JPS63166372A - On-screen display circuit - Google Patents

Abstract

PURPOSE:To stabilize the reproduction of a magnetic tape after copy preventing processing by inhibiting or making it ineffective the count of a horizontal synchronizing signal during a copy guard pulse CGP period and providing an on- screen display stabilizing circuit masking the CGP substantially giving adverse effect onto the positioning of on-screen display. CONSTITUTION:The on-screen display stabilizing circuit 5 consists of a low pass filter circuit 6, a waveform shaping circuit 7, and a delay circuit 8 such as a rear edge delay type monostable multivibrator. Since the on-screen display stabilizing circuit 5 is constituted such that the count of the horizontal synchronizing signal is inhibited or made ineffective and the CGP giving adverse effect onto the positioning of the on-screen display is masked substantially, disadvantages such as the deviation of the on-screen display position due to the effect of the CGP or vertical movement of the on-screen display in the field period are prevented surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an on-screen display circuit that stabilizes an on-screen display on a reproduced image of a magnetic tape subjected to copy prevention processing.

[Prior art] What about video tape recorders? - Due to the advent of social media, it is becoming common to enjoy video software by lending it to friends or borrowing it from a rental shop.

However, the copying of soft tapes prohibited by the Copyright Law continues, and for this reason, software manufacturers are required to insert and record copy guard pulses to prevent copying when recording produced videos. The number of places that are implementing software processing such as this is gradually increasing. As shown in Figure 3, in the composite synchronization signal recorded on this type of anti-duplication magnetic tape, in the even field, there are 7 locations at the end of the vertical synchronization signal carved into the equivalent pulse, and in the odd field. In this case, copy guard pulses each consisting of a pulse train as shown in the same figure (C) are inserted at eight locations, and a copy guard pulse consisting of a similar pulse train is inserted at one location in the valley field at the front of the vertical synchronization signal as well. A guard pulse is inserted.

For this reason, when attempting to dub a magnetic tape in which the number of horizontal synchronization signals that appear to be higher than the regular composite synchronization signal due to such copy guard pulses to another magnetic tape, the video tape recorder on the recording side AGC is used to prevent malfunctions in the servo system for synchronously driving magnetic tape and rotating drums, and to adjust the level of recorded video signals.
Problems such as circuit malfunctions occurred, and in the end, it became impossible to reproduce the product.

[Problems to be Solved by the Invention] The above-mentioned conventional magnetic tape that has been subjected to anti-duplication processing has no problem when displaying the reproduced video on a TV receiver or the like, but when the reproduced video is overlaid on the When a so-called on-screen display is performed in which other images such as text are inserted and displayed, there is a problem in that the on-screen text or the like shakes up and down, resulting in an extremely ugly screen. this is,
The insertion position of the image displayed by the on-screen display circuit is determined in the horizontal direction of the screen based on the count of oscillation pulses of the built-in self-excited oscillation circuit.
The vertical direction of the screen is determined based on the count value of the horizontal synchronization signal read from the magnetic tape.
For anti-duplication magnetic tapes that contain a large number of horizontal synchronization signals, the on-screen display is placed higher up on the screen than the normal insertion position, and copy protection is required after the vertical synchronization signals in even and odd fields. The cause was that the number of pulses was different, such as 7 and 8. For this reason, it is not possible to simply display on-screen information related to magnetic tape playback on magnetic tapes that have been treated to prevent duplication, and countermeasures must be taken to prevent this type of magnetic tape from increasing in the future. Unless it is implemented at an early stage, there are problems such as not being able to meet the diversifying demands of users.

[Means for Solving the Problems] The present invention solves the above-mentioned problems, and uses 14 raw video signals of a magnetic tape recorded by inserting a copy guard pulse to prevent duplication into a synchronization signal. is supplied, and inserts another video into a part of this reproduced video signal by specifying the position based on the count value of the horizontal synchronization signal, and during the copy guard pulse period, the horizontal synchronization signal is The present invention is characterized in that it is provided with an on-screen display stabilization circuit that prohibits or invalidates the counting of , and substantially masks the copy guard pulse that adversely affects the positioning of the on-screen display.

[Operation] This invention provides on-screen characters positioned based on the count value of the horizontal synchronization signal in a part of the reproduced video of a magnetic tape recorded by inserting a copy guard pulse for preventing duplication into the synchronization signal. When inserting and displaying, horizontal synchronizing signal counting is prohibited or invalidated during the copy guard pulse period, and the copy guard pulse that adversely affects the positioning of the on-screen display is substantially masked.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. 1.2. FIG. 1 is a circuit diagram showing an embodiment of the on-screen display circuit of the present invention, and FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG.

This mixer circuit 2 is built into an audio recorder, and is provided with a mixing circuit 2 for inserting a character signal in the middle of a transmission line for a reproduced video signal from a magnetic tape.

This mixing circuit 2 mixes a character signal into a blank area formed in a reproduced video signal by a blanking signal from a character signal generating circuit 3.

The character signal generation circuit 3 generates a character signal incorporating various information related to reproduction, and determines the insertion position of the character signal. As mentioned above, the insertion position of this character signal is determined based on the counted value of oscillation pulses of the built-in self-excited oscillation circuit in the horizontal direction of the screen, and the insertion position in the vertical direction of the screen is determined by reading from the magnetic tape. It is determined based on the horizontal synchronization signal count value. For this reason, the character signal generation circuit 3 is connected to a synchronization separation circuit 4 that separates the composite synchronization signal in the reproduced video signal, and an on-screen display stabilization circuit 5 that substantially masks the copy guard pulse.

In this embodiment, a low-frequency wave circuit 6 and a delay circuit 8 such as a waveform shaping circuit constitute an on-screen display stabilizing circuit 5.

By the way, the vertical synchronization signal included in the composite synchronization signal has its low frequency separated and extracted in the wave circuit 6, and then passes through the waveform shaping circuit 7.
The waveform is shaped into the signal shown in FIG. 2(A). Then, in the subsequent delay circuit 8, the signal is processed into a signal shown in FIG. 2(B) having a time width of approximately 900 μsec, including a copy guard pulse period (approximately 870 μsec) and a vertical synchronization signal period. The output of this delay circuit 8 is used as a prohibition pulse to prohibit counting of horizontal synchronization signals during the copy guard pulse period when the character signal generation circuit 3 specifies the upper and lower start and end points of the on-screen display. It will be done. Therefore, the copy guard pulse is effectively masked by the prohibition pulse when it comes to on-screen display, and the on-screen display position may shift due to the influence of the copy guard pulse, or the on-screen display may move up or down in the field period. Inconveniences such as shaking can be prevented.

As described above, in the on-screen display circuit 1, the on-screen display stabilization circuit 5 prohibits or disables counting of the horizontal synchronization signal during the copy guard pulse period, and prevents the copy guard pulse from adversely affecting the positioning of the on-screen display. Since it is configured to substantially mask the data, it is possible to reliably prevent inconveniences such as the on-screen display position shifting due to the influence of the copy guard pulse, or the on-screen display fluctuating up and down with the field period. .

Furthermore, detailed measures can be added to the functions of video tape recorders and the like, which are becoming more multi-functional, taking into account the playback of magnetic discs that have been subjected to duplication prevention processing, which is expected to increase in the future.

In the above embodiment, the on-screen display stabilization circuit 5 is configured to prohibit counting of the horizontal synchronizing signal during the copy guard pulse period, but it is also possible to configure the circuit to disable this counting. It is. Furthermore, instead of the character signal generation circuit 3, a video signal generation circuit that inserts images such as numbers, symbols, or still images may be used.

[Effects of the Invention] As explained above, the present invention includes the count value of the horizontal synchronization signal in a part of the reproduced video of a magnetic tape recorded by inserting a copy guard pulse for preventing duplication into the synchronization signal. When inserting and displaying on-screen characters that are positioned based on Because the configuration masks the data, even if the on-screen display is performed while playing a magnetic tape that has been protected from duplication by copy guard pulses, the on-screen display position may shift due to the influence of the copy guard pulses. It is possible to reliably prevent inconveniences such as the on-screen display shaking up and down with the field cycle, and we have developed a multi-functional system that takes detailed measures into consideration when playing magnetic tapes that have been treated with anti-duplication processing, which is expected to increase in the future. It has excellent effects such as being able to be added to one of the functions of video tape recorders, which are becoming increasingly popular.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing one embodiment of the on-screen display circuit of the present invention, FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG. 1, and FIG. 3 is a copy prevention processing implementation. FIG. 2 is a signal waveform diagram showing an example of a copy guard pulse recorded on a magnetic tape. l11. On-screen display circuit, 3. ,,Character signal generation circuit,5. ,,On-screen display stabilization circuit,8.
,,delay circuit.

Claims (1)

[Claims] A playback video signal from a magnetic tape recorded with a copy guard pulse inserted to prevent duplication in the synchronization signal is supplied, and a position is specified based on the count value of the horizontal synchronization signal as part of this playback video signal. This is an on-screen display circuit that inserts other images during the copy guard pulse period, and prohibits or disables horizontal synchronization signal counting during the copy guard pulse period, effectively masking the copy guard pulse that adversely affects the positioning of the on screen display. An on-screen display circuit equipped with an on-screen display stabilization circuit.