JPH0373688A - Moving area detecting circuit - Google Patents

Abstract

PURPOSE:To apply accurate movement interpolation to an image in a slightly moving area by selecting the output signal of the 1st movement detecting means at the time of deciding a large movement of a broadcasting image or selecting the output signal of the 2nd movement detecting means at the time of deciding a small movement. CONSTITUTION:The detecting signal of a moving area detected by the 1st movement detecting part 13 is supplied to a limiter circuit 16 and then supplied to an absolute value circuit 17. The 2nd movement detecting part 20 is provided with a subtractor 21 for detecting an 1-frame difference signal and a band pass filter(BPF) 22 for extracting a signal interleft in a high frequency area. In order to apply the output of the 2nd movement detecting part 20 to a signal >=4MHz necessary for the interpolation between a static image and a moving image, the output is outputted through the BPF of 4 to 12MHz, and when a small movement close to a static image exists, the movement is selected by a switch 27 and outputted. Thus, the 2nd movement detecting part 20 is constituted so as to increase the detecting value of a small movement of an image.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention performs different signal processing on image signals for still images and moving images, and detects moving areas of images from the transmitted high-quality video signals. The present invention relates to a motion area detection circuit that is suitable for use in a motion area detection circuit.

[Summary of the Invention] The image motion area detection circuit of the present invention subtracts a frame image signal received two frames later from a current frame image signal among received image signals.
The first motion area detection means for detecting a frame difference signal includes a filter means for extracting a high frequency signal component incremented in the received image signal, and a motion of the image based on the output level of the filter means. A second motion area detection means is provided which forms a signal indicative of the movement of the image, and when the second motion area detection means determines that the movement of the image is large, the output signal of the first motion area detection means is When it is determined that the motion area is small, the output signal of the second motion area detection means is selected and image processing is performed, so especially when there is a slight movement in the image, erroneous motion information due to noise etc. is no longer output, and signal interpolation processing operations for moving images and still images can be performed smoothly.

[Prior Art] In order to transmit a video signal with higher image quality than current television signals, the video signal band is, for example, 20MHz to 30MHz.
High-definition television signal (HDTV) such as Hz
is at the stage of practical application.

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

Therefore, in the above-mentioned HDTV, for example, MUS
As seen in the E system and EDTV system, the high frequency band of the video signal is interleafed to compress the transmission signal band, and the video signal is transmitted within a limited band. In some cases, interpolation operations are performed on different image data for still images and moving images to obtain substantially high-quality video.

Below, as an example of performing such image processing, for example, ED
A TV system video signal will be briefly explained.

For example, if the signal band of the luminance signal is set so that its high frequency is 6 MHz as shown in Fig. 6, the high frequency band of the luminance signal is set to 4 or 2 MHz, which is transmitted in the current broadcasting system.
In order to fit within the high frequency band of , in the case of still images, the signal Y in the frequency band of 4.2 MHz or higher is indicated by diagonal lines. is interleafed into a high frequency band YH' within 4.2 MHz using multiplexing technology and transmitted.

That is, as shown in the enlarged view of FIG. 7, in the high frequency band Y,'' there is a gap between the originally existing luminance signal spectrum YL and the color signal spectrum Yc.
By interleafing the high frequency signal component Y)l of the luminance signal in the gap and multiplexing it, the signal band is increased to 4.2MHz.
Compress to z.

In this case, when the transmitted image is a video, the spectral width is widened, causing mutual interference and interference, so high frequency interleaf is not performed in the video region. .

In addition, for the above-mentioned video signal, in the case of a still image, the data at the sampling point is processed in the field direction and the frame direction.
The fields to be transmitted are formed by sampling at a rate of one in four fields, one frame worth of video signal is transmitted using four fields, and on the receiving side interpolation is performed between the fields for the image data of these four fields. , to form an interlaced scanned video signal for l frames.

In addition, in the case of moving images, if an interpolation signal is created between different fields, an afterimage will occur, so a band-limited signal is transmitted at a rate of one at every four sampling points as described above, and on the receiving side, within the same field. An interpolated signal is formed from the signals at the sampling points.

In other words, while for still images, interpolation is performed between fields, for moving images, interpolation is performed within fields to form a high-quality video signal from a band-compressed video signal. There is.

FIG. 8 shows a block diagram for performing data interpolation for still images and moving images as described above, as seen in the MUSE method, for example.

The transmitted video signal in the band O~8MH is A/D.
The converter 1 converts the image data into image data at a sampling frequency of, for example, 16.2 MH2, and the synchronization control signal separation circuit 2 separates necessary control signals.

The sampled image data is sent to the de-emphasis circuit 3.
The frequency characteristics are compensated at , and the signal is supplied to the motion area detection section 4, which is the object of the present invention.

The image data is also supplied to an interframe interpolation circuit 5 for correcting still images and an intra-field opening circuit 6 for correcting moving images.

The interpolated signal (32, 4
MH2) passes through a 12MH low-pass filter, is subsampled at 24.3MH2 by a subsampling circuit 7A, is supplied to a 7-field interpolation circuit 8, and is converted into 48.6MH2 sampling data.

Further, the output signal for the moving image interpolated by the field interpolation circuit 6 is outputted by the subsampling circuit 7B.
Subsampled from 32.4 to 48.6MH2.

These outputs are each input to an adder 9.

The adder 9 has a function of mixing image data interpolated as a still image and image data interpolated as a moving image using the output of the motion area detection section 4, and in the case of a completely still image, it is formed by interpolation between fields. The video signal that was
In the case of a moving image, data is output as a video signal formed by interpolation within a field.

Then, this image data is supplied to the decoder IO together with interpolated data of a color signal (not shown), and is converted into baseband signals R, G, and B of, for example, 20 MH.

The output of the motion area detection section 4 is generally a so-called two-frame difference signal, which compares video signals separated by two frames and detects the absolute value of the difference signal.

This is because in a still image where a video signal of 1 frame is formed from an image signal interlaced by 1.4 fields, a 1 frame difference signal is always treated as a signal with motion because there is no image data at the corresponding sample point. This is to become.

[Problems to be Solved by the Invention] By the way, even if image data at the same sample point is compared using a two-frame difference signal, the S/N is low in actual broadcast waves.
The ratio may be degraded, and when a noise component is superimposed on the video signal, especially in areas where there is little movement, this noise often generates a signal output indicating that there is movement even in still image areas.

Therefore, in order to suppress false detection signals caused by this noise, a circuit with a dead band level (coring circuit) that does not output signals up to the level of the detection signal output circuit is installed. I am trying not to output .

However, if such a coring circuit is added to the two-frame difference signal output circuit, for example, the point at which movement starts or the slight movement just before stopping is judged to be a stationary area, and an incorrect interpolation operation is performed. As a result, there was a problem in that the monitor image flickered or appeared as double lines.

[Means for Solving the Problems] The present invention has been made with the aim of alleviating such problems, and uses a two-frame difference signal detection means to detect the movement of a signal interleaved in the high frequency range of a video signal. A second motion detecting means is provided, and this second motion detecting means detects whether the motion of the image is large or not, and when the motion of the image detected by the two frame difference signal is small (noise The signal obtained from the second motion detection means is used to perform interpolation processing on image data in an area where there is slight movement.

[Operation] The second motion detection means extracts the signal of the frequency spectrum (15H2) interleaved in the high frequency range of the video signal in the time direction and detects its level, so there is no noise in the still image area. This makes it possible to perform accurate motion interpolation for images in areas where there is slight movement.

[Embodiment] FIG. 1 shows a block diagram of a motion area detection circuit of the present invention.

In this figure, 11 is a video signal V that is said to be of high image quality and is supplied by interleafing frequencies outside the band into the high frequency region of the luminance signal, as seen in the MUSE and EDTV systems, for example. An A/D converter, 12 is a de-emphasis circuit, and 13, surrounded by a dotted chain line, is an IF delay circuit for providing a delay time of one field.
4A, 14B and the first unit consisting of the totalizer 15.
The motion detection unit outputs a two-frame difference signal of the video signal. The detection signal of the motion area detected by the first motion detection section 13 is supplied to a limiter circuit 16 and then to the next interval value circuit 17.

In addition, in the case of a conventional motion detection circuit, this absolute value circuit 1
After 7, a coring circuit was placed to remove noise components superimposed on the minute motion signal to obtain a motion detection signal.

The area surrounded by a dashed line 20 shows a second motion detecting section which is a feature of the present invention, and the one frame delay circuit 14A is commonly used.

This second motion detection unit 20 includes a subtracter 21 for detecting a one-frame difference signal, and a bandpass filter 22 for extracting a signal interleaved in a high frequency region.
is provided.

For example, in the case of the MUSE method, this bandpass filter 22 has a filter width of 4 to 12 MH2, and corresponds to a folded signal region of a video signal sampled at 16 MHI.

23 is a limiter circuit, 24 is an absolute value circuit, and the output of this second motion detection section 20 is also limited to a certain level,
The noise component superimposed on the detection signal is removed, and the signal is converted to a signal with a unidirectional polarity.

Reference numeral 25 denotes an amplifier constituting an inverting circuit, which outputs, for example, a signal of lK in response to the output K of the second motion detection section 20. (0<K>1) Reference numeral 26 denotes an amplifier constituting a comparator. For example, when the value of the motion detection signal becomes larger than a reference value, the switch 27 is switched to the b contact side. Then, the detection signal of the second motion detection section 20 outputted from the inverting circuit is supplied to the image processing section 30 via the switch 27, and the detection signal of the second motion detection section 20 is outputted from the inversion circuit to the image processing section 30, and the detection signal is outputted from the inversion circuit to the image processing section 30. Outputs a signal that has been subjected to interpolation processing.

By the way, in the MUSE method, the high frequency of the Y signal of a still image is interleafed in the frame direction and field direction, so it is multiplexed into a 15H2 frequency spectrum in the frame direction, as shown in Figure 2 (a). There is a particular thing. Here, 15H.

Focusing on the signal components, the frequency spectrum of the video signal can be summarized as the two-dimensional frequency spectrum shown in Figure 3,
The folding frequency of the interleaved original signal (0 to 12 MHz) exists in the band of 4 to 12 MHz. (However, 12 to 20 MHz is omitted.) Therefore, as shown in FIG.

When a comb-shaped bandpass filter is constructed and the signal is extracted in the time direction, 1582
However, as shown in Figure 2 (b), this spectrum is one frequency spectrum with a high peak value SP when it is a still image, but it has a high peak value SP when it is a moving image. As shown in FIG. 2(C), the position of the spectrum changes for each field due to the movement of the image, and the greater the movement, the wider the band and the lower the peak value SP becomes.

Therefore, the output of the subtracter 27 is a signal that has a large output when the image is a still image, but whose level decreases in a moving area.

The present invention applies the output of the second motion detection section 20 to signals of 4M82 or more required for interpolation between still images and moving images.
The image is output through a band pass filter 22 of 4 to 12 MHz, and when there is a small movement similar to a still image, the image is selected and output using a switch 27.

As described above, the second motion detection section 20 is configured so that the detected value becomes large when the motion of the image is small, so this motion detected value is supplied to the limiter circuit 23 and the absolute value circuit 24. By shaping the waveform, it is possible to create a unidirectional signal that is less affected by noise even for small motion areas.

Further, this signal is supplied to an amplifier 25 constituting an inverting circuit, and similarly to the first motion detection section 13, it is converted into a signal that increases when the motion is large, and is also supplied to an amplifier 26 constituting a comparator. By switching the switch 27 to output a portion close to a still image, signal processing of a portion where slight movement is observed is performed using the output of the second motion detection section.

FIG. 4 shows a signal waveform diagram for such motion detection.

Now, assume that the movement of a certain pixel in the image changes as shown in (2), and at the same time as it becomes stationary at time tl, it starts moving again at time t2.

In this case, the time point t is indicated by ■. Until then, it is assumed that the image is completely in the video area, and the signal between the inner and outer fields is output, improving the image quality, but between t + t 2, it is assumed that it is a still image, and the signal interpolated between the fields is output. is output to obtain a high-quality video signal.

Furthermore, since the period between jo j+ and between t2 and t3 is a quasi-still image area, image data in which a moving image interpolation signal and a still image interpolation signal are mixed at an appropriate ratio is obtained.

(2) indicates a two-frame difference signal obtained from the subtracter 15 of the first motion detection section due to the movement of the image as shown in (2) above, and this two-frame difference signal has a low level at time t. -t3, the influence of noise may cause malfunction.

Therefore, in the past, a coring circuit was used to reduce the signal below the - dotted chain line to zero level, making it a motion detection signal as shown by the thick line, but in this case, still images are processed even if there is slight movement. As a result, image quality deteriorates.

Therefore, in the motion area detection circuit of the present invention, the second motion detection section 20 generates the detection signal ■ whose level becomes higher as it approaches a still image, forms an inverted output ■ of this signal, and outputs the detection signal ■ The signal is output during period T3 when the level becomes higher than the one-dot chain line.

Therefore, as shown in ■, the signal from the first motion detection section 13 is output during the period TM, but the signal from the second motion detection section 20 is output during the period T3. As a result, the image processing circuit 30 is supplied with a motion detection signal that is less affected by noise, as shown in (2).

According to this motion detection, interpolation signals for both still images and videos are appropriate even during the period immediately before a still image with slight movement (T, period) or the period immediately before a moving image (T, period). Since the interpolation signal indicating movement remains in this area, the possibility of double images caused by afterimages due to interpolation between frames is reduced.

In addition, during the period when the image becomes a still image (t+t2), a signal interpolated with a still image is output using a motion detection signal without noise components, similar to the signal that has passed through the coring circuit 19, so flickering on the screen can be completely eliminated. can be eliminated.

FIG. 5 shows an example of a band pass filter of 4 to 12 MH, 22A and 22B.

22C122D is a 32.4MH delay circuit, and 2
2E and 22F indicate an adder and a subtracter. Also, 22G,
22H indicates a coefficient unit which adds 1/4 and 1/2 multiplication coefficients, respectively.

The configuration of this bandpass filter is a 3-tap system.
Since this is well known, detailed explanation thereof will be omitted.

[Effects of the Invention] As explained above, in the motion area detection circuit of the present invention,
The second motion detection means detects the level of the spectrum of the video signal that is interleaved in the bulk area, and this second motion detection signal is output in the screen area where there is minute movement. An interpolation operation using a moving image is also performed on the moving part of a quasi-still image that is lost by coring the motion detection signal detected by the two-frame difference signal, and the still image is erroneously output as a moving image due to noise components. This has the effect that appropriate signal processing can be performed even on semi-still image areas that are easy to use.

Furthermore, since the interpolation operation of a complete still image is performed without the influence of noise, interpolation improves the image quality and has the excellent effect of reducing the occurrence of flickering and double images. be.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the motion area detection circuit of the present invention, and FIGS. 2(a), (b), and (c) are explanatory diagrams showing the position and height of the spectrum of an interleaved video signal. , Figure 3 is an explanatory diagram showing the region of the second-order plane frequency spectrum of the folded signal extracted by the 15H bandpass filter, Figure 4 is a motion detection signal waveform diagram, and Figure 5 is an example of the bandpass filter. FIG. 6 is a diagram showing the band of a high-quality video signal. FIG. 7 is an explanatory diagram of frequency interleaf, and FIG. 8 is a block diagram showing an example of a signal processing circuit for high-quality video signals. 23 is a limiter circuit, 24 is an absolute value circuit, 25 is an inverting amplifier, 26 is an amplifier forming a comparator, 27
is a switch. In the figure, 13 is a first motion detection section, 14A is a 1-frame delay circuit, 20 is a second motion detection section, 1130 ←l715-' Vertical frequency (C/ph) U) Bran◆30 Hz→ Figure

Claims (1)

[Claims] In order to interleaf the out-of-band signal into the high frequency region of the video signal and detect the motion area of the broadcast image, which is made into a high-quality video signal, a two-frame difference signal of the video signal is generated and its output is a first motion detecting means for detecting a motion area from the video signal; and a second motion detecting means for extracting a signal interleaved with the video signal in the time axis direction; A motion area characterized in that when it is determined that the motion is large, the output signal of the first motion detection means is selected, and when it is determined that the motion is small, the output signal of the second motion detection means is selected. detection circuit.