JPH0748833B2 - Image synthesizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a function of inserting another image into a part of an image (hereinafter referred to as a picture-in-picture function, referred to as a PinP function).
And an image synthesizing apparatus having the

[Conventional technology]

In recent years, image quality has been improved based on advances in memory technology and digital technology. Digital television receivers have been announced for the purpose of multi-functionalization. The PinP function is a function that has been adopted in many of these digital television receivers (TV technology.December 1984 issue, pages 31 to 37, TV technology.
(August 1985, pages 19 to 23, etc.), and the basic operation of these PinPs is discussed in Japanese Examined Patent Publication No. 55-39472.

[Problems to be solved by the invention]

The conventional PinP function described above is adopted in a television receiver. For this reason, most of the signals that drive the cathode-ray tube are read from the video signal of the main screen in a part of the main screen, the video signal of the sub-screen (generally, such as an image memory is recorded and read from the image memory in synchronization with the main screen). Video signal). Therefore, at the stage of the standard composite video signal (for example, NTSC signal, PAL signal, etc.), the problem that occurs when the PinP function is realized by inserting the video signal of the sub-screen into the main screen is not often discussed. It was However, the PinP at the stage of the standard composite video signal does not require the change of the television receiver, and therefore video equipment other than the adapter or the television receiver, for example, video tape recorder; VTR, video disc player; VDP, etc. Is the most preferable method to realize the PinP function, and will be used in video equipment other than these television receivers in the future.
In order to realize the above, it is necessary to solve the above problems. As one of the problems, there is a synchronization defect of the main screen due to noise of the small screen in the television receiver.

As the video signal of the PinP sub-screen, a normal signal is not always input, but a signal including much noise may be input. For example, in a VTR or the like, it is expected that the use of a child screen as a monitor during high-speed playback will account for a large proportion of PinP usage. At the time of high-speed playback of this VTR, horizontal band noise generally called bar noise is generated, depending on the structure of the VTR. This bar noise contains a lot of noise components below the sync detection level of the television signal, and the noise components are erroneously recognized as a sync signal by the television receiver, and as a result, the above-mentioned sync droop occurs.
However, even if a normal video signal is input to the main screen, it is very unsightly that the synchronization is found due to the noise of the small screen.

It is an object of the present invention to provide an image synthesizing device that realizes the above-described PinP in which there is no synchronization defect in the parent screen due to the noise in the child screen.

[Means for solving problems]

In order to achieve the above object, a threshold value lower than the black level of the standard video signal of the sub-screen (sub-picture signal) and higher than the synchronization detection level of the television receiver is provided, and the sub-picture signal having a threshold value not more than the threshold value The portion is clipped, and the clipped child video signal is inserted into the standard composite video signal of the parent screen (hereinafter simply referred to as the parent video signal).

[Action]

The noise of the sub-screen that causes the synchronization bleeding of the main screen is a portion lower than the sync detection level when the sync signal is separated from the parent video signal in the television receiver. (This portion is erroneously recognized as a sync signal.) Therefore, the above-mentioned noise is removed from the sub-picture signal by the clipping circuit that clips a portion that is higher than the sync detection level and equal to or lower than the threshold value. It is possible to prevent synchronization drool. Further, since the threshold level is set to a level lower than black as described above, it contributes to the clipping circuit,
There is no adverse effect on the signal component of the sub-picture signal.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the first embodiment of the present invention. The operation of this embodiment will be described with reference to FIGS. 1 and 2. In FIG. 1, 1 and 2 are input terminals for the parent video signal and the child video signal, 3 and 4 are sync separation circuits, and 5
Is a decoder, 6 is a recording circuit, 7 is a control circuit, 8 is an encoder, 9 is an automatic phase control (hereinafter referred to as APC) circuit, 10 and 11
Is a clamp circuit, 12 is a clip circuit, and 13 is a switch circuit. In FIG. 2, 14 is the PinP video signal synthesized by this embodiment, 1 is the black level of the video signal 14, 17 is the threshold value of the clipping circuit 12, 18 is the sync detection level of the television receiver, and 20 is Is a synchronizing signal separated from the video signal 14 in the television receiver.

First, the parent video signal and the child video signal are input to the terminals 1 and 2, respectively. The sync separation circuits 3 and 4 separate the sync signal from the parent video signal and the child video signal, and supply the sync signal to the control circuit 7. The decoder 5 generates a luminance signal Y from the low frequency component of the supplied composite video signal of the sub-picture and color difference signals (RY) and (BY) from the modulated wave component thereof. These luminance signal Y, color difference signals (RY) and (BY)
According to the reduction ratio of the sub-screen, the data is thinned out, sampled, and recorded in the recording circuit 6 controlled by the control circuit 7. Further, according to the synchronizing signal separated from the parent video signal, the recorded superimposing signal is read again from the recording circuit 6, and the reduced luminance signal Y ', color signals (RY)' and (BY) are read. Get ′. However, the reduction of the video signal is discussed in, for example, Japanese Patent Publication No. 55-39472, and the detailed description thereof will be omitted here. In the encoder 8, the color difference signal (R-
Y) 'and (B-Y)' are modulated and the resulting modulated signal is mixed with the luminance signal Y'to synthesize a reduced child video signal. The parent video signal and the reduced child video signal are clamped by the clamp circuits 10 and 11 so that the black levels of these two video signals become equal after inserting the child screen, and the switch circuit 13 and the clip circuit 12 respectively. Supply to. The clip circuit 12 compresses a signal which is lower than the black level and lower than a threshold level which is set higher than the sync detection level of the television signal. Finally, in the switch circuit 13 controlled by the control circuit 7, the clip circuit 12
The reduced child video signal supplied by the above is inserted into the parent video signal. According to the present embodiment, as shown in FIG. 2, the noise 19 which causes the synchronization deviation of the sub-picture signal can be removed, so that the synchronization deviation of the main screen caused by the noise of the sub-picture signal can be completely prevented. it can.

FIG. 3 is a block diagram of the second embodiment of the present invention. A second embodiment will be described with reference to FIGS. 3 and 4. However, the portions having the same functions as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.
In FIG. 3, 21 is an A / D converter, 22 is a memory (generally 1 field memory to 2 frame memory), and 23 is
It is a D / A converter. In FIG. 4, 24 is a child video signal, 2
Reference numeral 5 is an input dynamic range of the A / D converter 21, 26 is a low level reference potential of the A / D converter 21, and 27 is a high level reference potential of the A / D converter. Recording circuit 6 described in the first embodiment
Is generally the A / D converter 21, memory, as shown in FIG.
22 and a D / A converter 23. In the second embodiment, the A / D conversion of the luminance signal Y is performed by the first conversion as shown in FIG.
By performing the threshold value 17 described in the above embodiment in conformity with the low-level reference potential 26 of the A / D converter 21, the noise 19 which causes the synchronization shift of the parent video signal is removed.
As a result, according to the present embodiment as well, similar to the first embodiment, it is possible to prevent the synchronization deviation of the parent video signal. In the second embodiment, the clip circuit described in the first embodiment is unnecessary, and the circuit can be simplified by the amount corresponding to that. Although detailed description is omitted, other parts (for example, DC stable D / A
Immediately after that), the same effect as that of the above-described embodiment can be obtained by similarly compressing the child video signal.

FIG. 5 shows a clamp circuit 1 which is the main part of the first embodiment.
An example of 0, 11, a clip circuit 12, and a switch circuit 13 is shown. In FIG. 5, R _{1 to} R ₇ are resistors, Q _{1 to} Q ₁₄ are transistors, C ₁ and C ₂ are capacitors, I ₁ and I ₂ are constant current sources, E _REF is a reference voltage source, and E _BAT is a power source. Is. The operation of each unit will be described below. In the clamp circuits 10 and 11, the transistors Q ₁ and Q ₅
The peaks of the lower ends of the synchronizing portions of the parent video signal and the child video signal input via the capacitors C ₁ and C ₂ are peak-clamped. Q ₂ ~ Q ₄
And R ₄ and R ₅ are bias circuits, and apply a potential to the base of Q ₅ so that the black levels of the parent video signal and the child video signal input to the switch circuit 13 become equal. (Here, the synchronization levels of the parent video signal and the child video signal are adjusted before the clamp circuit is input.) The clamped child video signal is supplied to the clip circuit 12, and a transistor that operates as a switch.
A portion lower than the base potential of the transistor Q ₆ is clipped by Q ₆ and Q ₇ and then supplied to the switch circuit 13. In the switch circuit 13, according to the control signal input to the base of the transistor Q ₁₃ , that is, when the control signal is higher than the base potential of Q ₁₂ (reference potential E _{REF in the} figure), the transistors Q ₁₃ and Q ₁₂ are turned on, off, selects and outputs the child picture signal, and when the control signal is lower than the base potential of the Q ₁₂ are turned on transistor Q _12, Q ₁₃ are each turned off, by leaving selecting a parent video signal , Insert the child video signal into the parent video signal. Therefore, according to the circuit example described above, by setting the voltage across the resistor R ₂ to an appropriate value (the clip level is located at + V _R12 from the lower end of the synchronizing portion when the voltage across the resistor is V _R12 ). Since the threshold value of the clipping circuit 12 can be stably set between the sync detection level and the black level of the television receiver, the sync bleeding of the parent screen due to the noise of the child video signal can be completely prevented.

〔The invention's effect〕

According to the present invention, in a video synthesizing device that realizes the PinP function by inserting the video signal of the sub-screen into the video signal of the main screen at the stage of the composite video signal, the synchronization of the main screen due to the noise of the sub-screen is achieved. We can prevent weeping.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, FIG. 2 is a diagram showing a video signal and a sync signal synthesized by the embodiment of the present invention, and FIG. 3 is a second embodiment of the present invention. An example block diagram, FIG. 4 is a diagram showing a luminance signal waveform of an A / D input section in the second embodiment, and FIG. 5 is a circuit diagram of a main part of the present invention. 3,4 …… Synchronous separation circuit 5 …… Decoder, 6 …… Recording circuit 7 …… Control circuit, 8 …… Encoder 9 …… APC circuit 10,11 …… Clamp circuit 12 …… Clip circuit 13 …… Switch circuit 21 …… A / D converter, 22 …… Memory 23 …… D / A converter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuyuki Okamoto, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Home Appliance Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-60-174 (JP, A) JP 60-229480 (JP, A)

Claims (1)

[Claims] 1. A reduction means for reducing the second composite video signal using the first composite video signal and the second composite video signal as input signals, and a second composite from the reduction means. A selection means for supplying a signal based on a reduced signal obtained by reducing the video signal to one input terminal and the first composite video signal to the other input terminal, and selectively outputting one of the supplied signals. And a signal based on the reduced signal is selectively output by the selection means only during a period corresponding to an arbitrary display area in the display area of the first composite video signal. An image synthesizing device for simultaneously displaying the first composite video signal and a signal obtained by reducing the second composite video signal on the same screen, wherein the image composite device is lower than a black level of the first composite video signal, And set it higher than the sync detection level of the television receiver. When the level of the reduced signal is lower than the predetermined threshold value, compression / removal means for compressing / removing the lowest level of the reduced signal to the level of the predetermined threshold value,
And an image synthesizing apparatus comprising: an output signal from the compression / removal means, which is supplied to one input terminal of the selection means.