JP3279803B2 - Video signal processing circuit - 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 signal processing circuit for determining a blank portion of a video signal, and more particularly to a conventional NTSC circuit.
The present invention relates to a video signal processing circuit suitable for generating a screen size switching signal of a video reproducing apparatus having a display screen having a wide aspect ratio (for example, a 16: 9 aspect ratio) wider than a standard television screen.

[0002]

SUMMARY OF THE INVENTION Current video software based on NTSC standard television signals is produced in a cinemascope size or a Vista size with blank portions at the top and bottom of the video. When playing such software on a video playback device equipped with a display screen with a wide aspect ratio, recognizing the screen size of the software and performing an enlarging sweep in accordance with this will produce a powerful image on the entire screen. Will be played. Therefore, a video reproducing apparatus having a display screen with a wide aspect ratio is provided with a video signal processing circuit for detecting a blank portion in a video signal. The video signal of the blank portion differs depending on the video software. However, if the software is the same, it can be expected that the video signal is created from the beginning to the end with the same level of the video signal.

On the other hand, devices that reproduce video software (laser disc players, video cassette recorders, and television tuners) have their own noise levels. Further, video signals transmitted via television broadcasting include: Different levels of noise are included depending on the reception state of radio waves.

A video signal processing circuit according to the present invention measures a setup level and a noise level of a blank portion of an input video signal, and adapts a threshold value for determining the blank portion in accordance with the measurement result, thereby obtaining an input video signal. This makes it possible to always determine a blank portion with an optimum threshold value regardless of the level.

[0005]

2. Description of the Related Art Wide aspect television receivers currently on the market are equipped with genuine Hi-Vision, simplified Hi-Vision, and MUSE-NTSC converters, and have 525 scanning lines, the same number as the current TV, and MUSE.
-There is a wide TV without an NTSC converter. Also the second
A generation of clear vision; EDTV2 has decided to use a wide aspect display screen.

On the other hand, conventionally, in television broadcasting and movie video software using a movie as a source, in order to display all of the original image without trimming, the image is displayed in the width of the display screen having an aspect ratio of 4: 3. Some have the same width. When such video software is displayed on a screen having a normal 4: 3 aspect ratio, portions without video are displayed as black bands (hereinafter, referred to as blank areas) at the top and bottom of the screen.

[0007] When reproducing video software having a width of 4: 3 such as a cinemascope size or a Vista size with a video reproduction device having a display screen with a wide aspect ratio, the video portion on the display screen is displayed in the same aspect ratio. When the image is stretched by the ratio and the vertical length of the video portion is made to coincide with the vertical length of the display screen, the video is reproduced to fill the entire display screen, and a powerful video can be enjoyed.

As a conventional technique for determining the aspect ratio of video content from a video signal in order to perform the above-described amplitude expansion, for example, Japanese Patent Laid-Open Publication No. Hei 1-305786 is known. FIG. 7 shows a block diagram of this prior art. According to the above publication, a counter for counting the horizontal synchronization signal for each field and a decoder for decoding the output of the counter are provided, and the upper end portion of the screen in the one field (first and second H),
A gate pulse for identifying the center part of the screen and the bottom part of the screen (262th and 263Hth) are created, and the added value of the video signal in each gate pulse period is compared with a predetermined threshold to detect the presence or absence of a video signal. However, the aspect ratio of the video is determined based on the detection result.

That is, NTSC having a normal aspect ratio
If it is a signal, the waveform is as shown in FIG. 8A, and a video signal is detected at any of the upper end, the center, and the lower end of the screen, so that the aspect ratio is determined to be 4: 3. On the other hand, in the case of a cinemascope-sized NTSC signal, FIG.
The waveform shown in (b) is obtained, and a video signal is detected at the center of the screen, but no video signal is detected at the upper and lower ends of the screen. Therefore, the aspect ratio is determined to be a cinemascope size.

In addition, as a method for discriminating a video portion from a blank portion, a video signal is sampled a plurality of times, each sample value is compared with a predetermined threshold value, and the video signal is determined based on the number of sample values exceeding the threshold value. There is a method of determining a blank portion.

[0011]

However, as shown in FIG. 6, some of the commonly distributed video software has a video signal level of the blank portion set higher than the pedestal level, and the reproduced video is Considering the noise level in the signal, it is necessary to set the threshold value that is the judgment level of the video signal to a slightly higher value, and the conventional aspect ratio discrimination method tends to cause malfunctions in dark parts of the video scene. There was a point.

In view of the above problems, it is an object of the present invention to automatically generate a threshold value according to an input video signal and compare the threshold value with the video signal to thereby obtain a video portion and a blank portion of the video signal. Is to provide a video signal processing circuit capable of detecting the video signal without error.

[0013]

In order to solve the above problems, the present invention has the following arrangement. That is, a first gist of the present invention is to provide a video signal processing circuit for determining whether an input video signal exceeds or does not exceed a threshold, wherein a plurality of video signal sample values are set within a period of the video signal forming the upper part of the screen. Sampling means for extracting, average value calculating means for calculating an average value from the plurality of sample values, and adding means for adding a predetermined value to the average value, wherein the added value is used as the threshold value. Video signal processing circuit.

According to a second aspect of the present invention, there is provided a video signal processing circuit characterized in that amplitude limiting means for limiting the threshold value to a predetermined limit value or less is added to the first aspect.

According to a third aspect of the present invention, there is provided a video signal processing circuit for determining whether an input video signal exceeds or does not exceed a threshold value, wherein a plurality of video signal sample values are set within a period of the video signal constituting an upper portion of a screen. Sampling means for extracting an average value, an average value calculating means for calculating an average value from a plurality of sample values, an error detecting means for detecting an error between a video signal and the average value, and a plurality of predetermined values according to the detection error. Selecting means for selecting one of the following, and adding means for obtaining an added value obtained by adding the average value and the predetermined value selected by the selecting means, wherein the added value obtained by the adding means is A video signal processing circuit that performs a threshold determination process on an input video signal input after the video signal used by the sampling means as the threshold.

According to a fourth aspect of the present invention, there is provided a video signal processing circuit characterized in that amplitude limiting means for limiting the threshold value to a predetermined limit value or less is added to the third aspect.

[0017]

According to the present invention, a video signal at the upper portion of a screen is sampled at a plurality of locations, and an average value obtained from the plurality of sample values is used as setup data. The value obtained by adding the predetermined value is set as a threshold. Then, the video portion and the blank portion of the video signal are determined based on the threshold.

[0018]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of a wide-screen television to which the video signal processing circuit of the present invention is applied. In the figure, 103 is a digitized input luminance signal, 104 is a luminance level comparison circuit, 105 is a threshold value determination circuit, 106 is a gate generation circuit, 107 is a horizontal synchronization signal, 108 is a vertical synchronization signal, and 109 is a video determination circuit. , 1
10 is a control microcomputer, and 111 is a screen size switching circuit. In the main part of the wide-screen television having the above configuration, the video signal processing circuit of the present invention is a portion including a luminance level comparison circuit 104 and a threshold value determination circuit 105.

The operation of the main part of the wide television shown in FIG. 1 is as follows. First, the input luminance signal 1
03 is distributed to a luminance level comparison circuit 104, a threshold value determination circuit 105, and a gate generation circuit 106 directly or via a buffer amplifier (not shown). The gate generation circuit 106 is supplied with a horizontal synchronization signal 107 and a vertical synchronization signal 108 from a synchronization separation circuit (not shown). The gate generation circuit 106 uses the vertical synchronization signal 108 as a reference
The number of pulses of the horizontal synchronizing signal 107 is counted, and the gate pulse 11 having a width of 1H indicating the upper part (for example, the 23rd H) of the image is displayed.
2 is generated and sent to the threshold determination circuit 105.

The threshold value determining circuit 105 determines a threshold value suitable for the input video signal, and sends the threshold value data 113 to the luminance level comparing circuit 104. The method of determining the threshold will be described later in detail corresponding to the gist of the invention. Brightness level comparison circuit 10
4 compares the magnitude of the threshold data 113 from the threshold determination circuit 105 with the luminance signal 103 and outputs a comparison result signal 114.
To the video determination circuit 109.

The video judging circuit 109 includes the gate generating circuit 1
The horizontal line is recognized based on the horizontal line number 115 sent from the control unit 06 and the luminance level comparison circuit 104 is provided for each horizontal line.
From the input image signal, the number of the horizontal line changing from the blank portion to the video portion is video start line data 116, and the number of the horizontal line changing from the video portion to the blank portion is video end line data 117.
To the control microcomputer 110. The control microcomputer 110 includes a video start line data 116 and a video end line data 11.
7 to calculate the image range and the like, and the screen size switching circuit 11
1 is given an optimal screen size switching instruction.

Next, the threshold value determining circuit 105 for each gist of the invention
Will be described in detail. FIG. 2 is a block diagram showing the internal configuration of the threshold value determination circuit corresponding to the first gist. In the figure, reference numeral 103 denotes a digital luminance signal which is an input video signal; 112, a gate pulse for instructing a sampling period; 201, a luminance signal adding circuit; 202, an average value calculation circuit; Data, 20
Reference numeral 4 denotes an adding circuit, 205 denotes a latch circuit for temporarily holding the added value, and 206 denotes a latch pulse generating circuit for generating a latch pulse.

The operation of the threshold value determining circuit shown in FIG. 2 will be described below. First, the luminance signal addition circuit 201 adds the luminance signal 103 when the gate pulse 112 is opened. When the gate pulse 112 is closed, the data added by the luminance signal addition circuit 201 is sent to the average value calculation circuit 202, and the average value 210 of the luminance signal is calculated. This average value indicates a luminance level corresponding to a setup value from which noise in a video blank portion has been removed. The addition circuit 204 determines the threshold value by adding external setting data 203 indicating a predetermined noise margin to the average value 210 calculated by the average value calculation circuit 202. The latch pulse generation circuit 206 generates a pulse obtained by delaying the gate pulse 112, and
The time from when is closed until the operations of 202 and 204 are completed is guaranteed, the addition result of the addition circuit 204 is held in the latch circuit 205, and is sent to the luminance level comparison circuit 104 as threshold data 113. With the above operation, even if the brightness level of the blank portion differs for each video software, the horizontal line between the blank portion and the video portion can always be identified by an appropriate threshold, so that the video can be determined without error. it can.

FIG. 3 is a block diagram showing the internal configuration of the threshold value determining circuit corresponding to the second aspect. In the figure,
103, a digital luminance signal which is an input video signal;
2 is a gate pulse indicating a sampling period, 201
Is a luminance signal adding circuit, 202 is an average value calculating circuit, 203
Is an external setting data which is a first predetermined value, 204 is an adder circuit, 307 is a limiter circuit, 308 is a limit value which is a second predetermined value, 205 is a latch circuit for temporarily holding the added value, and 206 is a latch pulse. Each of the generated latch pulse generation circuits is shown.

Next, the operation of the threshold value determining circuit shown in FIG. 3 will be described. First, the luminance signal addition circuit 201 adds the luminance signal 103 when the gate pulse 112 is opened. When the gate pulse 112 is closed, the data added by the luminance signal addition circuit 201 is sent to the average value calculation circuit 202, and the average value 210 of the luminance signal is calculated. This average value indicates a luminance level corresponding to a setup value from which noise in a video blank portion has been removed. The addition circuit 204 adds external setting data 203 indicating a predetermined noise margin to the average value 210 calculated by the average value calculation circuit 202.

Next, the limiter circuit 307 compares the limit value 308, which is the second predetermined value, with the addition value given from the addition circuit 204, and outputs the smaller value to the latch circuit 205. Latch pulse generation circuit 2
06 generates a pulse obtained by delaying the gate pulse 112, and after the gate pulse 112 is closed, 202, 204,
The time until the operation of the limiter 307 is completed is guaranteed, and the output of the limiter circuit 307 is held in the latch circuit 205.
It is sent to the luminance level comparison circuit 104 as threshold data 113. By the above operation, even if the brightness level of the blank portion differs for each video software, or even when the video signal at the sampling point is inappropriate, the horizontal line between the blank portion and the video portion is set with a threshold value more suitable than the conventional technology. Since the identification can be performed, the video can be determined without error.

FIG. 4 is a block diagram showing the internal configuration of the threshold value determination circuit corresponding to the third aspect. In the figure,
103, a digital luminance signal which is an input video signal;
2 is a gate pulse indicating a sampling period, 201
Is a luminance signal addition circuit, 202 is an average value calculation circuit, 403
Is a latch circuit, 404 is a latch pulse generation circuit, 405
Denotes an error detection circuit, 406 denotes a 1H delay circuit, 407 denotes an error level determination circuit, 408 denotes a latch circuit, and 409 denotes an addition circuit.

Next, the operation of the threshold value decision circuit shown in FIG. 4 will be described. First, the input luminance signal 103 is sent to the luminance signal addition circuit 201 and the error detection circuit 405. When the gate pulse 112 opens, the luminance signal addition circuit 201
The addition of the luminance signal 103 is performed. When the gate pulse 112 is closed, the data added by the luminance signal addition circuit 201 is sent to the average value calculation circuit 202 and the average value of the luminance signal 21 is calculated.
0 is calculated. This average value indicates a luminance level corresponding to a setup value from which noise in a video blank portion has been removed. The latch pulse generation circuit 404 outputs the gate pulse 11
A pulse is generated by delaying 2 to guarantee the time from the closing of the gate pulse 112 to the completion of the operations of 201 and 202, and the latch circuit 403 temporarily holds the average value 210.

The output 411 of the latch circuit 403 is sent to an error detection circuit 405 and an addition circuit 409. The error detection circuit 405 outputs the gate pulse 112 to the 1H delay circuit 40
6, the control signal 412 delayed by one horizontal period
A signal obtained by subtracting the output 411 of the latch circuit from the luminance signal 103 is created and output as an error signal 413.

Since the error signal 413 indicates the magnitude of noise contained in the video signal and the fluctuation value of the video signal level, the next error level determination circuit 407 determines the level. Since the large error signal 413 indicates that the level fluctuation of the input luminance signal is large, it is preferable to use a relatively high level as the threshold for determining the level of the blank portion, and conversely, the error signal 413 is small. Sometimes, it indicates that the level fluctuation of the input luminance signal is small, so that it is preferable to set a relatively low level as the threshold value for the level determination of the blank portion in order to prevent a malfunction in a dark scene of an image.

For this reason, the error level determination circuit 407
The level of the error signal 413 is determined, and according to the level of the level, a larger predetermined value is selected when the error level is higher, and a lower predetermined value is selected and output when the error level is low. The latch circuit 408 holds the value output from the error level determination circuit 407, and the addition circuit 409 adds the values held in the two latch circuits 403 and 408, and uses the addition result as a threshold value 113 to compare the brightness levels. Output to the circuit 104.

With the above operation, even if the brightness level of the blank portion differs for each video software or the level of the video signal fluctuates, the blank portion and the horizontal line of the video portion are always identified by an appropriate threshold value. Therefore, the video can be determined without error.

FIG. 5 is a block diagram showing the internal configuration of the threshold value determination circuit corresponding to the fourth aspect. In the figure,
103, a digital luminance signal which is an input video signal;
2 is a gate pulse indicating a sampling period, 201
Is a luminance signal addition circuit, 202 is an average value calculation circuit, 403
Is a latch circuit, 404 is a latch pulse generation circuit, 405
Denotes an error detection circuit, 406 denotes a 1H delay circuit, 407 denotes an error level determination circuit, 408 denotes a latch circuit, 409 denotes an addition circuit, and 510 denotes a limiter circuit.

Next, the operation of the threshold value determining circuit shown in FIG. 5 will be described. Since the operation up to the adding operation in the adding circuit 409 is the same as that of the threshold value determining circuit described in the third gist shown in FIG. Description is omitted.

The result of addition by the addition circuit 409 is compared with the limit value 511 in the next limiter circuit 510, and if the value of the addition result does not exceed the limit value 511, the addition result is output as it is as the threshold value 113, and If the value exceeds limit value 511, limit value 5
11 is output as the threshold value 113. By the above operation, even if the brightness level of the blank part is different for each video software, or even if the level of the video signal fluctuates,
Since the blank portion and the horizontal line of the video portion can always be identified by an appropriate threshold value, the video can be determined without error.

[0036]

As described above, in the present invention,
When detecting the blank part of the input video signal and determining the screen size, even if there is a level difference in the setup of the blank part of the input video signal, the noise level of the input video signal is different, or the setup level fluctuates. Even if there is, an optimal threshold value can be automatically set and video determination can be performed, so that the screen size can be determined without error.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a wide-screen television to which a video signal processing circuit according to the present invention is applied.

FIG. 2 is a block diagram showing a configuration of an embodiment of a threshold value generation circuit used in a video signal processing circuit corresponding to the first aspect.

FIG. 3 is a block diagram showing a configuration of an embodiment of a threshold value generation circuit used in a video signal processing circuit corresponding to the second aspect.

FIG. 4 is a block diagram showing a configuration of an embodiment of a threshold value generation circuit used in a video signal processing circuit corresponding to a third aspect.

FIG. 5 is a block diagram showing a configuration of an embodiment of a threshold value generation circuit used in a video signal processing circuit corresponding to a fourth aspect.

FIG. 6 is a waveform diagram showing a signal in a blank portion of a video signal.

FIG. 7 is a block diagram of an aspect ratio discrimination circuit according to the related art.

FIG. 8 is a waveform diagram illustrating the operation of the aspect ratio discrimination circuit according to the related art.

[Explanation of symbols]

 103 brightness signal 104 brightness level comparison circuit 105 threshold value determination circuit 106 gate generation circuit 107 horizontal synchronization signal 108 vertical synchronization signal 109 video determination circuit 110 control microcomputer 111 screen size switching circuit 113 threshold value 201 brightness signal addition circuit 202 average value calculation circuit 203 External setting data 204, 409 Addition circuit 205, 403, 408 Latch circuit 206, 404 Latch pulse generation circuit 307, 510 Limiter circuit 405 Error detection circuit 406 1H delay circuit 407 Error level determination circuit

Claims (2)

(57) [Claims] 1. A video signal processing circuit for determining whether an input video signal exceeds or does not exceed a threshold value, comprising: sampling means for extracting a plurality of video signal sample values during a period of the video signal forming an upper part of a screen; Average value calculating means for calculating an average value from the plurality of sample values; error detecting means for detecting an error between the video signal and the average value; selecting one of a plurality of predetermined values according to the error Selecting means; and adding means for obtaining an added value obtained by adding the average value and the predetermined value selected by the selecting means, wherein the sampling value obtained by the adding means is used as the threshold value. A video signal processing circuit for performing a threshold value determination process on an input video signal input after the video signal used in step (a). 2. The video signal processing circuit according to claim 1, further comprising amplitude limiting means for limiting the threshold value to a predetermined limit value or less.