JPH0746504A - Slave picture display circuit - Google Patents

Abstract

PURPOSE:To provide the slave picture display circuit which can turn the aspect ratio of a slave picture image to an aspect ratio originally provided for the video signal of a slave picture. CONSTITUTION:Synchronizing separator and horizontal AFC circuits 3 and 4 output synchronizing signal pulses synchronized with the video signals of master and slave pictures, and clamp circuits 5 and 6 perform the DC reproducing of respective video signals. An identification signal discriminating circuit 13 extracts an identification signal expressing aspect ratio information from the video signal of the slave picture and supplies aspect ratio data to a control circuit 10. Based on the aspect ratio data, the control circuit 10 changes the timing of write to a video memory 8. Then, a switch 11 switches the video signals of the master and slave pictures and fits the video signal of the slave picture into one part of the video signal of the master picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sub-screen display circuit (picture-in-picture) used in a television receiver or the like, and more particularly to displaying a plurality of images of different aspect sizes as a sub-screen. The present invention relates to a child screen display circuit suitable for use in some cases.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional child screen display circuit. The video signal of the main screen is input to the input terminal 1, and the video signal of the sub screen is input to the input terminal 2. The video signal will be described as a monochrome composite video signal. The video signal of the main screen input to the input terminal 1 is input to the sync signal separation / horizontal AFC circuit 3 and the clamp circuit 5, and the video signal of the sub-screen input to the input terminal 2 is the sync signal separation / horizontal AFC circuit. 4 and the clamp circuit 6. Sync signal separation / horizontal A
A clock and horizontal and vertical synchronization signals (synchronization signal pulses) synchronized with the respective video signals generated by the FC circuits 3 and 4 are input to the control circuit 10. The control circuit 10 supplies a clamp pulse to the clamp circuits 5 and 6, and supplies a clock to the A / D converter 7 and the D / A converter 9. Also,
The control circuit 10 supplies a write timing pulse and a read timing pulse to the video memory 8 and a switching timing pulse to the analog switch 11.

The video signal of the main screen reproduced by the clamp circuit 5 is input to one terminal of the switch 11. The video signal of the sub-screen is input to the other terminal of the switch 11 as described later, and the video signal of the main screen and the video signal of the sub-screen are switched and output. By the way, these two video signals are not generally synchronized, and if the switch 11 is switched at the timing of the parent screen, the timing of the video of the child screen is shifted, so that a normal image cannot be displayed. Further, even if they are synchronized, only a part of the child screen can be displayed as it is. Therefore, the video signal of the sub-screen input to the clamp circuit 6 is input to the switch 11 as follows.

That is, the picture signal of the sub-screen reproduced by the clamp circuit 6 is input to the A / D converter 7 and A
/ D converted and input to the memory 8. This video signal is written and stored in the memory 8 at the timing synchronized with the video signal of the child screen, and read out at the timing synchronized with the video signal of the parent screen. The video signal of the small screen read out from the memory 8 is input to the D / A converter 9, D / A converted, and input to the switch 11. As a result, the video signal of the parent screen and the video signal of the child screen are synchronized.

The picture signal of the sub-screen is reduced in writing. At this time, the reduction ratio must be reduced in both the vertical and horizontal directions at a ratio substantially equal to the aspect ratio of the original sub-screen. Therefore, the sampling rate at the time of writing to the memory 8 is reduced at almost the same rate in the vertical direction and the horizontal direction. That is, for example, only one line is written every three lines in the vertical direction, and writing is performed in the horizontal direction at a rate of 1/3 of the read timing.

The switch 11 switches the video signal of the main screen input from the clamp circuit 5 and the video signal of the sub-screen input from the D / A converter 9 according to the switching timing pulse, and the output terminal 12 Output more. As a result, if both the video signal of the parent screen and the video signal of the child screen have an aspect ratio of 4: 3, as shown in FIG. If the child screen P2 with a size of 1/3 and an aspect ratio of 4: 3 is displayed, or if the image signal of the parent screen has an aspect ratio of 16: 9 and the image signal of the child screen has an aspect ratio of 4: 3, the screen shown in FIG. B)
As shown in, the child screen P2 having the aspect ratio of 4: 3 is displayed in the parent screen P3 having the aspect ratio of 16: 9.

[0007]

However, in the above-mentioned conventional small screen display circuit, since the aspect ratio of the small screen image is fixed, a video signal having an aspect ratio different from the set aspect ratio is set. There is a problem in that when an image of is displayed on the small screen, a non-image part is generated in the small screen image, or a part which is not displayed is generated on the contrary. In addition, as in the case of the second generation EDTV, when the reinforcement signal is superimposed on the upper and lower non-picture portions of the letterboxed main screen, only the main screen cannot be displayed as a sub screen. However, there is a problem in that the supplementary signal may cause visual interference in the child screen.

The present invention has been made in view of the above problems, and provides a sub-screen display circuit capable of making the aspect ratio of a sub-screen image the aspect ratio originally possessed by the video signal of the sub-screen. The purpose is to do.

[0009]

In order to solve the above-mentioned problems of the conventional technique, the present invention receives a video signal of a main screen and generates a synchronizing signal pulse and a clock pulse synchronized with this video signal. 2nd which inputs the sync separation / horizontal AFC circuit of 1 and the picture signal of the child screen and generates the sync signal pulse and the clock pulse which are synchronized with this picture signal
A sync separation / horizontal AFC circuit, a first clamp circuit for DC-reproducing and outputting the parent screen video signal, a second clamp circuit for DC-reproducing and outputting the sub-screen video signal, An A / D converter for A / D-converting and outputting a sub-picture video signal; a video memory for writing the sub-picture video signal A / D converted by the A / D converter; and a video memory A D / A converter that D / A converts the video signal of the child screen read in synchronization with the video signal of the parent screen and outputs the D / A converter, and the D / A converter that outputs the parent screen of the parent screen. A switch for fitting the image signal of the child screen into a part of the image signal of the parent screen by switching between the image signal and the image signal of the child screen output from the D / A converter; 2 clamp circuit Control to supply a clock pulse to the A / D converter and the D / A converter, a write timing pulse and a read timing pulse to the video memory, and a switch timing pulse to the switch. A sub-screen display circuit including a circuit, and the video signal of the sub-screen and the sync signal pulse or the sync signal pulse and the clock pulse output from the second sync separation / horizontal AFC circuit are input, An identification signal discriminating circuit for extracting from the video signal of the sub-screen an identification signal indicating aspect ratio information or aspect ratio information and screen position information superimposed on the video signal of the sub-screen and supplying the data to the control circuit. And writing the video signal of the sub-screen to the video memory based on the data. Write timing,
The present invention provides a small screen display circuit characterized in that the read timing and the switch switching timing are changed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A child screen display circuit of the present invention will be described below with reference to the accompanying drawings. 1 is a block diagram showing an embodiment of a child screen display circuit of the present invention, and FIG. 2 is a diagram for explaining the child screen display circuit of the present invention. In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals.

As a premise of the present invention, the aspect ratio information of the image transmitted by the video signal is transmitted in a different form to a part of the video signal (for example, one place in one field, on a certain line). Consider the condition that As an example of this, for example, a second generation E that transmits a wide aspect image with an aspect ratio of 16: 9 in a letterbox format into an image with the current aspect ratio of 4: 3.
There is a DTV. In this new broadcasting system, the transmission line is
Since it is shared with the SC system, it is necessary to transmit the aspect ratio information of the image being transmitted by another code different from the analog video component. In the case of the second generation EDTV, the code is transmitted in the form of digital data on a predetermined line.

As can be seen from FIG. 1A, the identification signal discriminating circuit 13 is newly added according to the present invention. In FIG. 1A, the video signal of the parent screen is input to the input terminal 1, and the video signal of the child screen is input to the input terminal 2. The video signal will be described as a monochrome composite video signal. The video signal of the main screen input to the input terminal 1 is input to the sync signal separation / horizontal AFC circuit 3 and the clamp circuit 5, and the video signal of the sub-screen input to the input terminal 2 is the sync signal separation / horizontal AFC circuit. 4, the clamp circuit 6, and the identification signal determination circuit 13 are input. The clock, horizontal and vertical sync signals (sync signal pulses), which are generated by the sync signal separation / horizontal AFC circuit 3 and are synchronized with the video signal of the main screen, are input to the control circuit 10 and generated by the sync signal separation / horizontal AFC circuit 4. The clock, horizontal and vertical synchronization signals (synchronization signal pulses) synchronized with the video signal of the generated sub-screen are controlled circuit 10 and identification signal determination circuit 13
Entered in.

Here, the identification signal discriminating circuit 13 internally generates a timing signal for taking in the identification signal superimposed on the video signal of the child screen by the synchronizing signal pulse input from the synchronizing signal separating / horizontal AFC circuit 4. To do. And
The identification signal superimposed on the image signal of the small screen is fetched by this timing signal, and the aspect ratio information of the image signal of the small screen is read to supply the digital aspect ratio data to the control circuit 10. Note that, here, only the synchronizing signal pulse is input from the synchronizing signal separating / horizontal AFC circuit 4 to the identifying signal determining circuit 13, and the identifying signal determining circuit 13
Although the clock is internally generated based on the sync signal pulse, both the sync signal pulse and the clock may be input to the identification signal determination circuit 13 from the sync signal separation / horizontal AFC circuit 4. The control circuit 10 supplies a clamp pulse to the clamp circuits 5 and 6, and supplies a clock to the A / D converter 7 and the D / A converter 9. The control circuit 10 also supplies a write timing pulse and a read timing pulse to the video memory 8 and a switching timing pulse to the analog switch 11.

The video signal of the parent screen, which has been DC reproduced by the clamp circuit 5, is input to one terminal of the switch 11. The video signal of the sub-screen is input to the other terminal of the switch 11 as described later, and the video signal of the main screen and the video signal of the sub-screen are switched and output. By the way, these two video signals are not generally synchronized, and if the switch 11 is switched at the timing of the parent screen, the timing of the video of the child screen is shifted, so that a normal image cannot be displayed. Further, even if they are synchronized, only a part of the child screen can be displayed as it is. Therefore, the video signal of the sub-screen input to the clamp circuit 6 is input to the switch 11 as follows.

That is, the video signal of the sub-screen reproduced by the clamp circuit 6 is input to the A / D converter 7 and A
/ D converted and input to the memory 8. This video signal is synchronized with the video signal of the child screen at the timing of the control circuit 1
It is written and stored in the memory 8 for a period designated by 0, and is read out at a timing synchronized with the video signal of the main screen. The video signal of the small screen read out from the memory 8 is input to the D / A converter 9, D / A converted, and input to the switch 11. As a result, the video signal of the parent screen and the video signal of the child screen are synchronized.

At this time, in the child screen display circuit of the present invention, the write timing to the memory 8 is changed based on the aspect ratio data described above. For example, in the case of a letterbox-type image, writing is stopped during the upper and lower non-image areas. If the reduction ratio of the small screen is 1/3 when the aspect ratio is 4: 3, it is 1/2 when the letterbox format is used. This makes 3
/ 4 × 1/2 = 3/8, and the image of the small screen has almost the same size in the vertical direction.

The switch 11 switches the main screen video signal input from the clamp circuit 5 and the sub-screen video signal input from the D / A converter 9 to a switching timing pulse corresponding to the sub-screen video signal. And output from the output terminal 12. As a result, if both the parent screen video signal and the child screen video signal have an aspect ratio of 4: 3, as shown in FIG. 2A, the parent screen P having an aspect ratio of 4: 3 is displayed.
A child screen P2 having an aspect ratio of 4: 3 indicated by a solid line is displayed in 1 and a child screen P4 having an aspect ratio of 16: 9 indicated by a broken line is displayed when the image signal of the child screen is in the letterbox format. Also, the video signal of the main screen has an aspect ratio of 1
If the image signal of the sub-screen is 6: 9 in the letterbox format, as shown in FIG. 2B, the sub-screen having the aspect ratio of 16: 9 shown by the solid line in the main screen P3 having the aspect ratio of 16: 9. If P4 is displayed and the video signal of the child screen has an aspect ratio of 4: 3, the child screen P2 having an aspect ratio of 4: 3 indicated by a broken line is displayed.

By the way, in the second generation EDTV,
Since a wide aspect image with an aspect ratio of 16: 9 is arranged at the center in the vertical direction of an image with an aspect ratio of 4: 3, in the above-described embodiment, the identification signal superimposed on the video signal of the small screen has the aspect ratio. The case where only the ratio information is represented is described. However, in PAL Plus, which is planned in Europe, the position of the wide aspect image is not fixed, and the identification signal superimposed on the video signal in this case represents both aspect ratio information and screen position information. Therefore, in this case, the identification signal determination circuit 13
Extracts an identification signal representing aspect ratio information and screen position information superimposed on the image signal of the child screen, and supplies data representing the aspect ratio information and screen position information to the control circuit 10.

Further, the case where the identification signal is superimposed on a part of the video signal has been described as the premise of the present invention. However, in the case of a video signal which is in the letterbox format, but the identification signal is not superimposed, the identification signal is It is necessary to control the control circuit 10 by an external control signal instead of the output of the determination circuit 13. For that purpose, for example, the aspect ratio of the image of the small screen can be changed by applying the present invention as follows. That is, as shown in FIG. 1B, the digital data output from the identification signal discrimination circuit 13 is ORed.
The signal is input to one terminal of the circuit 14 and the external control signal (EXT) is input to the other terminal. This external control signal may be input by a remote control transmitter,
This is the output of the discrimination circuit that determines whether the video signal is in the letterbox format. As described above, if the switching compulsory circuit including the OR circuit 14 is provided between the identification signal determination circuit 13 and the control circuit 10, even if the identification signal is not superimposed, it is possible for the viewer to determine. Alternatively, the aspect ratio of the image on the inset screen can be automatically changed.

[0020]

As described in detail above, the child screen display circuit of the present invention extracts the identification signal representing the aspect ratio information (aspect ratio information and screen position information) superimposed on the image signal of the child screen. At the same time, an identification signal discriminating circuit for supplying the data to the control circuit is provided, and based on the data, the writing timing and the reading timing of the video signal of the sub-screen to the video memory and the switching timing of the parent screen / sub-screen switching switch are set. Since the change is made, it is possible to effectively display the sub-screen image without causing a non-image part in the sub-screen image or a part that is not displayed. In addition, as in the case of the second-generation EDTV, when the reinforcement signal is superimposed on the upper and lower non-picture parts of the letterboxed main screen, only the main screen can be displayed as a sub screen, The aspect ratio that the video signal of the small screen originally has can be set. As a result, the visual interference due to the reinforcement signal does not occur in the child screen. Further, since the aspect ratio of the sub-screen image is changed by the identification signal transmitted by being superimposed on the video signal of the sub-screen, the aspect ratio is automatically changed and no troublesome operation is required.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining the present invention.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a diagram for explaining a conventional example.

[Explanation of symbols]

 1, 2 input terminals 3, 4 sync separation / horizontal AFC circuit 5, 6 clamp circuit 7 A / D converter 8 video memory 9 D / A converter 10 control circuit 11 switch 12 output terminal 13 identification signal discrimination circuit 14 OR circuit

Claims (2)

[Claims] 1. A first sync separation / horizontal AFC circuit for inputting a video signal of a main screen, generating a sync signal pulse and a clock pulse synchronized with this video signal, and a video signal of a sub screen are inputted. A second sync separation / horizontal AFC circuit that generates a sync signal pulse and a clock pulse that are synchronized with a video signal, a first clamp circuit that reproduces and outputs the video signal of the parent screen by direct current, and a video of the child screen A second clamp circuit for DC-reproducing a signal and outputting the same, and an A / D for A / D converting and outputting the video signal of the sub-screen
A converter, a video memory for writing the video signal of the child screen A / D converted by the A / D converter, and the child screen read from the video memory in synchronization with the video signal of the parent screen A D / A converter for D / A converting the video signal and outputting the video signal of the parent screen output from the first clamp circuit and the sub-screen output from the D / A converter. A switch for fitting a video signal of the sub-screen to a part of the video signal of the main screen by switching the video signal, and supplying a clamp pulse to the first and second clamp circuits, and the A / D converter. And a D / A converter, a write timing pulse and a read timing pulse to the video memory, and a switching timing pulse to the switch. A sub-screen display circuit including a control circuit, wherein a video signal of the sub-screen and the second synchronous separation / horizontal AF are provided.
The synchronization signal pulse output from the C circuit or the synchronization signal pulse and the clock pulse are input,
From the video signal of the sub-screen, an identification signal representing aspect ratio information or aspect ratio information and screen position information superimposed on the video signal of the sub-screen is extracted, and the identification signal is supplied to the control circuit. A sub-screen display circuit, wherein a circuit is provided, and a writing timing, a reading timing, and a switch switching timing of the video signal of the sub-screen to the video memory are changed based on the data. 2. The output of the identification signal discrimination circuit and an external control signal are input, and when the identification signal exists, the data is supplied to the control circuit, and when the identification signal does not exist, the external signal is supplied. The child screen display circuit according to claim 1, further comprising means for supplying a control signal to the control circuit.