JPH08289222A - Letter box screen detector - Google Patents

Abstract

PURPOSE: To provide a letter box screen detector with which a display mode (screen size) of a letter box screen is prevented from being suddenly changed when the erroneous detection of the screen is generated. CONSTITUTION: An input video signal (a) inputted from a terminal 14 is respectively supplied to an aspect ratio detection part 12 and a scene change detection part 13. Besides, an aspect ratio detection output (c) from the aspect ratio detection part 12 and a scene change detect signal (d) from the scene change detection part 13 are respectively supplied to a switching logic circuit 11. Then, the switching logic circuit 11 supplies a switching pulse (e) to a display mode switching part 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a letterbox screen detecting device, and more particularly to a video signal having a different aspect ratio,
When displaying in the optimal display mode for each,
The present invention relates to a letterbox screen detection device capable of switching a display screen at an optimum switching timing for switching the display mode.

[0002]

2. Description of the Related Art NT in the television signal standard system
In the SC (National Television System Committee) system, the aspect ratio (aspect ratio) of a television screen is set to 4: 3, as is well known. By the way, in recent years, a television system called a high-definition (high-vision system) using a broadcasting satellite and having an aspect ratio of 16: 9 has been standardized. In addition, standardization of the EDTV2 system using the conventional terrestrial wave having the same aspect ratio 16: 9 as that of the high-definition system in parallel with it is also in progress. On the other hand, nowadays, television receivers called wide televisions, which are conscious of a horizontally long screen with an aspect ratio of 16: 9, are rapidly becoming popular in ordinary households.

FIG. 9 shows package software which is generally commercially available and has a display form commonly called a letterbox screen having a non-image part at the top and bottom of the screen and an aspect ratio of 4: 3.
It is a figure which shows an example at the time of displaying on the screen of FIG.

FIG. 9A shows a horizontally long image software (high definition size) having an aspect ratio of 16: 9, which has a panel portion (also referred to as a non-image portion) having no image on a screen having an aspect ratio of 4: 3. The display is shown. It is expected that such horizontal video package software will increase in the future. Among the existing major video software, there are video software having various different aspect ratios in addition to those having video signals with aspect ratios of 4: 3 and 16: 9. The representative ones are shown below.

9 (b) and 9 (c) show an aspect ratio of 1.85:
FIG. 9B is a display example of a movie software called Vista size, FIG. 9B shows a display example when the subtitle supermarket has two lines, and FIG. 9C shows a display example when the subtitle supermarket has one line. Are shown respectively. 9D and 9E are display examples of movie software called cinemascope with an aspect ratio of 2.35: 1, and FIG. 9D is a display example when the subtitle super is one line. (E) shows respective display examples when there is no subtitle supermarket.

The above is a typical horizontally long video software, and the actual video software is domestic software,
It's from overseas, dubbed in Japanese, subtitle supermarket is one or two lines,
There are various display modes, such as those without a subtitle supermarket. Taking the number of lines in the upper panel portion of the screen as an example, there is a variation of about 10 to 50 lines.

In the conventional wide television, it is possible to display in various display modes (methods) in order to cope with a variety of horizontally long video software as described above.

FIG. 10 is a diagram showing an example of a display mode in a conventional wide television receiver.

FIG. 10A shows an NTSC video signal (software) having an aspect ratio of 4: 3 with an aspect ratio of 1.
This is a normal display mode for displaying on a 6: 9 wide television receiver, and includes a non-image area 41 on the left and right of the image.
This is a display mode for displaying with 42 added, and is generally called "normal mode".

In FIG. 10B, the image is enlarged in both the vertical and horizontal directions so that the horizontal image area fills the display screen horizontally, and the upper and lower partial images (the upper image 43 and the lower image) protruding from the display screen are displayed. This is a display mode in which the side image 44) is cut and displayed, which is called a "zoom mode". In this zoom mode, the displayed image can be scrolled in the vertical direction, and this function is used to display the cut upper image 43 or lower image 44 on the display screen. It is possible to display.

In FIG. 10 (c), the image is enlarged in both the vertical and horizontal directions so that the horizontal image area is filled to the full width of the display screen, and then the vertical image is enlarged or reduced at a predetermined ratio. It is a display mode that is called "live mode". In the live mode, although not as in the zoom mode, the upper and lower partial images (the upper image 45 and the lower image 46) protruding from the display screen are cut and displayed.

FIG. 10 (d) shows a display mode in which the image is enlarged only in the horizontal direction and enlarged so that the image area fills the display screen, which is called "full mode".

Next, when an image signal having a display form called a letterbox screen is to be displayed on a wide television receiver having an aspect ratio of 16: 9, that is, in each of the four modes shown in FIG. The case will be discussed below.

First, in the case of displaying in the normal mode, in this case, in addition to the left and right non-image portions 41 and 42, a non-image portion is further generated in the upper and lower portions of the screen, and the area where the image is actually displayed is It will become smaller, and the benefits of the large screen (wide TV) display will be completely lost.

Next, in the case of displaying in the zoom mode. In this case, the upper and lower parts of the aspect ratio of 4: 3 are cut, but the image signal to be displayed is the letterbox screen. Therefore, the upper image 43 and the lower image 44 to be cut are highly likely to be the non-image portion, and the portion of the pattern (the portion other than the non-image portion) is displayed in the full screen. However, this is important in the case of video software in which the portion of the picture (other than the non-picture portion) is biased to the upper part or the lower part of the image with the aspect ratio of 4: 3, or subtitles are displayed at the lower part. There is a possibility that the picture information will be lost. Basically, in this mode, since the ratio of upper and lower image cuts is large, it is necessary to use the scroll function or the like described above so as to prevent the important pattern information and the like from being lost.

Next, in the case of displaying in the live mode, in this case, as compared with the case of the zoom mode, the ratio of the upper and lower parts of the aspect ratio of 4: 3 being cut is smaller, so that the upper and lower parts are cut. Move or enlarge the pattern in the direction
The need to adjust the reduction ratio etc. is reduced. Incidentally, in this mode, generally, the circularity ratio is slightly enlarged in the lateral direction, that is, the pattern becomes slightly horizontal, but this is not a serious problem.

Next, in the case of displaying in the full mode, in this case, all the images with the aspect ratio of 4: 3 are displayed without being cut, but compared with the case of displaying in the live mode, This is not a highly recommended mode because a pattern that extends horizontally is displayed.

The case where a video signal having a display form called a letterbox screen is displayed in each of the above four modes on a wide television receiver having an aspect ratio of 16: 9 has been described above. Even in this mode, the user looks at the video (picture) displayed on the screen and makes a judgment, and some kind of adjustment such as display switching is manually performed so that the video (picture) can be easily seen by the user. It is necessary to select the optimum display mode by the manual operation every time the aspect ratio (video software) of the video signal changes.

Therefore, conventionally, the complicated display mode selection by the manual operation as described above is automatically performed by determining the aspect ratio of the video signal having the display form called the letterbox screen. Various devices have been proposed. A method of detecting a letterbox signal by such a conventional letterbox discrimination device will be described below.

FIG. 11 is a diagram showing a vertical blanking period of an NTSC video signal and a horizontal scanning period of a video signal.

In FIG. 11, the period 49 of the display video signal is shown.
Is configured with a blanking period 47 and a video period 48 of a video in the horizontal direction as one cycle (set). The blanking period 47 of the image in the horizontal direction is a horizontal blanking period, and represents a period in which the image is not displayed on the cathode-ray tube (luminance is lowered). And the video period 48 is 1
It is the H scanning period, and shows the period during which the video signal is displayed on the cathode ray tube.

CCIR (International Radio Co
mmittee, International Wireless Communications Advisory Committee), the blanking level (c) shown in the figure is 0 IRE unit (1 IRE unit = 1/140 [V]), and the black level standard (b) is 4
It is recommended that the IRE unit and the white level reference (a) be 100 IRE units and the synchronization level (d) be -40 IRE units.

By the way, assuming that the video signal complies with the CCIR recommendation, the level of the video signal in the video period 48 is between 0 IRE unit (blanking level) and 4 IRE unit (reference of black level). It is possible to detect whether or not the video signal (video software) is a letterbox signal by detecting the scanning lines near the upper and lower parts, extracting the video signal, and checking the level in the video period 48 in the video signal. become. The conventional method of detecting a letterbox signal by the letterbox discriminating apparatus has been performed as described above. However, as a matter of course, according to this method, the level of the video signal of the non-image portion (mask portion) near the upper and lower portions of the screen during the video period 48 is
If the IR recommendation is not met, that is, if the level (bright) is much higher than 4 IRE units (black level standard), erroneous detection will be performed.

Actually, by examining the video software recorded on a number of letterbox screens, the level in the video period 48 in the video signal of the non-image part (mask part) near the upper and lower parts of the screen was as high as near 12 IRE units. There were a lot of things at the level. As a result, the letterbox screen is detected depending on whether the level of the video signal for scanning the non-image part near the upper and lower parts of the screen is higher or lower than 4IRE unit (reference of black level). Then, depending on the video software, there is a problem that false detection occurs.

Therefore, a proposal to improve such a defect is proposed in Japanese Patent Application No. 6-91232 (letterbox screen detection device).
It is made in. According to this proposal, since the number of lines at the boundary between the non-image part and the pattern part near the upper and lower parts of the letterbox screen is detected, the aspect ratio of the letterbox screen can be detected, and it can be compared with the above method. It is possible to detect the letterbox screen more reliably and accurately. Further, in the above-mentioned proposal, in order to prevent a phenomenon that the display mode of the screen is frequently switched when an erroneous detection occurs, detection of a video signal having a screen with an aspect ratio of 4: 3 and a video signal having a letterbox screen are performed. The determination time for detection of is taken to some extent long.

However, even if the above-mentioned improvements and the like are performed, erroneous detection will occur in a certain type of video signal. For example, when a subject with black bands at the top and bottom is displayed, such as a sumo wrestling bulletin board, this black band is determined to be a non-image part of the letterbox screen, and the video signal has a letterbox screen. It detects that it is something and automatically changes the display mode. As a result, the display mode of the screen is suddenly switched and the user (viewer) feels strange.

In addition to this, as a subject that frequently produces black bands at the top and bottom of the screen, there is a screen of a stage such as a music (live) program or a drama. That is, when the entire stage is displayed, the lower side of the screen shows the audience seats, and the upper side shows the tare. Part), and these may be erroneously determined to be non-image parts of the letterbox screen, resulting in erroneous detection. Further, a screen in which a spotlight is applied to the center of the screen and the periphery is displayed dark is likely to cause false detection in the same manner.

[0028]

As described above, even though the video software has a letterbox screen recorded,
Video signals reproduced from the video software are various,
Further, even in the case of a received signal (video signal) from a general television broadcast, there are various types of subjects to be projected, and the black band portion of the screen displayed by these video signals is detected from the video signal, Therefore, there is a problem (defect) that it is difficult to detect a letterbox screen with a probability close to 100%.

Therefore, in order to solve such a problem, the present invention solves the problem when a letterbox screen is erroneously detected.
An object of the present invention is to provide a letterbox screen detection device in which the screen display mode (screen size) does not suddenly change.

[0030]

According to a first aspect of the present invention, there is provided a letterbox screen detecting device, wherein a means for inputting a video signal, a means for displaying the video signal, and a video displayed by the video signal are letters. A letterbox image detecting means for detecting whether the image is a box image, a scene change detecting means for detecting a change in a scene of an image displayed by the image signal, and a change in aspect ratio by the letterbox image detecting means. After being detected, a letterbox video switching signal output means for outputting a signal for switching to the letterbox video at the timing when the scene change is first detected by the scene change detection means, and the output from the output means A display mode for switching the display mode of the display means based on a letterbox image switching signal. Characterized by comprising a switching means.

According to another aspect of the present invention, there is provided a letterbox screen detection device, an input means for inputting a video signal, a display means for displaying the video signal, an aspect ratio of a video displayed by the video signal, and an aspect ratio thereof. Means for detecting a change, scene change detecting means for detecting a change in a scene of an image displayed by the video signal, and a change in the aspect ratio detected by the aspect ratio and means for detecting the change, Aspect ratio output means for outputting the aspect ratio and the aspect ratio after the aspect ratio change detected by the aspect change detection means at the timing when the scene change detection means first detects the scene change; The display mode of the display means is switched based on the aspect ratio output from the ratio output means. Characterized by comprising a display mode switching means for obtaining.

According to a third aspect of the present invention, there is provided a letterbox screen detecting device according to the second aspect, wherein the means for detecting the aspect ratio and its change outputs a first DC reference value. First reference signal generating means and a first average signal level of a predetermined number of scanning lines near the start of the first vertical blanking period of the video signal or near the end of the first vertical blanking period. And a second average signal level detecting means for detecting the
Second average signal level detecting means for detecting a second average signal level of a predetermined number of scanning lines near the central portion of the video signal before the vertical blanking period is started, and the first average signal level. A means for obtaining a first absolute value by taking a difference from the second average signal level; a means for obtaining a magnitude relationship between the first average signal level and the second average signal level; The comparing means for comparing the absolute value level with the first DC reference value, and the result of the comparison by the comparing means are the first absolute value level from the first DC reference value for a predetermined number of consecutive times. Is larger, it is determined that the aspect ratio has been changed, and means for outputting the first absolute value level and the magnitude relationship is used.

In the letterbox screen detection device according to the present invention, means for inputting a video signal, means for displaying the video signal, and an aspect ratio of the video displayed by the video signal and its change are detected. Means to do
A display mode selection unit that selects a display mode of the display unit based on the changed aspect ratio, a scene change detection unit that detects a change in a scene of a video image displayed by the video signal, the aspect ratio and A display for outputting the display mode selected by the display mode selection means at the timing at which the scene change is first detected by the scene change detection means after the change in the aspect ratio is detected by the means for detecting the change. It is characterized by further comprising mode output means and display mode switching means for switching the display mode of the display means based on the display mode output from the output means.

The letterbox screen detecting device according to the invention of claim 5 is the letterbox screen detecting device according to claim 1, 2, 3 or 4, wherein the scene change detecting means delays the video signal by one frame period. The 1-frame delay means, the subtraction means for taking the difference between the video signal output from the 1-frame delay means and the video signal not passing through the 1-frame delay means, and the second absolute value that is the subtraction result. Pixel for comparing one frame for each pixel with a means for obtaining, a second reference signal generating means for outputting a second DC reference value, the second absolute value level, and the second DC reference value By the comparison means and the pixel comparison means,
The number of pixels for which the second absolute value level is determined to be larger than the second DC reference value is counted, and when the number exceeds a predetermined number, it is determined that there is a scene change, and a scene change signal is output. It is characterized by being configured with an output counter.

The letterbox screen detecting apparatus according to the invention of claim 6 is the letterbox screen detecting apparatus according to claim 1, 2, 3 or 4, wherein the scene change detecting means delays the video signal by one frame period. The 1-frame delay means, the subtraction means for taking the difference between the video signal output from the 1-frame delay means and the video signal not passing through the 1-frame delay means, and the third absolute value that is the subtraction result. Determining means, means for integrating the third absolute value for one frame, third reference signal generating means for outputting a third DC reference value, integration result of the third absolute value, and the third 3 is compared with the DC reference value of No. 3, and if the integration result of the third absolute value is larger, it is determined that there is a scene change, and a comparison circuit that outputs a scene change signal is used. You .

[0036]

According to the first aspect of the present invention, a letterbox image detecting means for detecting a letterbox image and a scene change detecting means for detecting a scene change of the image are provided, and the input image signal is a letter. In the case of a box image, the display mode (aspect ratio) of the wide television receiver is switched according to the timing of the scene change (change of display information on the screen) detected by the scene change detection means. The display modes can be switched without giving the viewer a feeling of strangeness.

According to the present invention, the aspect ratio of the input video signal and the means for detecting the change thereof and the scene change detecting means for detecting the change of the scene of the video are provided, and the input video is supplied. When a change in the aspect ratio of the signal is detected, the display mode (aspect ratio) of the television receiver is adjusted in time with the change in the scene (change in the display information on the screen) detected by the scene change detecting means. Since the display mode is switched, it is possible to naturally change the display mode without giving the viewer a feeling of strangeness.

[0038]

EXAMPLES Examples will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a letterbox screen detection device of the present invention.

In FIG. 1, the input video signal (a) input from the terminal 14 is supplied to the aspect ratio detecting section 12 and the scene change detecting section 13, respectively. An aspect ratio determination output (c) is supplied from the aspect ratio detection section 12 and a scene change detection signal (d) is supplied from the scene change detection section 13 to the switching logic circuit 11. Then, the switching logic circuit 11 sends a switching pulse (e) to the display mode switching unit 16.
Is being supplied.

Next, the operation of the letterbox screen detection device configured as described above will be described.

FIG. 2 is a flow chart showing the operation of the letterbox screen detection device of the present invention. FIG. 3 is a timing chart showing the operation timing of the letterbox screen detection device of the present invention.

First, the outline of the operation of the letterbox screen detection device of the present invention will be described with reference to the flowchart of FIG.

The aspect ratio detector 12 constituting the letterbox screen detector monitors the aspect ratio change from the video signal input from the terminal 14 (step s1). If it is not detected, normal processing such as displaying an image in the current display mode is performed (step s2). If a change is detected, the scene change detection unit 13 changes the scene (display of the screen). When a change in the scene is detected (step s3), the switching pulse (to the display mode switching unit 16) is detected at the same time when the change in the scene is detected, that is, at the timing when the scene changes. Output)
The screen display mode is switched (step s4).

That is, even if a change in the aspect ratio is detected, the screen display mode is not immediately switched, but the next scene change is waited for, and at the same time when the scene change is detected, the display mode is switched. This is the point of the present invention. As a result, the display mode is switched in accordance with the change of the scene, so that the uncomfortable feeling that the screen size is suddenly switched in the scene without the scene change is improved.

Next, a specific example for realizing the above operation will be described with reference to the timing chart of FIG.

First, assuming that the input video signal (a) is a 4-to-3 screen and a scene change occurs at the timing shown in (a) of the figure, the scene change detection section 13 outputs the scene change detection output (d). Is output to the switching logic circuit 11. At this time, since the input video signal (a) has a 4-to-3 screen, the aspect ratio detection unit 12 outputs L (low level) to the switching logic circuit 11 as the aspect ratio determination output (c). On the other hand, the switching logic circuit 11 uses the same signal L (low level) as the aspect ratio determination output (c) as a switching pulse (e) at the fall timing of the scene change detection output (d) as a display mode switching section. Output to 16. At this time, since the switching pulse (e) is L (low level), the display mode is not switched (4: 3 screen display remains).

Next, if the input video signal (a) is a 4-to-3 screen, and a scene change occurs at the timing shown in (b) of the figure, at the same time when the 4-to-3 screen is switched to the letterbox screen, the scene is changed. The change detection unit 13 outputs a scene change detection output (D) to the switching logic circuit 11. In addition, the aspect ratio detection unit 12 sets a predetermined time, that is, from the timing of (b) to the timing of (e) after the input video signal (a) is switched from the 4: 3 screen to the letterbox screen. During this period, if the input video signal (a) does not change (letterbox screen remains), the input video signal (a) is judged to be the letterbox screen, and the aspect ratio judgment output (c) is output. It outputs H (high level) to the logic circuit 11. On the other hand, the switching logic circuit 11 outputs the same signal L (low level) as the switching pulse (e) because the output level of the aspect ratio determination output (c) is L (low level) at the timing of (b). Is output to the display mode switching unit 16. At this time, since the switching pulse (e) is L (low level), the display mode is not switched (4: 3 screen display remains). Also, at the timing of (e), the output level of the aspect ratio determination output (c) has been switched to H (high level), but since no scene change has occurred,
Since the scene change detection output (d) is not output from the scene change detection unit 13, the switching pulse (e) remains L (low level) and the display mode is not switched (4: 3 screen display remains). ).

Next, when a scene change occurs at the timing of FIG. 3 (c), the scene change detection section 13 outputs a scene change detection output (d) to the switching logic circuit 11. At this time, since the input video signal (a) is a letterbox screen, the aspect ratio detection unit 12 outputs H (high level) as the aspect ratio determination output (c) to the logic circuit 11. On the other hand, the switching logic circuit 11 uses the same signal H (high level) as the aspect ratio determination output (c) as a switching pulse (e) at the fall timing of the scene change detection output (d) as the display mode switching section 16. Output to. At this time, since the switching pulse (e) is H (high level), the display mode is switched (switching to letterbox screen display).

Next, when a scene change occurs at the timing of FIG. 3 (d), the scene change detection section 13 outputs a scene change detection output (d) to the switching logic circuit 11. On the other hand, in the aspect ratio detection unit 12, since the input video signal (a) remains the letterbox screen, the aspect ratio determination output (c) does not change, and therefore the display mode is not switched (letterbox. On screen display).

Next, a configuration example of the aspect ratio detection unit 12, the scene change detection unit 13, and the switching logic circuit 11 will be described. FIG. 4 shows the aspect ratio detector 12.
3 is a diagram showing a configuration example of a scene change detection unit 13. FIG.

First, the aspect ratio detector 12 will be described. A terminal 14 to which a video signal is input from a video signal supply source (not shown) is connected to the input ends of the video signal delay circuit 1 and the vertical change amount detection circuit 2, and the output end of the video signal delay circuit 1 has a vertical change amount. It is connected to the input terminal of the detection circuit 2. Further, the output end of the reference signal generation circuit 4 is
Connected to the input terminal of the vertical change amount detection circuit 2,
The output terminal of the vertical change amount detection circuit 2 is connected to the input terminal of the aspect ratio change determination circuit 3. The output terminal of the aspect ratio change determination circuit 3 is the switching logic circuit 1
1 is connected to the input terminal.

The operation of the aspect ratio detector 12 configured as above will be described.

A video signal input from the terminal 14 (for example, a video signal of the upper non-image area) is input to the vertical change amount detection circuit 2.
And the video signal input from the terminal 14 and delayed by the video signal delay circuit 1 for a predetermined time (for example, the video signal of the picture portion in the center of the screen) are supplied to the vertical change amount detection circuit 2. The difference between the two signals is taken and compared with the DC reference value supplied from the reference signal generation circuit 4. Then, the comparison result is supplied to the aspect ratio change determination circuit 3 in the next stage, and the display screen format determined based on the comparison result (for example, letterbox screen display or 4-to-3 screen display) is erroneously detected. In order to prevent as much as possible, it is checked whether the same display screen format is continuously detected for a predetermined time (recheck is repeated a predetermined number of times), and the determined display screen format is When continuously detected for a predetermined time, the determination result is determined (detected) to be correct, and the result is output to the switching logic circuit 11. In the present embodiment, the video signal input from the terminal 14 is only judged in two ways: letterbox screen display or 4-to-3 screen display. The signal output from 3 to the switching logic circuit 11 is 2 (L level) or H (high level).
It suffices if it is a street signal (DC voltage knowledge).

Next, the scene change detector 13 will be described. A terminal 14 to which a video signal is input from a video signal supply source (not shown) is connected to the input ends of the 1-frame delay circuit 5 and the subtractor 6, and the output end of the 1-frame delay circuit 5 is the input end of the subtractor 6. Connected with. Further, the output terminal of the subtracter 6 is connected to the input terminal of the absolute value circuit 7, and the output terminals of the absolute value circuit 7 and the reference signal generating circuit 10 are connected to the input terminal of the comparison circuit 8, Circuit 8
The output terminal of is connected to the input terminal of the counter 9. The output terminal of the counter is the switching logic circuit 1
1 is connected to the input terminal.

The operation of the scene change detection unit 13 configured as above will be described.

The subtractor 6 is supplied with the video signal input from the terminal 14 and the video signal input from the terminal 14 and delayed by one frame by the one-frame delay circuit 5. Take the difference between these two signals,
The absolute value is taken by the absolute value circuit 7, and the DC reference value supplied from the reference signal generating circuit 4 and the level of the absolute value are compared by the comparison circuit 8 at the next stage for one frame for each pixel data. When it is determined that the pixel data has a level equal to or higher than the reference value, it is sent to the counter 9 in the next stage and counted by the counter 9. The count value counted by the counter 9 (the number of pieces of pixel data determined to have a signal level higher than the DC reference value in the pixel data for one frame) is equal to or larger than a predetermined value (number). If it becomes, that is, APL (average pict
ure lebel, the average level of the image signal) exceeds a reference value, it is determined that a scene change has occurred, and the determination result, that is, the scene change detection output is output to the switching logic circuit 11.

By the way, the scene change detector 13 can also be constructed as follows.

FIG. 5 is a diagram showing another configuration example of the aspect ratio detecting section 12 and the scene change detecting section 13.

A terminal 14 to which a video signal is input from a video signal supply source (not shown) is connected to the input ends of the 1-frame delay circuit 5 and the subtractor 6, and the output end of the 1-frame delay circuit 5 is the subtractor 6 Is connected to the input end of. The output terminal of the subtractor 6 is connected to the input terminal of the absolute value circuit 7, and the output terminal of the absolute value circuit 7 is connected to the input terminal of the integrating circuit 62. The output ends of the integration circuit 62 and the reference signal generation circuit 64 are connected to the input end of the comparison circuit 63, and the output end of the comparison circuit 63 is connected to the input end of the switching logic circuit 11.

The operation of the scene change detection unit 13 configured as above will be described.

The subtractor 6 is supplied with the video signal input from the terminal 14 and the video signal input from the terminal 14 and delayed by one frame by the one-frame delay circuit 5. Take the difference between these two signals,
The absolute value circuit 7 takes the absolute value, and the integration circuit 62 at the next stage integrates the absolute value for one frame pixel by pixel. The integration result is the reference signal generation circuit 6
4 is compared with the DC reference value supplied from No. 4, and if the integrated value level is equal to or higher than the reference value, it is determined that a scene change has occurred, and the scene change detection output is sent to the switching logic circuit 11. Is output.

FIG. 6 is a diagram showing an example of the configuration of the switching logic circuit 11.

In this embodiment, a D flip-flop is used as the switching logic circuit. As is well known, the D flip-flop controls the operation of the RS flip-flop 51 by the value of the input (D input) from the input terminal 52 as shown in FIG. 6B, and is input from the input terminal 53. The operation state is entered from the leading edge of the clock pulse, and the value (Q) equal to the input (D input) from the input terminal 52 at the trailing edge is output from the output terminal 56 and held until the next clock. Also, the input terminal 54 is set (P
R) and the input terminal 55 are auxiliary input terminals for reset (CLR). In general, in the circuit diagram and the like, the D flip-flop is arranged as shown in FIG.

On the other hand, FIG. 6C is a timing chart showing the operation of the D flip-flop. Now, assuming that the data input signal 58 is input from the input terminal 52 and the clock input signal 59 is input from the input terminal 53, the output Q signal 60 is output from the output terminal 56 of the D flip-flop. It will be. That is, the output Q
The signal 60 has a value equal to the value of the data input signal 58 at the timing of the trailing edge (trailing edge) of the clock input signal 59, and holds that state until the next clock. Therefore, at the timing (a), the value of the data input signal 58 is “1”,
The output Q signal 60 becomes "1", and this state is held until the next clock, that is, the timing (a). Since the value of the data input signal 58 is "0" at the timing (a), the output Q signal 60 becomes "0", and this state is held until the next clock, that is, the timing (c). After that, the value of the output Q signal 60 is determined in this manner.

By the way, the data input signal 58 shown in FIG.
If the clock input signal 59 is replaced with the scene change detection output of FIG. 3D and the output Q signal 60 is replaced with the switching pulse of FIG. 3E, the aspect ratio determination output of FIG. It can be seen that the operation is the same.

As described above, whether the screen is the 4 to 3 screen or the other screen (letterbox screen) is discriminated from the video signal, and when the discrimination (change) is confirmed, at the timing of the next scene change, An embodiment of a letterbox screen detection device that automatically changes the display mode of the screen of a wide television (having two modes for a 4 to 3 screen or a letterbox screen) has been described, but as described in the conventional example. There are four types of display modes of the screen of the wide television, for example, a normal mode (A mode), a zoom mode (B mode), a live mode (C mode), and a full mode (D mode). On the other hand, there are various letterbox screens, from standard sizes such as high-definition size, Vista size, and cinemascope to non-standard sizes.

Then, a letterbox screen detecting apparatus for selecting the optimum display mode for such various letterbox screens and automatically changing the display mode of the wide television screen will be briefly described below. To do.

FIG. 7 is a block diagram showing another embodiment of the letterbox screen detection device according to the present invention.

In FIG. 7, the input video signals input from the terminal 14 are supplied to the aspect ratio detector 21 and the scene change detector 23, respectively. Further, an aspect ratio determination output from the aspect ratio detection unit 21 is supplied to the display mode selection circuit 24, and a display mode designation signal from the display mode selection circuit 24 is sent to the switch circuit 25.
The scene change detection section 23 supplies a scene change detection signal to the switch circuit 25. Then, the switch circuit 25 supplies a switching pulse to the display mode switching unit 27. The display mode designating signal and the switching pulse are latched (holding the signal level state) by the latch circuits 22 and 26, respectively.

Next, the operation of the letterbox screen detecting device configured as described above will be described with reference to the flowchart shown in FIG. 8 which shows the operation of the letterbox screen detecting device of the present invention.

The aspect ratio detector 21 which constitutes the letterbox screen detector monitors the aspect ratio change from the video signal input from the terminal 14 (step t1). If it is not detected, normal processing (step t2) such as displaying an image in the current display mode is performed, and if a change is detected, the optimum display mode is selected from the changed screen size. (Step t3), the scene change detection unit 23 waits for a scene change (a large change in the display content of the screen) to be detected (step t4), and at the same time, the switch circuit 25 detects the scene change. In response to this, a switch-on signal (pulse) 61 is output to turn on the switch circuit 25, and the display mode designation signal latched is displayed in the display mode switching unit 27. Is output, based on the display mode designation signal, to switch the screen mode (step t5, t6, t7, t8, t9).

That is, even if a change in the aspect ratio is detected, the screen display mode is not immediately switched, and the scene change is detected after waiting for the next scene change. The screen display mode is switched based on. As a result, the display mode is switched according to the change of the scene, so that the problem that the screen size is suddenly switched and the viewer feels uncomfortable when the scene does not change is improved.

Although the letter box screen detecting device in the wide television receiver compatible with the NTSC system has been described in the above embodiment, the present invention is not limited to this, and the conventional television receiver (projection) according to the NTSC system is used. (Including a TV, etc.), a television receiver by a different television standard system (PAL, SECAM, etc.), or a different television standard system (P
It can be applied to wide television receivers and the like compatible with AL, SECAM, etc.

Further, the timing at which the aspect ratio detection unit first detects that the input video signal has changed (changed from the 4 to 3 screen to the letterbox screen or vice versa) and the scene change detection unit changes the scene. If the detection timings are the same, the aspect ratio detection unit is less likely to erroneously detect the aspect ratio, so the determination time (number of times) for determining the change in the aspect ratio can be shortened. It is possible. In this case, that is, by shortening the determination time (number of times), it is possible to shorten the automatic switching time of the screen display mode of the wide television receiver or the like.

[0075]

As described above, according to the present invention, the change of the scene, that is, the timing when the contents of the screen (APL, etc.) greatly changes is detected, and the wide television receiver according to the change of the scene. Since the screen display mode (such as enlarging or reducing the screen in the horizontal or vertical direction) is switched, erroneous detection occurs in the aspect ratio detection unit, that is, it is detected that there is no change in the aspect ratio Even if the video content does not change (there is no change in the scene), the screen display mode switching of the television receiver does not occur, so if the screen size suddenly changes, Expected "unnaturalness" can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a letterbox screen detection device of the present invention.

FIG. 2 is a flowchart showing the operation of the letterbox screen detection device of the present invention.

FIG. 3 is a timing chart showing the operation timing of the letterbox screen detection device of the present invention.

FIG. 4 is a diagram showing a configuration example of an aspect ratio detection unit 12 and a scene change detection unit 13.

5 is a diagram showing another configuration example of an aspect ratio detection unit 12 and a scene change detection unit 13. FIG.

FIG. 6 is a diagram showing a configuration example of a switching logic circuit 11.

FIG. 7 is a block diagram showing another embodiment of the letterbox screen detection device of the present invention.

FIG. 8 is a flowchart showing the operation of the letterbox screen detection device of the present invention.

FIG. 9 is a diagram showing an example in which package software which is generally commercially available and has a display form commonly referred to as a letterbox screen having non-image areas at the top and bottom of the screen is displayed on a screen with an aspect ratio of 4: 3. is there.

FIG. 10 is a diagram showing an example of a display mode in a conventional wide television receiver.

FIG. 11 is a diagram showing a vertical blanking period of an NTSC video signal and a horizontal scanning period of a video signal.

[Explanation of symbols]

 11 ... Switching logic circuit 12 ... Aspect ratio detection unit 13 ... Scene change detection unit 14 ... Video signal input terminal 16 ... Display mode switching unit (A) ... Input video signal (C) ... Aspect ratio judgment output (D) ... Scene change Detection output (e) ... Switching pulse

Claims (6)

[Claims] 1. A means for inputting a video signal, a means for displaying the video signal, a letterbox video detecting means for detecting whether or not the video displayed by the video signal is a letterbox video, and A scene change detecting means for detecting a change in a scene of a video displayed by a video signal, and a scene change detecting means for detecting a change in the aspect ratio after the aspect ratio change is detected by the letterbox video detecting means. And a letterbox video switching signal output means for outputting a signal for switching to the letterbox video at a specified timing, and a display for switching the display mode of the display means based on the letterbox video switching signal output from the output means. Letterbox screen detection device characterized by comprising mode switching means . 2. Input means for inputting a video signal, display means for displaying the video signal, means for detecting an aspect ratio of a video displayed by the video signal and its change, and display by the video signal. Scene change detection means for detecting a change in the scene of the image, and aspect ratio and means for detecting the change detect the aspect ratio change, and then the scene change detection means first detects a scene change. Based on the aspect ratio output means for outputting the aspect ratio after aspect ratio change detected by the means for detecting the aspect ratio and its change, and the aspect ratio output means And a display mode switching means for switching the display mode of the display means. Letterbox screen detecting device for. 3. A means for detecting the aspect ratio and its change, a first reference signal generating means for outputting a first direct current reference value, and a vicinity before the start of a first vertical blanking period of the video signal. Or a first average signal level detecting means for detecting a first average signal level of a predetermined number of scanning lines near the end of the first vertical blanking period, and after the end of the first vertical blanking period. Second average signal level detecting means for detecting a second average signal level of a predetermined number of scanning lines near the central portion of the video signal before the start of the subsequent second vertical blanking period, and the first average signal level detecting means. A means for obtaining a first absolute value by taking a difference between an average signal level and the second average signal level; a means for obtaining a magnitude relationship between the first average signal level and the second average signal level. The first The comparison means for comparing the value level with the first DC reference value, and the result of the comparison by the comparison means are the predetermined absolute value of the first absolute value level of the first absolute value level. 3. The letterbox screen detection device according to claim 2, further comprising means for determining that the aspect ratio has been changed and outputting the first absolute value level and the magnitude relationship if the aspect ratio is larger. 4. A means for inputting a video signal, a means for displaying the video signal, a means for detecting an aspect ratio of a video displayed by the video signal and its change, and an aspect ratio after the change. A display mode selecting means for selecting a display mode of the display means, a scene change detecting means for detecting a change in a scene of an image displayed by the video signal, and an aspect ratio by means for detecting the aspect ratio and the change. Display mode output means for outputting the display mode selected by the display mode selection means at a timing at which a scene change is first detected by the scene change detection means after a change in the ratio is detected, and the output means. Display mode switching means for switching the display mode of the display means based on the display mode output from Letterbox image detecting apparatus characterized by Bei was. 5. The scene change detection means, 1 frame delay means for delaying the video signal for 1 frame period, a video signal output from the 1 frame delay means, and a video signal not passing through the 1 frame delay means. A subtraction means for obtaining a difference between the second absolute value and a second absolute value as a result of the subtraction, a second reference signal generating means for outputting a second DC reference value, and a second absolute value level. If the second absolute value level is larger than the second direct current reference value by the pixel comparing means for comparing the second direct current reference value for one frame for each pixel, and the pixel comparing means. 4. A counter that counts the number of judged pixels, judges that there is a scene change when the number of pixels exceeds a predetermined number, and outputs a scene change signal. Described in 4 Tar box screen detection device. 6. The scene change detection means, one frame delay means for delaying the video signal for one frame period, a video signal output from the one frame delay means, and a video signal not passing through the one frame delay means. A subtraction means for obtaining a difference between the third absolute value and a third absolute value, a means for integrating the third absolute value for one frame, and a third direct current reference value output third The reference signal generating means, the third absolute value integration result, and the third DC reference value are compared, and if the third absolute value integration result is larger, there is a scene change. 5. The letterbox screen detection device according to claim 1, 2, 3 or 4, wherein the letterbox screen detection device comprises a comparator circuit that outputs a scene change signal.