JPH0472966A - Signal detection circuit - Google Patents

Abstract

PURPOSE:To detect a 'telecine picture' and to detect a field phase used for control or the like with high accuracy by dividing a picture into plural blocks, processing the result and providing a hysteresis characteristic to a 'telecine picture' detection circuit. CONSTITUTION:A sent television signal is inputted to an inter-frame movement detection circuit 2 and a block control circuit 8 uses a hold circuit 9 reset for each block to hold the signal for one field period. Then a 5-field period detection circuit 10 is used to detect the periodicity for each block and a field phase for the period. When a signal converted from the film is inputted, an L level (still field) is outputted for 5-field period without fail. In the case of the signal converted from the film, an H level as a 'telecine picture' is outputted and in other case, an L level as a 'general picture' is outputted for each block.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal detection circuit, and more particularly to a circuit for detecting a television signal converted from a movie film or the like.

[Conventional technology]

In the current television viewing system (NTSC system), images are transmitted by dividing one frame into two fields using interlaced scanning, and the number of images is 30 frames (60 fields) per second.

On the other hand, mark 7 (I) such as 16nwn and 35nwn
! Film has 24 frames per second. If a standard screen projector is used in conjunction with a television camera to transmit film, the relationship between the shutter of the projector and the scanning of the television will cause distinct horizontal stripes that move up and down or severe flickering to appear in the image, making it impractical. A projector called a telecine converts the film image into a television signal.

Telecine has 24 frames per second for film and 6 frames per second for television.
In order to correspond to the 0 field, 2 frames of film are converted into 5 fields, with 1/12 second being one period. The 2-3 pulldown method (or
In telecine using an improved fast pull-down method, odd-numbered films are processed in two fields (2/2).
By scraping off every 60 seconds) and scraping off every 3 fields for even-numbered films, 2 frames of film correspond to 5 fields.

This type of technology is available, for example, in 1) Yu Iwase - 1 "Video Terminology Dictionary," Shashin Kogyo Publishing, August 1989, and 2) "Television Engineering Handbook," edited by the Television Society of Japan.
7 Oichimusha, December 1969, etc.

One example of a method for detecting a telecine image signal converted from a film into a television signal as described above is the method described in Japanese Patent Application No. 2-45408.

As mentioned above, two frames of film correspond to five fields of television signals. At this time, for example, as shown in FIG. 3, first and second field images are created from the first film, and 3.4.
It is assumed that 5 field images are created. On this occasion,
Since the low frequency components (below 2M Iz) of the third field image and the fifth field image become exactly the same signal, the result is a static field in which no frame difference signal occurs during one field period. It is detected that this is repeated every five fields.

FIG. 4 shows a configuration example of a conventionally known [telecine image] detection circuit. First, the transmitted television signal is input to the interframe motion detection circuit 2.

In the interframe motion detection circuit 2, a 525H delay circuit 3 and a subtraction circuit 4 create a difference between one frame of the signal. When the input signal is an NTSC signal, the color signal is multiplexed with polarity inversion for each frame, so only the movement of the luminance signal is separated by the low-pass filter 5 to prevent erroneous detection of movement. A comparison circuit 7 is used to compare the value (TH) set by the threshold setting circuit 6,
When the output of the filter 5 is larger than TH, it is regarded as a moving image, and, for example, "H" is output. Other images are regarded as still images, and, for example, II L )+ is output. Since this is output for each pixel, it is held for one field period using a hold circuit 9 which is reset for each field by the field control circuit 12.

In other words, if the level reaches tt H)l even once in one field period, that field becomes It HP+ level (
motion field). At this time, if a signal converted from the filter l\ is input, an "L" level (static field) is always output at a period of 5 fields. 5
This is detected by the field period detection circuit 10, and if the signal is converted from film, the II HP+ level is output as a [telecine image], and in other cases, the tg L P+ level is output as a [general image]. .

If the above conventional method is applied to a television receiver such as IDTV or EDTV, it is possible to detect [telecine image] and [general image] by signal processing only on the receiver side, and in the case of [telecine image], the above Using the periodicity and the phase in the period [
Since luminance-chrominance signal separation and sequential scanning suitable for the properties of telecine images can be performed, a significant image quality improvement effect can be obtained.

[Problem to be solved by the invention]

In the above conventional example, the low frequency component of the frame difference signal,
A comparison is made for each pixel with a certain set value TH.

If the low-frequency component of the frame difference becomes larger than TH for even one pixel during one field period, it is considered a motion field, and otherwise it is considered a still field.

[In the case of telecine images, taking advantage of the property that this static field always appears at least once in five fields, [
[Telecine image] and [General image] are determined.

On the other hand, normally aired movie programs are often superimposed with Japanese subtitles and special news. Generally, these superimposed images are inserted into the television signal after conversion from the film, regardless of the properties of the above-mentioned [telecine image], so in conventional detection methods, the entire screen is determined to be a [general image].

In addition, if there is a lot of transmission line noise, even if it is originally a static field, the difference in one frame will be “0” due to the noise.
”, it is determined to be a motion field, and in conventional detection methods, it is determined to be a general image.

If such false detections (missed detections) occur, image quality improvement effects cannot be obtained because signal processing suitable for [Telecine image] cannot be performed, and signal processing for [Telecine mode] and [
If the signal processing in [General mode] is switched frequently, the reproduced image may become unnatural.

Therefore, an object of the present invention is to provide a ``telecine image detection circuit'' that can accurately and stably detect that it is a ``telecine image'' and detect the field phase used for control and the like.

[Means to solve the problem]

The above object is achieved by the following means.

1) Divide the screen into multiple blocks for processing 2) Use an area filter to remove isolated points 3) Provide hysteresis characteristics to the [telecine image] detection circuit 4) Bilingual broadcast (audio multiplex broadcast) mode 5) Providing a manual mode switching means [Operation] The operating principle of the present invention will be explained with reference to FIG. 1.

First, the screen of the television receiver 1 is divided into a plurality of blocks, and each block is determined to be a ``telecine image'' or a ``general image.'' In the figure, a breaking news text is inserted at the top of the screen, and a subtitle text is inserted at the bottom of the screen, and only these blocks are determined to be [general images]. Other blocks undergo signal processing suitable for a [telecine image], so the image quality improvement effect is greater than processing the entire screen as a [general image].

On the other hand, the above problem can be solved by using a superimposer that changes the superimposition content when switching films in accordance with the properties of [telecine images].

Furthermore, by applying an area filter that removes isolated points to the inter-frame motion detection results, false detection of impulsive noise as image movement is reduced, and the detection accuracy of noisy [telecine images] is improved.

In addition, in movie programs, etc., the [telecine image] is continuous for several minutes to several tens of minutes, and does not switch frequently to the [general image]. By providing a characteristic in which the mode does not change for several fields when the processing mode changes, it is possible to eliminate the unnaturalness of the reproduced image caused by frequent changes in the processing mode.

Furthermore, when broadcasting foreign movies, etc., foreign language may be simultaneously transmitted as sub-audio of audio multiplex broadcasting. On the other hand, in the case of such bilingual broadcasting, there is a high possibility that it is a ``telecine image'', so by setting the parameters of the detection circuit so that it is likely to be determined as a ``telecine image'', it is possible to eliminate noise, subtitles, etc. It is possible to reduce false positives due to

Furthermore, if the reception conditions are poor due to strong noise or difficult viewing areas, it may be difficult to detect the telecine image, or the image may frequently switch to the general image. In such a case, the quality of the reproduced image may be improved by manually switching to [forced telecine mode] or [forced general mode] instead of using the automatic detection results.

Therefore, by using the above means, it is possible to reduce false detections due to subtitle superimposition and noise, so that the periodicity and the field phase during the period can be reliably detected, and the above object can be achieved.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 shows a specific configuration diagram of an embodiment of the present invention that performs block processing. First, the transmitted television signal is input to the interframe motion detection circuit 2. In the interframe motion detection circuit 2, a 525H delay circuit 3 and a subtraction circuit 4 create a difference between one frame of the signal. When the input signal is a composite signal, since the polarity of the color signal is inverted for each frame, only the movement of the luminance signal is separated by the low-pass filter 5 to prevent erroneous detection of movement. A comparison circuit 7 is used to compare the value (TH) set by the threshold setting circuit 6, and if the output of the filter 5 is larger than TH, it is regarded as a moving image.
For example, output tt i (II).

Others are considered still images, for example 11. Output L II. Since this is output for each pixel, it is held for one field period using a hold circuit 9 which is reset for each block by a block control circuit 8. In other words, if it reaches the HI+ level even once in one block,
The block is at the "I-I" level (motion block). This result is stored in the block memory 11,
A five-field period detection circuit 10 is used to detect the periodicity of each block and the field phase during the period. At this time, if a signal converted from film is input, a tzL'' level (still field) is always output at a period of 5 fields.If the signal is converted from film, it is output as a [telecine image]. HI+ level is output for each block. Otherwise, [KL A control signal may be generated to mix the signal processing results of [Telecine Detection] with the signal processing results of [Telecine Detection].Furthermore, the locations where superimpressions are likely to be inserted (for example, the top, bottom, left, and right edges of the screen) are not subject to [Telecine Detection]. It is also possible to simplify the process by removing the screen and performing [telecine detection] only in other areas (for example, the center of the screen).

Furthermore, if several blocks or more are determined to be "telecine images", the entire screen can also be determined to be "telecine images". Furthermore, the mode and field phase of the entire field may be determined by ANDing the field phases detected for each block or by taking a majority vote.

FIG. 5 shows a specific configuration diagram of another embodiment of the present invention using an area filter. In the figure, the output of the interframe motion detection circuit 2 is passed through an area filter 13, which will be described later. This output is used to detect a telecine image using a hold circuit 9 controlled by a field control circuit 12 and a 5-field period detection circuit 10, which will be described later.

FIG. 6 shows a detailed configuration example of the area filter 13.

In the same figure, the input motion detection result is transferred to the delay circuit 1.
4 to 17 are used to delay each pixel (one clock), and an AND circuit 18 performs a logical product of each output. In this case, since the motion detection result is a 1-bit signal representing the presence or absence of motion for each pixel, a simple AND circuit may be used. This output is further processed by IH (
1 horizontal scanning period), and the AND circuit 21 calculates the AND of the respective outputs. In this configuration, 5 horizontal pixels x 3 vertical lines (total 15
Only when all five pixels are in motion is determined to be motion.

If this area is made too large, the original movement will be mistaken for stationary, so the size of the area is determined by making a trade-off with the amount of noise.

FIG. 7 shows a detailed configuration example of the five-field period detection circuit 1o. In the figure, motion detection results input corresponding to fields are delayed by clocks at field intervals using delay circuits 22 to 31. The appearance of every five fields is input to a determination circuit 32 (to be described later), and is used as a detection result of a [telecine image].

FIG. 8 shows a detailed configuration example of the determination circuit 32.

In the figure, a NOR circuit 33 calculates the inverted AND of the motion detection results for every five fields. That is, in this case, the It Hlj level is output when "still fields" of 5 field periods occur three times in a row. This is delayed by delay circuits 34 to 37 driven by field pulses, and an OR circuit 38 calculates the logical sum of five fields. That is, if even one of the five fields is "three consecutive still fields", it is determined to be a [telecine image]. Of course, it is not limited to 3 times''' and 1'5 fields'', and the higher the number of times, the more continuous still images in [General mode] and [Telecine image]
The accuracy of the judgment will be improved, but it will take time to make the judgment. Further, as shown in FIG. 9, the NOR circuit 33 shown in FIG.
By using the majority circuit 39 instead, a hysteresis effect can be provided.

FIG. 10 shows the third embodiment of the present invention with a hysteresis effect.
A specific configuration diagram of the embodiment is shown. The output signal of the inter-frame motion detection circuit 2 is passed through a hold circuit 9 controlled by a field control circuit 12, and then passed through a free-running circuit 40, which will be described later, to detect a [telecine image] by a 5-field detection circuit 10. do.

FIG. 11 shows a detailed configuration example of the free-running circuit 40. This circuit prevents frequent changes in mode by forcibly treating a static field that occurs every five fields as a static field even though it is determined to be a motion field due to noise or the like. In the figure, the counter 41 is made to run automatically from the last stationary field, and a count of the number of fields (1-) is started. tt 5
The multiple of 5 is detected by the tr detection circuit 42, the It 10 I+ detection circuit 43, etc., and the NOR circuit 44 and the AN
The D circuit 45 is used to perform a logical sum with the original motion detection result.

After detecting "10", hold the counter and stop counting. With this circuit configuration, even two missing pulses can be saved. However, this will change the [General image] to [
Therefore, the number of pulses to be repaired is a trade-off with noise, etc., as this may lead to false detections.

The above-mentioned means are independent technologies, for example, the first
As shown in Figure 2, Ikkuga's technology can be used in combination. In the figure, the output of the inter-frame motion detection circuit 2 is passed through an area filter 13, passed through a bold circuit 9 controlled by a block control circuit 8, and further passed through a free-running circuit 40, and then five-field period detection is performed. A circuit 10 and a block memory 11 detect a [telecine image] for each block. Each operation is as described above. Furthermore, detection accuracy can be increased by using the bilingual mode detection circuit 46. In other words, if a foreign language is multiplexed as sub-audio in an audio multiplex broadcast, there is a high possibility that the broadcast is a foreign movie.

Utilizing this, when the bilingual mode detection circuit 46 detects this, the processing parameters of the above-mentioned means are changed to [
By changing the parameters to those that are easier to detect (telecine image), it is possible to avoid false detections caused by noise or the like. For example, you can increase the TH setting value in the frame difference detection circuit 2 to make it easier to determine that it is a still image, increase the area of the area filter, or use the block control circuit 8 to convert several blocks or more into a telecine image. If it is detected, the entire screen is determined to be a ``telecine image'', the number of fields that are self-running in the free-running circuit 40 is increased, the internal operation of the 5-field period detection circuit 10 is switched to majority decision, etc. Then, the entire or part of the circuit is switched to processing that makes it easier to determine that it is a telecine image. Even if the above processing is performed, if the reception condition is poor due to strong noise or difficult-to-view areas, it may be difficult to detect the ``telecine image'' or the ``telecine image'' may be frequently switched to the ``general image.'' In such a case, do not use the automatic detection result and use the switch 47 to select [
You can also switch to [Forced Telecine Mode] or [Forced General Mode].

The above explanation was based on the current NTSC signal, but it is not limited to this, and for example, MUSE
The present invention can be similarly applied to television signals such as high-definition signals and EDTV signals. Also,
The present invention is not limited to movie films, and can be similarly applied to cases where the number of transmitted frames is greater than the number of frames of the signal source (including signals in which frames of the signal source are intentionally dropped).

Furthermore, the present invention can be used not only for transmitted television signals but also for signals recorded on VTRs, video discs, and the like.

〔Effect of the invention〕

By applying the present invention, it is possible to accurately determine between a ``telecine image'' and a ``-general image'' by signal processing only on the television receiver side, and when it is a ``telecine image'', a suitable Since signal processing can be performed, the effect of implementation is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the operating principle of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a diagram explaining the principle of [telecine image] detection, and Fig. 4 is a diagram explaining the principle of [telecine image] detection. The configuration diagrams of the detection circuit, FIGS. 5 to 12, are configuration diagrams of other embodiments of the present invention and diagrams for explaining the details thereof. 1... Television receiver, 2... Inter-frame motion detection circuit, 3, 14, 15, 16, 17, 19° 20.
22, 23, 24, 25, 26, 27° 28.29, 3
0, 31, 34, 35, 36° 37...Delay circuit, 4
... Subtraction circuit, 5... Filter, 6... Threshold setting circuit, 7... Comparison circuit, 8... Block control circuit, 9... Hold circuit, 10... 5th filter Cold period detection circuit, 11... Block memory, 12... Field control circuit, 13... Area filter, 1.8
,21. ．． 45... AND circuit, 32... Judgment circuit, 33, 44, NOR circuit, 38, OR circuit, 39...
・Majority circuit, 4o...Free-running circuit, 41...Counter, 42-"5" detection circuit, 43-"10" detection circuit, 46...2 is Japanese language mode detection circuit, 47...
Lolo

Claims (1)

[Claims] 1. A signal detection circuit that detects that the number of frames per second transmitted by a television signal is greater than the number of frames per second transmitted by a signal source, which includes a motion detection circuit and at least periodicity of the detection result or periodicity of the detection result. A signal detection circuit comprising: a period detection circuit that detects a phase in a period. 2. The signal detection circuit according to claim 1, further comprising means for processing a television signal by dividing it into a plurality of spatial blocks. 3. The signal detection circuit according to claim 1, further comprising means for removing isolated points from the motion detection result or the period detection result. 4. The signal detection circuit according to claim 1, further comprising means for imparting hysteresis characteristics to the motion detection circuit or the period detection circuit. 5. In a signal detection circuit that detects that the number of transmitted frames per second of a television signal is greater than the number of frames per second of a signal source, a motion detection circuit detects at least the periodicity of the detection result or the phase during the period. What is claimed is: 1. A signal detection circuit comprising: a period detection circuit for detecting a period of detection; and an audio multiplex broadcast mode detection circuit. 6. The signal detection circuit according to claim 5, wherein the signal detection circuit is provided with means for manually controlling the output result.