JPH0720251B2 - Image synthesizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention has a function of inserting another image into a part of an image displayed on a screen (Picture in Picture function; hereinafter referred to as Pi).
An image synthesizing device having an nP function).

[Conventional technology]

In recent years, based on the progress of memory technology and digital technology, digital television receivers have been announced for the purpose of high image quality and multifunction. A function adopted in many of these digital television receivers is the PinP function. For basic operations of these, see TV Technology, 1984.
December issue (pages 31 to 37) and JP-A-54-92015.

The PinP function in the above-described conventional technology is adopted in a television receiver, and for example, the main screen displays an image of a VTR, including a television broadcast, and a part of the image is a VTR, a video disc. , Images such as satellite broadcasting will be displayed. For this reason, in most devices, the signal for driving the cathode-ray tube is adjusted from the video signal of the main screen to the video signal of the sub screen (generally after being recorded in the image memory etc., in synchronization with the main screen in a part of the main screen). The PinP function is realized by switching from the image memory to another video signal that can be read out so that it can be inserted into the main screen.

[Problems to be solved by the invention]

In the above-mentioned conventional technology, if the color signal levels of the parent video signal and the child video signal to be combined do not match, the color depths of the parent screen and the child screen change and it becomes unnatural. In order to solve this problem, it has been conventionally considered to perform ACC processing on the parent composite video signal. In this case, both parent and child composite video signals are processed.
It is necessary to perform processing such as Y / C separation and modulation / demodulation.
However, conventionally, whether or not PinP is possible at the stage of a standard composite video signal (for example, NTSC signal, PAL signal, etc.) and its problems have not been considered,
It has never been considered.

The level control of the carrier color signal of the parent composite video signal (hereinafter also simply referred to as a color signal) of the above conventional technology (Auto
The problems with matic color control (ACC) are as follows.

Generally, in a color television receiver, a burst level of a color signal separated from a composite video signal is detected and a level of the burst signal becomes constant in order to prevent a color change due to a color level fluctuation of an input composite video signal. As described above, the gain of the color signal is controlled (ACC), and then the color adjustment is performed. This also applies to the PinP in the color television receiver described above, and the ACC and color demodulation may be performed as usual after separating the color signals from the parent and child video signals.

Thus, in the conventional ACC system, the parent signal is
The luminance signal Y and the carrier color signal C are separated from the composite video signal by a low pass filter (LPF) and a band pass filter (BPF), respectively, and ACC is performed on the color signal. Although the luminance signal and color signal are mixed again, unlike the child screen, each YC signal of the parent screen requires the entire frequency band, so the frequency characteristics generally deteriorate during Y / C separation (especially Luminance signal). On the contrary, in order to reduce the deterioration of the frequency characteristic at the time of Y / C separation, for example, a comb filter using an IH delay line or the like is required, which causes a problem that the circuit scale increases.

On the other hand, regarding the child video signal, in the PinP at the stage of the composite video signal, it is generally necessary to separate the luminance signal Y and the carrier color signal C at the time of memory storage and perform color demodulation. ACC can be performed by the method, that is, by controlling the gain of the color signal after Y / C separation. However, in the case of the small screen, the reduction is generally performed. Now, if the small screen is reduced to I / N (for example, N = 2 to 4), the required band of the luminance signal and the color signal is the original I. Therefore, the frequency characteristic of each YC signal does not deteriorate during the Y / C separation, and there is no particular problem in image quality and signal processing.

Since the PinP at the stage of the standard video signal does not require any change in the television receiver, the video device other than the adapter or the television receiver (for example, video tape recorder; VTR, video disc player; VDP
Etc.) is preferable as a method for realizing the PinP function, and can be said to be useful in video equipment other than these television receivers.

The object of the present invention is to provide PinP in the above-mentioned composite video signal stage.
The above problems have been solved, and with a small circuit scale, there is little deterioration in the frequency band and image quality of the composite video signal of the parent and child, and the coloring of the parent and child screens is maintained at a fixed ratio. An object is to provide a drooping image synthesizing device.

[Means for solving problems]

In order to achieve the above object, the present invention is provided with a detecting means for detecting the carrier color signal level of the parent composite video signal, and a variable gain amplifying means for adjusting the gain of the carrier color signal of the child screen.
Accordingly, in accordance with the detected value of the carrier color signal level obtained by the detecting means, the variable amplifying means controls the gain of the color signal of the child screen so that the relative value of the color signal levels of the parent and child is always constant. Configure to keep.

[Action]

In the detection means, after extracting the burst signal in the carrier color signal from the parent composite video signal, the burst signal is detected, and the detected value is compared with a reference level to determine the amount of attenuation with respect to the rated level of the carrier color signal. (Or increase amount)
To detect. The gain of the variable gain amplifying means is controlled according to the detection level to attenuate (increase) the child screen carrier color signal level of the output, whereby the child carrier level is always constant with respect to the parent carrier level. It is designed to be kept at a level ratio. Here, for example, if the parent carrier color signal level is attenuated (or increased) by 3 dB from the rated level, the child color signal is attenuated (or increased) by 3 dB according to the set level.

The PinP composite video signal synthesized using the color signal after the gain adjustment is supplied to the color television receiver. In this color television receiver, ACC processing is performed based on the burst signal of the parent, but at this time, since the relationship between the parent and child carrier color signal levels is a fixed ratio, as a result, the child carrier color is The signal level is also kept constant. Thereby, the coloring of the parent and child screens is kept constant. Further, at this time, the parent composite video signal is not subjected to any special signal processing other than the insertion of the child composite video signal, so that no image quality deterioration phenomenon such as frequency deterioration occurs.

〔Example〕

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

FIG. 1 is a block diagram showing a basic configuration of an image synthesizing apparatus according to the present invention. Reference numerals 1 and 2 are input terminals for a parent composite video signal and a child composite video signal, 3 is a burst level detection circuit, and 4 is an automatic phase. Control (Auto Phose Control; hereinafter abbreviated as APC) circuit, 5 LPF, 6 BPF, 7 ACC circuit, 8 color demodulation circuit, 9 recording circuit, 10 control circuit, 11 color modulation circuit, 12 The gain adjusting circuit, 13 is a switch.

In the figure, the parent composite video signal S _M is input from the input terminal 1 and supplied to the switch circuit 13, the burst level detection circuit 3 and the APC circuit 4 whose switching is controlled by the control circuit 10. The burst level detection circuit 3 extracts the burst signal of the color carrier signal from the supplied parent composite video signal S _M , detects the burst signal level to detect the burst signal level, and outputs the detection level to the gain adjustment circuit 12. Supply. Also, the APC circuit 4 extracts a burst signal of the carrier chrominance signal S _M of the parent, the color modulation color subcarrier f _SC of the child screen is phase lock occurs the burst signal, the color subcarrier f _SC Is supplied to the color modulation circuit 11.

The child composite video signal S _S is input from the input terminal 2, and LPF5 and
The BPF 6 separates the luminance signal Y and the carrier color signal C, respectively. Separated luminance signal Y and carrier color signal C
Are supplied to the recording circuit 9 and the ACC circuit 7, respectively.
The carrier color signal C is further adjusted in gain so as to have a desired constant level by the ACC circuit 7, and then demodulated into color difference signals (RY) (BY) by the color demodulation circuit 8. The luminance signal Y and the color difference signals (RY) (BY) thus obtained
Is recorded in the memory circuit 9 whose writing and reading are controlled by the control circuit 10. Each signal once recorded is read again in synchronization with the sync signal of the parent video signal. This reading is performed faster than writing, and each signal is reduced to a size that can be inserted into the parent composite video signal S _M. The read color difference signal (RY) ′,
(B-Y) 'is supplied to the color modulation circuit 11, it is again modulated by the color subcarrier f _gc phase-lock to the burst signal of the carrier chrominance signal of the parent video signal. The modulated child carrier color signal C _S is supplied to the gain adjustment circuit 12 which is controlled by the detection value of the burst level detection circuit 3, and ACC is supplied in accordance with the attenuation amount (or increase amount) with respect to the rated level of the parent carrier color signal. The circuit 7 attenuates (increases) this child carrier color signal C _S , which is kept at a constant level, by the required level. The gain adjusted child carrier chrominance signal C _S ′ is mixed with the luminance signal Y ′ to obtain a reduced child composite video signal that can be inserted into the parent composite video signal S _M. Finally, the switch 13 selectively outputs the supplied two composite video signals (the parent composite video signal and the reduced child composite video signal) according to the control signal of the control circuit 10, and inserts the child composite video signal. Form a PinP composite video signal.

In the PinP composite video signal formed in this manner, the level of the child carrier color signal is always kept constant with respect to the parent carrier color signal, and as a result, as described above, the television to which the PinP composite video signal is supplied. In the Jyon receiver, the ACC processing is performed based on the burst signal of the parent carrier color signal, so that the coloring of the parent and child can be maintained at a desired constant level without degrading the image quality of the parent screen.

FIG. 2 is a block diagram showing the essential parts of the first embodiment of the image synthesizing apparatus according to the present invention, in which 14 and 17 are burst extraction circuits, 15 and 18 are detection circuits, 16 is a variable gain amplifier, and 19 is a variable gain amplifier. Is a comparator, and the parts corresponding to those in FIG.

In this embodiment, the burst level detecting circuit 3 and the gain adjusting circuit 12 in FIG.
Detection circuit 15, variable gain amplifier 16, burst extraction circuit 1
7, a detection circuit 18, and a comparator 19.

Next, the operation of this embodiment will be described below with reference to FIGS. 2 and 3. However, the parts not shown in FIG. 2 are the same as those in FIG. 1, and the description thereof is omitted here. Further, FIG. 3 shows the signal waveforms of the respective parts of FIG. 2, in which both the parent composite video signal and the child composite video signal are
As the signal, a luminance order color bar signal was assumed.

The parent composite video signal is a switch circuit 13 and a burst extraction circuit
Supplied to 14. The burst extraction circuit 14 extracts the signal of the period A of the parent composite video signal S _M shown in FIG. 3A and extracts the burst signal of the parent composite video signal S _M. The extracted burst signal is supplied to the detection circuit 15, and the detection amplitude of the burst amplitude level e _CM (FIG. 3A) is detected by the detection circuit 15, and the detected value is supplied to the comparator 19. The reduced child carrier color signal C _S is supplied to the variable gain amplifier 16, where the gain is adjusted by the output of the comparator 19.
In the burst extraction circuit 17, the child carrier color signal after gain adjustment
The burst is extracted by extracting the signal of the period B from C _S ′ (FIG. 3 (b)). In the detection circuit 18, the burst extraction circuit
The burst amplitude level e _CS (FIG. 3 (b)) is detected from the burst signal supplied by 17, and the detected value is supplied to the comparator 19. Here, the comparator 19 sets the gain to a sufficiently large value, and the variable gain amplifier 16, burst extraction circuit 17, detection circuit
18, the comparator 19 is configured to form a control loop. This control loop works so that the detected value of the burst level of the child carrier color signal becomes equal to the detected value of the burst level of the parent carrier color signal. In this way, the level of the child carrier chrominance signal is always kept constant with respect to the parent carrier chrominance signal level.

The gain-adjusted child carrier color signal C _S ′ is mixed with the child luminance signal Y ′. Child composite video signal thus obtained (Fig. 3 (c))
Is supplied to the switch 13 and inserted at a desired position (position C in FIG. 3 (c)) of the parent composite video signal to obtain a PinP composite video signal (FIG. 3 (d)).

Here, the characteristic of the detection circuit is non-linear, and therefore, when the level of the burst signal is detected by the detection circuit, the non-linear characteristic influences the detection result. Therefore, the first
As shown in the figure, when the burst level detection circuit 3 is composed of a burst extraction circuit and a detection circuit, and the gain of the gain adjustment circuit 12 is adjusted by the detection output of the burst level detection circuit 3 having such a configuration, the parent composite video signal is obtained. Gain control that accurately corresponds to the burst signal level of S _M cannot be performed.

However, in the embodiment shown in FIG. 2, the burst level detection circuit 3 is provided with the detection circuit 15 and the gain adjustment circuit 12 is also provided with the detection circuit 18, and the detection outputs of these detection circuits 15 and 18 are Since it is compared by the comparator 19,
The effects of the nonlinear characteristics of the detection circuits 15 and 18 are offset and eliminated, and the variable gain amplifier 16 performs gain control that is not affected by the nonlinear characteristics. Therefore, the carrier color signal levels of the parent and child can be kept relatively constant.

FIG. 4 is a block diagram showing a main part of a second embodiment of the image synthesizing apparatus according to the present invention.

In this embodiment, unlike the first embodiment described above, the burst signal of the child carrier color signal is not recorded, but the burst signal is added again to the color signal read from the recording circuit. This embodiment has substantially the same structure as that of the first embodiment except the part shown in FIG. Further, FIG. 5 shows how a burst signal is inserted. FIG. 5A shows a (BY) ′ signal, and FIG. 5B shows a carrier color signal after color modulation.

Before the (BY) 'signal is input to the color modulation circuit 11, a pulse BF for a burst signal is added, for example, as shown by the broken line in FIG. 5 (a). As a result, as shown in FIG. 5B, the child carrier color signal having the pulse BF for the burst signal.
C _S is output from the color modulation circuit 11. However, in this embodiment, the burst signal pulse BF is added as a negative pulse to the (BY) ′ signal, but in the subsequent processing, only the amplitude level of the burst signal is detected, so that a positive pulse for the burst signal is used. It may be added as the pulse BF, or in some cases, may be added to the (RY) ′ signal instead of the (BY) ′ signal.

FIG. 6 shows an essential part of the third embodiment in which the burst signal of the child carrier color signal is added after being read from the recording circuit. In this embodiment, unlike the second embodiment, the burst signal BF 'is added to the carrier color signal after color modulation as shown in FIG.

Also in the above-described second and third embodiments, the color signal of the sub-screen is kept at a constant level by the ACC circuit before recording, and even if the burst signal is fixedly added later,
The relative ratio does not change. Therefore, also in these embodiments, there is basically no difference from the first embodiment, and similar effects can be obtained. Further, in the second and third embodiments, since it is not necessary to record the burst signal, there is an advantage that the memory capacity of the recording circuit can be reduced by the burst period.

FIG. 7 is a block diagram showing an essential part of a fourth embodiment of the image forming apparatus according to the present invention, in which 28 is a BPF and 29 is a variable gain amplifier.

In this embodiment, as shown in FIG. 1, the burst level detection circuit 3 is a BPF 28, a variable gain amplification circuit 29, and a burst extraction circuit 1.
4 and the detection circuit 15, and the gain adjustment circuit 12 has a variable gain amplifier 16 having a control characteristic opposite to that of the variable gain amplifier 29.
It is configured by. The operation of this embodiment will be described below with reference to FIGS. 7 and 8.

The BPF 28 extracts a carrier color signal from the supplied parent composite video signal S _M. The extracted carrier color signal is detected by the detection circuit 15
After the gain is adjusted by the variable gain amplifier 29 whose gain is controlled by the output of the signal, the signal is supplied to the burst extraction circuit 14. Further, the burst extraction circuit 14 extracts a burst signal from the supplied carrier color signal and supplies the burst signal to the detection circuit 15. The detection circuit 15 detects the burst signal and detects the amplitude level of the burst signal. The gain of the variable gain amplifier 29 is controlled according to this detection level. As described above, the variable gain amplifier 29, the burst extraction circuit 14, and the detection circuit 15 form a so-called ACC loop, and the variable gain amplifier 2
It works so that the burst signal level at the output of 9 is always constant. Therefore, the detection circuit 15 is a variable gain amplifier.
At 29, a control voltage Vc for amplifying (or attenuating) the gain of the carrier color signal is generated by the amount of attenuation (or increase) with respect to the rated level of the parent carrier color signal. The control voltage Vc is
It is also supplied to the variable gain amplifier 16. However, since the variable gain amplifier 16 has a gain control characteristic opposite to that of the variable gain amplifier 29, the control voltage Vc causes the carrier color signal of the sub-screen by the amount of attenuation (or increase) with respect to the rated level of the carrier color signal. The gain is controlled so as to attenuate (or increase).

An example of the gain control characteristics of the variable gain amplifiers 29 and 16 is shown in FIG. In FIG. 8, the vertical axis is the gain, the horizontal axis is the control voltage, and reference numerals 30 and 31 are the gain control characteristics of the variable gain amplifiers 29 and 16, respectively.

Now, since the variable gain amplifier circuit 29, the burst extraction circuit 14, and the detection circuit 15 form a feedback loop, for example,
Assuming that the parent carrier color signal has increased by more than adB from the rated level, the detection circuit 15 generates a control voltage V _CI that attenuates the gain of the variable gain amplification circuit 29 by adB, as shown in FIG.
Variable gain amplifier 12 controlled by this control voltage V _CI
Gain increases by adB. Therefore, the child carrier color signal C
_S 'is increased from the desired level by adB equal to the increase in the parent carrier chrominance signal.

Such an operation is not affected by the non-linear characteristic of the detection circuit 15 at all because the two variable gain amplifier circuits 29, 16 having opposite gain control characteristics are gain-controlled by the same control voltage Vc.

As described above, also in this embodiment, as in the previous embodiments, the parent carrier color signal and the child carrier color signal in the PinP composite video signal are kept at relatively constant levels. Further, since it is not necessary to record the burst signal of the child carrier color signal, the memory capacity of the recording circuit can be reduced by the same amount as in the second and third embodiments.

Although the above description has been given by taking PinP as an example, the present invention is effective in various image synthesizing apparatuses that synthesize two composite video signals such as superimpose and realize display on the same screen. is there.

〔The invention's effect〕

As described above, according to the present invention, it is not necessary to perform any processing such as Y / C separation by a filter or modulation / demodulation of color signals on the parent composite video signal, and the burst level of the parent composite video signal can be set. Since the child carrier chrominance signal level can be adjusted to the parent carrier chrominance signal level without being affected by the non-linear characteristic of the detection circuit used for detection, there is no deterioration of the image quality of the parent screen and the parent screen and the child screen. The color of the screen can always be kept constant.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic structure of an image synthesizing apparatus according to the present invention, FIG. 2 is a block diagram showing the essential parts of a first embodiment of the image synthesizing apparatus according to the present invention, and FIG. FIG. 4 is a waveform diagram showing signals of respective parts, FIG. 4 is a block diagram showing essential parts of the second embodiment of the image synthesizing apparatus according to the present invention, and FIG.
FIG. 6 is a waveform diagram showing signals of respective parts of the figure, FIG. 6 is a block diagram showing essential parts of a third embodiment of the image synthesizing apparatus according to the present invention, and FIG.
FIG. 8 is a block diagram showing the essential parts of a fourth embodiment of the image synthesizing apparatus according to the present invention, and FIG. 8 is a diagram showing the gain control characteristics of the two variable gain amplifiers in FIG. 3 ... Burst level detection circuit, 4 ... APC circuit, 5 ...
... LPF, 6 ... BPF, 7 ... ACC circuit, 8 ... color demodulator,
9 ... Recording circuit, 10 ... Control circuit, 11 ... Color modulation circuit,
12 ... Gain adjustment circuit, 13 ... Switch, 14,17 ... Burst extraction circuit, 15, 16, 18 ... Detection circuit.

 ─────────────────────────────────────────────────── ─── 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-63-74388 (JP, A)

Claims (4)

[Claims] 1. An image synthesizing apparatus for inserting a second composite video signal into a first composite video signal to display two screens on the same screen, wherein a burst of a carrier color signal of the first composite video signal. First level detecting means for detecting the level, gain adjusting means for adjusting the gain of the carrier color signal of the second composite video signal, and detecting the burst level of the carrier color signal output from the gain adjusting means. A second level detecting means, a detection output of the first level detecting means and a detection output of the second level detecting means are compared in level, and a gain control means for controlling the gain of the gain adjusting means according to a comparison result. A comparing means for generating a gain control signal; and a synthesizing means for inserting the second composite video signal, the gain of the carrier color signal having been adjusted by the gain adjusting means, into the first composite video signal, The gain control signal The gain adjusting means adjusts the gain of the carrier color signal of the second composite video signal so that the detection output of the first level detecting means becomes equal to the detection output of the second level detecting means. An image synthesizing device. 2. A reduction means for reducing the image of the second composite video signal is provided, and the second composite video signal is reduced and then inserted into the first composite video signal. The image synthesizing apparatus according to claim 1. 3. An image synthesizing apparatus for inserting a second composite video signal into a first composite video signal to display two screens on the same screen, wherein a burst of a carrier color signal of the first composite video signal. Level detecting means for generating a gain control signal according to the level; and first gain adjusting means for adjusting the level of the carrier color signal of the second composite video signal, the gain of which changes according to the gain control signal. Synthesizing means for inserting the second composite video signal, of which the carrier color signal has been gain-adjusted by the first gain adjusting means, into the first composite video signal, the level detecting means comprising: A second gain adjusting means to which at least a burst signal of one composite video signal is supplied; and a burst signal output from the second gain adjusting means, and the second gain adjusting means detects the burst signal of the burst signal. Level to a certain predetermined level Detecting means for generating a gain control signal for adjusting the gain of the second gain adjusting means so that the first gain adjusting means is controlled by the gain control signal.
The gain control characteristic is opposite to the gain control characteristic of the second gain adjusting means, and the second gain adjusting means controls the gain control signal for the same control amount.
An image synthesizing device, wherein the magnitudes of gain changes of the first and second gain adjusting means are equal. 4. A reduction means for reducing the image of the second composite video signal is provided, and the second composite video signal is reduced and then inserted into the first composite video signal. The image synthesizing apparatus according to claim 3.