JP2508419B2 - Video signal frame frequency converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a television signal format conversion device,
In particular, the present invention relates to an apparatus for converting a frame (field) frequency after the line number conversion processing.

[Outline of Invention]

In the frame frequency conversion device for a video signal according to the present invention, when outputting the image signal interpolated between the frames from the video signal to be converted by the interpolation filter, the first and second coefficients supplied to the interpolation filter are respectively It is set so as to continuously change for each predetermined number of fields. Therefore, it is possible to reduce the discomfort of the motion of the screen represented by the image signal between the frames output from the interpolation filter.

[Conventional technology]

NTSC, PAL, and SECAM are internationally adopted as standard television systems, and each system has its own characteristics.

Therefore, when exchanging programs internationally, a conversion device for converting the television signal system is required.

Also, the frame frequency differs depending on the difference in the standard system, and is roughly classified into a 525 line / 60 field system and a 625 line / 50 field system.

Among these, as a field frequency conversion method, for example, a television signal to be converted is displayed on a CRT,
There is a photoelectric conversion method that re-images the optical image with a TV camera that operates at the conversion field frequency, but this method demodulates the modulated signal and modulates this reproduced signal again, so the overall resolution is And the deterioration of gradation are involved.

Therefore, a method of electronically converting the field frequency has been developed and put into practical use.

FIG. 3 shows a conventional example of a field frequency conversion system (60 Hz → 50 Hz) by such an electronic system, where 1 is a frame memory, 2 and 3 are multipliers, 4 is a filter coefficient generator, and 5 is an adder. , 6 are field frequency converters for period conversion.

An embodiment of the conversion system using an interpolation filter (transversal filter) using the frame memory 1 is, for example, an interlaced scanning image of a high-definition television 1125/60 on a scanning line 625/6.
This is an example of converting the signal S1 line-converted into a progressive scan image of 0 to a field frequency of 625/50 Hertz. First, a digitized video signal is input to the frame memory 1 and 1 field is input from the input. Form a delayed signal S ₂ . Then, the signal S ₁ one field before is supplied to the multipliers 2 and 3, respectively. The multipliers 2 and 3 are respectively provided with filter coefficients K ₁ and K ₂ , for example, as shown in FIG. 4 (a), each field (1, 2,
Every 3, 4, 5) (0, 1.0) (0.2, 0.8) (0.4, 0.
6) Change to become (0.6, 0.4) (0.8, 0.2) 5
The coefficient value set for the type is supplied from the filter coefficient generator 4.

The solid line in FIG. 4 (b) shows the signal S ₁ input to the frame memory arranged in the field unit in the time direction (horizontal axis), and the vertical axis shows the vertical position (scan line position). ing. The dotted line shows the interpolated video signal when each field signal of this signal S ₁ is output through the interpolation filter which is interpolated with the above-mentioned coefficient value.

That is, the video signal corresponding to the time position indicated by the dotted line with respect to the signal S ₁ is output as [(K ₁ · S ₁ ) + (K ₂ · S ₂ )], and this interpolated video signal is output from the adder 5. Therefore, if the interpolated video signal is expanded by the field frequency conversion unit 6 along the time axis so as to have a cycle of 50 Hz, the fourth
As shown in FIG. 7C, an image signal S _{3 that} is periodically converted from 60 Hz to 50 Hz is obtained.

[Problems to be solved by the invention]

According to this field frequency conversion method, the filter coefficients K ₁ and K ₂ are set to constant values within the field to be converted, so the interpolation image signal (K ₁
・ S ₁ + K ₂ · S ₂ ) is only the interpolated image at a position apart from the image of the signal S ₁ (60 Hz) system before conversion by a certain time as shown by the dotted line.

Therefore, if this interpolated image is moved to a position displaced in time by the field frequency conversion, it cannot be said to be an accurate converted image, and there is a problem that a feeling of strangeness occurs especially when the image is a moving image.

That is, the conventional field interpolation is simply averaging by multiplying _two images separated by one field by predetermined coefficients K ₁ and K _2, and the movement of the image within one field time is reflected. Not not.

The present invention has been made in view of the above problems, and provides a frame frequency conversion device for a video signal, which is capable of obtaining a more accurate interpolated image signal with respect to the movement of the screen.

[Means for solving problems]

In the video signal frame frequency conversion apparatus of the present invention, the coefficient of the filter supplied to the above-described interpolation filter is continuously changed within one field.

[Action]

Since the filter coefficients K ₁ and K ₂ are configured to continuously change within one field for the interpolation filter to which the original signal before conversion is supplied, for example, an interpolation field formed in a certain time space is used. The video signal in the scanning line on the side of the start point of the signal has a higher weight in the image signal of the field before the original signal, and the video signal of the last scanning line of the interpolation field is the image signal of the field next to the original signal. Since the interpolation is performed so as to have a strong influence, the interpolation of the image changing within one field time also becomes stronger in continuity between frames, and conversion of the number of frames having a better moving screen is performed. .

〔Example〕

FIG. 1 is a block diagram showing an outline of a frame frequency conversion system of a video signal showing an embodiment of the present invention. As in FIG. 3, 11 is a frame memory, 12 and 13 are multipliers, 15
Is an adder, and 16 is a field frequency converter.

14 is (0 → 1.0), (1.0 → 1.0) as shown in FIG.
0) Filter coefficient K that changes linearly in the opposite direction
₁₁ , a coefficient generator that outputs K ₁₂ , such as a counter 14a that counts the horizontal synchronizing signal HD and the counter 1
A decoder 14b that outputs coefficient signals (K ₁₁ , K ₁₂ ) that are inclined in the positive and negative directions from the output of 4a, and a vertical synchronizing signal VD are frequency-divided, and the counter 14a is output at, for example, 1/6. It is composed of a frequency divider 14c and the like for resetting to 0.

Therefore, also in this case, when the frame-converted video signal S ₁₁ is displayed in the time axis direction (horizontal axis) in units of fields, it is output from the frame memory 11 as shown by the solid line in FIG. Screen signal F ₁ one field before
And the current screen signal F ₂ are input to the multipliers 12 and 13, respectively, and the signals weighted by the coefficients K ₁₁ and K ₁₂ are output from the adder 15, which are formed by this addition. Interpolation screen signal F ₁₂ is 1 as shown by the dotted line
It is formed by the weighting that changes linearly in the field, and similarly, the interpolation screen signal F ₂₃ formed by the next screen signals F ₂ and F ₃ also has the weighting that changes in one field. Become.

Therefore, the interpolation screen signal F output from the adder 15
_{12 to} F ₅₆ form different weighted interpolation screens within one field, so the conversion field frequency (50Hz)
It is possible to obtain an image close to the interpolated image signal S ₁₃ corresponding to the same time position as the screen by the scanning of, and a better frame frequency conversion is performed for a moving screen.

In the above-described embodiments, one screen is represented by a unit of field, but it is not necessary to represent one screen by a frame for a video signal having no interlaced scanning.

Further, although one frame memory or field memory is used to form the interpolated video signal, it goes without saying that the present invention can be applied to the case where a plurality of frame memories are used to form an interpolation filter for weighted addition. .

Further, although the case where the filter coefficient changes linearly has been described, the motion of the screen is detected by the motion vector detection unit (MV
If the detection is performed by D) and the filter coefficient is changed in a curve by this detection signal, it becomes possible to perform the field period conversion exhibiting better movement.

〔The invention's effect〕

As described above, in the television signal frame frequency conversion device of the present invention, the interpolation filter for forming the interpolated image is supplied with the coefficient signal having the filter characteristic that continuously changes in the same field. Therefore, it is possible to obtain a more accurate interpolation signal, and it is possible to obtain a field-converted television signal with less discomfort even when the screen of the television signal to be converted has a motion.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a frame frequency conversion system of a television signal of the present invention, and FIGS. 2 (a) and 2 (b) are change diagrams of filter coefficients supplied to a multiplier forming an interpolation filter. Waveform diagram showing the position of the output interpolated image signal, FIG. 3 is a schematic diagram of a conventional frame frequency conversion system,
FIGS. 4 (a), (b), and (c) are change diagrams of the filter coefficient supplied to the conventional interpolation filter and waveform diagrams showing the positions of the video signal before conversion and the interpolated image signal. In the figure, 11 is a frame memory, 12 and 13 are multipliers, 15 is a coefficient generator, and 15 is an adder.

Claims (1)

(57) [Claims] 1. A frame memory for storing a signal for at least one field of a television signal and delaying and outputting at a time corresponding to an output time for one field, and a synchronizing signal in the television signal are supplied, From (0.0) to (1.0) for each predetermined number of fields based on the synchronization signal
To a first filter coefficient that changes substantially linearly up to and a second filter coefficient that changes substantially linearly from (1.0) to (0.0) every predetermined number of fields, A first multiplier for multiplying the output signal of the memory by the second filter coefficient output from the coefficient generator, and a multiplier for the video signal and the first filter coefficient output from the coefficient generator. A second multiplier, an adder for adding the output of the first multiplier and the output of the second multiplier, and a signal output from the adder after being converted into a predetermined frame frequency. A frame frequency conversion device for a video signal, comprising: