JP3469307B2 - Letterbox screen detector - Google Patents

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 is originally a horizontally long screen, but as shown in FIG.
Packaged software having a display form commonly referred to as a letterbox screen in which panel portions P1 and P2 having no image on the top and bottom are provided is also popular.

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 videos with various display forms with various aspect ratios.

For example, FIGS. 11 (a) and 11 (b) show two types of so-called Vista size movie software having aspect ratios of 1.85: 1 and different subtitle positions. In addition, FIGS.
This shows two types of movie software with a so-called cinema scope having an aspect ratio of 2.35: 1 and different subtitle superposition positions.

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 the number of lines in the upper panel portion of the non-image area is only about 10 to 5
There is 0 variation.

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 of being lost. 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 judged, there arises a problem that an erroneous judgment easily occurs.

[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. is 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 detection apparatus according to the present invention is an input terminal to which a video signal is input.
And a specified line at the top and bottom of the display screen
Enable signal that generates an enable signal that represents the
Signal generation means and enable of the video signal input to the input terminal
Maximum level holding means for detecting and holding the maximum level during the generation period of the video signal, and the image input to the input end.
A minimum value level holding means for detecting and holding the minimum value level during the generation period of the signal enable signal , a maximum value level held by the maximum value level holding means, and a minimum value level held by the minimum value level holding means. The level difference obtained by this calculation means is compared with a predetermined reference level, and the level difference is determined by this comparison result.
A detection unit that detects the non-image portion of the video signal by determining that it is below the reference level, and a letterbox by detecting that the state detected as the non-image portion by this detection unit has continued for a predetermined period or more. A determination means for determining the screen is provided.

[0016]

According to the above-mentioned structure, the table by the video signal is displayed.
An enable line that indicates the predetermined line period at the top and bottom of the display screen.
The maximum value level and the minimum value level of the input video signal are detected during the bull signal generation period, and the level difference between the two is detected as the reference level.
Detecting a non-image portion of the video signal to determine that in the following, since the detection state is to be determined as a letter box screen when the continued more than a predetermined time period, various display letterbox screen There is a form and a signal level of the upper and lower non-picture part, and even if the signal level of the non-picture part is higher than the vertical blanking level, erroneous judgment does not occur and it is possible to judge the letterbox screen with high accuracy Become.

[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, the video signal supplied to the input terminal 11 is supplied to the maximum value level holding circuit 12 and the minimum value level holding circuit 13, respectively. The maximum value level holding circuit 12 and the minimum value level holding circuit 13 hold the maximum value level and the minimum value level of the video signal during the H (high) level period of the enable signal supplied to the input terminal 14, respectively. is there.

Then, the maximum value level and the minimum value level of the video signal respectively held in the maximum value level holding circuit 12 and the minimum value level holding circuit 13 are supplied to the arithmetic circuit 15 to be subtracted, and the level difference between them is compared. 16 are supplied. The comparator 16 compares the level difference between the maximum value level and the minimum value level with a predetermined reference level supplied to the input terminal 17 to determine the horizontal and horizontal black and white panels corresponding to the upper and lower black panel portions of the letterbox screen. It detects whether or not there is a change in the signal level in the vertical period, and the detection result is supplied to the letterbox judgment circuit 18 to judge the letterbox screen.

Here, the reference level supplied to the input terminal 17 is an arbitrary threshold level for determining that it is not a letterbox screen. That is,
As shown in FIG. 2, the maximum value level and the minimum value level of the video signal in the H level period of the enable signal are obtained,
It is a threshold level for determining that the letterbox screen is not displayed when the difference between the levels is larger than a certain threshold. The value of the reference level differs depending on the dynamic range of the video signal level to be judged and is set as a parameter. For example, when the maximum dynamic range of the video signal is expressed by 6-bit digital data, it is preferable to set the reference level to a value of 10 or less.

FIG. 3 shows a circuit for generating the enable signal. The enable signal is generated by counting the number of horizontal lines in the vertical direction by the counter 19 and decoding only a specific horizontal line by the decoder 20 from the count value. That is, as shown in FIG. 2, the vertical synchronizing signal VD becomes L (low) level in the vertical synchronizing period to clear the counter 19, and the horizontal synchronizing signal HD becomes a clock for the count-up operation of the counter 19. To be done.

Since most of the upper and lower non-picture portions of the letterbox screen are each several tens of lines, the decoder 20 always has the non-picture portion of the letterbox screen based on the count value of the counter 19. H only during the period corresponding to several lines above and below the video signal
An enable signal that becomes a level is generated. Specifically, it is appropriate that the period A in FIG. 2 is from line number 24 to 10 lines and the period B is from line number 256 to 10 lines, but there is no particular problem even if these 10 lines are slightly changed. is there.

The maximum value level holding circuit 12 and the minimum value level holding circuit 13 respectively hold the maximum value level and the minimum value level of the video signal in the H level period of the enable signal, that is, the periods A and B in FIG. It is a thing. Further, the maximum value level holding circuit 12 and the minimum value level holding circuit 13 can be realized with almost the same circuit configuration, and FIG. 4 shows the maximum value level holding circuit 12 and the minimum value when the video signal is digitally processed. A specific example of the level holding circuit 13 is shown.

First, the case of configuring the maximum value level holding circuit 12 will be described with reference to the waveform diagrams shown in FIGS. That is, the input terminal 21 has
The 6-bit digital video signal shown in (a) is supplied,
The input terminal 22 is supplied with a clock signal having a constant cycle shown in FIG. The digital video signal supplied to the input terminal 21 is latched by the latch circuit 23 in synchronization with the clock signal and output from the latch circuit 23 at the timing shown in FIG.

The digital video signal output from the latch circuit 23 is supplied to one input ends of the latch circuit 24 and the comparator 25. Of these, the latch circuit 24 is supplied to the input terminal 26 from the end of the period B shown in FIG. 2 to the start of the period A shown in FIG.
The latch signal is reset to 0 by the reset signal shown in FIG. Then, the latch circuit 24 latches the output of the latch circuit 23 in synchronization with the clock signal while the output of the AND circuit 27 is at the H level. The latch output shown in FIG. Is supplied to the other input terminal and is taken out from the output terminal 28.

Here, the comparator 25 compares the outputs of the latch circuits 23 and 24 in level, and the output level of the latch circuit 23 is higher than the output level of the latch circuit 24 as shown in FIG. 5 (g). At this time, the H level is output. The AND circuit 27 operates when the enable signal shown in FIG. 5D supplied to the input terminal 14 is at H level and the output of the comparator 25 is at H level.
The output becomes H level. Therefore, the latch circuit 23
Only when the output level of is higher than the output level of the latch circuit 24, the latch circuit 24 latches the output of the latch circuit 23 in synchronization with the clock signal.
The maximum level can be retained.

Next, the case of configuring the minimum value level holding circuit 13 will be described with reference to the waveform diagrams shown in FIGS. 6 (a) to 6 (g). That is, the input terminal 21 has
The 6-bit digital video signal shown in (a) is supplied,
The input terminal 22 is supplied with a clock signal having a constant cycle shown in FIG. The digital video signal supplied to the input terminal 21 is latched by the latch circuit 23 in synchronization with the clock signal, and output from the latch circuit 23 at the timing shown in FIG.

The digital video signal output from the latch circuit 23 is supplied to one input end of each of the latch circuit 24 and the comparator 25. Of these, the latch circuit 24 is supplied to the input terminal 26 from the end of the period B shown in FIG. 2 to the start of the period A shown in FIG.
By the reset signal shown in (c), the latch contents are reset to the digital maximum value (64 in this case).
The latch circuit 24 latches the output of the latch circuit 23 in synchronization with the clock signal while the output of the AND circuit 27 is at the H level. The latch output shown in FIG. It is supplied to the other input end of 25 and is taken out from the output terminal 28.

Here, the comparator 25 compares the outputs of the latch circuits 23 and 24 in level, and the output level of the latch circuit 23 is lower than the output level of the latch circuit 24 as shown in FIG. 6 (g). At this time, the H level is output. Then, the AND circuit 27, when the enable signal shown in FIG. 6D supplied to the input terminal 14 is at H level and the output of the comparator 25 is at H level,
The output becomes H level. Therefore, the latch circuit 23
Only when the output level of is lower than the output level of the latch circuit 24, the latch circuit 24 latches the output of the latch circuit 23 in synchronization with the clock signal.
The minimum value level can be retained.

Next, the arithmetic circuit 15 shown in FIG. 1 subtracts the minimum value level held in the minimum value level holding circuit 13 from the maximum value level held in the maximum value level holding circuit 12 to obtain the level difference. Is being detected. Then, the comparator 16 compares the level difference output from the arithmetic circuit 15 with the reference level supplied to the input terminal 17, and outputs the H level if the level difference is less than or equal to the reference level, and outputs the level difference. Is higher than the reference level, L level is output.

FIG. 7 shows the letterbox decision circuit 18 described above.
Shows the details of. That is, the output of the comparator 16 supplied to the input terminal 29 is supplied to the counter 30. The counter 30 is reset to 0 by the reset signal supplied to the input terminal 31 from the end of the period B to the start of the period A shown in FIG. The counter 30 determines that the level difference between the maximum value level and the minimum value level of the video signal in the periods A and B shown in FIG.
The number of times the states below the reference level compared in 6 continuously exist are counted. The larger the count value is, the flatter the video signals in the periods A and B are.

Then, the count value of the counter 30 is supplied to the comparator 32 and compared with the reference value m supplied to the input terminal 33. The comparator 32 generates an H level determination signal for determining a letterbox screen when the count value of the counter 30 is larger than the reference value m, and this determination signal is taken out from the output terminal 34.

FIGS. 8A to 8D are waveforms at points (a) to (d) of the letterbox determination circuit 18 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 30 is, as shown in FIG.
The counter 3 has almost the same waveform as the enable signal shown in FIG. 2 and counts the duration of the H level.
The output of No. 2 changes as shown in FIG. Then, the count value and the reference value m are compared by the comparator 32, 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 18 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 30 has almost no H level period as shown in FIG. 9A, and the output of the counter 32 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 32 generates an L level determination signal indicating that the screen is not the letterbox screen.

Therefore, according to the configuration of the above embodiment, the maximum value level and the minimum value level of the portion corresponding to the upper and lower panel portions are detected in the letterbox screen of the video signal, and the level difference between the two is detected. It is determined that the letterbox screen is displayed when the level difference between the reference level and the level difference is equal to or less than the reference level, and the letterbox screen is displayed when the condition is longer than the period corresponding to the reference value m. Depending on the form and the signal level of the upper and lower panel portions, even if the signal level of the panel portion is equal to or higher than the vertical blanking level, erroneous determination does not occur, and the letterbox screen can be determined with high accuracy.

Further, in order to improve the determination accuracy of the letterbox determination circuit 18, for example, if the final determination is made by looking at 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, only when the image is a bright screen as a whole, the determination result is valid, or when the S / N is bad, the reference level or the reference value m can be adjusted to reduce erroneous determination. The present invention is not limited to the above-described embodiments, and various modifications can be made 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 the present invention.

FIG. 2 is a waveform chart shown for explaining a period for detecting a maximum value and a minimum value level in the embodiment.

FIG. 3 is a block configuration diagram showing an enable signal generation circuit in the embodiment.

FIG. 4 is a block configuration diagram showing details of a maximum value level holding circuit and a minimum value level holding circuit in the embodiment.

FIG. 5 is a waveform diagram shown for explaining the operation of the maximum value level holding circuit.

FIG. 6 is a waveform chart shown for explaining the operation of the minimum value level holding circuit.

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 ... Maximum value level holding circuit, 13 ...
Minimum value level holding circuit, 14 ... Input terminal, 15 ... Arithmetic circuit, 16 ... Comparator, 17 ... Input terminal, 18 ... Letterbox determination circuit, 19 ... Counter, 20 ... Decoder, 21, 22 ... Input terminal, 23, 24 … Latch circuit,
25 ... Comparator, 26 ... Input terminal, 27 ... AND circuit, 28 ... Output terminal, 29 ... Input terminal, 30 ... Counter, 31 ... Input terminal, 32 ... Comparator, 33 ... Input terminal, 34 ... Output terminal.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N ^7/ 00-7/088 H04N 5/38-5/46 H04N 5/262-5/278

Claims (5)

(57) [Claims] 1. An input terminal for inputting a video signal , and a predetermined line at the upper and lower portions of a display screen by the video signal.
Enable signal that generates an enable signal that represents the
Signal generation means and the enable signal of the video signal input to the input terminal
Maximum value level holding means for detecting and holding the maximum value level during the generation period of, and the enable signal of the video signal input to the input terminal.
The minimum value level holding means for detecting and holding the minimum value level in the occurrence period of, and the level of the maximum value level held by the maximum value level holding means and the minimum value level held by the minimum value level holding means The calculation means for obtaining the difference and the level difference obtained by this calculation means are compared with a predetermined reference level, and the level difference is determined by the comparison result.
Detecting means for detecting a non-image portion of the video signal by determining that the non-image portion is below, and letterboxing by detecting that the state detected as the non-image portion by the detecting means continues for a predetermined period or more. A letterbox screen detection device comprising a determination means for determining that the screen is a screen. 2.The enable signal generating means is configured to
Vertical line of signal
A counter that counts the number and a count of the counter
Based on the value,
A decoder that generates an enable signal during the corresponding period
Consists of The maximum value level holding means is,PreviousVideo signal level
A first latch that latches based on a clock with a fixed period
Circuit, and set to the minimum level of the video signal,
Level of the video signal latched by the first latch circuit
Is latched based on the clock.
And the level and front latched in this second latch circuit
The level latched by the first latch circuit is compared with the level ratio.
And a level comparison circuit for comparing, said level comparison circuit
The level latched by the first latch circuit is
Judged to be higher than the level latched by the 2 latch circuit
AndDuring the generation period of the enable signalThe second
Do not configure the latch circuit to perform the latch operation.
The letterbox screen according to claim 1, characterized in that
Detection device. 3.The enable signal generating means is configured to
Vertical line of signal
A counter that counts the number and a count of the counter
Based on the value,
A decoder that generates an enable signal during the corresponding period
Consists of The minimum value level holding means is,PreviousVideo signal level
A first latch that latches based on a clock with a fixed period
Circuit, set to the maximum level of the video signal,
Level of the video signal latched by the first latch circuit
Is latched based on the clock.
And the level and front latched in this second latch circuit
The level latched by the first latch circuit is compared with the level ratio.
And a level comparison circuit for comparing, said level comparison circuit
The level latched by the first latch circuit is
It is judged that it is lower than the level latched by the latch circuit of 2
AndDuring the generation period of the enable signalThe second
Do not configure the latch circuit to perform the latch operation.
The letterbox screen according to claim 1, characterized in that
Detection device. 4. The upper and lower parts of the display screen according to the input video signal
Generate an enable signal representing a predetermined line period
In the enable signal generation step and the generation period of the enable signal of the input video signal,
In the maximum value level holding step of detecting and holding the maximum value level of the input video signal and the generation period of the enable signal of the input video signal.
And a minimum value level holding step of detecting and holding the minimum value level, and a level difference between the maximum value level held in the maximum value level holding step and the minimum value level held in the minimum value level holding step. The calculation step and the level difference obtained in this calculation step are compared with a predetermined reference level, and the level difference is determined by the comparison result.
And a letterbox by detecting that the state detected as the non-image portion by the detecting means continues for a predetermined period or more. A letterbox screen detection method comprising: a determination step of determining that the screen is a screen. 5. The received video signal is displayed on a letterbox screen .
In a television broadcast receiving apparatus that determines whether or not a signal , and switches the display mode, an input terminal to which a video signal is input and a predetermined line at the upper and lower portions of a display screen by the video signal.
Enable signal that generates an enable signal that represents the
Signal generation means, and the video signal input to the input terminal
Maximum value level holding means for detecting and holding the maximum value level during the generation period of the enable signal, and an input to the input terminal.
During the generation period of the enable signal of the input video signal.
Obtaining the minimum value level holding means, the level difference between the minimum value level held in the maximum value level and the minimum value level holding means which is held in the maximum value level holding means for detecting and holding a minimum value level takes The calculation means is compared with the level difference obtained by the calculation means and a predetermined reference level ,
According to the comparison result, the level difference may be below the reference level.
And a letter box screen by detecting that the non-image portion of the video signal is detected and the state in which the non-image portion is detected by the detection means continues for a predetermined period or more. determining means and the television broadcast receiving apparatus characterized by being provided with letterbox image detecting means, the having.