JPS6267992A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To remarkably delete a circuit scale when processing a recording and reproducing device by a digital signal by approaching respective operating clock frequencies of a means for FM modulating or FM demodulating respective delay units and a digital FM signal to a lower limit frequency capable of processing the respective signals, namely Nyquist frequency. CONSTITUTION:During a reproducing, a mixing signal M re[produced from a reproducing head 117 becomes a digital mixing signal Md and is guided to an HPF119 and an LPF125. A digital luminance signal Yd from an interpolating filter 123 and a digital carrier chrominance signal Cd from a modulator 130 are mixed by a mixer 124 to be a digital composite video signal, converted into an analog quantity by a DC converter 131 and outputted from a terminal 132. As a clock frequency fc is eight times of the least common multiple 2.25MHz of a horizontal scanning frequency of both systems of NTSC and PAL, a 1H delay unit in a comb-line filter and a drop out compensating device can be correctly constituted by integer numbers of delay steps in any case of fc/2, fc/4, fc/8 of an operating frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to household VTRs (Video Tape Rec
The present invention relates to a recording/reproducing device for video signals such as (order) and the like.

BACKGROUND OF THE INVENTION As a conventional recording and reproducing device, there is a familiar one, the home VTR, whose signal processing techniques are described, for example, in the document ``Introduction to Home VTR J'' (Television Society of Japan).

Corona Co., Ltd.).

FIG. 2 shows a configuration diagram of this conventional recording and reproducing apparatus, where 201 is an input terminal for a composite video signal (hereinafter referred to as input terminal), and 202 is a terminal for receiving a luminance signal Y and a carrier color signal C from the composite video signal. 203 is an FM modulator that frequency-modulates the luminance signal Y to obtain an FM signal; 204 is a frequency converter that frequency-converts the carrier color signal C to a low frequency (for example, 630 KH → to obtain the carrier color signal S); converter, 20
5 is an HPF high-pass filter (hereinafter referred to as HPF); 2
0 is a mixer, 207 is a recording head, 208 is a playback head, 209 is an HPF, 210 is an FM demodulator, and 211 is a delay device that produces a time delay that is an integral multiple of the horizontal scanning period. 212 is an L low-pass filter (hereinafter referred to as LPF), 213 is a frequency converter, and 214 is an integral multiple of 1/fH (where fH is the horizontal scanning frequency). 215 is a mixer, and 216 is an output terminal (hereinafter referred to as output terminal) for a composite video signal.

The operation of the conventional recording/reproducing apparatus configured as described above will be explained. Composite video signal I'1Y input to input terminal 201 during recording (separated into luminance signal Y and carrier color signal C by 4-separation filter 202, luminance signal Y becomes FM signal F by FM modulator 203 and carrier color signal Signal C
becomes a carrier color signal S by the frequency converter 204. HP
The FM signal from which frequency components overlapping with the carrier color signal S have been removed by F205 and the converted carrier color signal S are sent to the mixer 20
6 and becomes a mixed signal M, which is sent to the recording head 20.
7 is recorded on the magnetic tape. During reproduction, the mixed signal M reproduced from the magnetic tape by the reproduction head 208 is separated into an FM signal F and a carrier color signal S by the HPF 209 and the LPF 2126, respectively. The FM signal F is demodulated by the FM demodulator 210 and becomes a luminance signal Y. Since the demodulated luminance signal Y may have signal loss due to dropout, the dropout compensator 211 adjusts it to 1/f during the dropout period.
A signal from a delay device that generates a time delay that is an integral multiple of H compensates for the loss of the luminance signal Y. The carrier color signal S is transmitted to the frequency converter 21
3, and unnecessary components are removed by a comb filter 214, resulting in a carrier color signal C. The luminance signal from the dropout compensator 211 and the comb filter 21
The carrier color signal C from 4 is mixed by a mixer 216 to form a composite video signal, which is output from an output terminal 216.

It should be noted that the delay device used in the dropout compensator 211 can also serve as a noise removal device that forms a comb filter for a minute level signal in the luminance signal Y when no double-D dropout occurs.

The above signal processing is performed using analog IC (Integrate
dCircuit), thereby reducing the number of parts.

To 7-7 Cost reduction, reduction of adjustment points, and miniaturization of equipment have been achieved. However, it is difficult to convert various filters consisting of inductors and capacitors and glass delay lines, which are delay devices, into analog ICs, and there is a limit to the reduction in the number of parts by converting them into analog ICs. Therefore, a method using digital signal processing can be considered to overcome this limit. This is because if digital signal processing is used, various filters, delay devices, etc. can all be implemented using digital circuits that can be implemented as ICs, and by implementing ICs, the number of external parts of the IC can be significantly reduced.

Problems to be Solved by the Invention However, if a conventional recording/reproducing device were to be used for digital signal processing as is, the digital signal processing circuit would have to be large-scale, making it difficult to realize an economical IC implementation. In other words, in general, the scale of the circuit required to process the same signal in a digital signal processing circuit increases as the operating clock frequency increases; ) required for digital signal processing.
This is because an operating clock frequency of about 1 or more is required. For example, if a 1H delay device which produces a time delay of 1/fH during one horizontal scanning period is implemented using an operating clock frequency of 171M, approximately 1080 stages (in the case of the NTSC system) of shift registers or memories are required. If the number of signal quantization is 8 bits, it will be about 8 kbits, and if a 1-bit memory is constructed from a Noritub flop having a general CMO36) transistor configuration, 51,840 transistors will be required per 1H delay device.

In this case, the dropout compensator 211 has one 1H delay device, and the comb filter for the carrier color signal has one in the NTSC system.
One H delay device is required, and two 1H delay devices (that is, one 2H delay device) are required in the PAL system. Since the delay device can be shared for recording and playback, a 1H delay device is required for signal processing.
The SC system requires two, and the 9-PAL system requires three. Taking only this delay device as an example, it can be seen that the scale of the digital signal processing circuit becomes large and it is difficult to economically implement it into an IC.

In addition, the ability to support not only the NTSC system but also the PAL system without major changes to the circuit means that the IC can be shared and N
This is necessary to support VTRs that have a TSC/PAL switching function.

Means for Solving the Problems The present invention provides a first means for separating a digital luminance signal from a digital composite video signal using a comb filter, and a first means for separating a digital luminance signal from a digital composite video signal using a comb filter.
The second means for obtaining the M signal is to roughly remove the digital luminance signal component from the digital composite video signal, demodulate it, and then convert the frequency to a low frequency [-1] using a comb filter to generate the digital color signal Bd, , Bd, A third means for separating the digital carrier color signal Td or the digital carrier color signal Td, and converting the frequency of the digital carrier color signal Td by modulating or separating the digital carrier color signal to generate a digital carrier color signal having a carrier frequency suitable for recording. Obtain the signal Sd, add the digital FM signal and convert it to an analog signal to obtain a mixed signal, or convert the digital carrier color signal Td and the digital FM signal to analog signals and add them to obtain a mixed signal,
The comb filter of the first means has a recording frequency of fc/2 (where fc is 8 times 2.25, which is the least common multiple of the horizontal scanning frequency of both NTSC and PAL systems. clocks with substantially equal frequencies), and
/fH (where fH is a horizontal scanning frequency), the second means operates with a clock of fc, and the comb filter of the m3 means has a delay device that produces a time delay of an integral multiple of fH (where fH is a horizontal scanning frequency); The present invention is a recording/reproducing apparatus characterized by having a delay device that operates with a clock of 4 or fc/8 and generates a time delay that is an integral multiple of 1/fH.

The present invention also converts the reproduced mixed signal into a digital signal and separates it to obtain a digital FM signal and a digital carrier color signal Sd of a carrier frequency suitable for recording, or converts the reproduced mixed signal into an FM signal and a carrier color signal Sd. a first means for obtaining a digital FM signal and a digital carrier color signal by separating the color signal and converting the signal into a digital signal;
a second means for demodulating the signal to obtain a digital luminance signal; a third means for performing dropout compensation of the digital luminance signal; and demodulating or frequency converting the digital carrier color signal Sd using a comb filter. Color signal Bd
1. Bd, J or a digital carrier color signal Td; fourth means for separating said digital color signals Bd1. Bd2 is modulated or the digital carrier color signal Td is frequency converted to obtain a digital carrier color signal Cd for obtaining a digital composite video signal, and the digital carrier color signal Cd is added to the dropout compensated digital luminance signal to be digitally transmitted. a fifth means for obtaining a color signal; the second means is fc (where fc is a frequency substantially equal to 8 times 2, 25&, which is the least common multiple of horizontal scanning frequencies for both NTSC and PAL systems); The third means operates with a clock of fc/2.
The comb filter of the fourth means has a delay device that operates with a clock of 1/fH (where fH is a horizontal scanning frequency) and produces a time delay of an integral multiple of
The present invention is a recording/reproducing device characterized by having a delay device that operates with a clock of /8 and generates a time delay that is an integral multiple of 1/fH.

Function In the present invention, the signal processing is digitalized as described above, and the digital luminance signal Yd, the tritone digital color signal Bd1 . The operating clock frequency of each delay device for delaying Bd2-5 or the frequency-converted carrier color signal Td by an integer multiple of 1/fH and the means for FM modulating or demodulating the digital FM signal are determined respectively. NTSC, PAL In both types, the delay device can be realized with high accuracy and the circuit scale can be reduced, including the scale of the circuit for realizing other loan processing.

Embodiment FIG. 1 (,) shows record 13 in the first embodiment of the present invention.
FIG. 1(b) is a block diagram of the recording system of the playback apparatus. FIG. 1(b) shows a block diagram of the playback system. In Figure 1, 10
1d, input terminal for composite video signal; 102, AD converter (
103 is a decimation filter for making the sampling frequency negative; 104 is a comb filter for taking out the digital luminance signal Yd; 105 is an interpolation filter for doubling the sampling frequency; F
M modulator, 107 is an HPF, 108 is a mixer, 109 obtains and demodulates a digital carrier color signal CD, and outputs a digital signal Bd1. A color demodulator outputs Bd2, 110 is a thinning filter that sets the sampling frequency to -, and 111 is a digital color signal Bd1. A comb filter removes the digital luminance signal component from Bd2, 112 is an interpolation filter for increasing the sampling frequency by 8 times, 113 is the digital color signal B
d1. A color modulator that modulates Bd2 to obtain a digital carrier color signal Sd, 114 is a DA converter (digital/analog converter), 115 is a recording head, 116 is NTSC,
Least common multiple of horizontal scanning frequency for both PAL systems: 2.26M
1) 814' A clock generator that generates a clock (sampling clock), 117 a playback head, 118 an AD converter, 119 an HPF 1120 that removes the digital carrier color signal Sd, an FM demodulator, and 121 a sampling frequency. 122 is a dropout compensator, 123 is an interpolation filter for doubling the sampling frequency, 124 is a mixer, and 125 is an LP for removing the digital FM signal Fd.
F.

126 demodulates the digital carrier color signal Sd to generate digital color signals Bd1. A color demodulator for obtaining Bd2, 127 a decimation filter that makes the sampling frequency negative, 128 a comb filter that removes unnecessary components from the digital color signal Bd, Bd2, and 129 a comb filter that doubles the sampling frequency. An interpolation filter 130 is a digital F signal Bd1. Bd2
a color modulator that modulates the digital carrier color signal Cd to obtain a digital carrier color signal Cd;
131 is a DA converter, 132 is an output terminal for a composite video signal, and 133 is a clock generator.

The recording/reproducing device 15 of this embodiment configured as described above has the following configuration: The operation of the position will be explained below.

At the time of recording, the composite video signal input to the terminal A 101 is sampled at the sampling frequency fc by the AD converter 102.
The digital carrier color signal Cd component is removed by a digital composite video signal type filter 1o4 to become a digital luminance signal Yd.

The digital luminance signal Yd is converted into a signal having a sampling frequency fc by an interpolation filter 105, converted into a digital FM signal Fd by an FM modulator 106, and a low frequency component is removed by an HPF 107. Further, the digital composite video signal is subjected to a color demodulator 109 in which the digital luminance signal component is roughly removed, and then demodulated to produce the digital color signal Bd1. It becomes Bd2. A digital color signal from which residual digital luminance components are removed is obtained by a digital comb filter 111. The digital color signal from the comb filter 111 is converted into a signal having a sampling frequency fc by an interpolation filter 112, and is modulated by a color modulator 113 to become a digital carrier color signal Sd.

The digital FM signal Fd from which low-frequency components have been removed by the HPF 107 and the digital carrier color signal Sd are mixed by a mixer 108 to become a digital mixed signal Md, which is converted into an analog quantity by a DA converter 114 and recorded as a mixed signal M. It is recorded on the magnetic tape by the hect 116.

During reproduction, the mixed signal M reproduced by the reproducing head 117 is converted by the AD converter 118 into a digital signal having a sampling frequency fc to become a digital mixed signal Md, which is guided to the HPF 119 and the LPF 125. H
The digital mixed signal from which the component of the digital carrier color signal Sd is removed by the PF 119 becomes a digital FM signal Fd, which is demodulated by the FM demodulator 120 to become a digital luminance signal Yd. After the deaud compensator 122 performs dropout compensation (17'), the interpolation filter 123 converts the signal into a signal whose sampling frequency is fc. On the other hand, the digital mixed signal Md from which the digital FM signal has been removed by the LPF 125 becomes the digital carrier color signal Sd, which is demodulated by the color demodulator 126 to generate the digital color signal Bd1. The digital chrominance signal Bd, . Digital luminance signal Yd from interpolation filter 123
and the digital carrier color signal Cd from the modulator 130 are mixed by a mixer 124 to form a digital composite video signal, which is converted into an analog quantity by a DA converter 131 to become a composite video signal, and is output from a terminal 132.

In the above, the clock frequency fc is NTSC.

Least common multiple of horizontal scanning frequency for both PAL systems is 2.25■
Since it is 8 times as large as the comb filter and drawer, it is possible to accurately configure the comb-shaped filter and the drawer. Note that the accuracy of the clock frequency fC is sufficient as long as the characteristics of the comb filter and dropout compensator are within a practically acceptable range1.The above explanation will be made separately for recording and playback. There are many blocks with almost the same functions and characteristics, and most of the circuitry can be shared. That is, the AD converters 102 and 118, the decimation filters 103 and 121, the 1H delay device in the comb filter 104 and the 1H delay device in the dropout compensator 122, and the interpolation filters 105 and 123.
, HPFs 107 and 119, mixers 108 and 124, thinning filters 110 and 127, comb filters 111 and 12
8. Most of the interpolation filters 112 and 129 can be shared in common. Furthermore, since the decimation filter and the interpolation filter basically have the same characteristics, most of the circuit can be shared by time-division operation. Therefore, most of the four digital filters 103, 121, interpolation filter 19, and 105, 123 can be shared, and the decimation filters 110, 12
7. The same applies to the interpolation filters 112 and 129. The color demodulator also outputs a digital carrier color signal Cd or Sd.
The color modulator is a frequency converter that converts the frequency of the digital color signal Bd1. Since it is a frequency converter that converts the frequency of Bd2 to each carrier frequency, it is possible to easily change a color modulator into a color demodulator or vice versa. Therefore, most of the processing in the reproduction system can be performed by reversing the flow of processing in the recording system.

This means that when the processing of the recording and reproducing device is converted to digital signal processing and integrated circuit is implemented, the wiring length of each block can be shortened, that is, it is suitable for integrated circuit.

In particular, the comb filters 104 and 111 during recording are different from the conventional arrangement and are provided separately for luminance signal processing and chrominance signal processing. If it is unnecessary during processing, it can be easily removed.

Next, the circuit scale of this embodiment will be described. First, regarding the circuit scale of the delay device, the number of delay stages that make up the delay device is determined by the clock operating frequency.If the operating clock frequency is twice the horizontal scanning frequency fH (I! is an integer),
The H delay device consists of L delay stages. If fc-1-fH, then fc-1811! -1+, ff=1144. in the NTSC system. In the PAL system, the 1H delay device for digital luminance signal 1152 in the comb filter 04 or the double-out compensator 122 consists of i delay stages;
The 1H delay device for digital color signals in 8 requires two delay stages, Bdl (e.g., B-Y) and Bd2 (e.g., R-Y), for a total of 7 delay stages. is necessary. On the other hand, as described in the conventional example, when all delay devices are operated at a single clock frequency fc, a 1H delay device for digital luminance signal, a 1H delay device for digital color signal processing (in this case, ) consists of 21-.beta delay stages, requiring a total of 2.beta. Therefore, according to this embodiment, compared to the case where the configuration described in the conventional example is converted into digital signal processing using a single clock frequency, there is a significant delay of (^・p)/(2・f!,)-1. The number of stages, that is, the circuit scale can be reduced. In the case of PAL system, the digital color signal delay device is 2H.
The time delay required is reduced by -.

The circuit size of the delay device could be significantly reduced by lowering its operating clock frequency, that is, the sampling frequency, but this required circuits for sampling frequency conversion before and after the delay device, that is, when lowering the sampling frequency. A decimation filter that limits the band so that aliasing components do not occur even when signal data is thinned out, and an interpolation filter that interpolates new data between input signal data without creating unnecessary components when increasing the sampling frequency. became necessary. However, since the conversion ratio of the sampling frequency is an integer, especially 2m (m is an integer), +'15m can be expressed with a relatively small-scale circuit, and the decimation filter and interpolation filter can have the same 22' characteristics. Since they can have almost the same configuration, most of the circuit can be shared by time-division operation, and the scale of the circuit for sampling frequency conversion can be reduced. Since the processing of the carrier color signal is realized by color demodulation and color modulation, the scale of the processing circuit seems to increase at first glance, but since the passband center frequency is different, it is NTSC.

Since it is difficult to share both types of PAL and requires steep frequency characteristics, a bandpass filter (hereinafter referred to as BPF), which has a large circuit scale, is no longer necessary, and instead, it is possible to use both NTSC and PA.
Since it can be realized by an LPF that can be used in both types and has a simple configuration, the circuit size can be reduced compared to converting conventional processing to digital processing as it is. Therefore, the circuit increase due to sampling frequency conversion is sufficiently smaller than the circuit scale reduction of the delay device, and the circuit scale of the entire recording/reproduction processing device can be significantly reduced.

As described above, according to this embodiment, by operating the 1H delay device fC (2H delay device in the PAL system) that delays the digital color signals Bd, , Bd2 at 100%, the basic An accurate 1H delay device can be configured with an integral number of delay stages without switching the clock frequency fC, and the 1H delay device that delays the digital luminance signal and the digital color signal can be used both during recording and playback. As a result, the circuit scale can be reduced and a configuration suitable for use in integrated circuits can be realized.

Even if operated in Instead of the color borrowing Bd1, E d2 obtained by demodulating the digital luminance signal Cd or Sd, the digital carrier color signal Cd, Sd is used in the low range (for example e OO
It is clear that the same effect can be obtained by a configuration in which the digital carrier color signal Td obtained by frequency conversion to a band having a center frequency of about kHz to 1.7 kHz is passed through a delay device. Rather than directly demodulating the digital carrier color signal Cd in the color demodulator 109, the digital carrier color signal Cd is first demodulated at another low carrier frequency (for example, 920 kHz in the case of NTSC system).
It is also possible to demodulate the frequency after converting the frequency to
In this case, the operating frequency of the demodulator should be lowered (e.g. f C
/8) signal processing, it is possible to reduce the circuit scale of the color demodulator. Also, the color modulator 130
Instead of directly converting the digital color signal into a digital carrier color signal Cd, the digital color signal is first converted to a different frequency (for example, N
After modulating the carrier frequency (920 kHz in the case of the TSC method), the frequency is converted to generate the digital carrier color signal C.
A method of obtaining d can also be considered, and in this case, the operating frequency of the color modulator can be lowered (for example, fc/8) to perform signal processing, so it is also possible to reduce the circuit scale of the color modulator.

Unfortunately, instead of having a configuration that performs sampling frequency conversion of 1 and 8 times at once as in the embodiment, it is - times the sampling frequency.

It is also possible to adopt a configuration in which double sampling frequency conversion is performed three times.

5A- Also, for the sake of brevity, the explanation is omitted. For example, emphasis is placed on the high frequency range before FM modulation of the luminance signal during recording, and the emphasized high frequency range of the luminance signal after FM demodulation during playback. By de-emphasis to restore the image to its original state, and other noise removal9 image quality correction, it is possible to reduce the scale of the circuit that implements these processes, and by processing the carrier color signal at the ACC frequency, these processes can be reduced. It is clear that the scale of the circuit that implements this can be reduced.

In this embodiment, one AD converter and one ODA are used.
Processing was performed using a converter, but I would like to know how to input and output the luminance signal and carrier color signal, or the FM signal and the converted carrier color signal, separately using two AD converters, and how to operate them at different operating frequencies. \Shinashi-kun - Kuda IA-7-I- and the kidnapping 1 [Mukaihirori Marikinuta] 4th chapter 26''.

As described in detail, according to the present invention, it is possible to significantly reduce the circuit scale when a recording/reproducing device is converted to digital signal processing, and it is possible to significantly reduce the circuit scale by simply switching the circuit integrated in an IC. It is compatible with NTSC and PAL systems, and has great practical effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a recording/reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional recording/reproducing apparatus. 101...Composite video signal input terminal, 102°11
8...AD converter, 103, 110, 121°12
7... Thinning filter, 104, 111. 128...-Comb filter, 105, 112, 1
23゜129...Interpolation filter, 106...FM
Modulator, 107.119-HPF, 108.124-=
Mixer, 109, 126... Color demodulator, 113°13
0--color modulator, 114, 131...-DA change 27
to converter, 116... recording head, 117-... reproducing head, 116, 133... clock generator.

Claims (2)

[Claims] (1) A first means of separating a digital luminance signal from a digital composite video signal using a comb filter, and FM modulating the separated digital luminance signal to generate a digital FM signal.
a second means for obtaining a signal; and after substantially removing a digital luminance signal component from the digital composite video signal, demodulating or converting the frequency to a low frequency band, and using a comb filter to obtain a digital color signal Bd_1, Bd_2 or a digital carrier color; third means for separating the signal Td and modulating said digital color signal or said digital carrier color signal Td;
A digital carrier color signal Sd with a carrier frequency suitable for recording is obtained by converting the frequency of the comb filter of the first means comprises a fourth means for converting and adding the mixed signal to an analog signal to obtain and record the mixed signal, and the comb filter of the first means:
f_C/2 (however, f_C is 8 of 2.25MHz, which is the least common multiple of the horizontal scanning frequency of both NTSC and PAL systems.
clock frequency substantially equal to 1/2
The second means includes a delay device that produces a time delay that is an integral multiple of f_H (where f_H is a horizontal scanning frequency), and the second means
The comb filter of the third means operates with a clock of f_C/4 or f_C/8, and the comb filter of the third means operates with a clock of f_C/4 or f_C/8.
1. A recording/reproducing device comprising a delay device that generates a time delay that is an integral multiple of /f_H. (2) Convert the reproduced mixed signal to a digital signal,
Separate to obtain a digital FM signal and a digital carrier color signal Sd of a carrier frequency suitable for recording, or separate the FM signal and carrier color signal from the reproduced mixed signal and convert it to a digital signal to generate a digital FM signal, digital a first means for obtaining a carrier color signal Sd; a second means for demodulating the digital FM signal to obtain a digital luminance signal; and a third means for performing dropout compensation of the digital luminance signal.
means, demodulates or frequency converts the digital carrier color signal Sd, and uses a comb filter to generate the color signal Bd_1.
, Bd_2 or a digital carrier color signal Td; and said digital color signals Bd_1, Bd_2;
2 or frequency converting the digital carrier color signal Td to obtain a digital carrier color signal Cd for obtaining a digital composite video signal, and add it to the dropout compensated digital luminance signal to obtain a digital composite video signal. fifth means for obtaining f_
C (however, f_C is a frequency substantially equal to eight times 2.25 MHz, which is the least common multiple of the horizontal scanning frequencies of both NTSC and PAL systems), and the third means operates with a clock of f_C/2. The comb filter of the fourth means operates at f_
Operates with C/4 or f_C/8 clock and 1/f_H
1. A recording/reproducing device comprising a delay device that produces a time delay that is an integral multiple of .