JPH02238786A - Scanning line changeover circuit - Google Patents

Abstract

PURPOSE:To simplify the hardware and to reduce the cost by applying moving and still discrimination after a vertical high frequency signal is eliminated by the vertical direction filter independently of a moving picture or a still picture, outputting the output of the vertical direction filter in the case of the moving picture and outputting selectively an output of a time direction filter further in the case of the still picture. CONSTITUTION:An interlace signal for moving picture is obtained by a filter characteristic of a vertical direction filter 12, The equal characteristic of a conventional time-vertical filter is obtained by synthesizing the filter characteristic of the vertical direction filter 12 and the filter characteristic of a time direction filter 15 thereby obtaining the interlace signal for the still picture. Thus, without the use of a complicated filter such as a time-vertical filter, the time direction filter 15 is used in place of the time-vertical filter. Thus, the hardware is simplified and the scanning line conversion in response to the movement equal to a conventional circuit is attained and a circuit device with low cost is obtained.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field)
The present invention relates to a scanning line conversion circuit that converts a signal (abbreviated as V) into a non-interlaced signal having 525 scanning lines.

(Prior art) Scanning line conversion from a high-definition TV signal (1125 scanning lines) to a current NTSC TV signal requires HD
This is an important technology in terms of securing the TV signal source and sharing the source with high-definition systems. This conversion has 1125 scanning lines and a field frequency of 60! lz (hereinafter abbreviated as 1125/60) interlace 5 2
5/6 0 non-interlaced, then 5 2 5
It can be considered in two stages, from /60 non-ink single lace to 525/59.95 interlace.

Figure 9 shows the configuration of a scanning line conversion circuit for converting from 1125/60 interlace of high-definition TV system to 525/60 interlace of NTSC system. The interlaced signal is supplied to a time-series vertical filter 22 and is processed by a field delay circuit 23 for one field (525 lines).
The signal is delayed by 1 minute and fed to the vertical filter 22 by 1 hour. This time-vertical filter 22 has filter characteristics as shown in FIG. 10 (the shaded area in the figure is the passband), and suppresses the frequency in the time direction and the vertical direction to provide interlacing for still images in the NTSC system. Get a signal.

On the other hand, the 1125/60 interlaced signal is supplied to the vertical filter 24. This vertical filter 2
4 has filter characteristics as shown in FIG. 11 (the shaded area in the figure is the passband), and suppresses frequency components in the vertical direction to obtain an NTSC video interlaced signal.

The still image interlace signal obtained by the vertical filter 22 and the moving image interlace signal obtained by the vertical filter 24 are supplied to a mixer circuit 25.

Furthermore, the 1125/60 interlaced signal is supplied to a motion detection circuit 26. This motion detection circuit 26
The motion is detected from the signal difference between fields, and the detection result is supplied to the mixer circuit 25. This mixer circuit 25 selectively outputs the output of the vertical direction filter 24 when the motion detection circuit 26 determines that it is a moving image, and selectively outputs the output of the temporal vertical filter 22 when it is determined that it is a still image. The output of the mixer circuit 25 is appropriately expanded in a time expansion circuit 27 in accordance with the time position of the NTSC system, and outputted from an output terminal 28 as a 5 2 5/6 0 interlaced signal.

This will be explained with reference to the diagram of the principle of operation shown in FIG. The operation is different for videos and still images. The fields of the input interlaced signal come in the order of first field a1 and second field b. When obtaining an image of output field C, in the case of a moving image, the weighted average of several scanning lines at the position of the 0 mark in field a is taken, and the scanning line at the position of the O mark of field C is interpolated. In the case of a still image, interpolation is performed using the scanning lines of both the first field a and the second field b. 'This is because a still image is one in which scanning lines from both screens of fields a and b are interposed alternately to form one image.

By the way, the above-mentioned time-vertical filter 22 is specifically constructed as shown in FIG. 13. In the same figure, an input signal is applied to an input terminal 221 and a plurality of line delay lines 2
22, signals of multiple lines within the same field are obtained. On the other hand, a plurality of line signals of one field past are obtained from the field delay line 223 and the plurality of line delay lines 224. A coefficient multiplier 22 is applied to each of these multiple line signals.
5, and the output is sent to an adder (Σ) 22
6 to obtain an interpolated signal. The coefficient of the coefficient unit 225 is
It is changed appropriately depending on the positional relationship between the scanning line of the input image and the scanning line of the output image.

The above operation will be explained from the perspective of the spectrum.

Fig. 11 also shows the spectral distribution during moving images. The base spectrum of the image spectrum is located at A, and the folded component due to interlacing is located at B. For spectrum manipulation in scanning line conversion, it is important that the base spectrum and folded spectrum do not overlap when resampling is performed at intervals of 525 lines, so 5 2
All spectra of 5/2 [C P H] or more are removed by the vertical filter 24 and sampled into 525 lines.

A band C below 525/2 [CPH] becomes the passband of the moving image vertical filter 24.

FIG. 10 also shows the spectral distribution during a still image.

That is, in the case of a still image, both the base spectrum A and the folded spectrum B extend in the vertical direction, so in order to remove the folded spectrum B, it is necessary to cut off the band around 30 Hz in the temporal direction. This is because the vertically extended spectrum B' appears to flicker at a low frequency of 30 Hz in the vertical direction.

In this way, the conventional circuit is easy to understand because it has independent moving image filters and still image filters and obtains their respective signals independently. However, a complicated filter such as a time-vertical filter is required, which increases the complexity of the circuit configuration.

(Problems to be Solved by the Invention) As mentioned above, conventional scanning line conversion circuits have separate video filters and still image filters, which is easy to understand; Required complex filters.

This invention was made in order to solve the above problems, and it is possible to perform scanning line conversion according to movement without using a complicated filter such as a time-vertical filter. It is an object of the present invention to provide a simple and extremely low-cost scanning line conversion circuit.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the scanning line conversion circuit according to the present invention has the following features: In a scanning line conversion circuit that converts the number of scanning lines between the two, the interlaced signal of the first television system is input and the first field and the second field are converted to the scanning line position of the screen of the second television system. a vertical filter that extracts only the corresponding vertical component; a temporal filter that inputs the output of the vertical filter and extracts only the temporal component that corresponds to the scanning line position of the screen of the second television system; a motion detection circuit that detects motion between fields from the output of the vertical filter;
The present invention is characterized by comprising a mixer circuit which receives the outputs of the vertical filter and the temporal filter and switches or mixes the two input signals in accordance with the motion detection output of the motion detection circuit.

Second, the vertical filter is characterized in that the output section includes a time conversion section that moves the output signal to the time position of the scanning line of the screen of the second television system.

(Function) In the above configuration, regardless of whether the image is a moving image or a still image, a vertical filter is used to remove vertical high-frequency signals before motion/static judgment is made, and when a moving image is used, the vertical filter output is output as is, and when a still image is processed, a temporal filter is further applied. I am trying to output the selection through .

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 8.

Figure 1 shows the interlaced signal of the high-definition TV system.
This shows a configuration to which the present invention is applied when converting to an interlace signal of the C system, and a 1125/60 interlace signal of the high quality TV system is applied to the input terminal 11. This signal is fed to a vertical filter l2. This vertical filter l2 removes vertical components of 525/2 [CPH] or more and extracts only the vertical components corresponding to the scanning line position of the NTSC screen for the first and second fields. The interlaced signal extracted here is supplied to a time expansion circuit l3. This time expansion circuit 13 expands the input interlace signal and moves it to the time position of the scanning line of the NTSC screen.The interlace signal obtained here is supplied to the mixer circuit 14 for moving pictures, and at the same time Directional filter! 5 and a motion detection circuit l6.

The time direction filter I5 extracts only the time direction component corresponding to the scanning line position of the NTSC screen from the input signal, and the interlaced signal obtained here is supplied to the mixer circuit I4 for still images. The motion detection circuit 16 determines the motion of the image, that is, whether it is a moving image or a still image, by taking the λ between the first field and the second field of the input interlaced signal, and the determination result is supplied to the mixer circuit 14. Ru. This mixer circuit 14 passes the signal from the time expansion circuit 3 when the detection result of the motion detection circuit 16 is a moving image, and passes the output of the temporal direction filter 15 when the detection result is a still image. The output of the mixer circuit 14 is outputted as an NTSC interlaced signal via an output terminal 17.

The vertical filter l2 is specifically constructed as shown in FIG. That is, the interlaced signal input to the input terminal 121 is sequentially transmitted through the plurality of line delay lines 12.
2 times to obtain signals of multiple lines within the same field. Coefficient unit 1 is applied to each of these multiple line signals.
23 performs weighting, and each output is sent to an adder (Σ) 12
4 to obtain an interpolated signal from the output terminal 125. The coefficients of the coefficient unit 123 are appropriately changed based on the positional relationship between the scanning line of the input image and the scanning line of the output image. FIG. 3 shows the filter characteristics of the vertical filter l2. In FIG. 3, the shaded area is the pass area.

The time expansion circuit 13 is specifically constructed as shown in FIG. That is, the interlace signal applied to the input terminal 131 is written into the dual port memory 132 using the clock CKw applied to the write clock input terminal 133. As this write clock CKw, a clock having n times the horizontal frequency of the 1125 interlaced signal is used. The interlaced signal written in the memory 132 is read out and the read clock (5
CKR (a clock with n times the horizontal frequency of the non-interlaced signal) and output from the output terminal 135. In other words, the frequency ratio of the write clock CKw and the read clock CKR is 1125/2 and 525, and since the read clock CKR has a lower frequency than the write clock CKW, the number of scanning lines is 1 1 2.
The number will decrease from 5/2 to 525.

The time direction filter l5 is specifically constructed as shown in FIG. In other words, input. An adder (Σ) 153 adds the current field signal of the interlaced signal input to the terminal 151 and a signal delayed by one field (525 lines) by the field delayer 152, and then the divider 15
The average value between the fields is taken as 1/2 by 4 and outputted from the output terminal 155.

FIG. 6 shows the filter characteristics of the time direction filter.

In FIG. 6, the shaded area is the pass area.

The operation of the above configuration will be explained below.

FIG. 7 shows the situation when scanning line conversion is performed by the circuit of the above embodiment. First, an interlaced signal having a first field a1 and a second field b2 of a 1125-scan screen that is co-supplied to an input terminal 11 is input to a vertical filter l2 to generate fields a2 and b2.
The scanning line corresponding to the scanning line position of the 25th screen is found. Next, the time expansion circuit l4 moves to the time position of the scanning line of the 525 screen to obtain the signals of fields a3 and b3. The interlaced signal obtained here is supplied to the mixer circuit 14, and simultaneously supplied to the temporal filter l5 and the motion detection circuit l6.

Here, if the motion detection circuit l6 determines that the field a3 is a moving image, the mixer circuit l4 selects and outputs the field a3 as it is as the output field C.

In addition, when it is determined that the image is a still image, the temporal direction filter l5
Accordingly, a signal obtained by taking the average of field a3 and field b3 is selectively outputted as output field C from mixer circuit l4.

That is, in the above configuration, an interlaced signal for a moving image can be obtained by the filter characteristics of the vertical filter 12 shown in FIG. 3, and the filter characteristics of the vertical filter l2 and the filter characteristics of the temporal filter l5 shown in FIG. By combining the characteristics, the filter characteristics shown in FIG. 7, that is, characteristics equivalent to those of the conventional time-vertical filter, are obtained, and thereby an interlaced signal for still images is obtained.

Therefore, the scanning line conversion circuit with the above configuration does not use a complicated filter such as a time-vertical filter.
Since a time-direction filter can be used instead of this time-vertical filter, the system can be configured to be small and inexpensive. The hardware is simple, and scan line conversion can be performed in response to motion in the same manner as in the past, thereby making it possible to realize an extremely low-cost circuit device.

FIG. 8 shows, as another embodiment of the present invention, a case where the input signal is an interlaced signal having, for example, 1050 scanning lines. In FIG. 8, the same parts as in FIG. 1 are designated by the same reference numerals. As can be seen from FIG. 8, in this case, the time expansion circuit 13 shown in FIG. 1 is unnecessary.

This means that the horizontal frequency for both input and output is 525 fv (fv
- field frequency).

〔Effect of the invention〕

As described above, according to the present invention, it is possible to perform scan line conversion according to movement without using a complicated filter such as a time-vertical filter, and in addition, the hardware is simple and the scan line conversion is extremely low cost. A conversion circuit can be provided.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of a scanning line conversion circuit according to the present invention, FIG. 2 is a block circuit diagram showing a specific configuration of a vertical filter of the same embodiment, and FIG. A characteristic diagram showing the filter characteristics of the directional filter, FIG. 4 is a block circuit diagram showing the specific configuration of the time warping circuit of the same embodiment, and FIG. 5 shows the specific configuration of the time direction filter of the same embodiment. A block circuit diagram, FIG. 6 is a characteristic diagram showing the filter characteristics of the above-mentioned time-direction filter, FIG. 7 is a characteristic diagram when the filter characteristics of the above-mentioned vertical direction filter and time-direction filter are combined, and FIG. 8 is a characteristic diagram of the invention. 9 is a block circuit diagram showing the configuration of a conventional scanning line conversion circuit, and FIG. 10 is a block circuit diagram showing the filter characteristics of a still image time-vertical filter of the conventional circuit. 11 is a characteristic diagram showing the filter characteristics of a moving image vertical filter of the conventional circuit, FIG. 12 is a diagram for explaining the operation of the conventional circuit, and FIG. 13 is a specific example of the time-vertical filter of the conventional circuit. FIG. 2 is a block circuit diagram showing a general configuration. 12... Vertical direction filter, l3... Time expansion circuit, l4... Mixer circuit, l5... Time direction filter, l6... Motion detection circuit, 122... Line delay line, 123...・Coefficient unit, 124...Adder, 132・
...Dual port memory, 152...Field delay circuit, 153...Adder, 154...Divider, A
...Base spectrum, B...Folded spectrum, a...First field, b...Second field,
C...Output field. Applicant's agent Patent attorney Takehiko Suzue Figure 10 Figure 11 Port a b C Figure 12

Claims (2)

[Claims] (1) In a scanning line conversion circuit that converts the number of scanning lines between first and second television systems having different numbers of scanning lines, an interlaced signal of the first television system is input and the first field thereof and a vertical filter that extracts only the vertical component corresponding to the scanning line position of the screen of the second television system for the second field; A temporal filter that extracts only the temporal component corresponding to the scanning line position, a motion detection circuit that detects inter-field motion from the output of the vertical filter, and inputs each output of the vertical filter and the temporal filter. and a mixer circuit that switches or mixes two input signals in accordance with the motion detection output of the motion detection circuit. (2) The vertical filter has a time conversion section in the output section that moves the output signal to the time position of the scanning line of the screen of the second television system.
) scanning line conversion circuit.