JP2784806B2 - Motion area detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention performs different signal processing on an image signal between a still image and a moving image, and converts the image signal from a transmitted high-quality image signal.
The present invention relates to a motion area detection circuit suitable for detecting a motion area of an image.

[Summary of the Invention] An image motion area detection circuit of the present invention calculates a frame image signal received two frames after a current frame image signal in a received image signal, thereby obtaining a 2D image.
A temporal low-pass filter for removing a high-frequency signal in the space-time direction of the two-frame difference signal is provided for the first motion region detecting means for detecting the frame difference signal, and the noise component has been removed by the temporal low-pass filter. A second motion area detecting means is formed, and by selectively using an output of the first motion area detecting means and an output of the second motion area detecting means, a motion state of an image is detected. Therefore, for example, erroneous motion information is not output even for the beginning of image movement or for minute movement immediately before stopping, and the signal interpolation operation for moving images and still images can be performed smoothly. .

[Prior Art] In order to transmit a video signal of higher image quality than a current television signal, a high-definition television signal (HDTV) having a video signal band of, for example, 20 MHz to 30 MHz is in the stage of practical use. I have.

In such an HDTV, it is extremely difficult to transmit over a transmission radio wave due to a wide band of a video signal.

Therefore, in the HDTV, for example, as in the MUSE method or the EDTV, image information is subjected to different signal processing in a still image and a moving image, and a video signal is transmitted within a limited band. There is a type in which different image data is interpolated between a still image and a moving image so that a substantially high-quality image is obtained. .

 Hereinafter, this point will be described.

For example, when the signal band of the luminance signal is set so that its high frequency is 8 MHz as shown in FIG.
In order to keep it within the high frequency band of 4.2 MHz transmitted by the current broadcasting system, still images are indicated by diagonal lines 4.
4 a signal Y _H of the frequency band above 2MHz by multiplexing techniques.
Transmitted in less than 2MHz high frequency band Y _H '.

That is, as shown in the enlarged view of FIG. 5, the luminance signal spectrum originally existing in the high frequency band Y _H ′.
Since there is a gap between Y _L and the color signal spectrum Y _C , the high-frequency signal component Y _H of the luminance signal is interleaved in the gap,
The signal band is compressed to 4.2 MHz by multiplexing.

In this case, when the transmission image is a moving image, since the width of the spectrum is widened, interference occurs and interference occurs, so that high-frequency interleaving is not performed in the moving image region.

In the case of a still image, the video signal is sub-sampled at a rate of one out of four sampling points to form a field to be transmitted, and a video signal for one frame is transmitted in four fields. Interpolation between the fields is performed on the image data of the four fields to form a video signal for one frame that is interlaced and scanned.

In the case of a moving image, if an interpolated signal is generated between different fields, an afterimage occurs. Therefore, a signal whose band has been limited as described above is transmitted at a rate of one to four sampling points, and the receiving side transmits the signal within the same field. An interpolation signal is formed from the signals at the sampling points of the above.

That is, while a still image is interpolated between fields, a high-quality video signal is formed by interpolating within a field for a moving image.

FIG. 6 is a block diagram for performing interpolation of data on the still image and the moving image as described above.

The transmitted video signal is converted into image data by the A / D converter 1, and the necessary control signal is separated by the synchronous control signal separation circuit 2. The frequency characteristics of the image data are compensated by a de-emphasis circuit 3 and supplied to a moving area detecting section 4 according to the present invention.

The image data is supplied to an inter-frame interpolation circuit 5 for correcting a still image and an in-field interpolation circuit 6 for correcting a moving image. The sub-sample frequencies of these outputs are converted by the sample data converters 7A and 7B, respectively, and the interpolation data of the still image is further supplied to the field interpolation circuit 8.

Reference numeral 9 denotes an adder that mixes the image data interpolated as a still image and the image data interpolated as a moving image by the output of the motion area detection unit 4. In the case of a complete still image, when the interpolation data between frames is a moving image. Outputs interpolation data in the field.

Then, the image data is supplied to the decoder 10 and converted into, for example, baseband signals R, G, and B.

In order to detect the motion area, a so-called two-frame difference signal is used, which compares video signals separated by two frames and detects the absolute value of the difference signal.

This is because, in a still image forming a video signal of one frame interlaced by four fields, a one-frame difference signal is always a motion signal because there is no image data at the corresponding sample point from the beginning. is there.

[Problems to be Solved by the Invention] By the way, even if the image data of the same sample point is compared by the two-frame difference signal, the S / N is not obtained in the actual broadcast wave.
In some cases, the ratio is degraded, and when a noise component is superimposed on the video signal, a signal output indicating that the still image area is also moving is generated by the two-frame difference signal.

Therefore, in order to suppress the erroneous detection signal due to the noise, a circuit having a dead band level (coring circuit) which does not output a signal up to a certain level to the detection signal output circuit is attached, and erroneous motion detection due to the noise is performed. No signal is output.

However, if such a coring circuit is added to the two-frame difference signal output circuit, for example, a point at which movement starts, or a minute movement immediately before stopping, is determined as a still area,
An erroneous interpolation operation is performed, and the monitor image flickers or has a double line.

[Means for Solving the Problems] The present invention has been made for the purpose of reducing such problems, and together with a two-frame difference signal detecting means, a signal output from the two-frame difference signal detecting means is used. A signal is supplied to a temporal low-pass filter having a pass characteristic of only a low-frequency signal in a frame direction of an image, and an output of the temporal low-pass filter and a minimum value and a maximum value between two-frame difference signals. The output is supplied as a motion detection signal output and used as a control signal for an interpolation operation.

[Operation] Since the temporal low-pass filter outputs a motion detection signal in which the noise component superimposed on the small level of the two-frame difference signal is output, the motion detection signal and the two-frame difference signal are selected according to the level. By doing so, the detection of a minute motion region that is easily affected by the noise component can be correctly performed.

Embodiment FIG. 1 is a block diagram showing a motion area detecting circuit according to the present invention.

In this figure, reference numeral 11 denotes a video signal v of high image quality supplied by interleaving out-of-band frequencies in a high-frequency region of a luminance signal as seen in, for example, the MUSE and EDIV schemes. / D converter, 12 is a de-emphasis circuit, 13 is to give one field delay time
1F delay circuit.

The video signal based on the main line is supplied to the signal processing unit 30 that performs different interpolation processing in the still image and the moving image area as described above, and is demodulated to the original video signal waveform.

On the other hand, the digital video signal whose high-frequency signal component has been enhanced by the de-emphasis circuit 12 is supplied to a detection circuit for a moving image area.

14 shows a 2F memory circuit for delaying signals for two frames, the output of the 2F memory circuit 14, by two frames before the image signal is subtracted in subtractor 15, detects the two frames difference signal D _0.

The two-frame difference signal D ₀ is _{0 in the case} of a complete still image, but in a moving image area, a signal of a level corresponding to the motion is output, and the signal passes through the next limiter circuit 16. Is limited to a certain value.
The two-frame difference signal is supplied to an absolute value circuit 18 via a 1F delay circuit 17 which gives a delay time of one more frame, and forms a _first two-frame difference signal D1, which is a signal independent of the direction of motion. Molded into Then, the signal is supplied to the coring circuit 19, and forms a _second two-frame difference signal D2 obtained by cutting out the two-frame difference signal of a certain level or less.

For example, as shown in FIG. 2, the coring circuit 19 can be realized by a non-linear circuit having a dead zone in which a signal below a threshold level V _th becomes 0 level. Formed 2
The frame difference signal is removed to form a signal indicating a stationary state.

A portion 20 surrounded by a dashed line constitutes a temporal low-pass filter for integrating a video signal in a frame direction, and reference numerals 21 and 22 denote a 1-field memory or the like.
Field delay circuits, 23 and 25 indicate adders, and 23A and 23B indicate 1/2 and 1/4 coefficient circuits, respectively.

As is well known, the temporal low-pass filter 20 removes random noise included in the two-frame difference signal by adding the same sample point of the video signal of each frame every time, and removes the same noise every field. This is to extract only the two-frame difference signal component generated at the sampling point.

Therefore, an output signal obtained by averaging the two-frame difference signal for each field is obtained.

The output signal of the temporal low-pass filter 20 is also converted by the absolute value circuit 26 into a signal having one-way polarity.
To form a two-frame difference signal D ₃ of.

Reference numeral 27 denotes a signal level processing unit for selecting the level of the second and third two-frame difference signals, and a minimum value selection circuit 28 for selecting a signal of the smaller level from both signals.
It comprises a maximum value selection circuit 29 for selecting a higher level from the two signals.

The motion area detection signal obtained from the signal level processing unit 27 is supplied to the signal processing unit 30. As described above, in the case of a still image, an interpolation signal obtained by performing an interpolating operation between fields is output. At the same time, in the case of a moving image, a signal interpolated by interpolation in the field is output.

When the image is close to a quasi-still image, a signal obtained by mixing the signals obtained by the two interpolation operations at an appropriate ratio is output.

Next, the motion detection operation of the present invention will be described with reference to the waveform diagram of FIG.

Now, the movement of a pixel in the image changes as shown in
It is assumed that at the time point t ₁ , the robot is brought into a stationary state and starts moving again at the time point t ₂ .

In this case, until the time t ₀ as shown in regarded as entirely in video area, performs intra-field interpolation, between the t ₁ -t ₂ is performed to improve the picture quality is regarded as a still image, interpolation between fields To obtain a high quality video signal.

Also, t ₀ between -t ₂ and t ₂ -t ₃ during because a semi-still image region, so as to obtain an image data interpolation signal and still image interpolation signal is mixed in an appropriate ratio of the moving image.

Is a subtractor based on the motion of the image as shown above.
Are shown two frames difference signal D ₀ obtained from 15, as can be seen from the two-frame difference signal, the influence of noise between two frames difference signal D time t ₀ ~t ₃ levels decreases ₀ 2 frame difference signal D ₀ that received is outputted.

Then, so that the two-frame difference signal D ₀ is it passes through the absolute value circuit 18 and the coring circuit 19 is waveform shaping on the first two frames difference signal D ₁ as shown in.

2 frame difference signal D ₁ of the first, since that would indicate a period T ₁ and T ₂ in the still image to be subjected to interpolation processing of the original semi-still images, so that the resolution of the image deteriorates in this period .

Therefore, in the motion area detection circuit of the present invention supplies the two-frame difference signal D ₀ of the the temporal low pass filter 20 removes high-frequency components of the frequency of the field direction, indicated by by passing the absolute value circuit 26 Third like
Molding the two-frame difference signal D ₃ waveforms. Then, the third two-frame difference signal D ₃ of the first two frames difference signal
By selecting the lower signal level of the D ₁ in a minimum value selection circuit 28, formed into a signal waveform as shown by the signal waveform shown in this and further wherein the second second frame difference signal D ₂ By selecting the higher level of the waveform by the maximum value selection circuit 29, a motion region detection signal as shown by is indicated.

According to the motion area detection signal, the period (T ₁ period) immediately before the still-image region or time period immediately before the moving image (T ₂ period), the interpolation signal of both still and moving is suitably mix outputs Therefore, an interpolation signal indicating motion remains in this area, and the possibility of a double image caused by an afterimage due to interpolation between frames is reduced.

In the period during which a still image is formed (t ₁ −t ₂ ), a signal for noise image removal from which a noise component has been removed is obtained in the same manner as the signal that has passed through the coring circuit 19. Can be eliminated.

In the actual circuit, the 1F delay circuit 17 can be omitted by connecting the output of the one-field delay circuit 21 as shown by a dotted line in FIG.

[Effects of the Invention] As described above, in the motion area detection circuit of the present invention, a motion part of a quasi-still picture lost by coring a motion detection signal detected by a two-frame difference signal is also interpolated by a moving image. The operation is performed, and a still image region in which a still image is likely to be erroneously output as a moving image due to noise components is completely interpolated by a coring effect due to the effect of coring. And an excellent effect that flickering and double images can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a motion area detecting circuit according to the present invention, FIG. 2 is an explanatory diagram of the operation of a coring circuit, FIG. 3 is a signal waveform diagram showing a motion area, and FIG. 5 is a frequency characteristic diagram of a television signal, FIG. 5 is a spectrum diagram of a frequency interleaved high frequency band, FIG. 6 is a block diagram showing an example of performing interpolation of an image signal by motion detection, and FIG. Is a 2-frame delay circuit, 20 is a temporal low-pass filter, 21 and 22 are 1-field delay circuits,
26 is an absolute value circuit and 27 is a signal level processing unit.

Claims (1)

(57) [Claims] 1. A two-frame difference signal generating means for generating a two-frame difference signal of an image signal in order to detect a motion region of a broadcast image signal interleaved in a high-frequency region of a video signal; A first means for obtaining a signal obtained by removing the small amplitude signal from the output of the difference signal generating means;
Motion detecting means, a second motion detecting means comprising a temporal low-pass filter to which an output of the two-frame difference signal generating means is inputted and which removes a high frequency signal in a space-time direction; A motion selecting means for selecting a smaller one of an output and the two-frame difference signal and further selecting a larger one of the selected signal and an output of the first motion detecting means. Area detection circuit.