JPH0420092A - Video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To output a color signal subjected to noise reduction with matching or time base at all times with respect to a luminance signal by forming a frame memory of a noise reduction circuit with two field memories and controlling the write of one field memory at reproduction of a still picture. CONSTITUTION:A frame memory of a noise reduction circuit 8 consists of two field memories 11, 12. Then a control circuit 18 controlling switches 16, 17 with a still picture mode signal and a frame pulse receives a still picture mode signal to select a still picture mode and references a frame pulse to stop the write of one of the two field memories 11, 12 and uses the output of one field memory to reduce noise of a color signal. Thus, even in the still picture mode, outputs of a color signal subjected to noise reduction and a luminance signal are always made to match with respect to a time base.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to devices for recording and reproducing video signals, such as video tape recorders and video disc players, and particularly to a technique for removing noise from color signals thereof.

[Conventional technology]

Figure 4 shows how to remove noise components superimposed on the video signal.
FIG. 2 is a block configuration diagram of a digital noise reduction circuit in the time axis direction using a frame memory in a video signal recording and reproducing device. In the figure, 20 is a multiplier that multiplies input digital data by K. However, K is O<K
is a constant of <1. A frame memory 19 delays input data by one frame and outputs the delayed data. A subtracter 13 subtracts the output of the frame memory 19 from the input signal data. 14 is the same (a subtracter, which subtracts the output of the multiplier 20 from the input signal data.

The above circuits 13, 14, 19, and 20 constitute a digital noise reduction circuit in the time axis direction.

Writing the transfer function of the second circuit, H(Z)=(1-/(
1-KZ-'), and it can be seen that it operates as a low-pass filter in the time axis direction.

Such a digital filter in the time axis direction has an excellent effect of removing noise in still images, but causes blurring in images in moving images. For this reason, there is a method of changing the gain of the multiplier 20 in the range of O≦K<1 according to the movement (details will be described later).

Here, using FIG. 5 and FIG. 6, the above noise reduction circuit is applied to a video tape recorder (hereinafter, VTR
The actual operation will be explained when applied to the noise removal of color signals in the reproduction system of (referred to as ). It is assumed that this VTR records and reproduces a color signal line sequential time-division color TV signal (hereinafter referred to as TCI signal). Regarding this TCI signal, please refer to Chapter 5, 2 of ``Image Digital Signal Processing (written by Takahiko Fukinuki; published by Nikkan Kogyo Shimbun).
．． Since it is well known including pages 360 to 61, detailed explanation will be omitted.

In FIG. 5, 1 is a magnetic tape which is a recording medium. 2a and 2b are rotary heads for recording and reproducing signals;
3 is a head amplifier, 4 is an FM demodulation circuit that demodulates the FM signal to be reproduced, 5 is an A/D converter that performs A/D conversion, 6
is a field memory that performs time axis correction on the TCI signal, 7
separates a luminance signal and a color difference signal from the TCI signal output from the field memory 6, performs time axis expansion on each, and restores the restored luminance signal Y and line sequential signal to the original length of one horizontal scanning period. Reproduction signal processing circuit that outputs (RY)/(B-Y), 21 is line sequential color signal (R-Y)
9 is a digital noise reduction circuit in the time axis direction that reduces the noise component of (B-y), and 9 is a line-sequential color signal (
Color difference signal (RY), (B-Y) from (RY)/(B-Y)
-Y) vertical interpolator, loa, 10b, 10
c is D/A that converts digital data to analog data
It is a converter.

Further, FIG. 6 shows the configuration of the noise reduction circuit of FIG. 5. In the figure, 16 is a switch, and the configuration is such that no input signal is input to the noise reduction circuit 21 when it is off.

Further, 15 is a ROM. A control circuit 22 controls the switch 16 from frame pulses, vertical synchronization signals, and still image mode signals. 13 and 14 are the subtracters shown in FIG. 4, and 19 is the same frame memory as shown in FIG. 4, so a detailed explanation will be omitted.

Here, the line-sequential color signal output from the reproduced signal processing circuit 7 in FIG. 5 is input to the noise reduction circuit 21. The switch 16 in FIG. 6 is o when the VTR is in normal playback mode.
It is in state n. Input line sequential color signal (R-Y)/
(B-Y) is Xl, the noise-reduced output signal is Yi
, the output of one frame before that, that is, the output of the frame memory 19, is Y, -2, then the configuration of FIG. 6 is y=
=x.

It can be expressed as -K. (Xi-Yi,). However, i is a field number. When recording a video, in order to prevent temporal blurring, it is determined according to the movement, that is, according to the value of Xl-Y, ~2 (if the value of X i Y i -1 is large, it is determined that it is a video), It is necessary to change K. (X, ~Y=-z). If we set this as f (Xi -Yi-2), the configuration in Fig. 6 is Y, -X, -f (X,
Yi-z) Tonal. Kono function f (X, −Yi
-2 is set in the ROM 15 in FIG.

Regarding this noise reduction circuit in the time axis direction, please refer to the article 7 of the above-mentioned document "Digital signal processing of images".
Since it is well known including chapters 3.3P, 115-P, and 117, a detailed explanation will be omitted.

The output signal Y8 whose noise has been reduced in this way, that is, the line sequential color signal (R-Y)/(B-Y) is input to the vertical interpolation circuit 9 in FIG. ,B-
The signal is converted into analog data by the D/A converters lOb and IOC, and output as a noise-reduced color difference signal.

Here, the operation of the noise reduction circuit when the VTR shifts from the normal reproduction mode to the still image mode will be explained using the time chart shown in FIG.

In FIG. 7, D represents the TCI signal written into the field memory, and C represents the line sequential color signal (R-Y)/
(B-y) data, Y indicates luminance signal data, and i indicates a field number.

Further, the vertical synchronizing signal a is a vertical synchronizing signal separated from the reproduced video signal, and the frame pulse e is generated inside the VTR, and serves as a reading reference for the field memory 6 shown in FIG.

First, when the VTR shifts from the normal reproduction mode to the still picture mode, the still picture mode signal changes from "L" to "H". This is latched in the control circuit 22 of FIG. 6 at the rising edge of the vertical synchronizing signal a, and becomes the still image mode signal C. This still image mode signal C
By changing from “L” to “H” (at time t□)
, the writing of the main field memory 6 in FIG. 5 is 5T.
Open. Next, after the still image mode signal C becomes H'', the control circuit 22 detects the rise or fall of the first frame pulse e, and the switch 16 in FIG. 6 is turned off.
f, and the input data is output from the ROM 15 as is (at the time of tsz).

Therefore, no data is input to the noise reduction circuit 21 from the time of Lsl, and the frame memory 19
The read data m becomes the output data of the noise reduction circuit 21. Here, from the time ts, the output P of the noise reduction circuit 21 is C,,C,,C,-
,,C,,... data are repeated, but the data of the luminance signal Y is Y.

is always being output from the reproduced signal processing circuit of FIG. 5 from time t.

In other words, the output of the luminance signal Y repeats the information of the same field, but the output of the color difference signals R-Y and B-Y repeats the information of the same field as the luminance signal and the information of the previous field on a field-by-field basis. It is.

[Problem to be solved by the invention]

In a conventional video signal recording and reproducing device that employs a digital noise reduction circuit that uses a frame memory to remove noise from color signals, in still image mode, there is a mismatch between the color signal and the luminance signal on the time axis for each field. This caused problems such as brightness and color shifts occurring in moving images.

This invention was made in order to solve the above-mentioned problems, and allows the video signal recording and reproducing device to always output the noise-reduced color signal and luminance signal to match on the time axis even in still image mode. The object of the present invention is to obtain a video signal recording and reproducing device that can perform the following functions.

[Means to solve the problem]

In the video signal recording and reproducing apparatus according to the present invention, the writing operation of the frame memory of the digital noise reduction circuit is controlled so that the noise-reduced color signal is always output in agreement with the luminance signal on the time axis. This is what I did.

[Effect]

In a video signal recording and reproducing device incorporating a digital noise reduction circuit using a frame memory configured as described above, the noise-reduced color signal is always combined with the luminance signal with respect to the time axis, both in still image mode and during normal playback. It is possible to output a match.

〔Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a video signal recording and reproducing apparatus according to an embodiment of the present invention, in which a VT incorporating a noise reduction circuit records and reproduces a color signal line sequential time-division color TV signal.
The sonoflock configuration is shown using the R regeneration system as an example.

In the figure, 8 is a noise reduction circuit employed in this embodiment. 1 to 7 and 9.10 are the same as those in the conventional example shown in FIG. 5, so the same reference numerals are given and detailed explanation thereof will be omitted.

Further, FIG. 2 is a block diagram showing the configuration of a noise reduction circuit in an embodiment of the present invention, and in the figure, 11.
12 is a field memory, and 13 is a subtracter, which subtracts the input signal data by data delayed by one frame by the above two field memories. 15 is ROM,
Similar to the conventional example, a functional form for the output of the subtracter is set. A subtracter 14 subtracts the output of the ROM 15 from the human input signal data. 16 and 17 are switches. When the switch 16 is on, the input signal data is transmitted to the noise reduction circuit 8, and when it is off, it is not transmitted. When the switch 17 is on, the data read from the field memory 11 is written into the field memory 12, and when it is off, the data is written in steps. Further, 18 is a control circuit that controls the switches 14 and 15 using a still image mode signal and a frame pulse.

Next, the actual operation will be explained using the time charts of FIGS. 1, 2, and 3.

As in the conventional example, in FIG. 3, D represents the TCI signal written in the field memory, C represents the line sequential color signal (R-Y)/(B-Y) data, and Y represents the luminance signal data. , i indicates the field number.

Also, as in the conventional example, the vertical synchronizing signal a is a vertical synchronizing signal separated from the reproduced video signal, and the frame pulse e
is generated inside the VTR and serves as a reading reference for the field memory 6 in FIG.

First, when the VTR shifts from normal playback to still image mode,
The still picture mode signal changes from "L11" to "HI+". This signal is latched in the control circuit 18 of FIG. 2 by the rising edge of the vertical synchronizing signal a, and becomes the still picture mode signal C.

In the control circuit 18 of FIG. 2, the still picture mode signal C is "'L".
” to “H”, the first rising edge or falling edge (at 1+) of the frame pulse e is detected, the switch 16 in FIG. 2 is turned off, and the line sequential color signal (R The transmission of the input signal data of -Y)/(B-Y) to the noise reduction circuit 8 is stopped.At the same time, the input data is outputted as is from the ROM 15 in FIG.

Therefore, the read data m from the field memory 12 is outputted from the noise reduction circuit 8 as is.

Subsequently, the control circuit 18 detects the second rising or falling edge of the frame pulse e (that is, at time t2), turns off the switch 17 shown in FIG. 2, and stops the write operation of the field memory 12. ,
From the time t2 onwards, the field memory 12 always continues to read data C0), and from the noise reduction circuit 8, the input data to the noise reduction circuit 8 is cut off at the time t, and the functional form of the ROM 15 is read out. is set so that the input data is output as it is, so data C,(n) continues to be output at all times.

Here, the still image mode signal 2C changes from "L" to "."

After changing to "H", that is, from the time of to, the write operation of the main field memory 6 in FIG. 1 is 5TOPL.
, the data of the luminance signal Y from the reproduced signal processing circuit 7 is Yi
(n) continues to be output.

Therefore, from the time when the still image mode signal 2C changes from "L" to H, that is, one frame after the time to, the noise-reduced line-sequential color signal matches the luminance signal for each field. The resulting data is output from the noise reduction circuit 1.8.

This line-sequential color signal (RY)/(B-Y) is converted into color signals RY and BY by the vertical interpolation circuit 9 in FIG.

Then, along with the luminance signal, the D/A converter 10a in FIG.
Y which is analog data by 10b 10c
, RY, and B-Y, and a still image is obtained using the luminance signal and the color signal, which matches the time axis for each field and has noise reduced.

[Effects of the Invention] As described above, according to the video signal recording and reproducing apparatus according to the present invention, the frame memory of the color signal digital noise reduction circuit is composed of two field memories, and one of the field memories is used during still image reproduction. Since the writing operation of the field memory is controlled, the luminance signal and the color signal always match on the time axis, and a still image of the color signal with noise reduction can be output.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a VTR playback system according to an embodiment of the invention, FIG. 2 is a block diagram showing the configuration of a digital noise reduction circuit in the time axis direction according to an embodiment of the invention, and FIG. A time chart diagram showing the actual operation of an embodiment of the present invention; FIG. 4 is a configuration diagram showing the principle of a digital noise reduction circuit in the time axis direction;
Figure 5 is a block diagram of a conventional VTR playback system, Figure 6 is a block diagram showing the configuration of a conventional digital noise reduction circuit in the time axis direction, and Figure 7 is a block diagram of a conventional digital noise reduction circuit in the time axis direction. FIG. 3 is a time chart diagram showing an operation when transitioning to a still image mode. In the figure, 11.12 is a field memory that constitutes a frame memory, 13.14 is a subtracter, 15 is a ROM,
16 and 17 are switches, and 18 is a control circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a video recording and reproducing apparatus that includes a noise reduction means that reduces noise in a color signal using a digital filter using a frame memory during reproduction, and a mode switching means that can switch from normal reproduction mode to still image mode, The frame memory is composed of two field memories, and after receiving a still image mode signal when switching to the still image mode from the mode switching means, writing in one of the two field memories is performed with reference to the frame pulse. 1. A video signal recording and reproducing apparatus, comprising a control means for stopping said field memory, and for reducing noise in a color signal using the output of said one field memory.