JPS6043708B2 - Automatic control method of frame synchronizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mode switching control method based on an input signal of a frame synchronizer (Fs) used in television broadcasting, and in particular to a method for controlling mode switching using an input signal of a frame synchronizer (Fs) used in television broadcasting.
This invention relates to an automatic control system for a frame synchronizer that has the following functions.

Conventionally, a frame synchronizer has been used not only as a simple video signal phase converter, but also as a time base stabilizing device for VTR signals with large time base errors by applying its built-in memory.

When used as a stabilizing device, due to the characteristics of the VTR output signal, such as large time base errors or noise such as dropouts, the input signal writing operation to the frame synchronizer memory may not match the input signal. Due to the risk of not responding correctly,
A TBC adapter is added to the Fs, and the Fs is configured so that the write control pulse to the Fs and the write address are controlled by the output pulse of a synchronization signal regeneration circuit that is phase-coupled with the input video signal provided in the TBC adapter. The intended purpose was achieved by switching the operating state of the device. However, with this method, the TBC function must be turned on and off depending on the mode (a mode in which VTR output and a stable time-axis signal such as camera output are input), and there is always an output screen shock when switching modes. was.

It is also possible to keep this η℃ adapter connected all the time, but in this case, characteristic deterioration due to the TBC adapter cannot be avoided, and the write control pulse to Fs is
Since the synchronization signal is supplied from the synchronization signal regeneration circuit inside the adapter, due to the inertia of the phase coupling operation by the N°C loop of this regeneration section, there is a phenomenon in which it is not possible to follow the phase change between the input signals when the input signal is instantaneously switched. Occur. At this time, since the write address does not correspond to the input image, the picture appearing in the memory output cannot reproduce the correct arrangement of the input image. From the above points, the Fs has the disadvantage that the mode must be manually switched according to the input signal, and that the output image always contains some kind of shock.

Therefore, the object of the present invention is to eliminate the conventional drawbacks and to improve Fs
Even if the signal input to the Fs changes instantaneously, the operating mode of the Fs will automatically change according to the changed signal.
An automatic control system for the frame synchronizer is obtained in which no screen shock occurs due to switching to the s output. According to the present invention, a pilot signal indicating that it is a VTR output is added to the VTR output, a change in the presence or absence of this pilot signal is detected within Fs, and the write inhibit control circuit is activated immediately, and the path of the input video signal is , an automatic control system for a frame synchronizer is obtained which controls mode switching such as switching of the write clock to the memory and the address clear pulse 9 at the break of the memory write operation sequence.

Next, the present invention will be described in detail with reference to the drawings showing one embodiment of the present invention.

FIG. 1 is a diagram showing an example of a system according to the present invention, in which the band corresponding to the pilot signal is removed from the signal from TRl by a band exclusion filter 2. The pilot signal generator 3 generates a fixed frequency of, for example, 4.5 MHz, and the mixer 4 mixes it with the VTR output. The frequency of the pilot signal is selected to have no effect on the video information output from the VTR. The output of mixer 4 is supplied to switch 5.
Unlike the TR output, a signal with a stable time axis, such as the output of the camera 6, is also supplied to the switch 5 at the same time.In the end, the output of the switch 5 has both a signal with a stable time axis and an unstable signal. The signal will be switched and output. This signal is transmitted to the base station 8 via the microwave repeater 7, for example. Generally, in such systems, the base station. 8 is often installed outdoors. Within the base station 8, the signal from the microwave repeater 7 is supplied to a TBC adapter 9 and a pilot signal receiver 10.

The output of the adapter 9 and the pilot signal receiver 10 is FR! It is sent to Musynchronizer (Fs) 11. The pilot signal receiver 10 detects the presence or absence of a pilot signal and, as a result, sends a mode switching signal and a write inhibit control signal to the FSll. TBC adapter 9 is ■TR
When a signal is input, a synchronization signal, video 1 signal, and clock pulse are sent to FSll. FIG. 2 is a diagram showing the timing of mode switching and write prohibition control using pilot signals. The operation will be explained in more detail with reference to FIG. (2) The output signal of the TR device is once supplied to a band exclusion filter 2, where the same frequency components as the pilot signal are removed, and then the pilot signal is superimposed on the VTR signal by a mixer 4. This superimposition is performed continuously and uniformly without synchronization with the waveform of the VTR signal. At time 1 in FIG. 2, the Fs input signal is instantaneously switched from the signal A (camera signal) 1, which is stable on the time axis, to the signal B (■TR signal) 2, which is unstable on the time axis.
As a result, the pilot signal receiver installed on the receiving side detects pilot signals continuously from time t1.
Figure 3 shows this situation.

Immediately when the pilot signal is detected at time t1, the write inhibit control circuit operates and inhibits writing for a time span of t1 as shown in 4. With this control, F
Since writing to the built-in memory of s is prohibited, as shown in 5, the signal before switching appears on the Fs output side and continues until the write prohibition is released. Therefore, the image with a shock at the time when the input signal is switched does not appear in the Fs output.On the other hand, the switching of the Fs operation mode is caused by the first image that appears after time t1 as shown in 6. This is done depending on the vertical pulse timing of the input signal. (Field type Fs
) Therefore, the shock associated with mode switching is also performed during the write-inhibited period, so it does not appear in the Fs output image at all. In addition, in Fig. 2, the prohibition period is set to 4 fields, but this is to take into account the phase coupling completion time of the synchronization signal regeneration circuit in the adapter, and the synchronization signal reproduction with a fast coupling time It is possible to make it even shorter by using a circuit. Next, when the input signal is switched again at time {circle around (2)}, writing is inhibited from T3 to T4 in the same manner as described above, and mode switching is performed according to the first vertical pulse timing that appears during that time. or,
Since the switched signal appears on the Fs output side at time ζ, a signal without any shock can be obtained. Write inhibit control as shown in FIG. 4 can be easily achieved by forming a logic circuit whose state changes depending on the presence or absence of a pilot signal.

As explained above in detail, according to the present invention, even if the signal input to the Fs is switched instantaneously, the operation mode of the Fs is automatically switched according to the switched signal, and moreover, the operation mode is automatically switched to the Fs output. An automatic control method of the frame synchronizer is obtained in which no screen shocks appear.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a system according to the present invention, and FIG. 2 is a diagram showing mode switching by pilot signals and timing of write prohibition control.
TRl2...Band exclusion filter, 3...
...Pilot signal generator, 4...Mixer, 5
...Switcher, 6...TV camera, 7.
...Microwave repeater, 8...Base station,
9...TBC adapter, 10...Pilot signal receiver, 11...Frame synchronizer.

Claims (1)

[Claims] 1 The operation mode changes depending on whether the input is a stable signal on the time axis or an unstable signal.In a frame synchronizer with a time base collector function, the input is a first input signal with a stable time axis and an unstable signal on the time axis. When a stable second input signal is input, a pilot signal for discrimination is added to the second input signal, the frame synchronizer detects a change in the presence or absence of the pilot signal, and a predetermined signal is detected from the point of change. An automatic control method for a frame synchronizer, characterized in that write prohibition control is performed for a time period, and the mode switching is performed at a break in a write operation sequence in an input signal.