JPH05145949A - Drop-out compensator - Google Patents

Abstract

PURPOSE:To execute drop-out compensation to reduce image distortion by executing line interpolation in a moving image and executing frame interpolation in a still picture concerning the drop-out part of an input video signal based on the discriminated result of the moving image/still picture. CONSTITUTION:A drop-out signal RF-DOP from a drop-out detection circuit 13 is supplied to a reproducing PLL circuit 14, and a drop-out signal DOP is outputted. An adder 18 adds a moving image/still picture discriminating signal D/P and the signal DOP and further, the added output is added to the end of a TDM signal by an adder 6 and supplied to a frame memory 7. The TDM signal processed in the memory 7 is supplied to a decoder 8, and a time- base compressed source digital luminance signal Y and a time-base extended source line sequentiality chrominance signal C are outputted. Then, the respective signals are supplied to line interpolation drop-out compensation circuits 9 and 10, and drop-out compensation is executed. Thus, the drop-out compensation can be executed so as to reduce the image distortion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dropout compensator suitable for use in a VTR for high definition video signals (television signals).

[0002]

2. Description of the Related Art In a conventional dropout compensation device provided in a VTR reproduction system, a reproduced video signal, that is,
When the input video signal has a dropout, the dropout portion is interpolated using the corresponding portion of the video signal one frame period before the input video signal (frame interpolation), There is a case where interpolation is performed using the corresponding portion of the video signal before the line period (line interpolation).

[0003]

[Problems to be Solved by the Invention]

The dropout compensating apparatus for performing frame interpolation is preferable when the image of the input video signal is a still image because there is no image shift based on the position shift on the screen, but in the case of a moving image, it is based on the time shift. This is not preferable because the image shift is large.

A dropout compensating device for performing line interpolation is preferable when the image of the input video signal is a moving image because the image shift due to time shift is small, but in the case of a still image, the position shift on the screen is preferable. This is not preferable because the image shift based on the is remarkable.

In view of the above point, the present invention provides a dropout compensating device capable of performing dropout compensation so that the image shift is reduced regardless of whether the image of the input video signal is a moving image or a still image. Is to be proposed.

[0007]

SUMMARY OF THE INVENTION According to the present invention, when an input video signal has a dropout, the dropout portion corresponds to a video signal having a time difference of one or a plurality of frame periods of the input video signal. First dropout compensating means 5 and 7 for interpolating by using a portion and an image having a dropout in the input video signal when there is a dropout in the input video signal. The second dropout compensating means 9 and 10 for interpolating using the corresponding portions of the signals are compared with the input video signal and the video signal having a time difference of one or a plurality of frame periods of the input video signal, and the input video signal is compared. And the moving image / still image determining means 16 and 17 for determining whether the image is a moving image or a still image.

Then, the moving image / still image discrimination means 16 and 17
The presence / absence of the dropout compensation operation in the first and second dropout compensation means 5, 7; 9, 10 is controlled based on the discrimination output from the moving image / still image discrimination means 16,
When it is determined by 17 that the input video signal is a still image, the dropout portion of the input video signal is interpolated with the corresponding portion of the video signal having a time difference of one or a plurality of frame periods of the input video signal, When it is determined that the input video signal is a moving image, the dropout portion of the input video signal is interpolated with the corresponding portion of the video signal having a time difference of one or a plurality of line periods of the input video signal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a dropout compensating device to which the present invention is applied to a high definition video signal (television signal) VTR will be described in detail below. Figure 1 shows this V
1 shows a reproduction system including a TR dropout compensation device. FIG. 2 shows a timing chart for explaining the operation of the circuit of FIG. FIG. 3 shows a specific circuit of the line interpolation dropout compensation circuit for the luminance signal in the dropout compensation device of FIG. FIG. 4 shows a timing chart for explaining the operation of the circuit of FIG. FIG. 5 shows the recording system of the VTR. FIG. 6 shows a tape guide drum device of a VTR. FIG. 7 shows a recording pattern of the magnetic tape.

[Recording Method] The recording method of this VTR is such that after the first and second color signals of the color image signal composed of the luminance signal and the first and second color signals are line-sequential and time-axis compressed. , A color line sequential TDM signal (time division multiplex signal) obtained by multiplexing this with a luminance signal is approximately doubled in time axis and divided into two channel signals, and the two channel signals 1 field of 2 is recorded by scanning twice (three times is also possible) so that two pairs, that is, four inclined tracks are formed.

This color-line-sequential TDM signal signal is a high-definition signal in which one frame consists of 1125 scanning lines.
The effective line of the first feed is from the 40th line to the 557th line.
Up to the line, the effective lines of the second feed are from the 603rd line to the 1120th line.

[Recording System] (FIGS. 5 to 7) FIG. 5 shows a recording system, which will be described below. The luminance signal and the line-sequential color signal from the input terminals 32 and 33 are supplied to the A / D converters 34 and 35, respectively, and then digitized, and then supplied to the encoder 36, and the time axis is expanded to approximately twice. It is converted into a 2-channel digital color line sequential TDM signal. The 2-channel digital TDM signals are supplied to the 2-channel frame memories 37 and shuffled. The 2-channel digital TDM signals are respectively supplied to 2-channel adders 39 through 2-channel horizontal non-linear emphasis circuits 38, and the horizontal and vertical synchronization signals, burst signals and A type code signal representing the first and second colors of the color signal for each horizontal period and other necessary synchronization signals are added. The 2-channel digital TDM signal from the adder 39 is supplied to the 2-channel D / A converter 41, converted into the analog TDM signal, and then supplied to the 2-channel FM modulator 42. And is FM-modulated. 2 channel FM modulated T
The DM signal passes through a 2-channel recording amplifier (not shown), and a 2-channel rotary magnetic head (see FIG. 6).
(Refer to FIG. 2) for each channel (A and B channels) and recorded on the magnetic tape so that two inclined tracks are formed at the same time.

FIG. 6 shows a magnetic tape guide drum device.
This is a pair of A-channel recording / reproducing rotary magnetic heads H1 having the same azimuth magnetic gap on the rotary drum RD.
A and H2A are attached with an angular interval of 180 degrees, and a pair of rotary magnetic heads H1A and H1A, respectively.
A pair of B channel recording / reproducing rotary magnetic heads H1B having the same azimuth of the magnetic gap so as to be close to H2A,
H2B is attached with an angular interval of 180 degrees, and the azimuth of the magnetic gap of the pair of rotary magnetic heads H1A and H2A and another pair of rotary magnetic heads H.
The azimuths of the magnetic gaps of 1B and H2B are made different from each other. A recording pattern is shown in FIG. 7, and the FM-modulated TDM signal for one frame is magnetically formed by two pairs of rotary magnetic heads H1A, H1B; H2A, H2B to form four segments, that is, eight inclined tracks. Recorded on tape. The recording pattern of each segment SEG1 to 4 is composed of a video signal (FM modulated TDM signal) of 136H and a preamble of 3H (note that H is H).
Indicates the horizontal period).

In the video signal, the frame indicates the line number and the color signal (red difference signal R and blue difference signal B) of the luminance signal Y in the line signal, and the line signal is displayed on eight adjacent inclined tracks. The recording positions are aligned. In addition, the video signals of four consecutive lines are adjacent to each other.
They are recorded side by side on the slanted track of the book. In the preamble, R is a ramp signal, VL is a segment synchronization signal, CW is a CW signal, and X is an X signal.

[Reproduction System Including Dropout Compensation Device] (FIGS. 1 and 2) FIG. 1 shows a reproduction system including a dropout compensation device, which is a reproduction FM-modulated TD reproduced from the rotary magnetic head in FIG.
The M signal is supplied from a pair of input terminals 1 to a 2-channel FM demodulator 2 and a dropout detection circuit 13 through a 2-channel regenerative amplifier (not shown). The 2-channel reproduction TDM signal is demodulated by the 2-channel FM demodulator 2 and then supplied to the 2-channel A / D converter 3 to be converted into a digital signal, and the 2-channel reproduction PLL circuit is also provided. (Playback synchronization generator) 14 is supplied. The 2-channel digital TDM signal is supplied to one fixed contact of the 2-channel changeover switch 5 through the 2-channel horizontal non-linear de-emphasis circuit 4. The 2-channel switching output from the movable contact of the change-over switch 5 is supplied to the 2-channel 3-port frame memory 7 through the 2-channel adder 6, respectively, and subjected to deshuffling and time axis error correction, and then the decoder 8 Is delayed by one frame period,
It is supplied to the other fixed contact of the changeover switch 5 without being subjected to deshuffling and time axis error correction.

The two-channel digital TDM signal from the horizontal non-linear de-emphasis circuit 4 and the two-channel digital TDM signal delayed by one frame period from the two-channel frame memory 7 are supplied to the two-channel subtractor 15, respectively. The latter is supplied and the latter (synchronized with the former) is subtracted from the former, and the absolute value of the subtracted output is supplied to the 2-channel difference counter 16 and integrated. The 2-channel integrated value data from the counter 16 is supplied to a 2-channel moving image / still image discrimination circuit 17 and compared with a reference value, respectively. And the moving image / still image determination signal obtained therefrom is supplied to the two-channel adder 18. It should be noted that the difference counter 16 and the discrimination circuit 1 for each of the two channels are provided.
7 is reset by a horizontal synchronization signal PB-H from a 2-channel reproduction PLL circuit (reproduction synchronization generator) 14, and a counter 16 drops a dropout signal DO.
By P, the integration operation by counting is stopped during the dropout period.

The dropout signal RF-DOP from the dropout detection circuit 13 is supplied to the reproduction PLL circuit 14 and is synchronized with the synchronization signal.
P is output. And a two-channel adder 18
, 2 channel video / still image discrimination signal D /
P and the dropout signal DOP are added, and the added output is supplied to a 2-channel adder 6 and added to the end of each line signal of the digital TDM signal from the changeover switch 5, and then a 2-channel frame memory 7
Is supplied to.

The deshuffling and time-axis error-corrected digital TDM signal from the frame memory 7 is supplied to a decoder 8 where it is decoded and time-axis compressed to obtain the original digital luminance signal Y and time-axis expanded original signal. The line-sequential color signal C is output and supplied to the line interpolation dropout compensation circuits 9 and 10 to be dropout-compensated. Then, the dropout-compensated digital luminance signal Y and digital color signal C are output to the output terminals 11 and 12.

Next, the operation of dropout compensation by frame interpolation will be described with reference to FIG. For every 4 lines in the video signal (TDM signal) of the nth frame ...
..., m, m + 4, m + 8, m + 12, m + 16, m + 2
0 ………………………………………………………………………………………………………………………………………………………………………
It is assumed that the line signals of the +8 line and the m + 20 line have dropouts. Therefore, a high frequency dropout signal RF-DOP is generated from the dropout detector 13 corresponding to the dropout portion, and the reproduction PL
The horizontal synchronizing signal PB-H and the dropout signal DOP separated from the line signal of each line are generated from L14.

Then, the video signal of the nth frame (TDM
Signal) every 4 lines in m, m + 4, m
+8, m + 12, m + 16, m + 20, ······················································································. For each line
..., m, m + 4, m + 8, m + 12, m + 16, m
+20, ... m + 8 of the line signal of the line
Interpolation, that is, replacement at each corresponding portion of the line signal of the line and the line signal of m + 20 line, the dropout-compensated video signal of the nth frame is obtained. The difference counter 16 and the moving image / still image discriminating circuit 17 are reset for each reproduction horizontal synchronizing signal PB-H, and also have a dropout signal DOP (having a slightly longer time width than the time width of the actual dropout portion). ) Period, counter 1
The count of 6, that is, the integration operation is stopped. In addition, video /
The still image discrimination signal D / S is a signal obtained by latching the integrated output of the difference counter 16 at the timing of each horizontal cycle,
It is "1" only when distinguishing moving images, and "0" when distinguishing still images.
The signal is

[Line Interpolation Dropout Compensation Circuit for Luminance Signal]
(FIGS. 3 and 4) FIG. 3 shows a line interpolation dropout compensation circuit for a luminance signal, which will be described below. Since the inter-line interpolation dropout compensation circuit 10 for color signals has the same configuration as the inter-line interpolation dropout compensation circuit 9 for luminance signals, the description thereof will be omitted. The luminance signal from the input terminal 21 is supplied to another 1-line memory 23 through the 1-line memory 22 as a delay element. Adder 24
In, the luminance signal from the input terminal 21 and the luminance signal from the 1-line memory 23 delayed for one line period are added. The luminance signal from the memory 22 and the level of the added luminance signal from the adder 24 are supplied to the 1/2 multiplier 25, and the luminance signal whose level has been halved is fixed to each of the changeover switches 26. It is supplied to the contact and switched.
The movable contact is connected to the output terminal 27.

The luminance signal from the memory 22 is supplied to the moving picture / still picture discrimination signal D / S and the dropout signal DOP separating circuit 28, and the moving picture / still picture discrimination signal D / S and the drop for each line are supplied. The out signal DOP is separated. The separated moving image / still image discrimination signal D / S is supplied to the latch circuit 29, and the dropout signal DOP is directly supplied to the AND gate 30, and the logical product output thereof is supplied to the changeover switch 26 as a switching signal.

Next, the operation of the dropout compensation circuit will be described with reference to FIG. Line signals for each line of the luminance signal of n frames supplied to the input terminal 21 ... Ym, Ym + 1, Ym + 2, Ym + 3, Y
It is assumed that, of m + 4, Ym + 5, ..., For example, part of the line signals Ym + 2 and Ym + 5 have already been dropout-compensated by frame interpolation.

Then, the luminance signal read from the memory 22 is applied to one fixed contact of the changeover switch 26, and the luminance signal of n frames and the luminance signal thereof are applied to the other fixed contact of the changeover switch 26 by the adder 24 and the 1/2 multiplier 25. And the line interpolation luminance signal obtained by averaging the signal delayed by 1H are supplied to the switch 26. And the changeover switch 2
6 is normally switched to the line memory 22 side, and the pulse of the moving image / still image determination signal D / S at the time of moving image is latched by the latch circuit 2
When the dropout signal DOP is obtained during the period in which the latch output is latched at 9, and the latch output is "1", the output of the AND gate 30 becomes "1" and the changeover switch 26 causes the coefficient multiplication. The portion of the line signal Ym + 2 that has been subjected to the frame interpolation dropout compensation by switching to the device 25 side corresponds to the line signal {(Ym + 1) + (Ym + 3)} / 2 of the line interpolation luminance signal. Then, the luminance signal of the n frames, which has been subjected to the re-interpolation in step (1) and is subjected to the dropout compensation by the line interpolation, is obtained.

The above-described frame interpolation and line interpolation can also be performed by interpolation of signals of adjacent frames or lines themselves or signals of adjacent frames or lines by arithmetically averaged signals.

In the above-described embodiment, when there is a dropout in the video signal, frame interpolation is performed regardless of whether the image is a moving image or a still image, and thereafter, frame interpolation is performed only in the case of a moving image. The line-interpolated portion is re-interpolated, but line-interpolation is performed regardless of whether the image is a moving image or a still image.After that, only in the case of a still image, the line-interpolated portion is re-framed. Interpolation may be performed, or only line interpolation and frame interpolation may be performed depending on whether the image is a moving image or a still image.

In the above-described embodiment, whether or not the line interpolation is performed is determined depending on whether the image one line before the line signal in which the dropout has occurred is a moving image or a still image. , May be performed depending on whether the image of one line or several lines before and after is a moving image or a still image.

Further, in the above-described embodiment, it is determined whether to perform the line interpolation or the frame interpolation depending on whether the image of the line signal in the vicinity of the line signal in which the dropout has occurred is a moving image or a still image. Although it was performed (suitable for dropout compensation of high definition video signals), in the case of dropout compensation of low definition video signals, the entire image of the frame in which the dropout occurred is a moving image or is still. You may go depending on whether it is a picture.

[0029]

According to the present invention described above, it is possible to perform dropout compensation so as to reduce the image shift regardless of whether the image of the input video signal is a moving image or a still image. The device can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a reproduction system of a VTR as an embodiment of the present invention.

FIG. 2 is a timing chart used to explain the operation of the embodiment of FIG.

FIG. 3 is a block diagram showing a luminance signal line interpolation dropout compensation circuit according to the embodiment of FIG. 1;

FIG. 4 is a timing chart used to explain the operation of the dropout compensation circuit of FIG.

FIG. 5 is a block diagram showing a recording system of a VTR.

FIG. 6 is a diagram showing a tape guide drum device of a VTR.

FIG. 7 is a block diagram showing a recording pattern on a magnetic tape.

[Explanation of symbols]

 2 FM demodulator 3 A / D converter 5 selector switch 6 adder 7 frame memory 8 decoder 9 luminance signal line interpolation dropout compensation circuit 10 color signal line interpolation dropout compensation circuit 18 adder 22 line memory 23 line memory 24 Adder 25 1/2 Multiplier 26 Changeover Switch 28 Separation Circuit 29 Latch Circuit 30 AND Gate

Claims (1)

[Claims] 1. When there is a dropout in the input video signal, the dropout portion is replaced by 1 of the input video signal.
Alternatively, a first dropout compensating means for interpolating by using a corresponding portion of the video signal having a time difference of a plurality of frame periods, and when the input video signal has a dropout, the dropout portion is Second dropout compensation means for interpolating using corresponding portions of the video signal having a time difference of one or a plurality of line periods; and the input video signal and a video signal having a time difference of one or a plurality of frame periods of the input video signal. And a moving image / still image discriminating means for judging whether the image of the input video signal is a moving image or a still image for comparison, and based on the discrimination output from the moving image / still image discriminating means, The presence / absence of dropout compensation operation in the first and second dropout compensation means is controlled, and the input video signal is stopped by the moving image / still image determination means. If it is determined that the input video signal is a moving image, the dropout portion of the input video signal is interpolated with the corresponding portion of the video signal having a time difference of one or a plurality of frame periods of the input video signal. If it is determined that the dropout portion of the input video signal is interpolated with a corresponding portion of the video signal having a time difference of one or a plurality of line periods of the input video signal. Compensation device.