JP3380940B2 - Recording and playback device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus in which an interpolation filter for increasing a sampling rate of a luminance signal during recording and a Hilbert converter for phase-shifting a luminance signal during reproduction are commonly used.

[0002]

2. Description of the Related Art Conventionally, when a video signal is processed, a sampling rate of the brightness signal is increased by an interpolation filter before the clipping process at the time of recording the brightness signal, and then the clipping process is performed by the magnetic head. The luminance signal is recorded. Further, at the time of reproducing the brightness signal, the phase of the brightness signal is shifted by the Hilbert converter, and then various kinds of processing are performed to extract the brightness signal.

[0003]

However, in the conventional processing of the luminance signal at the time of recording and reproducing as described above, the design of the interpolation filter used at the time of recording and the Hilbert converter used at the time of reproducing is designed. Since the method is largely different, the conventional method is provided separately for recording and reproduction, and therefore there is a problem that the circuit scale must be increased. Also,
It is possible to record without using an interpolation filter at the time of recording, but in this case, there is a problem that the image quality is deteriorated due to the folding of high-order higher harmonics in the clip processing.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to improve image quality by allowing a Hilbert transformer and an interpolation filter to be commonly used in the circuit configuration. It is an object of the present invention to provide a recording / reproducing device capable of reducing the circuit scale.

[0005]

In order to achieve the above object, a recording / reproducing apparatus according to the present invention records by a magnetic head through a Y process circuit, and reproduces by the magnetic head to obtain a luminance extracted from the Y process circuit. A signal recording / reproducing apparatus, wherein an interpolation filter is provided between the Y process circuit and a magnetic head to increase a sampling rate of a luminance signal at the time of recording before clipping processing, the magnetic head and the Y process. And a Hilbert converter for shifting the phase of the luminance signal at the time of reproduction, provided between the plurality of delay circuits and a plurality of delay circuits.
Predetermined coefficient in the shared circuit consisting of
It is characterized in that each is configured by switching .

[0006] The recording and reproducing apparatus according to the present invention, prior Symbol Interpolation filter, by shifting by 1/4 the sampling frequency fs, characterized by being shared with Hilbert transformer.

[0007]

When the luminance signal is recorded, the luminance signal is subjected to the emphasis processing by the Y process circuit, the sampling rate is raised by the interpolation filter of the shared circuit, and then the clipping processing and the FM modulation processing are performed to perform the magnetic processing. It is recorded on the tape by the head. On the other hand, when the luminance signal is reproduced, the luminance signal reproduced by the Hilbert converter of the shared circuit is phase-shifted, and the de-emphasis processing is performed on the luminance signal by the Y process circuit to reduce the noise of the tape and the head system. Is performed and taken out.

Therefore, since the interpolation filter and the Hilbert converter, which have been conventionally provided separately, are configured by the common circuit, the image quality can be improved and the circuit scale can be reduced. The cost for circuit configuration can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram of a luminance signal processing circuit in the recording / reproducing apparatus of the present embodiment, FIG. 2 is a circuit configuration diagram showing an example of a shared circuit, and FIG. 3 is a diagram showing characteristics of a Hilbert converter of the shared circuit. .

In the luminance signal recording / reproducing apparatus of the present embodiment,
A processing circuit 1 for a luminance signal (Y signal) as shown in FIG. 1 is provided. The luminance signal processing circuit 1 includes a Y-process circuit 3 for inputting and outputting a luminance signal, an interpolation filter 17 of the shared circuit 5, and a luminance signal generated by an emphasis applied in the Y-process circuit 3 in the recording system. It is composed of a clip circuit 7 for processing overshoot and an FM modulation circuit 9 for performing FM modulation processing. In addition, the reproducing system uses the magnetic head 11
It is composed of a Hilbert transformer 19 of the shared circuit 5 for phase-shifting the luminance signal from and the demodulation circuit 15 for FM demodulation. Incidentally, in FIG. 1, 13 indicates a magnetic tape.

The Y process circuit 3 emphasizes high-frequency harmonics by performing emphasis processing on the luminance signal during recording of the luminance signal, while de-emphasis is applied to the luminance signal during reproduction of the luminance signal. , The emphasized harmonics are returned to the original level, and processing for reducing the noise of the tape 13 and the head system is performed. In the interpolation filter 17 of the shared circuit 5, a harmonic is generated by the clipping circuit 7 during recording of a luminance signal, and when the sampling frequency at the time of input is low, the aliasing signal interferes with this signal. As a result, the image quality is deteriorated, and in order to prevent this, the process of doubling the sampling frequency to increase the sampling rate is performed, and then the clipping process is performed before inputting to the FM modulator 9. Recording on the tape 13 is performed by the head 11. In the Hilbert converter 19 of the shared circuit 5, the FM modulated brightness signal from the magnetic head 11 is reproduced by the Hilbert converter 19 of the shared circuit 5 when the brightness signal is reproduced.
The signal processing is performed with the phase shifted by 90 °, and then demodulated by the demodulation circuit 15, and the demodulated luminance signal is de-emphasized by the Y process circuit 3 and output.

In the present embodiment, the shared circuit 5 is, for example, as shown in FIG. 2, a plurality of delay circuits 21 indicated by "Z-1", a plurality of adder circuits 23 indicated by x in ◯, and a plurality of adder circuits 23 indicated by x. The EOR circuit (Exclusive OR) 25 is configured to have a circuit configuration having two upper and lower paths. In FIG. 2, Iin represents the input side of the shared circuit 5, Fout represents the filter output side, H1 represents the 90 ° output side of the Hilbert converter 19, and H2 represents the 0 ° output side of the Hilbert converter 19. Is shown. Also, FIG.
Among them, S1 is a changeover switch, Sf is a changeover switch for a filter, fs is a sampling frequency, P
B indicates the reproduction mode, and FIG. 2 shows the recording mode. In such a shared circuit 5, the Hilbert converter 19 used at the time of reproduction is devised to have a circuit configuration that can be shared with the interpolation filter with a simple correspondence.

The structure of the shared circuit will be described below.
As a conventional general interpolation filter 27, a filter as shown in FIG. 4 can be considered as an example. In the figure, "Z-1" indicates the delay circuit 21, the symbol + indicates the adding circuit 23, fs indicates the sampling frequency, PB indicates the reproduction mode, and Sf indicates the changeover switch for the filter. Is shown. Considering the transfer function of the general interpolation filter 27, the transfer function H (z) of the filter 27 is H (z) = K1 (1 + Z- ¹⁸ ) + K2 (Z- ² + Z ^-16 ) + K3 (Z ^-4 + Z ^-14 ) + K4 (Z ^-6 + Z ^-12 ) + K5 (Z ^-8 + Z ^-10 ) + 0.5Z ^-9 (1). Incidentally, K1 = 3/512, K2 = −3 / 128,
K3 = 17/256, K4 = -87 / 512, K5 = 1
59/256. Among the transfer functions, the coefficients K1 to
Each term of K5 is composed of the upper path of FIG. 4, and the constant term is composed of the lower path of FIG. As shown in FIG. 5, the characteristic of the filter 27 is a half-band filter characteristic of 6 dB at half the sampling frequency fs of the circuit.

Therefore, such an interpolation
The Hilbert transformer 19 can be shared with the filter 27.
As described above, in this embodiment, as shown in FIG.
Shift the number by 1/4 fs and move the Hilbert transformer 19
Interpolation that can be configured and shared
The filter 17 is configured. In this case,
The transfer function (H (z)) of the filter 27 and the frequency as described above.
Transfer function (Hc (z)) of the wave number-shifted filter 17
As for the relationship with, if the angular frequency to be shifted is ω,               Hc (z) = H (e^-jw z) …… (2) Becomes In the above equation 2, the coefficient is a complex number,
Is 1/4 of the sampling frequency (fs)
Does not make the coefficient complex. To use this
, A shared circuit shifted from H (z) by 1 / 4fs
And the transfer function Hc (z) of the filter 17 is
Is   Hc (z) = K1 (1-Z^-18 ) -K2 (Z^-2-Z^-16 ) + K3 (Z^-Four-Z^{-1 Four}  ) -K4 (Z^-6-Z^-12 ) + K5 (Z^-8-Z^-Ten ) + 0.5Z^-9                                                                 …… (3) Becomes Comparing Equations 1 and 3 above, the relation of each term
By converting only the sign of the number, the interpolation flag
The filter 17 can be commonly used as the Hilbert converter 19.
You can see that And Z of the transfer function
^-Ten ~ Z^-18 The inversion of the terms and the signs of K2 and K4
Uses a plurality of EOR circuits 25, as shown in FIG.
As a result, inversion of all bits can be realized.

On the other hand, when the interpolation filter 17 having the above-mentioned configuration is used as the Hilbert transformer 19, the path above the shared circuit 5 is diverted and the EOR in the circuit is used.
The circuit (Exclusive OR) 25 can be configured by inverting the luminance signal at the time of reproduction, and when the upper path in the circuit operates as the Hilbert converter 19, the lower path in the circuit is delayed. It is used as a signal extraction for.

In such a recording / reproducing apparatus, at the time of recording the luminance signal, the Y process circuit 3 performs emphasis processing on the luminance signal to emphasize high-frequency harmonics, and interpolation of the shared circuit 5 is performed. The filter 17 doubles the sampling frequency to increase the sampling rate, and then is clipped by the clipping circuit 7 and F by the FM modulator 9.
The data is M-modulated and recorded on the tape 13 by the magnetic head 11. On the other hand, at the time of reproducing the luminance signal, the Hilbert transformer 19 of the shared circuit 5 phase-shifts the luminance signal reproduced by the magnetic head 11, and the Y process circuit 3 deemphasizes the luminance signal to emphasize the harmonics. The wave is returned to the original level, a process for reducing the noise of the tape 13 and the head system is performed, and the wave is taken out.

When the shared circuit 5 is used as the interpolation filter 17, the PB signal is set to Low and the selector switch S1 is set to the recording mode shown in FIG. 2, and the filter selector switch Sf is set to the sampling frequency fs. The luminance signal is taken out by alternately switching the upper and lower paths in the circuit every 1 sampling, and the coefficient K shown in the equation (3) is taken from the upper path.
The respective terms 1 to K5 are obtained, and the constant term of the equation (3) is obtained from the lower path. On the other hand, when it is used as the Hilbert transformer 19 of the shared circuit 5, the PB signal is set to High.
Then, the changeover switch S1 is changed over to the reproduction mode, whereby the phase shift processing is performed. In this case, the lower path in the circuit passes through the delay circuit 21 set to 2fs, and the luminance signal 90 ° phase-shifted is taken out from the output side H1 of the Hilbert converter 19 to obtain the Hilbert converter. The phase is 0 from the output side H2 of the converter 19.
The signal for delay adjustment is taken out at. As described above, in the recording / reproducing apparatus of the present embodiment, the interpolation filter 17 which is conventionally provided separately.
By configuring the Hilbert converter 19 and the Hilbert converter 19 by the shared circuit 5, it is possible to improve the image quality, and at the same time,
The circuit scale can be reduced, and the cost in the circuit configuration can be reduced.

[0018]

As described above, the recording / reproducing apparatus according to the present invention is a recording / reproducing apparatus of a luminance signal which is recorded by the magnetic head through the Y process circuit and reproduced by the magnetic head and taken out from the Y process circuit. And an interpolation filter provided between the Y process circuit and the magnetic head to increase the sampling rate of the luminance signal during recording before clipping processing.
A shared circuit is provided between the magnetic head and the Y process and a Hilbert converter that shifts the phase of the luminance signal at the time of reproduction. Therefore, the image quality can be improved, and at the same time, the circuit scale can be reduced, and the cost in the circuit configuration can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a luminance signal processing circuit in a recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing an example of a shared circuit.

FIG. 3 is a diagram showing frequency characteristics of a Hilbert transformer in a shared circuit.

FIG. 4 is a circuit configuration diagram of a conventional interpolation filter.

FIG. 5 is a diagram showing characteristics of a conventional interpolation filter.

[Explanation of symbols]

3 Y process circuit 5 shared circuits 11 magnetic head 17 Interpolation filter 19 Hilbert transformer 21 delay circuit 23 Adder circuit 25 Exclusive OR Circuit

Claims (2)

(57) [Claims] 1. A recording is performed by a magnetic head through a Y process circuit, and the Y is reproduced by the magnetic head.
A recording / reproducing apparatus for a luminance signal taken out from a process circuit, comprising: an interpolation filter provided between the Y process circuit and a magnetic head to increase a sampling rate of the luminance signal during recording before clipping processing. a Hilbert transformer for shifting the phase of the luminance signal during the playback is provided between the magnetic head and the Y process, a plurality
By switching the predetermined coefficient in the shared circuit consisting of the delay circuit and multiple adders,
A recording / reproducing apparatus characterized by being configured . 2. The interpolation filter is shared with a Hilbert transformer by shifting the sampling frequency fs by a quarter frequency.
1. The recording / reproducing apparatus according to 1 .