DE2249213A1 - CIRCUIT ARRANGEMENT FOR PICTURE TELEPHONE SYSTEMS WITH CONFERENCE EQUIPMENT - Google Patents

Description

Circuit arrangement for video telephone systems with conference facilities The invention relates to a circuit arrangement for generating collective images in video intercoms with conference facilities, in which those with one Speech hearing aid, a recording camera and an image playback monitor Subscriber stations are connected to an exchange in which the subscriber stations arbitrarily via a switching device and a video mixer to conference connections are interconnected, and with a central clock line and image synchronization pulses delivers to all subscriber locations.

In known television telephone systems with conference facilities (DT-AS 1 930 925) are all image receivers of those connected to a conference Subscriber sites-with a first manifold connected and it is the recording camera of the respective verbal participant station to another Manifold connected to the first manifold via an amplifier connected is. The picture of the participant who leads the speech always appears on all connected picture monitors.

However, it is desirable to have all participants in a picture-speech conference all participants at the same time as possible in a pictorial compilation to make visible.

It has already been proposed (DT-AS 2 104 337) that the Individual images recorded by individual recording cameras via monitor lines to be transmitted to an image mixing device and there the reproduced by monitors To take up single images again by a collective image camera and as a collective image to transmit a collective image generator on a collective image line.

In this known device, it becomes the Saelbild on the detour generated via an optical mix of the individual images. It can be the collective picture via the common collective image line on the monitors of all participating stations during the breaks in the conversation or when the participant leaves the conference while normally only the picture of the speaking participant is included.

It is known per se in the studio directing technology of television (see at H. Schönfelder "Farbfernsehen 3", Justus von Liebig Verlag, Darmstadt, 1968, especially pages 27 to 45), cross-fading between individual image signal sources perform. With the so-called trick cross-fades, the switch between two image signal sources controlled by special sequences of blanking pulses. It Any number of contours for generate the mixed image. For this purpose, the combinations of horizontal and / or vertical pulse trains via a rectangular shaper and a template amplifier fed to a clock pulse shaper, at the output of which then clock pulses in antiphase for the alternating keying of gates connected to the image signal sources for To be available. These transitions are carried out using purely electronic means. In all of these switching and cross-fading processes, there is a frequency and phase correspondence the horizontal and vertical deflection of the image signal; sources required. Every television camera can be equipped with a synchronizable sub-clock generator for this purpose its output signal is fed to a phase comparison circuit (DT-OS 2 062 749), in which the clock signal is compared with a central clock signal will. The derived control voltage, which is dependent on the phase difference, is used for the control of the frequency and the phase of the sub-clock generator is exploited. Through this Measure will be mutual interference due to interference between the image signals supplied by the individual television cameras avoided, so that Switching and cross-fading between individual image signals can be carried out are.

The invention is based on the object of the signals from the recording cameras of the subscriber stations interconnected to form a conference connection directly to summarize to a $ ammelbild avoiding detours, for example about optical devices, which can be the cause of image deterioration, and to make this collective picture continuously visible to all conference participants.

The invention is characterized in that blanking generators are provided, depending on the clock generator individually to all for Conference connection of interconnected subscriber stations Horizontal and vertical blanking pulses send out through which only a section assigned to the relevant subscriber station of the image area of the recording camera, the rest is suppressed, whereby the Image mixer converts the individual image sections of the participant's camera into one The entire image area of the monitors is mixed together.

In a development of the inventive concept, the Abt steering coils are the admission kaueras of the individual participant positions individually acted upon by deflection currents through which those actively controlled by the blanking pulses Image sections are shifted to the center of the screen area of the recording cameras. The line and image deflection voltages of the recording cameras are dimensioned in such a way that that the actively controlled image sections are stretched over the entire screen area. It is also the result of the collective image lines that are individual to the participant transmitted blanking pulses suppressed portion of the subscriber's own image signal of the collective image can be delivered from the recording camera itself to the assigned monitor.

This has the advantage that every participant in a Conference connection of all interlocutors at the same time via his screen Monitor evenly distributed with unadulterated reproduction quality. Requests to speak, applause and the like can therefore be made during the conversation, for example by a show of hands. Since the blanking pulses with the appropriate dimensioning is given to all recording cameras by the central clock generator is for the correct position of all images on the screens of the monitors, so they have been put together to form a collective picture. Every conference participant holds himself in the usual position for video transmissions in front of his Device without having to fear cropping. He sees himself doing it in the picture itself and all other participant.

The invention is explained using the block diagram.

The video facilities of an intercom system are shown there. In this embodiment, up to four participants can be on one at the same time Attend picture conference. There is a quadrant of the each participant station Assigned to the monitor screen. Of course, these systems can also be used for other numbers of participants are designed or designed to be switchable. then a share of the Assigned to the screen.

The speech and connection devices belonging to this system are not shown because they can be constructed in a known manner.

At each subscriber station Tnl... Tn4 there is a recording camera K1 ... K4 and a picture monitor M1 ... M4 are provided. The camera output lines 1 ... 4 are connected to the Mix video mixer located at the switchboard. The output line 5 of the video mixer is via the encoder C1 ... C4, through the the video signals of the picture mixer are mixed with synchronizing and picture blanking signals are connected via the lines 51 ... 54 with the inputs of the monitors M1 ... M4 Of the central clock generator G generates line and image synchronization signals through which the frequency and phase of the deflection voltages for the cameras and monitors in all subscriber stations are determined, These Synchro nisiersignalen are in the blanking circuits Al ... A4 blending blanking pulses through the in the individual Xameras the line and image deflection voltages of one of the subscriber stations concerned The assigned image section is activated. Therefore, only the assigned Transfer the video signal generated in the image section to the image mixer Mis. There will be the video signals are combined to form a collective image that is displayed on all monitors wird0 There is a not shown amplitude filter at the subscriber stations provided, by which the synchronization and blanking signals are removed and the line and image generators are supplied.

However, the effects supplied by the blanking generators A1 ... A4 Blanking pulses suppress the transmission of each of the subscriber station assigned image section from the image mixer Mix to the monitor of the subscriber station. It therefore needs to complete the collective image of the output signal each Camera can also be handed over to your own monitor - the connections 11 * ». i4 provided.

Each part number is one of the highest permitted number associated with the conference participant positions resulting image section. It is desirable for each camera to place this image section in the center of the recording field to move and at the same time to enlarge only for the camera itself in such a way that that the entire recording area of the camera is filled.

Each blanking circuit supplies this image shift individually Al ... A4 a displacement current that occurs when using magnetic deflection in the Recording cameras can be a direct current, which in the right proportion to the vertical and horizontal deflection coils. The enlargement of the image section is determined in the subscriber station itself by suitable measurement of the slope of the line and image deflection currents achieved.

During the handling of the usual video calls of conference interconnections is the assignment of a picture section for each Camera picked up.

Claims (4)

Claims Circuit arrangement for generating collective images in video telephone systems with conference facilities, each with a speech hearing aid, one Recording camera and an image playback monitor equipped subscriber stations with a switching center are connected, in which the subscriber stations arbitrarily over a switching device and a video mixer can be interconnected to form conference connections are, and with a central clock line and frame synchronization pulses all subscriber stations supplies1 characterized in that blanking generators (Al ... A4) are provided, which are individually dependent on the clock generator (G) to all subscriber stations connected to the conference connection (Tnt .... Tn4) Send horizontal and vertical blanking pulses through which only one of the relevant Section of the image area of the recording camera (K1 ... K4) transferred, the rest is suppressed 1 whereby the video mixer (Mix) the individual Image sections from the participant's camera to form a collective image that fills the entire image area mixes together. 2. Circuit arrangement according to claim 1, characterized in that the deflection coils of the recording cameras (K1 ... K4) the individual Subscriber stations (Tnl ... Tn4) are individually acted upon by deflection currents, through the image sections actively controlled by the blanking pulses into the center the screen surface of the recording cameras are shifted. 3. Circuit arrangement according to Claims 1 and 2, characterized in that that the line and image deflection voltages of the recording cameras (K1 ... K4) are such are dimensioned so that the actively controlled image sections cover the entire screen area the recording camera are stretched. 4. Circuit arrangement according to claims 1 to 4, characterized in that that the collective image lines (51 ... 54) transmitted blanking pulses suppressed portion of the subscriber's own image signal of the collective image from the recording camera (K1 ... K4) itself to the assigned monitor (1 ... M4) is available.