circuit 40A with a simple configuration
Low-pass filter circuits 8A and 8B using ~40C
It is possible to obtain a video signal that has the same amplitude and phase characteristics as the conventional one within the frequency band of , and whose signal level attenuates more gently than the conventional one outside the frequency band of the low-pass filter circuits 8A and 8B.

Therefore, by band-limiting the output signals of the digital-to-analog conversion circuits 6A and 6B with the low-pass filter circuits 8A and 8B, it is possible to obtain a video signal having amplitude characteristics and phase characteristics similar to those of the conventional one. Equivalent video information can be recorded on magnetic tape 20.

By the way, in this embodiment, although the configuration of the low-pass filter circuits 40A to 40C can be simplified, the clock frequency f1g. and fts. As the value becomes higher, a digital signal processing circuit 44 with a large memory capacity, analog/digital conversion circuits 3A to 3C and digital/analog conversion circuits 8A to 8B with high operating speed are required.

However, the conventional analog-to-digital conversion circuits 3A to 3C
And the digital-to-analog conversion circuits 8A and 8B have a clock frequency Ls. and rts. Even if it becomes about 10% higher,
Works well enough.

Furthermore, the reference signal generation circuit 42 includes, for example, a PLL (pha
In the case of the circuit configuration (se 1ocked 1oop), the clock frequencies f+s and r can be easily increased by increasing the frequency division ratio compared to the conventional one.

Furthermore, the digital signal processing circuit 44 can utilize a conventionally unused memory area if there is one, and even if there is no unused memory area, by adding a memory circuit, the clock frequency f13° and rzs can be adjusted. Even if the value increases by about 10%, the input signal can be digitally processed with a configuration that is almost the same as the conventional one.

Therefore, the clock frequencies f13° and f150 are set to high (
If the band is limited by the low-pass filter circuits 8A and 8B at the output stage, the configuration of the low-pass filter circuits 40A to 40C can be simplified, and the video tape recorder 41 can have a simple configuration as a whole.

Furthermore, since the adjustment work of the low-pass filter circuits 40A to 40C can be simplified, the video tape recorder 4 as a whole can be
The adjustment work in step 1 can be made easier.

On the other hand, on the reproduction side, instead of the low-pass filter circuits 30A, 30B, the digital signal processing circuit 34, and the low-pass filter circuits 34A-34C, a low-pass filter circuit 46A146B, a digital signal processing circuit 48, and a low-pass filter circuit 50A-50C are used, respectively. It is made to use.

As shown in FIG. 3, low-pass filter circuits 46A, 46
B is selected to have a cutoff frequency f tea that is approximately 10% higher than that of the conventional low-pass filter circuits 30A and 30B, and the low-pass filter circuits 30A and 30B are selected within the frequency band of the low-pass filter circuits 30A and 30B.
With amplitude characteristics and group delay characteristics equivalent to , the cutoff frequency f ! c.

The attenuation characteristics are set to be gentler than those of the low-pass filter circuits 3QA and 30B due to the higher height.

That is, when reproducing a video signal recorded with sufficient band limitation by the low-pass filter circuits 8A and 8B, if sufficient linearity is obtained in the recording and reproducing system, the low-pass filter circuits 46A and 46B are equipped with a low-pass filter circuit. 8A,
An input signal having amplitude characteristics and phase characteristics equivalent to those of the 8B output signal can be obtained.

In practice, in this type of video tape recorder, if there is linear distortion in the recording/reproducing system, distortion, beat stripes, etc. will occur, so it is designed to obtain sufficient linearity.

Therefore, as shown in FIG.
For A and 46B, one cutoff frequency. Even if it is set to a 10% higher frequency, it is possible to output a band-limited video signal as before, and because the attenuation characteristics are made gentler, the configuration is simpler and simpler than before. Desired frequency characteristics can be obtained through adjustment work.

Therefore, as a whole of the video tape recorder 41,
A simple configuration can be obtained.

On the other hand, analog-to-digital conversion circuits 32A, 32
B is made to operate with the same clock signal as the digital-to-analog converter circuits 6A and 6B, and thereby the low-pass filter circuit 46A.

The cutoff frequency f of 46B is set to a 10% higher frequency, so the clock frequency f is 10% higher than before.
It is designed to operate at 0°.

The digital signal processing circuit 48, like the digital signal processing circuit 44, has a clock frequency f1m.

and f'm. 10% higher than the conventional one, it is set to have a memory circuit with a larger capacity than the conventional digital signal processing circuit 34, and thereby performs digital signal processing opposite to that of the digital signal processing circuit 44. , the repetition period is 10% shorter than that of the conventional digital signal processing circuit 34.

As a result, it is possible to obtain a video signal obtained by time-axis-expanding the original video signal via the digital signal processing circuit 48 with a repetition period that is 10% shorter than that of the conventional video signal.

At this time, since the video signal has only a frequency band band-limited by the low-pass filter circuits 8A and 8B, the clock frequency f is 10% higher than that of the conventional one.
1m. Digital-to-analog conversion circuit 34A that operates with
By converting to an analog signal at 34C, the Nycast frequency f II as shown in FIG. An analog video signal having frequency characteristics similar to those of the video signals output from the conventional low-pass filter circuits 2A to 2C can be obtained in a frequency band of /2 or less.

Similar to the low-pass filter circuits 40A-40G, the low-pass filter circuits 50A-50C have a cutoff frequency f compared to the conventional low-pass filter circuits 36A-36C.
lco is selected to be about 10% higher in frequency, and has amplitude characteristics and group delay characteristics equivalent to those of the low-pass filter circuits 36A-36C within the frequency band of the low-pass filter circuits 36A-36C, and has a higher cutoff frequency f tco. The attenuation characteristics are set to be gentler than those of the low-pass filter circuits 36A to 36C.

Thus, the Nycast frequency f1m is transmitted through the low-pass filter circuits 50A to 50C. An output luminance signal Y that can obtain a video signal by suppressing frequency bands of 72 or more and has frequency characteristics similar to conventional ones. □, output color difference signal P,. ut, P one. You can get □.

Therefore, in the reproduction system, low-pass filter circuits 46A, 46B, and 50A to 50C, which have a simpler configuration than the conventional ones, can be used by limiting the band and increasing the clock frequency by the low-pass filter circuits 8A and 8B on the recording side. Thus, it is possible to obtain a video tape recorder 41 having an easily segmentable configuration.

In the above configuration, the luminance signal YIN% color difference signal P□ and P□ are band-limited more gently than the frequency band recorded on the magnetic tape 20 by the low-pass filter circuits 40A to 40C.

Band-limited luminance signal YIN% Color difference signal P□A and P
□N is converted into a digital signal at a higher frequency corresponding to the gradual band limitation, and then subjected to digital signal processing in the digital signal processing circuit 44.

Therefore, a digital signal having a higher repetition frequency corresponding to the gradual band limitation is output from the digital signal processing circuit 44, and is band limited to the frequency band recorded on the magnetic tape 20 by the low pass filter circuits 8A and 8B.

On the other hand, the reproduced signals SIIFA and S□ are demodulated into video signals at the time of recording via demodulation circuits 26A and 26B and signal processing circuits 28A and 28B.

Therefore, during recording, the video signal is transmitted to the low-pass filter circuit 8A.
, 8B, the video signal having the same frequency band as the video signal is input to the low-pass filter circuits 46A and 46B.

The video signal input to the low-pass filter circuits 46A, 46B is
After being gently band-limited, the signal is converted into a digital signal at a higher frequency corresponding to the gentle band-limiting, and then subjected to digital signal processing in the digital signal processing circuit 48.

Therefore, a digital signal that includes video information band-limited by the low-pass filter circuits 8A and 8B and has a high repetition frequency corresponding to the gradual band-limiting is output from the digital signal processing circuit 48, and is outputted from the digital signal processing circuit 48,
, 50B, and is output in the same frequency band as the conventional one.

According to the above configuration, a low-pass filter circuit with a simple configuration can be used by restricting the band of a video signal that is recorded on a magnetic tape. I can do it,
Accordingly, a video tape recorder with a simpler configuration can be obtained.

In the above-mentioned embodiment, a case has been described in which the cutoff frequency and clock frequency are increased by 10% compared to conventional ones, but the present invention is not limited to this, and various cutoff frequencies and clock frequencies can be used as necessary. Can be set to .

Further, in the above-described embodiments, the case where time axis compression and time axis expansion are performed using a digital signal processing circuit has been described, but the present invention is not limited to this, and can be broadly applied to cases where various signal processing is performed by converting to a digital signal. It can be applied.

Further, in the above-described embodiments, a case was described in which a luminance signal and a color difference signal were input/output, but the present invention is not limited to this, but can be widely applied to cases where a color signal is input/output, etc.

Furthermore, in the above-described embodiment, a case was described in which the digital signal is processed and then separated into two channels of signals and recorded in segments. However, the present invention is not limited to this, and the present invention is not limited to this. It can be widely applied when recording directly without separating into channels.

Furthermore, in the above-described embodiments, the present invention was applied to a video tape recorder that records high-definition television video signals, but the present invention is not limited to high-definition television video signals, but can be applied to various video It can be widely used in video tape recorders that record signals.

Furthermore, the invention is not limited to video tape recorders, but can be widely applied to video signal recording devices that record video signals on various recording media.

Effects of the Invention As described above, according to the present invention, by limiting the band of the video signal to be recorded using a low-pass filter circuit that band-limits the digital signal-processed video signal, a low-pass filter circuit with a simple configuration can be realized. Accordingly, it is possible to obtain a video signal recording device with a simpler configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a video tape recorder according to an embodiment of the present invention, FIGS. 2 to 5 are characteristic curve diagrams showing characteristics of a low-pass filter circuit, and FIGS. 6 and 7 are diagrams showing a conventional low-pass filter. FIG. 3 is a characteristic curve diagram showing the characteristics of the circuit. 1.41...Video tape recorder, 2A~2
B, 8A, 8B, 30A, 30B, 36A-36C, 4
0A~40G, 46A, 46B, 50A~50C...
...Low pass filter circuit, 3A to 3B. 32A, 32B...Analog-digital conversion circuit, 6A, 6B, 34A-34C...Digital-analog conversion circuit, 5.34.44.48 Old...Digital signal processing circuit.

Claims (1)

[Claims] A video signal inputted through the first low-pass filter circuit is converted into a digital signal and subjected to digital signal processing in a digital signal processing circuit, and then converted into an analog signal and passed through the second low-pass filter. In a video signal recording device that records the video signal on the recording medium by outputting the video signal to a circuit and recording the output signal of the second low-pass filter circuit on a predetermined recording medium, the video signal is recorded on the recording medium. the frequency band of the signal,
limiting by the second low-pass filter circuit, and setting the frequency characteristics of the first low-pass filter circuit to flat amplitude characteristics and group delay characteristics within the frequency band of the video signal to be recorded on the recording medium; Outside the frequency band of the video signal to be recorded on the recording medium, the second low-pass filter circuit is set to have a gentler attenuation characteristic, and the clock frequency of the digital signal processing circuit is set to be lower than the second low-pass filter circuit. A video signal recording device characterized in that settings are made according to a frequency band of a filter circuit.