JPS62203483A - Synchronizing signal inserting device - Google Patents

Abstract

PURPOSE:To obtain a camposite video signal having no generation of the distortion in waveform such as ringing in the vicinity of a synchronizing signal even if a band is limited in the process of a transmission by controlling the waveforms in the rise and the fall parts of the synchronizing signal added to the video signal. CONSTITUTION:The video signal including no synchronizing signal is inputted from an input terminal 6, the video signal is converted into a digital signal in an A/D converting circuit 1, and thereafter outputted to the input terminal 41 of a change over switch 4. From an input terminal 7, a pulse indicating the position of the synchronizing signal is inputted and inputted to a timing control circuit 2. The timing control circuit 2 controls a read only memory (ROM)3, reads the digital data written previously in the ROM3 at the position of the synchronizing signal, thereby, outputs the digital data corresponding to the waveform of the synchronizing signal to the input terminal 42 of the change over switch 4. At the same time, the timing control circuit 2 changes over the change over switch 4 to the input terminal 42 while inserting synchronizing signal waveform data is outputted and to the input terminal 41 during other period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a synchronization signal insertion device, and more particularly to a synchronization signal addition device necessary for transmitting a video signal.

[Conventional technology]

To transmit a video signal, it is necessary to send synchronization signals such as a vertical synchronization signal and a horizontal synchronization signal together with the video signal. These synchronization signals are generally inserted into the blanking period of the video signal as shown in Figures 3 (al to (C)). It is only necessary to replace the video signal data of the ranking period with the data of the synchronization signal.

Conventionally, the synchronization signal data to be inserted here is shown in Fig. 4 (al.
The data transitions from the blanking level to the synchronization signal level without a transition point, as shown in Figure 4(b), or the synchronization signal changes from the blanking level to the novel along a straight line, as shown in Figure 4(b). Met.

[Problem that the invention seeks to solve]

However, when the synchronization signal is added to the video signal as described above, if the rise and fall of the synchronization signal are steep,
The video signal into which the synchronization signal to be transmitted is inserted, that is, the composite video signal, contains high frequency components, and if the band is limited during the transmission process, waveform distortion such as ringing will occur, and the synchronization signal level will oscillate. This may adversely affect the waveforms before and after the synchronization signal.

This invention was made to solve the above-mentioned problems, and it is a synchronization method that can obtain a composite video signal that does not cause waveform distortion such as ringing near the synchronization signal even if the band is limited during the transmission process. The purpose of the present invention is to provide a signal insertion device.

[Means for solving problems]

The present invention provides a synchronization signal insertion device that generates a synchronization signal based on data written in a memory in advance. This data is set to include values corresponding to the levels in between, and the values between adjacent data are different.

[Effect]

In this invention, since the rise and fall of the synchronization signal are changed in a curve between the blanking level and the synchronization signal level, even if the band is limited during the transmission process and high frequency components are attenuated, A composite video signal with less occurrence of waveform distortion such as ringing is output.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a synchronization signal insertion device according to an embodiment of the present invention. In the figure, 6 is an input terminal to which a video signal that does not include synchronization number 43 is input manually, 7 is an input terminal to which a pulse indicating the position of the synchronization signal is input, 1 is an A/D conversion circuit, and 3 is a synchronization signal that has been input in advance. A read-only memory (ROM) in which digital data corresponding to the waveform is stored, 2 is a timing control circuit that reads and controls the ROM 3, 4 is a switch,
5 is a D/A conversion circuit.

Next, the operation will be explained. In FIG. 1, a video signal that does not include a synchronization signal is manually input from an input terminal 6, and after being converted into a digital signal by an A/D conversion circuit 1, it is output to an input terminal 41 of a changeover switch 4. .

On the other hand, a pulse indicating the position of the synchronization signal is input from the input terminal 7 and is input to the timing control circuit 2. The timing control circuit 2 includes a read-only memory (ROM) 3
By controlling the ROM 3 and reading out digital data previously written in the ROM 3 at the synchronizing signal position, digital data corresponding to the waveform of the synchronizing signal is output to the input terminal 42 of the changeover switch 4.

At the same time, the timing control circuit 2 causes the changeover switch 4 to
During the period in which the insertion synchronization signal waveform data is output, the input terminal is switched to the input terminal 42 side, and during other periods, the input terminal is switched to the input terminal 41 side.

In this way, the output terminal 43 of the changeover switch 4 outputs a composite of the digital data of the video signal and the digital data of the synchronization signal, so by inputting the output of the changeover switch 4 to the D/A conversion circuit 5, , a decoded video signal is obtained at the output of the D/A conversion circuit 5.

According to the above configuration, the synchronizing signal waveform can be freely set by changing the digital data written in the ROM 3. Therefore, by appropriately setting the digital data of the rising and falling portions of the synchronization signal, waveform distortion such as ringing due to band limitation in the transmission system can be reduced.

This effect will be shown below using computer simulation results. First, consider synchronization signal data that transitions from the blanking level to the synchronization signal level without a transition point, as shown in Figure 2 (al).The high frequency components of the synchronization signal generated from this data are cut off. and the second
The waveform is shown in Figure (b), and it can be seen that large ringing occurs.

Next, when the waveform after band limitation is determined using the synchronizing signal waveform data shown in Figure 2 (fU), which has a transition point that changes linearly from the blanking level to the synchronizing signal level, the waveform shown in Figure 2 (dl) is obtained. In Fig. 2 (d), Fig. 2 (
Although the ringing is considerably improved compared to bl, it is still clearly observed near the edges.

On the other hand, the transition point is the curve f(t) = 1/2 + 1/2
Figure 2 (e
If the waveform shown in FIG. 1 is used, even if the band is limited, the waveform becomes the waveform shown in FIG. 2 (fl), and almost no waveform distortion such as ringing occurs.

As described above, by changing the value of the transition point from the blanking level to the synchronization signal level along an appropriate curve, even if the transmission system is band-limited by λ, waveform distortion such as ringing can be minimized. It is possible to create a decoded video signal that does not occur.

In addition, in the above example, a curve in a form known as Hanning's window function in digital signal processing was used, but there are other window functions such as Hamming, Blackman, and Kaiser, and even if these curves are used, good. Furthermore, in addition to the method of determining the transition point using these window functions, it is also possible to determine the value of the transition point such that the high frequency component is minimized using Fourier transform.

Furthermore, in the above embodiment, the digital data of the synchronization signal was inserted after the video signal was A/D converted into digital data, but the data read from the ROM was
By creating an analog synchronization signal waveform using a method such as /A conversion, it is possible to insert a complete synchronization signal into an analog video signal as is. [Effects of the Invention] As described above, according to the present invention, since the waveforms of the rising and falling parts of the synchronization signal added to the video signal are appropriately controlled, the band is limited in the transmission system and high frequency Even if the component is attenuated, there is an effect that generation of waveform distortion such as ringing in the sync signal insertion portion can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a synchronization signal insertion device according to an embodiment of the present invention, and FIGS. Diagrams showing simulation results, Figure 3(a)~
tc) are a video signal, a synchronization signal, and a sync signal, respectively. Diagrams showing the relationship between decoded video signals, FIG. 4(a), (bl
Both are diagrams showing the data size of a digital composite video signal for explaining the conventional technology. In the figure, 1 is an A/D conversion circuit, 2 is a timing control circuit, 3 is a read-only memory (ROM), 4 is a changeover switch, and 5 is a D/A conversion circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In a synchronization signal insertion device that generates a synchronization signal based on data written in a memory in advance and inserts it into a video signal, the data in the memory corresponding to the rising and falling parts of the synchronization signal is A synchronization signal that includes a value corresponding to a level between the video signal level before and after the synchronization signal and the synchronization signal level, and is set to data such that the difference in value between adjacent data is different. Insertion device. (2) The values of the data in the memory corresponding to the rising and falling parts of the synchronization signal are obtained by sampling window functions such as Hanning window, Hamming window, Blackman window, Kaiser window, etc. used in digital signal processing. 2. The synchronization signal insertion device according to claim 1, wherein the synchronization signal insertion device is set to a value of