JPH03283776A - Video image changeover mixing device - Google Patents

Abstract

PURPOSE:To eliminate noise generated up to establishment of synchronization just after the changeover by fixing an output of a synchronizing signal replacement means to a black level for a prescribed period including a period till a black burst signal generating means detects a synchronizing signal from the changeover point of time of a video input signal at the changeover means. CONSTITUTION:At a point of time of changeover of a cross point when a 1st control signal C1 outputted from a control circuit 1 is switched from a signal designating a 1st video input signal to a signal designating a 2nd video input signal, a 3rd control signal C3 predicting the changeover is outputted from the control circuit 1. Then a black burst signal generating circuit 6 receives the 3rd control signal C3 and fixes the black burst data BB to the black level data for a prescribed period (t). Thus, the output of a synchronizing signal replacement circuit 8 is fixed to a black level at the point of time of changeover and production of noise for the period is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video switching/mixing device that is used in an image processing device or the like and switches and mixes a plurality of mutually asynchronous video input signals.

[Prior Art] A device shown in FIG. 3 is conventionally known as this type of video switching and mixing device.

Mutually asynchronous first to nth video input signals Sll+S
1□, . . . S, are input to the video signal switching circuit 12. This video signal switching circuit 12 includes a control circuit 11
These video input signals S-th to S-In are sequentially switched based on the first control signal C11 outputted from the first control signal C11. Video input signal Sl output from this video signal switching circuit 12
is input to the first synchronization signal separation circuit 13.

The first synchronization signal separation circuit 13 separates the synchronization signal 5YNC from the video input signal S. The synchronization signal 5YNC separated here is input to the blanking signal generation circuit 14.

The blanking signal generation circuit 14 outputs a blanking signal BL indicating the blanking period of the video input signal SI based on the synchronization signal 5YNC.

On the other hand, the video input signal SI output from the video signal switching circuit 12 is also input to the video mixing amplification circuit 15 .

The video mixing amplification circuit 15 also receives a second control signal C2 from the control circuit 11 and a blanking signal generation circuit 1.
The blanking signal BL from 4 is also input. The video mixing amplification circuit 15 passes the video input signal S as it is during the blanking period specified by the blanking signal BL, and passes through the video input signal S as it is during the blanking period specified by the blanking signal BL. and the video input signal S. This video mixing amplification circuit 15
The output S is input to the second synchronizing signal separation circuit 16, where the synchronizing signal 5YNC is separated.

Sync signal 5Y separated by second sync signal separation circuit 16
NC is input to the black burst signal generation circuit 17. This black burst signal generation circuit 17 generates a synchronization signal 5YN separated by a second synchronization signal separation circuit 1θ.
Based on the black burst signal BB, the black burst signal BB and a timing signal T indicating the timing to replace the black burst signal BB are output based on the black burst signal BB. These signals are input to the synchronization signal change circuit 18. The synchronizing signal changing circuit 18 inputs the video signal synthesized with the black level by the video mixing amplifier circuit 15, changes the black burst signal BB according to the timing signal T, and outputs this as the video signal S0. ing.

In the video switching and mixing device configured in this way, each time a plurality of mutually asynchronous video input signals are sequentially switched and input, the first and second synchronization signal separation circuits 13 and 18
detects the synchronization signal in the video input signal. Then, a blanking signal and a black burst signal are respectively generated based on the detected synchronization signal, and a video signal S in which the synchronization signal is replaced and mixed is output.

[Problems to be Solved by the Invention] However, in the conventional video switching and mixing device described above,
When switching between multiple video input signals that are asynchronous to each other,
Since synchronization has not yet been established from the time of switching until the synchronization signal is first detected, there is a problem in that the signal obtained as the final output appears as noise.

Furthermore, in the conventional video switching/mixing device described above, since the synchronizing signal separating circuits 13 and 16 have a two-stage configuration, after switching the video input signal, the synchronizing signal separating circuit 13 and 16 in the subsequent stage
There is also the problem that it takes time to detect the synchronization signal of the video input signal after switching, and the above-described noise occurs for a long time, which affects the image quality.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a video switching and mixing device that can improve image quality by preventing noise from occurring at the time of switching video input signals that are asynchronous with each other.

[Means for Solving the Problems] A video switching and mixing device according to the present invention includes a switching means for switching and outputting a plurality of mutually asynchronous video input signals, and a synchronous signal separated from the video input signal output from this means. a blanking signal generating means for generating and outputting a signal indicating a blanking period from the synchronizing signal separated by the means; and a blanking signal generating means for generating and outputting a signal indicating a blanking period from the synchronizing signal separated by the means, video mixing means for performing predetermined mixing processing on the video input signal of the video input signal; black burst signal generating means for generating a black burst signal synchronized with a synchronization signal included in the output from the means; and a black burst signal output from the means. synchronizing signal changing means for changing the synchronizing signal of the output of the video mixing means based on the burst signal; and from the time when the video input signal is switched in the switching means until the black burst signal generating means detects the synchronizing signal. and means for fixing the output of the synchronizing signal changing means to a black level for a predetermined period including the period.

[Function] According to the present invention, the output of the synchronizing signal changing means is blacked out for a predetermined period including the period from the time when the switching means switches the video input signal until the black burst signal generating means detects the synchronizing signal. Since the level is fixed, noise that occurs immediately after switching until synchronization is established can be removed.

Furthermore, by using only one synchronizing signal separating means and generating a black burst signal using the synchronizing signal separated by this synchronizing signal separating means, the above-mentioned black level fixing period can be further shortened. Image quality can be improved.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of a video switching and mixing device according to an embodiment of the present invention.

In this device, the control signal 1 includes a first control signal CI that performs cross-point control of which video input signal is output, and a second control signal C2 that controls the mixing of video inputs. A third control signal C3 is outputted immediately before switching the video input signal.

Mutually asynchronous first to nth video signals 5iltS l1
1 m m is is input to the video signal switching circuit 2 . The video signal switching circuit 2 selects these video input signals S11 to S11 . based on the first control signal C8 output from the control circuit 1 . is switched, and one video input signal Sl is output. From this video signal switching circuit 2! The output video input signal S1 is supplied to a synchronization separation circuit 4.

The synchronization/separation circuit 4 separates a synchronization signal from the video input signal Si. The synchronization signal 5YNC separated here is input to the blanking signal generation circuit 5 and the black burst signal generation circuit 6.

Blanking signal generation circuit 5 outputs blanking signal BL based on synchronization signal 5YNC.

Black burst signal light 1 time-6 is synchronization signal 5YNC
is input, and outputs a black burst signal BB synchronized with the synchronization signal 5YNC and a timing signal T indicating the timing at which this black burst signal BB is replaced. Further, this black burst signal generation circuit e is connected to the control circuit 1.
Based on the third control signal C8 indicating the switching timing of the video input signal output from Signal BB
is fixed to the black level signal.

On the other hand, the video input signal S output from the video switching circuit 2,
is also input to the video mixing amplification circuit 7. Further, the second control signal C2 from the control circuit 1 and the blanking signal BL from the blanking signal generation circuit 5 are also input to the video mixing amplification circuit 7. Video mixing amplification circuit 7
In the blanking period specified by the blanking signal BL, the video input signal S1 is passed through as is,
Outside the blanking period, black level data generated internally based on the second control signal C2 and the video input signal S
't. Output S1 of this video mixing amplification circuit 7
is input to the synchronization signal change circuit 8.

The synchronization signal changing circuit 8 inputs the video signal synthesized with the black level by the video mixing amplifier circuit 7, changes the black burst signal BB according to the timing signal T from the black burst signal generating circuit 6, and converts it into a video signal. Output as S.

Next, the operation of the video switching and mixing device according to this embodiment configured as described above will be explained.

FIG. 2 is a timing chart showing the operation of this device.

The first control signal C1 output from the control circuit 1 is
As shown in the figure, at the point in time when the crosspoint is switched from the data specifying the first video input signal to the data specifying the second video input signal, the control circuit 1 sends a message indicating this switching in advance. A third control signal C3 that foretells is output. Then, the black burst signal generation circuit 6 receives this and fixes the black burst data BB to the black level data for a certain period t, as shown in FIG. This period t is set to a length that includes at least the period from the switching of the video input signal until the black burst signal generation circuit e first detects the synchronization signal. Furthermore, during this period, the replacement timing data T also outputs data for maintaining the black level of the black burst data BB.

As a result, the output of the synchronization signal switching circuit 8 is fixed at the black level at the time of switching, and it is possible to prevent noise from occurring during that time.

In addition, in the above embodiment, the blanking signal generation circuit 5
The synchronization signal supplied to the black burst signal generation circuit 6 is obtained from one synchronization signal separation circuit 4, but the synchronization signal supplied to the black burst signal generation circuit 6 is obtained from the output of the video mixing amplifier circuit 7. You may also obtain it from

[Effects of the Invention] As described above, according to the present invention, synchronization is performed only for a predetermined period including the period from the time when the switching means switches the video input signal until the black burst signal generation means detects the synchronization signal. Since the output of the signal switching means is fixed at the black level, it is possible to remove noise that occurs immediately after switching until synchronization is established.

Further, by using only one synchronizing signal separating means and generating a black burst signal using the synchronizing signal separated by this synchronizing signal separating means, the black level fixing period can be shortened, and the image quality can be further improved. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video switching and mixing device according to an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of the same device, and FIG. 3 is a block diagram of a conventional video switching and mixing device.

Claims (2)

[Claims] (1) A switching means for switching and outputting a plurality of mutually asynchronous video input signals, a synchronizing signal separating means for separating a synchronizing signal from the video input signal output from this means, and a synchronizing signal separated by this means. blanking signal generating means for generating and outputting a signal indicating a blanking period; video mixing means for performing predetermined mixing processing on the video input signal from the switching means during the non-blanking period based on the output from the means; black burst signal generating means for generating a black burst signal synchronized with the synchronizing signal included in the output from this means; and changing the synchronizing signal of the output of the video mixing means based on the black burst signal output from this means. a synchronizing signal changing means; and an output of the synchronizing signal changing means for a predetermined period including a period from the time when the video input signal is switched in the switching means until the black burst signal generating means detects the synchronizing signal. 1. A video switching and mixing device, comprising means for fixing a black level. (2) The video switching and mixing device according to claim 1, wherein the black burst signal generation means outputs the black burst signal based on the synchronization signal separated by the synchronization signal separation means. .