JPH0435578A - Time filter device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of noise due to channel switching by stopping the time filter processing of a switching frame in a time filter at the time of detecting the channel switching by a detecting circuit. CONSTITUTION:A time filter 101 performs the time filter processing of an input picture signal, and a channel switching circuit 102 performs channel switching of the picture signal inputted to the time filter 101. A detecting circuit 103 detects channel switching of the picture signal inputted to the time filter 101. The time filter 101 stops the time filter processing of the switching frame when channel switching is detected by the detecting circuit 103. Thus, the occurrence of noise due to channel switching is prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding a temporal filter device used, for example, in an image transmission device, a temporal filter that performs temporal filter processing on an input image signal for the purpose of preventing noise from occurring due to channel switching. , a channel switching circuit that switches the channel of the image signal input to the temporal filter, and a detection circuit that detects channel switching of the image signal input to the temporal filter, and the temporal filter detects channel switching by the detection circuit. The switching frame is configured to stop temporal filtering of the switching frame when the switching frame is detected.

[Industrial Field of Application] The present invention relates to a temporal filter device used, for example, in an image transmission device.

[Prior Art] FIG. 12 shows an example of an image transmission device using this temporal filter device. In the figure, 41 is an A/D conversion unit that A/D converts the TV image signal, 42 is a time filter unit that filters the TV image signal after A/D conversion, and 4
3 is an encoder that encodes the filtered television image signal. This temporal filter section 42 functions to remove noise occurring between consecutive image frames by applying a filter in the temporal direction. For example, the current input image signal is compared with the previous image signal from one screen before, and a correction value is generated to remove the noise generated between the screens.
This correction value is added to the current image signal or the previous image signal to generate a filter output signal from which noise has been removed.

For example, as shown in FIG. 13, this temporal filter section 42 has image signals of two or more channels CHI to CHn as input signals, and selects one of them by a selector 422 in accordance with a channel switching signal C8W. Thus, the channel is switched and inputted to the temporal filter 421.

[Problems to be Solved by the Invention] In a temporal filter device having image signals of two or more channels as input signals as described above, even when the input signals are switched due to channel switching, the human input image signal at the time of the switching is A time filter is applied to it. For this reason,
When switching channels, temporal filter processing is performed even though there is no correlation between the images before and after switching, so there is a problem in that noise that is supposed to be removed is instead generated. .

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a temporal filter device that does not generate noise due to channel switching.

[Means to solve the problem] FIG. 1 is a diagram explaining the principle of the present invention.

The temporal filter device according to the present invention includes a temporal filter 101 that performs temporal filter processing on an input image signal, a channel switching circuit 102 that performs channel switching of an image signal input to the temporal filter 101, and a channel switching circuit 102 that performs channel switching of an image signal input to the temporal filter 101. The temporal filter 101 includes a detection circuit 103 that detects channel switching of an image signal.
is configured to stop temporal filtering of the switching frame when a channel switching is detected.

The temporal filter 101 includes a delay circuit that delays a filter output signal to generate a filtered previous image signal, and a difference circuit that calculates the difference between the current image signal and the previous image signal generated by the delay circuit. , a correction value calculation circuit that calculates a correction value for temporal filter processing according to the difference value of the difference circuit, and a filter output signal by adding the correction value from the correction value calculation circuit and the previous image signal from the delay circuit. The filter output calculation circuit may be configured to include a filter output calculation circuit, and a selection circuit that performs switching to select the current image signal of the switching frame as the filter output signal when channel switching is detected by the detection circuit.

This temporal filter also includes a delay circuit that delays the input image signal to generate a previous image signal, a difference circuit that calculates the difference between the current image signal and the previous image signal generated by the delay circuit, and a difference circuit that calculates the difference between the current image signal and the previous image signal generated by the delay circuit. A correction value calculation circuit that calculates a correction value for temporal filter processing according to the difference value of the circuit, and a correction value from the correction value calculation circuit and a previous image signal from the delay circuit are added to form a filter output signal. It can be constructed of a filter output arithmetic circuit and a selection circuit that performs switching to select the current image signal of the switching frame as the filter output signal when channel switching is detected by the detection circuit.

Furthermore, the selection circuit further includes a current image calculation circuit that calculates a current image signal based on each signal in the temporal filter, and the selection circuit uses the calculated current image signal from the current image calculation circuit instead of the currently input current image signal. It can be configured to switch so that the output signal is the filter output signal.

[Function] When channel switching is detected by the detection circuit 103,
The temporal filter 101 stops filtering the image signal of the frame in which the channel has been switched.

This makes it possible to prevent noise caused by channel switching.

The method for stopping filter processing in the temporal filter 101 is to use a selection circuit to switch the current image signal currently input or the current image signal obtained by the current image calculation circuit to the filter output signal when switching channels. It can be achieved by doing.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings. In addition,
Circuits with the same reference numerals throughout the drawings below represent circuits with the same function.

FIG. 2 shows the overall configuration of a temporal filter device as an embodiment of the present invention. In FIG. 2, 1 is a time filter, 2 is a detection circuit, and 3 is a selector. Selector 3
is a circuit that selects one of the n-channel CHI-CHn image signals in accordance with the channel switching signal C8W and supplies it to the time filter. The detection circuit 2 also monitors the channel switching signal C8W, and is a circuit that provides the time filter 1 with an ON10FF signal indicating that a channel switching has occurred at the time of channel switching.

FIG. 3 shows an example of the configuration of the detection circuit 2. In FIG. In FIG. 3, the channel switching signal C8W is branched into two, one of which is input to the comparison circuit 22 as a signal representing the channel of the current frame, and the other is inputted to the comparison circuit 22 as a signal representing the channel of the previous frame through the delay circuit 21. It is input to the comparison circuit 22. The comparison circuit 22 compares both switching signals, and ANDs the comparison result signal of 10" if the channels of the previous frame and the current frame match, and 1"' if they do not match.
to the circuit 23.

A clock at the pixel timing is input to the other input terminal of the AND circuit 23, and the AND circuit 23 is opened/closed in response to the comparison result signal to control blocking/passing of this clock. The clock passed through the AND circuit 23 is input to a clock terminal of a flip-flop 24 serving as a latch circuit. A fixed value "1"' is input to the data terminal of the floating flop 24, and its inverted output *Q is ON1.
It is given to the time filter 1 as an 0FF signal. Further, this flip-flop 24 is cleared by a clear signal that is manually input in frame units (one pulse per frame).

FIG. 4 shows a time chart explaining the operation of this detection circuit 2. In Figure 4, (a) is a frame synchronization signal of the image signal, (b) is a clear signal input to the flip-flop 24 and is generated in synchronization with the frame synchronization signal, and (C) is a channel switching signal. Signal C8W, (d
) is output from the flip-flop 24.
FF signal.

First, when the channel shown in FIG. 4(A) is switched, the contents of the flip-flop 24 are cleared by the clear signal, and when the channel switching signal C8W of the previous frame and the current frame become inconsistent, the clock is ANDed. The ON10 F F signal (
That is, the inverted output (IQ) changes from the ON signal -1'' to the OFF signal -0'', and this state continues for one frame.

Further, if the channel shown in FIG. 4(B) is not switched, the channel switching signal C8W does not change, and therefore the ON10FF signal becomes the ON signal "1"'.

In this way, the detection circuit 2 provides the OFF signal "O" to the time filter I when switching channels, and the ON signal "1" to the time filter I at other times.

An example of the configuration of the temporal filter 1 is shown in FIG. In FIG. 5, the input current image signal a is input to the subtracter 11, where the difference value (a − B) between it and the filtered previous image signal B from the frame memory 12 is calculated and stored in the ROM 13. Output. A filter output signal is manually input to the frame memory 12, and the frame memory 12
serves to delay this filter output signal by one frame.

The ROM 13 is a circuit that calculates a correction value f(a-B) for noise removal based on the input difference value (a-B), and this correction value f(aB) is calculated by the selector 14.
is input to one input end of the . Further, the difference value (a-B) from the subtracter 11 is input to the other input terminal of the selector 14.

This selector ]4 is configured to perform switching by the 0N10FF signal from the detection circuit 2, and the ON signal "O"
゛When the manual power is applied, the correction value f(a-B) side is set to OFF signal ゛1
”, the difference value (a − B) side is selected and the adder 15
to one input end of the .

The previous image signal B from the frame memory 12 is input to the other input terminal of the adder 15, and the adder 15 adds the two human power signals and outputs the result as a filter output signal.

The operation of this embodiment device will be explained below.

When channel switching is not performed, the signal input to the selector 14 becomes the ON signal "1", and the selector 14 selects the correction value f(a-B) from the ROM 13 and outputs it to the adder 15. .

Therefore, in the adder 15, this correction value f(a-B)
and the previous image signal B from the frame memory 12, f(a-B)+B, is output as a filter output signal.

On the other hand, when channel switching is performed, the selector 14 selects the difference value (a-B) from the subtracter 11 and sends it to the adder 15.
The output can be switched to . This allows adder I
5, the current image signal a obtained by adding the difference value (a-B) and the previous image signal B from the frame memory 12 is output as a filter output signal.

As a result, at the time of channel switching, the currently input current image signal a will be output as is, and the filtering process of the temporal filter 1 will be stopped in the frame where the channel switching occurred.

Various modifications are possible in implementing the invention. For example, the configuration of the temporal filter 1 in the above-described embodiment device can be in various forms as described below.

FIG. 6 shows another example of the configuration of the temporal filter 1. As a difference between this embodiment and the embodiment shown in FIG.
4 is input with a fixed value "0''' instead of the difference value (a-B) from the subtracter 11, and the adder 15 is input with the frame memory 1
Instead of the previous image signal B from 2, the current image signal a that is currently being input is input. Further, the ROM 18 stores correction values for noise removal that are different from those in the ROM 13 described above. With this configuration, when the ON10FF signal from the detection circuit 2 is ON, f(a-B)+a is the filter output signal from the adder 15, and also OF
At time F, the current image signal a is output.

FIG. 7 shows yet another example of the configuration of the temporal filter 1. The difference between this embodiment and the embodiment shown in FIG. 6 is that the selector 14 is provided after the adder 15, and the current image signal a is directly sent to the selector 14 instead of the fixed value 0'. and the output signal of this selector 14 is the filter output signal. Even in such a configuration, when the ON10FF signal from the detection circuit 2 is ON, the output signal from the adder 15 is the filter output signal. f(a-
B) +a is output, and the current image signal a is output when the switch is OFF.

FIG. 8 shows still another example of the configuration of the temporal filter l. In this embodiment, instead of the current image signal a input to the selector 14 in the embodiment of FIG. A current image signal a is obtained by subtracting B, and this calculated current image signal a is input to the selector 14. Even in this configuration, the 0 from the detection circuit 2
When the N10FF signal is ON, f(a-B)+B is output as the filter output signal from the adder 15, and when the N10FF signal is OFF, the current image signal a is output.

FIG. 9 shows still another example of the configuration of the temporal filter 1. In this embodiment, instead of the current image signal a input to the selector 14 in the embodiment of FIG.
The current image signal a is obtained by subtracting the correction f(a-B) from
This is what you input. Even in this configuration, when the ON10FF signal from the detection circuit 2 is ON, the adder 15
f(a-B)+a is output as the filter output signal from the filter, and the current image signal a is output when it is OFF.

FIG. 10 shows still another example of the configuration of the temporal filter l. In this embodiment, the current image signal a is stored in the frame memory 12.
is input, and by subtracting the unfiltered previous image signal output from the frame memory 12 from the current image signal a in the subtracter 11, the difference value (a
-b), and the other configuration is the same as that shown in the embodiment of FIG. In this configuration, when the ON10 F F signal from the detection circuit 2 is ON, the filter output signal from the adder 15 is f(a-b) +a.
However, when it is OFF, the current image signal a is output.

FIG. 11 shows still another example of the configuration of the temporal filter 1. In this embodiment as well, the current image signal a is stored in the frame memory 12.
The previous image signal is obtained by manually inputting the previous image signal from the output thereof, and the other configurations are the same as the embodiment shown in FIG.

In this configuration, ON10 F from the detection circuit 2
When the F signal is ON, f(ab)+b is output as the filter output signal from the adder 15, and when the F signal is OFF, the current image signal a is output.

In addition, in the embodiments shown in FIGS. 7, 8, and 9, the current image signal a is input as the signal input to frame memo 1/12 instead of the filter output signal. Modifications such as the following are also possible.

[Effects of the Invention] As described above, according to the present invention, when channel switching of an image signal is performed, noise can be prevented from being generated due to temporal filter processing.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is an overall configuration diagram of a temporal filter device as an embodiment of the present invention, and FIG. 3 is a block diagram showing an example of the configuration of a detection circuit of the embodiment device. FIG. 4 is a time chart for explaining the operation of the detection circuit shown in FIG. 3, FIG. 5 is a block diagram showing an example of the configuration of the time filter of the embodiment device, and FIGS. FIG. 12 is a block diagram of an image transmission device using a temporal filter device, and FIG. 13 is a block diagram showing a schematic configuration of a conventional temporal filter device. In the figure, 1... Temporal filter 2... Detection circuit 3... Selector 11, l2, 13, 14, 15. 21 ・ 22 ・ 23 ・ 24 ・ ... Subtractor Frame memory OM Sector ... Adder Delay circuit Comparison circuit AND circuit Flip-flop Fig. 2 shows the valley structure of the x crime example of the present invention. 0) I'm salivating! I HI CB) + Y channel γtl) Knockdown Usui t (Tanibe 1 of the combination detection circuit 1@ No. Soi 4 Chi V-to Fig. 4 OFF Gin: Haruma fill L5'Haku's structure example Fig. 7 Time +ig (7) side of F415'Example OFF 20 hour filter (W configuration (evening 1)

Claims (1)

[Claims] 1. A temporal filter (101) that performs temporal filter processing on an input image signal; a channel switching circuit (102) that performs channel switching of the image signal input to the temporal filter (101); A detection circuit (103) detects channel switching of the image signal input to the temporal filter (101), and the temporal filter (101) detects the switching frame when the channel switching is detected by the detection circuit (103). A temporal filter device configured to stop temporal filtering of. 2. The temporal filter (101) includes a delay circuit that delays the filter output signal to generate a filtered previous image signal, and a difference value between the current image signal and the previous image signal generated by the delay circuit. A difference circuit that calculates, a correction value calculation circuit that calculates a correction value for temporal filter processing according to the difference value of the difference circuit, and a correction value from the correction value calculation circuit and a previous image signal from the delay circuit. and a selection circuit that performs switching to select the current image signal of the switching frame as the filter output signal when channel switching is detected by the detection circuit. 2. The temporal filter device according to claim 1. 3. The temporal filter (101) includes a delay circuit that delays an input image signal to generate a previous image signal, and calculates a difference value between the current image signal and the previous image signal generated by the delay circuit. a difference circuit; a correction value calculation circuit that calculates a correction value for temporal filter processing according to the difference value of the difference circuit; and a correction value from the correction value calculation circuit and a previous image signal from the delay circuit. A filter output arithmetic circuit that adds the signal to obtain a filter output signal, and a selection circuit that performs switching to select the current image signal of the switching frame as the filter output signal when channel switching is detected by the detection circuit. The temporal filter device according to claim 1. 4. Further comprising a current image calculation circuit that calculates a current image signal based on each signal in the temporal filter, and the selection circuit uses the calculated current image signal from the current image calculation circuit instead of the currently input current image signal. 3. A temporal filter device according to claim 1 or 2, wherein the temporal filter device is configured to switch the current image signal as the filter output signal.