DE1168477B - Method and device for fading or switching television signals - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school KL: H 04 η

Number:
File number:
Registration date:
Display day:

German class: 21 al - 34/12

F 37947 VIII a / 21 al
3rd October 1962
April 23, 1964

The invention relates to a method and a device for cross-fading or switching from Television signals, which'in the vertical blanking gaps contain a so-called test line with a reference pulse.

The test line is used to monitor the transmission paths and, in addition to a gray staircase, contains one Reference pulse, which usually corresponds to the white value of the image signal. This reference value is under among other things used to automatically adjust the level of the television signal for the modulation of the television station to regulate the prescribed value.

When fading between two television signals, the first signal is gradually weakened, so that the image of a first imager gradually disappears, and then the second image signal gradually enlarged so that the image of a second imager appears. The synchronous part of the two TV signals are not also regulated; switching from the sync signal to the first signal the synchronizing signal of the second signal takes place in the time in which both image signals have the zero level.

With such a cross-fading, the test line is also dated in the same way as the image portion Control process detected, so that the white level of the test line of the first signal is weakened to zero and is then enlarged to the white level of the second television signal. The aforementioned automatic Gain control in television broadcasts now strives to adjust the gain accordingly to increase the falling level and therefore counteracts the falling signal level. The automatic Control of the television station has a large time constant of z. B. 1 to 2 seconds, so that readjustment only takes place after this time. If therefore the fade in less time expires, there will be no error, but will occur if the cross-fading process takes longer than the onset the regulation in the television channels.

When switching between two television signals, the control process can also be disrupted in the television channels come when the switching occurs overlapping and both signals some Time are present at the same time, so that the white pulses of the test cells of the two signals add up.

To avoid these difficulties, it could be seen as obvious to exclude the test line from the cross-fading and, like the synchronous signal, to transmit it without being weakened. For this purpose, the test line with the test signals from the television signal would have to be blanked and via a separate method and device for cross-fading
or switching of television signals

Applicant:
TV G. mb H.,
Darmstadt, Am Alten Bahnhof 6

Named as inventor:

Dipl.-Ing. Johannes Günther,

Darmstadt-Eberstadt,

Dipl.-Ing. Ernst Legier, Darmstadt,

Gero Förster, Traisa near Dannstadt

Channel. However, this method has the disadvantage that by transferring the Test line and the image signal via separate paths the correspondence between the white value in the image signal and the amplitude of the white pulse in the test line is no longer guaranteed. The invention makes use of the feature of automatic level control in television broadcasters that when Sudden absence of the modulation signal the previously existing gain for the signal remains the same for a long time.

In a method for cross-fading or switching of television signals, which are in the vertical blanking gaps a test line with a reference pulse, e.g. B. for image white, is included according to the invention the test line is suppressed during the fade or toggle process.

The method has the advantage that the crossfade or switching process no longer falsify the automatic gain control of the television stations can. If the test line is suppressed before the cross-fading process begins, the gain remains the station remains unchanged during the fading process. Only when the check line of the new TV signal after the fade, the amplification is automatically effective again and compensates for level differences between the second television signal and the first signal.

In this case, the fading process of the automatic gain control of the television stations can no longer be falsified, since the control is designed in such a way that in the event of a sudden failure

409 560/157

of the television signal or the test line, the gain of the transmitter remains the same over a longer period of time remain. If the test line is therefore suppressed before the cross-fading process begins, the gain remains the transmitter remains unchanged during the fading process. Only when the check line of the new TV signal after the fade, the automatic amplification comes into effect again and is the same Differences in the signal level in the new television signal compared to the previous signal.

There are various possibilities for carrying out the method according to the invention. Since the Difficulty resolved by the procedure according to the above only with manual control of the fading process occurs, the test line can be blanked by mechanical contacts on the handheld controller to be triggered. The blanking can also be dependent on the strength of the anode current of the control tube make, which changes the picture component of the television signals. In this case the arrangement is also at automatic sequence of the fading process effective, so that the automatic sequence in case of need can also be selected longer than the response time of the gain control of the television transmitter.

To suppress the test line during the fading process, a blanking pulse is generated in the fading device which is about three lines wide and coincides with the 18th to 20th lines of the vertical gap.

The dissolving device is often combined with a device for regenerating the television signals. In this, the signal is blanked and a new one is inserted into the interference-free gaps thus created Synchronous signal used. According to another proposal (patent application 845/62) is in such a Regeneration of television signals made the vertical blanking pulse only so long that it does the im Test line contained in the television signal is not detected, so that it is transmitted together with the image signal. In a fading device with a regeneration device designed in this way, the inventive Method can be applied in a particularly simple manner by the shortened blanking pulse is brought to the full width during the fading process, so that the test line during the fading is blanked with.

The invention will now be explained in more detail with the aid of the figures representing the exemplary embodiments. Of these shows

F i g. 1 the block diagram of a fading device without regeneration and

F i g. 2 shows the block diagram of a cross-fading device with a device for regenerating the television signals.

The device according to FIG. 1 the two television signals are fed in at 1 and 2, between which should be crossfaded. After passing through amplifier stages 3 and 4, the signals enter a electronic changeover switch 5. By the changeover contacts at 51 it is indicated that by the Device 5 supplied switching pulses either the first or second television signal is forwarded. In the device 6, the synchronous component of the TV signal cut off and the test line blanked. The blanking pulse of z. B. three lines Width in the 18th to 20th lines of the vertical gap is generated in the device 7. Subsequently arrives the picture portion of the television signal in the fade-out stage 8, in which the television signal by means of a tube (Transistor) can be regulated between zero and the maximum value by one of these supplied voltages can. In the right position of the switch 9, the regulation takes place by means of the hand controller 10, in the left position automatically by a control signal generated in device 11. The sync signal is separated in the amplitude filter 12 from the television signal. It is described in accordance with the above The mode of operation of the cross-fading device is not also controlled, but with the full level of the output signal added in stage 13 after it has passed through a limiter 14 in which the synchronous value is adjusted to the correct size by the controller 15 can be asked.

From the synchronizing signal, the vertical synchronizing pulse is formed in an integrating stage 16, which is fed to the electronic switch and ensures that the switch is from a television signal on the other in the vertical gap.

The vertical sync pulse supplied by stage 16 is converted into a delay device 17 in stage 7 of the test line blanking pulse produced.

The activation of the test line blanking pulse by the switch 18 can be done with manual control a mechanical contact can be triggered on the handheld controller 10, as indicated by the line 19. A second possibility is to switch the switch 18 through the anode current of the regulated tube in to operate the fade-out stage 8, as indicated by the dash-dotted line 20.

F i g. 2 shows the block diagram of a combined device for fading and for regeneration of the television signals.

The signals between which there is to be cross-fading are fed to the device at 1 and 2 and, after amplification in 3 and 4, reach the electronic switch5. The television signal is blanked in device 21, and the black level can be adjusted by controller 22. The blanked television signal (without a sync signal) now reaches a fade-out stage 8, in which the signal can be regulated between zero and the maximum value by means of a control tube (transistor). The horizontal and vertical synchronizing pulses H and V are taken from the synchronous signal separated after the switching stage 5 in the amplitude filter 23. From this, the regenerated sync signal is formed in the device 24 and added to the television signal again in the output stage 13. A controller 25 in stage 24 allows the synchronization value to be set. The regenerated blanking signal for blanking stage 21 is generated in stage 26 from the synchronizing pulses H and V obtained in the amplitude filter. By means of the switch 27, the duration of the vertical blanking pulse can be set between the full width of 21 lines, which the test line also covers, to a reduced width of 17 lines

6u toggle.

This can be done, for example, in that the time constant or the operating voltage of a Formation of the vertical blanking pulse provided univibrator in the device 26 is changed. Of the In the case of manual control, the changeover switch 27 can be operated by means of the controller 10 through a contact attached to it can be controlled (dashed line 19) or as a function of the anode current of the regulated tube

(Transistor) are operated in the fade-out stage 8 (dash-dotted line 20).

Claims (5)

Patent claims: 1. Method for cross-fading or switching of television signals, which are in the vertical blanking gaps contain a test line with a reference pulse, e.g. for image white, thereby characterized in that the test line during the fading or switching process is suppressed. 2. Device for performing the method according to claim 1, characterized in that that from the synchronous signal separated from the television signal by means of an amplitude filter the vertical sync pulse obtained and from this a blanking pulse in a delay device is generated during the duration of the test line. 3. Device for performing the method according to claim 1, characterized in that that the vertical blanking pulse generated to regenerate the vertical gap changes in width so that the test line is blanked with during the switchover process. 4. The method according to claim 1, characterized in that the suppression of the test line is triggered by a mechanical contact of the hand controller. 5. The method according to claim 1, characterized in that the suppression of the test line is made automatically depending on the current of the regulated amplifier (8). 1 sheet of drawings 409 560/157 4.64 © Bundesdruckerei Berlin