JPH08237566A - Letterbox screen detector - Google Patents

Abstract

(57) [Abstract] [Object] An object of the present invention is to provide a letterbox screen detection device capable of highly accurately determining a letterbox screen. [Structure] Detecting means 12, 14, 15 for detecting the color signal levels of portions corresponding to upper and lower non-image areas of a letterbox screen of a video signal, and color signal levels detected by these detecting means 12, 14, 15. By comparing the level with a predetermined reference level, a comparison unit 17 for detecting a non-image portion of the video signal, and detecting that the state detected by the comparison unit 17 as the non-image portion has continued for a predetermined period or more And a determination means 19 for determining the letterbox screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video display system capable of displaying video signals having different aspect ratios, and more particularly to improvement of a letterbox screen detection device for determining the letterbox screen.

[0002]

2. Description of the Related Art As is well known, in the NTSC system, the aspect ratio of a video signal is regulated to 4: 3, but it is one of the high definition (high definition) television systems, MU.
In the SE system, the aspect ratio of the video signal is standardized to 16: 9, and accordingly, a television receiver capable of displaying a landscape screen called a wide TV (television) is rapidly spread. Is beginning to Also, for example, a movie originally has a horizontally long screen, but as shown in FIG. 10, packaged software having a display form commonly referred to as a letterbox screen in which panel portions P1 and P2 having no image are provided at the top and bottom is also popular. ing.

As described above, in the future, it is expected that the video software of the horizontally long screen will increase. However, the problem in this case is that the aspect ratio is 4: 3, 16: 9, movie software, etc. This means that video signals having various different aspect ratios are mixed, and even if it is called a letterbox screen, there are actually various display modes of video images with various aspect ratios.

For example, FIGS. 11 (a) and 11 (b) show two kinds of so-called Vista size movie software each having an aspect ratio of 1.85: 1 and different subtitle superposition positions. Further, FIGS. 11C and 11D show two types of movie software of a so-called cinema scope having an aspect ratio of 2.35: 1 and different positions of the subtitle super.

Of course, in addition to this, the display form is really various, such as whether the movie software is domestic or foreign, the number of lines of the subtitle super, the dubbing does not need the subtitle super, etc. Therefore, for example, even if only the number of lines in the upper panel portion of the screen non-image area is about 10 to 50,
There are variations in books.

In the conventional wide TV, various display means have been considered in order to cope with the above-mentioned horizontally long software. For example, FIG. 12A shows a mode in which a non-image area is displayed on the left and right sides of the image, which is commonly called a normal mode. In addition, in FIG. 12B, the image is enlarged vertically and horizontally, and the horizontal image area is displayed in the full width of the display screen.
A mode in which the upper and lower images are cut and displayed, which is commonly called the zoom mode. Further, FIG. 12C is a mode in which the horizontal image area of the image is displayed in the horizontal direction of the display screen and the vertical direction is enlarged at a certain ratio for display, which is commonly called a live mode. Further, FIG. 12D is a mode in which the image is enlarged in the horizontal direction only and the image area is enlarged in the horizontal direction of the display screen, which is commonly called the full mode.

Now, when an image signal of a letterbox screen is to be displayed on a wide TV, it is displayed in the above-mentioned four modes, but in the normal mode,
The area for actually displaying the image becomes small, and the advantage of the large screen display is lost.
In the case of the zoom mode, the upper and lower images of 4: 3 are cut, but there is no problem because there is no picture originally, and rather the picture part is displayed on the full screen, which is convenient.

However, when the video signal having subtitles or the picture portion is shifted to the upper or lower side in movie software or the like, important picture information may be overlaid. In this case, it is necessary to change the enlargement ratio or move the displayed pattern up and down. In any case, since the ratio of upper and lower image cuts is large, adjustment or the like is necessary.

In the live mode, the upper and lower images of 4: 3 are slightly cut, and the circularity ratio is slightly enlarged horizontally. However, the upper and lower image cuts are smaller than in the zoom mode, It is less necessary to make adjustments such as moving the pattern. Also, although the design is a little horizontally long, it is not so problematic. In the case of the full mode, the 4: 3 image is not cut, but it is a pattern that extends laterally as compared with the live mode, and thus is not a mode that is actively adopted.

In any of the display modes, it is necessary for the person to make adjustments such as switching the display while seeing the pattern, and it is necessary to select the optimum mode for display each time the aspect ratio of the video signal changes.

Therefore, conventionally, a device for automatically performing such complicated mode selection has been considered, and various letterbox screen detection devices have been devised for this device. However, in the method of determining a letterbox screen by detecting the vertical blanking period as shown in Japanese Patent Application No. 63-198487, it is impossible to determine that the upper and lower panels of the letterbox screen are slightly bright. There is an inconvenience that it will end up. In fact, when I looked up a lot of movie software with letterbox screens, I found that the signal level of the panel part increased to nearly 12 IRE.

On a normal screen having an aspect ratio of 4: 3 and a dark screen in which red and blue colors are dark, there are many video signals having a level lower than the signal level of the panel. When the letterbox screen is determined, there is a problem that an erroneous determination is likely to occur.

[0013]

As described above, in the conventional letterbox screen detection device, the letterbox screen is determined only by the signal levels of the upper and lower panels, so that there is a problem that there are many erroneous determinations. are doing.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a very good letterbox screen detection device capable of highly accurately determining a letterbox screen.

[0015]

A letterbox screen detecting apparatus according to the present invention includes a detecting means for detecting a color signal level of a portion corresponding to upper and lower non-image areas in a letterbox screen of a video signal, and the detecting means. A comparing means for detecting a non-image portion of the video signal by comparing the detected color signal level with a predetermined reference level, and a state in which the non-image portion is detected by the comparing means continues for a predetermined period or more. It is provided with a determination means for detecting that the letter box screen is detected.

[0016]

With the above arrangement, the color signal level of the portion corresponding to the upper and lower non-picture portions in the letterbox screen of the video signal is detected, and the level is compared with the reference level to detect the non-picture portion of the video signal. However, when this detection state continues for a predetermined period or more, it is determined that the letterbox screen is displayed.Therefore, the letterbox screen has various display modes and the signal levels of the upper and lower panels, and the signal level of the panel is Even if the blanking level is higher than the vertical blanking level, erroneous determination does not occur, and the letterbox screen can be determined with high accuracy.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, reference numeral 11 is an input terminal to which a video color signal is supplied. This input terminal 11
The video color signal supplied to the clamp circuit 12 is supplied to the clamp circuit 12. The clamp circuit 12 has a clamp signal which becomes H (high) level during the burst period of the video color signal, that is, a clamp signal which becomes H level after the rise of the horizontal synchronizing signal shown in FIG. ) Reference] is supplied via the input terminal 13.

Then, the clamp circuit 12 clamps the input video color signal during the burst period thereof, that is, during the H level period of the clamp signal, so that FIG.
It is converted into a signal as shown in (d). Note that FIG.
In (d), the symbol a indicates a clamp level.

The video color signal output from the clamp circuit 12 in this manner is supplied to the full-wave rectifier circuit 14.
The full-wave rectifier circuit 14 performs full-wave rectification on the input video color signal with the clamp level a as a reference, thereby converting it into a signal as shown in FIG. Note that FIG.
In (e), the portion indicated by the dotted line shows the waveform that has been full-wave rectified.

Here, the output signal of the full-wave rectifier circuit 14 is
It is supplied to the integrating circuit 15. A horizontal blanking signal [see FIG. 2 (c)] which is at H level during the horizontal blanking period of the video color signal is input to the input terminal 16 of the integrating circuit 15.
Is being supplied through. Then, this integrating circuit 15
By integrating the input signal and clearing the result in the horizontal blanking period, that is, in the H level period of the horizontal blanking signal, the video color signal for one horizontal period is obtained as shown in FIG. It is integrating.

After that, the output signal of the integrating circuit 15 is supplied to the comparing circuit 17. A constant reference level b [see FIG. 2 (f)] is supplied to the comparison circuit 17 via the input terminal 18. Then, the comparison circuit 17 compares the output signal of the integration circuit 15 with the reference level b to make L (L) in the period corresponding to the upper and lower black panel portions of the letterbox screen as shown in FIG. It generates a low level detection signal. The detection signal output from the comparison circuit 17 in this manner is supplied to the letterbox determination circuit 19 where the letterbox screen determination is performed.

Here, FIG. 3 shows a means for generating the clamp signal and the horizontal blanking signal. That is, in FIG. 3, reference numeral 20 is an input terminal to which the horizontal synchronizing signal is supplied. The horizontal synchronizing signal supplied to the input terminal 20 is supplied to the counter circuit 21. A clock signal having a frequency that is a positive multiple of the color subcarrier frequency fsc, which is phase-synchronized with the horizontal synchronizing signal, is supplied to the counter circuit 21 via an input terminal 22.

Then, the counter circuit 21 repeats the operation of counting the input clock signal and resetting the count value in the horizontal synchronizing period, that is, in the L level period of the horizontal synchronizing signal. The outputs of the counter circuit 21 are supplied to the decoder circuits 23 and 24, respectively. These decoder circuits 23 and 24 each generate an H level pulse signal when the output count value of the counter circuit 21 reaches a predetermined value, and the output of the decoder circuit 23 is taken out from the output terminal 25 as a clamp signal. The output of the decoder circuit 24 is taken out from the output terminal 26 as a horizontal blanking signal.

Next, the reference level b supplied to the comparison circuit 17 via the input terminal 18 is as shown in FIG.
This is a threshold level for determining that the screen is not a letterbox screen when there is a signal having a level higher than the reference level b during the H level period of the enable signal described later. The reference level b differs depending on the dynamic range of the signal level output from the full-wave rectifier circuit 14 shown in FIG. 2 (e) and is set as a parameter. For example, the value of the reference level b is preferably set to 10% or less of the dynamic range.

FIG. 5 shows a means for generating the enable signal. The enable signal is generated by counting the number of horizontal lines in the vertical direction by the counter 27 and decoding only a certain horizontal line by the decoder 28 from the count value. That is, as shown in FIG. 4, the vertical synchronizing signal VD becomes L level in the vertical synchronizing period to clear the counter 27, and the horizontal synchronizing signal HD
Is used as a clock to count up the counter 27.

Since most of the upper and lower non-picture portions of the letterbox screen are each several tens of lines, the decoder 28 always has the non-picture portion of the letterbox screen based on the count value of the counter 27. An enable signal that is at H level is generated only during a period corresponding to several lines above and below the video color signal. Specifically, it is appropriate that the period A of FIG. 4 is from line number 24 to 10 lines and the period B is from line number 256 to 10 lines, but there is no problem even if these 10 lines are slightly changed.

FIG. 6 shows the detailed construction of the clamp circuit 12, the full-wave rectifier circuit 14, and the integrator circuit 15.
First, the clamp circuit 12 uses the capacitor C for removing the DC (direct current) component from the video color signal supplied to the input terminal 29.
1 to the buffer circuit 30 through the input terminal 31
The analog switch 32 is turned on only during the H level period of the clamp signal supplied to the input terminal 33 to clamp to the clamp level a applied to the input terminal 33.

Further, the full-wave rectifier circuit 14 removes components of the video color signal outputted from the clamp circuit 12 from the slice circuit 34 without removing the component having the clamp level a or less, and the polarity inversion circuit 35 to the clamp level. a
After inverting the polarity on the basis of, the signal obtained by removing components below the clamp level a by the slice circuit 36 is added by the adder circuit 37 to perform full-wave rectification with the clamp level a as the reference. .

Further, the integrating circuit 15 has an operational amplifier OP to which a reference potential is applied via a resistor R1 and an input terminal 38.
1. An analog switch 40 which is in an ON state to reset the integration result during the L level period of the horizontal synchronization signal supplied to the input terminal 39, that is, the horizontal synchronization period. From 41, the result of integrating the video color signal for each horizontal line is obtained.

FIG. 7 shows the letterbox decision circuit 19 described above.
3 shows the detailed configuration of the. That is, the output of the comparison circuit 17 supplied to the input terminal 42 is supplied to the counter 43. This counter 43 has the period B shown in FIG.
Between the end of the period and the beginning of the period A
It is reset to "0" by the reset signal supplied to. The counter 43 counts how continuously the state in which the output signal level of the integration circuit 15 is equal to or lower than the reference level b exists based on the output of the comparison circuit 17 in the periods A and B shown in FIG. However, the larger the count value is, the flatter the image color signals in the periods A and B are.

The count value of the counter 43 is supplied to the comparator 45 and compared with the reference value m supplied to the input terminal 46. The comparator 45 generates an H level determination signal for determining a letterbox screen when the count value of the counter 43 is larger than the reference value m, and this determination signal is taken out from the output terminal 47.

FIGS. 8A to 8D are waveforms at points (a) to (d) of the letterbox determination circuit 19 shown in FIG. 7 for the video signal of the letterbox screen shown in FIG. 8E. Is shown. In the case of the letterbox screen, the signal input to the counter 43 is, as shown in FIG.
Counter 4 which has almost the same waveform as the enable signal shown in FIG. 4 and counts the duration of the H level
The output of No. 3 changes as shown in FIG. Then, the count value and the reference value m are compared by the comparator 45, and when the count value becomes larger than the reference value m, an H level determination signal is generated as shown in FIG. 8D.

Further, FIGS. 9A, 9C and 9D show the letterbox judging circuit 19 shown in FIG. 7 for the video signal of the screen having the aspect ratio of 4: 3 shown in FIG. The waveforms at points (a), (c), and (d) are shown. In this case, the signal input to the counter 43 has almost no H level period as shown in FIG. 9A, and the output of the counter 43 for counting the duration of this H level is as shown in FIG.
As shown in (c), it does not become larger than the reference value m. Therefore, as shown in FIG. 9D, the comparator 45 generates an L level determination signal indicating that the screen is not the letterbox screen.

Therefore, according to the configuration of the above embodiment, in the case of the letterbox screen of the video signal, the color signal level of the portion corresponding to the upper and lower panel portions is compared with the reference level b, and the color signal level becomes the reference. Since it is determined that the letterbox screen is a letterbox screen when the level is equal to or lower than the level b, the letterbox screen has various display forms and signal levels of the upper and lower panels. Even if the signal level of the panel unit is equal to or higher than the vertical blanking level, the letterbox screen can be determined with high accuracy without causing an erroneous determination.

Further, in order to improve the determination accuracy of the letterbox determination circuit 19, for example, if the final determination is made by checking the continuity of the determination results over several fields, erroneous determination due to noise or the like can be further avoided. It can be further reduced.

Further, in the above embodiment, the judgment can be adjusted based on the information such as the overall brightness of the image and the S / N of the signal. From such a point, the judgment of the letterbox screen can be made. The performance can be further improved.
For example, erroneous determination can be reduced by validating the determination result only when the image is a bright screen as a whole or by adjusting the reference level b or the reference value m when the S / N is bad. The present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the scope of the invention.

[0037]

As described above in detail, according to the present invention,
It is possible to provide a very good letterbox screen detection device capable of highly accurately determining a letterbox screen.

[Brief description of drawings]

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

FIG. 2 is a waveform chart shown for explaining the operation of the embodiment.

FIG. 3 is a block configuration diagram showing a means for generating a clamp signal and a horizontal blanking signal in the embodiment.

FIG. 4 is a waveform chart shown for explaining a detection period in the embodiment.

FIG. 5 is a block configuration diagram showing an enable signal generating means in the embodiment.

FIG. 6 is a block configuration diagram showing details of a clamp circuit, a full-wave rectifier circuit, and an integrator circuit in the embodiment.

FIG. 7 is a block configuration diagram showing details of a letterbox determination circuit in the embodiment.

FIG. 8 is a waveform diagram showing an operation of the letterbox determination circuit when a video signal of a letterbox screen is supplied.

FIG. 9 is a waveform chart showing the operation of the same letterbox determination circuit when a video signal that is not a letterbox screen is supplied.

FIG. 10 is a diagram shown for explaining a letterbox screen.

FIG. 11 is a diagram shown for explaining various examples of a letterbox screen.

FIG. 12 is a diagram shown for explaining a display mode of a wide TV.

[Explanation of symbols]

11 ... Input terminal, 12 ... Clamp circuit, 13 ... Input terminal, 14 ... Full wave rectification circuit, 15 ... Integration circuit, 16 ... Input terminal, 17 ... Comparison circuit, 18 ... Input terminal, 19 ... Letterbox determination circuit, 20 ... input terminal, 21 ... counter circuit, 22 ... input terminal, 23, 24 ... decoder circuit, 2
5, 26 ... Output terminal, 27 ... Counter, 28 ... Decoder, 29 ... Input terminal, 30 ... Buffer circuit, 31 ... Input terminal, 32 ... Analog switch, 33 ... Input terminal, 34
... Slice circuit, 35 ... Polarity inversion circuit, 36 ... Slice circuit, 37 ... Addition circuit, 38, 39 ... Input terminal, 40 ...
Analog switch, 41 ... Output terminal, 42 ... Input terminal,
43 ... Counter, 44 ... Input terminal, 45 ... Comparator, 46 ... Input terminal, 47 ... Output terminal.

Claims (4)

[Claims] 1. A detection means for detecting a color signal level of a portion corresponding to upper and lower non-image areas of a letterbox screen of a video signal, and a level comparison between the color signal level detected by this detection means and a predetermined reference level. By doing so, comparing means for detecting the non-image portion of the video signal, and detecting that the state detected as the non-image portion by the comparing means has continued for a predetermined period or more, it is determined to be a letterbox screen. A letterbox screen detection device comprising a determination means. 2. The detecting means clamps the video color signal to a predetermined clamp level in a burst period, a rectifying means for full-wave rectifying the output of the clamp means with the clamp level as a reference, and the rectifying means. Means for integrating the output of the means in a horizontal period, and the comparing means compares the output of the integrating means with a predetermined reference level to obtain a video color signal corresponding to the non-image part of the letterbox screen. The letterbox screen detection device according to claim 1, wherein the presence or absence of the letterbox is detected. 3. The clamp means includes a first capacitor for removing a DC component from the video color signal, and the clamp for the video color signal extracted via the first capacitor during a burst period. First level application
Switching means, the rectifying means removes the level component below the clamp level from the output of the clamp means, and the polarity of the output of the clamp means based on the clamp level. And inverting means for removing the level component below the clamp level from the output of the inverting means, and adding means for adding the outputs of the first and second slicing means, The integrating means includes an operational amplifier to which the output of the rectifying means is supplied, a second capacitor which is feedback-connected to the operational amplifier and accumulates an integration result, and a horizontal result obtained by horizontally integrating the integration result accumulated in the second capacitor. The letterbox screen detection device according to claim 1, further comprising a second switch means for resetting during a ranking period. 4. The determination means includes a counter for counting the duration of a state in which the comparison means detects a non-image portion, and a comparison circuit for comparing the count value of the counter with a reference value. The letterbox screen detection device according to claim 1, wherein the letterbox screen detection device is provided.