JPH0723342A - Device for reproducing video signal - Google Patents

Abstract

PURPOSE:To prevent the resolution in the vertical direction from being deteriorated even in a slow reproducing mode by extracting respective vertical high band signals from brightness signals in fields obtained before and after an interpolation field brightness signal and adding the extracted signals to the original brightness signal. CONSTITUTION:A brightness signal Y obtained by Y/C separation is applied to a scanning line conversion circuit 20 and the signal Y in an interpolation field is interpolated by scanning line conversion. The signal Y in a reproducing field can also be obtained from the circuit 20 but its signal processing is not executed. The circuit 20 has a pair of HPFs 21, 23 and an LPF 22 for the vertical direction and their filter outputs are synthesized by a synthesizer 24. The processing of the LPF 22 is applied to the signal Y in a current field, so that low pass characteristics in the vertical direction are applied. The processing of the HPFs 21, 23 is applied to the signals Y in the fields before and after the interpolating field, so that high pass characteristics in the vertical direction are applied. The signal Y in the interpolation field which is outputted from the synthesizer 24 is supplied to a switch 25 together with the reproducing field signal Y.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can prevent resolution deterioration in the vertical direction when reproducing in slow mode.
The present invention relates to a video signal reproducing apparatus suitable for application to a TR reproducing system or the like.

[0002]

2. Description of the Related Art When a VTR is set to a slow playback mode and a playback video is played back in slow motion, a video signal for slow playback is generated by repeatedly using a video signal of the same field that is normally played back.

FIG. 7 shows a typical circuit configuration (reproduction device 10) used at that time, and a reproduced video signal is supplied to a terminal 1. The VTR used is an analog VT
It may be either R or a digital VTR such as a D1 or D2 type. In this example, a digital VTR is used for convenience of explanation.
The case of using will be described.

As the reproduced video signal in the slow reproduction mode, the video signal of the same field is repeatedly reproduced and output according to the variable speed. The reproduced video signal is supplied to the Y / C separation circuit 2 and separated into a luminance signal Y and a color signal C, and the luminance signal Y is supplied to the scanning line conversion circuit 3 to generate a video signal of the second field (interpolation field). Generated by scan line interpolation. When the reproduced video signal is an odd field, the interpolated field is an even field.

The color signal C is supplied to the phase conversion circuit 4,
The color subcarriers of the same field are converted to the color subcarrier phase corresponding to the interpolated field so that the phases are continuous.

The luminance signal Y of the frame structure interpolated by the scanning line and the color signal C whose phase is converted so as to correspond to the luminance signal Y are again synthesized by the synthesizer 5, and then the mode changeover switch 6 is used.
And the reproduction video signal supplied to the terminal 1 is switched. In the normal playback mode (1 × speed), the playback video signal (playback field) on the terminal 1 side is selected and
In slow reproduction modes other than double speed, the interpolated video signal (interpolation field) output from the synthesizer 5 side is selected. A mode switching signal is supplied to the terminal 7.

[0007]

In the reproducing apparatus 10 as shown in FIG. 7, the video signal of the field different from the reproduction field at the slow reproduction is generated by using the video signal of the reproduction field as described above. To be done. The scanning line interpolation processing in this case is usually mainly performed by average value interpolation using upper and lower scanning lines (see FIG. 2) and filter processing including upper and lower scanning lines.

Since such scanning line interpolation processing uses upper and lower scanning lines, the resolution in the vertical direction is reduced to 1/2. When the normal vertical resolution is 480 TV lines, it is reduced to 240 TV lines. The slow playback mode sacrifices such vertical resolution degradation.

In the conventional interpolation processing, the resolution of the reproduction field (480 TV lines) and the resolution of the interpolation field (24
(0 TV book) has a large difference, so it will naturally be an unnatural image.

Therefore, the present invention solves such a conventional problem, and proposes a video signal reproducing apparatus in which the vertical resolution is not deteriorated even in the slow reproduction mode.

[0011]

In order to solve the above problems, in the invention described in claim 1, a luminance signal separated from a reproduced video signal is supplied to the scanning line conversion circuit in the slow reproduction mode. In this scanning line conversion circuit, the luminance signal of the reproduced field is output as it is, and in the field to be interpolated, of the luminance signals separated from the reproduced video signal, the vertical scanning direction is applied to the field. The low-pass filter characteristic is added to the above, and the high-pass filter characteristic is added to the preceding and following fields in the vertical scanning direction, so that the high-resolution luminance signal for slow reproduction is output from this scanning line conversion circuit. It is characterized by what has been done.

In the invention described in claim 6, Y / C separation means for separating the input video signal into a luminance signal and a color signal, a scanning line conversion circuit to which the separated luminance signal is supplied, and the color It is characterized by comprising a phase conversion circuit for adjusting the phase of a signal in field units, and a combiner for combining the scanning line converted luminance signal and the phase converted color signal. .

[0013]

The operation of only the invention described in claim 1 will be described with reference to FIG. 1. In the reproduction field, the video signal of the reproduction field is output from the low-pass filter 22 provided in the scanning line conversion circuit 20. While it is used as it is, in the interpolation field, a low-pass filter characteristic (FIG. 3La) in the vertical scanning direction is given to the interpolation field in the luminance signal separated from the reproduced video signal by the low-pass filter 22. High-pass filters 21 and 23 provide high-pass filter characteristics (FIG. 3Lb) in the vertical scanning direction to the preceding and succeeding fields, and these filter outputs are combined and output as a luminance signal after interpolation.

As described above, with respect to the video signal (luminance signal) of the interpolation field, the luminance signal of the immediately preceding field,
When each vertical high frequency signal of the luminance signal of the field immediately after that is taken out and added to the luminance signal of the interpolation field, the filter characteristic of the interpolated luminance signal becomes as shown by the curve Lc in FIG. 3, and the high resolution ( It is possible to obtain a luminance signal of about 360 TV lines.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a case where an example of a video signal reproducing apparatus according to the present invention is applied to a reproducing system of a digital VTR will be described in detail with reference to the drawings. The television system of the video signal is the NTSC system.

The digital reproduction video signal obtained at the terminal 1 is separated into a luminance signal Y and a chrominance signal C by a Y / C separation circuit 2, and the chrominance signal C is phase-converted by a phase conversion circuit 4 in an interpolated field. The phase conversion is performed so as to be continuous, and then supplied to the combiner 5 as in the conventional case.

The Y / C separated luminance signal (digital signal) Y is read by the scanning line conversion circuit 20 from the reproduction field (usually an odd field) to the next field (even field, which is called an interpolation field). Luminance signals are interpolated by scanning line conversion. The luminance signal regarding the reproduction field is also obtained from the scanning line conversion circuit 20, but the signal processing in this case is output without any processing.

As shown in the figure, the scanning line conversion circuit 20 has a pair of high-pass filters 21 and 23 in the vertical direction and a low-pass filter 22 in the vertical direction, and their filter outputs are combined by a combiner 24.

The luminance signal in the interpolation field (luminance signal after interpolation) output from the synthesizer 24 is supplied to the changeover switch 25 together with the luminance signal in the reproduction field and selected in field units. In this case, as shown in FIG. 2, the luminance signal of the reproduction field is selected in the odd field, and the luminance signal of the interpolation field is selected in the even field. The selected luminance signal Y is combined with the color signal C by the combiner 5 as in the conventional case.

The processing of the low-pass filter 22 is performed on the luminance signal of the field (current field) to be interpolated, whereby the low-pass characteristic as shown by the curve La in FIG. 3 is given in the vertical direction (vertical scanning direction). The processing of the high-pass filters 21 and 23 is performed on the luminance signal in the field before and after the interpolation field, and thereby the high-pass characteristic as shown by the curve Lb in FIG. 3 is given in the vertical direction. Therefore, the overall filter characteristic in the vertical direction is as shown by the curve Lc in FIG. 3, and even in the interpolation field, the vertical resolution extends to about 360 TV lines.

FIG. 4 shows a specific example of the scanning line conversion circuit 20 described above. FIG. 4 shows a case where the scanning line conversion circuit 20 is configured by using a digital filter. The reproduction luminance signal supplied to the input terminal 28 is first supplied to the first high pass filter 21.

The first high-pass filter 21 has a pair of delay means (delay elements or the like are used) 211 and 21 connected in cascade having a delay time of 1H (H is a horizontal scanning period).
2, the luminance signals of the input and output stages are combined by the adder 217 via the corresponding coefficient multipliers 214, 215 and 216.

The multipliers of the coefficient units 214 to 216 are determined according to the filter characteristic (high-pass characteristic Lb) of FIG. 3, and an example thereof is shown in FIG. In FIG. 5, the horizontal direction is the field and the vertical direction is the vertical direction V in the field.
Indicates. A filter coefficient as shown in the figure is set for each line in the same field. Therefore, corresponding to FIG. 4, the coefficient of the coefficient unit 215 is 6/24, and the upper and lower coefficient units 214 and 216 are both -3/24. An amplifier can be used for the coefficient units 214 to 216. When an amplifier is used, the upper and lower coefficient units 214 and 216 are as shown in the figure.
Is an inverter configuration.

The reproduction luminance signal delayed by 2H obtains a delay time of approximately one field, so that the delay means 30 of 260H is used.
And the luminance signal supplied to the input terminal 28 is delayed by exactly one field and output.

This luminance signal delayed by one field is supplied to the low pass filter 22. Low pass filter 22
Has three delay means 221 to 223 connected in cascade having a delay time of 1H, and respective input / output signals are multiplied by a predetermined coefficient by corresponding coefficient units 224 to 227 and then combined by an adder 228. To be done. First-stage delay means 22
The luminance signal output from No. 1 is used as the luminance signal F1 in the reproduction field, and this is supplied to the changeover switch 25.

The coefficients of the low-pass filter 22 are selected so as to have the low-pass characteristic La shown in FIG. An example thereof is shown in FIG.

The low-pass filter 22 further causes 3H
The luminance signal delayed by the amount is further delayed by the delay means 31 of 260H.
Is supplied to the second high-pass filter 23 via. By providing the delay means 31, the luminance signal supplied to the input terminal 28 is delayed by 2 fields.

The luminance signal delayed by two fields is passed through the second high pass filter 23 to the high pass characteristic Lb shown in FIG.
Is added to the first high-pass filter 2
Since the configuration is the same as that of No. 1, the corresponding reference numerals are given and the description thereof is omitted. Therefore, the coefficient units 233, 23
The coefficients of 4,235 are the same as those of the first high pass filter 21 (see FIG. 5).

By such delay processing, the output relationship of each coefficient unit in FIG. 4 in the current field and the fields before and after the current field and the positional relationship of the filter coefficient (multiplier of coefficient unit) shown in FIG.

The output of the adder 236 is further supplied to the adder 24 and the respective filter outputs are combined, and the filter characteristic of the combined result is as shown by the curve Lc in FIG. Therefore, a high-resolution luminance signal (about 360 TV lines) can be obtained even in the interpolation field.

This is because with respect to the luminance signal of the interpolation field, the luminance signal of the field immediately before that and the vertical high frequency signals of the luminance signal of the field immediately after that are extracted and added to the luminance signal of the interpolation field. .

The resolution of the luminance signal F2 in the interpolation field output from the adder 24 is 3 as shown in FIG.
It is about 60 TV lines, which is a great improvement over the conventional one, and the resolution of the luminance signal F1 in the reproduction field (480
The image quality of the slow image is improved by reducing the difference with the TV book).

When the luminance signal F1 of the reproduction field is output from the connection point p as shown in FIG. 4, the line marked with "x" in the current field in FIG. 5 becomes the interpolation position in the interpolation field.

To improve the resolution in the interpolation field, it is only necessary to approximate the filter characteristics shown in FIG. 3, so the filter coefficient shown in FIG. 5 is an example, and other filter coefficients may be adopted. Good. In the example in the figure, the resolution in the interpolation field is about 360 TV lines, but this value is also an example and is not limited to this value, so a filter coefficient is appropriately selected according to the resolution to be obtained. It is possible. Therefore, the filter coefficient as shown in FIG. 6 can be adopted. When this filter coefficient is adopted, the number of delay means used is reduced by that much, so that the filter structure can be simplified.

When the present invention is applied to an analog VTR, if the separated luminance signal Y is A / D converted and once digitized, the above-mentioned processing is performed, and after the interpolation processing, the analog signal is restored. Good.

[0036]

As described above, in the video signal reproducing apparatus according to the present invention, the vertical high range of the luminance signal of the field immediately before the luminance signal of the interpolation field and the vertical high range of the luminance signal of the field immediately after that. Since the signal is extracted and added to the luminance signal of the interpolation field, it has a feature that deterioration of the vertical resolution in the interpolation field can be significantly improved. Therefore, even in the slow reproduction mode, the difference in resolution between fields is reduced, and the image quality in the vertical direction can be significantly improved as compared with the conventional one, and a more natural slow image can be obtained.

Therefore, the present invention is extremely suitable when applied to a reproducing system of a VTR which intends to improve reproduced image quality.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a video signal reproducing apparatus according to the present invention.

FIG. 2 is a diagram showing an example of scanning line conversion.

FIG. 3 is a diagram showing an example of filter characteristics of a scanning line conversion circuit.

FIG. 4 is a system diagram showing a specific example of a scanning line conversion circuit.

FIG. 5 is a diagram showing filter coefficients.

FIG. 6 is a diagram showing filter coefficients.

FIG. 7 is a system diagram of a conventional video signal reproducing apparatus.

FIG. 8 is a diagram showing a conventional scanning line conversion process.

[Explanation of symbols]

 10 Video signal reproducing device 2 Y / C separation circuit 4 Phase conversion circuit 20 Scan line conversion circuit 21, 23 High-pass filter 22 Low-pass filter 25 Changeover switch

Claims (6)

[Claims] 1. In the slow reproduction mode, a luminance signal separated from a video signal reproduced in units of fields is supplied to a scanning line conversion circuit, and in this scanning line conversion circuit, the luminance signal of the reproduced field is unchanged. In the field to be output and interpolated, a low-pass filter characteristic is added in the vertical scanning direction to the interpolation field of the luminance signal separated from the reproduced video signal, and to the fields preceding and succeeding it is vertical. A high-pass filter characteristic is added in the scanning direction, and a high-resolution slow-playback luminance signal is interpolated and output from this scanning line conversion circuit and output. . 2. The scanning line conversion circuit includes a high-pass filter for high-passing a current luminance signal, a low-pass filter for low-passing a luminance signal delayed by almost 1 field, and a high-pass filter for high-passing a luminance signal delayed by almost 2 fields. And a synthesizer for synthesizing these outputs, the video signal reproducing apparatus according to claim 1. 3. The luminance signal corresponding to the reproduced field output from the delay means provided in the low pass filter and the interpolated luminance signal output from the synthesizer are selected in field units. A video signal reproducing device characterized by the above. 4. The low-pass filter according to claim 1, wherein the low-pass filter comprises three 1H delay means and a coefficient unit for multiplying respective input / output signals by a predetermined coefficient. Video signal playback device. 5. The high-pass filter according to claim 1, wherein the high-pass filter is composed of two 1H delay means and a coefficient unit for multiplying respective input / output signals by a predetermined coefficient. Video signal playback device. 6. A Y / C separation means for separating an input video signal into a luminance signal and a chrominance signal, a scanning line conversion circuit to which the separated luminance signal is supplied, and a phase of the chrominance signal is adjusted in units of fields. And a phase converter circuit that makes the phases thereof continuous within a frame, and a combiner that combines the scanning line converted luminance signal and the phase converted color signal. Video signal playback device.