KR100195977B1 - Circuit for auto change broadcasting type in multi-vcr - Google Patents

Abstract

end. The technical field to which the invention described in the claims belongs

In a multi video cassette recorder that combines two broadcasting methods, the broadcasting method of the reproduction signal processing is switched according to the broadcasting method of the signal recorded on the video tape.

I. The technical problem to be solved by the invention

Provided is a broadcast method automatic switching circuit that can automatically switch a broadcast method according to a signal reproduced from a video tape.

All. Summary of Solution of the Invention

When the phase is out of phase by comparing the color burst signal included in the signal reproduced from the videotape with the color carrier signal of the currently selected broadcasting method, an error pulse signal is generated. If it appears, switch to another broadcast method.

la. Important uses of the invention

It is used in a multi video cassette recorder that combines two broadcasting methods.

Description

Broadcasting method automatic switching circuit of multi video cassette recorder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi video cassette recorder (hereinafter referred to as a VCR) that combines two broadcast methods. In particular, the broadcast method of playback signal processing is switched according to the broadcast method of a signal recorded on a video tape. It relates to a circuit.

In general, a multi-VCR refers to a VCR that can be used to play back video tapes in which signals with different broadcast methods are recorded. For example, a multi-VCR that combines the NTSC (National Television System Committe) and PAL (Phase Alternation by Line) -M methods can play both video tapes with NTSC signals and video tapes with PAL-M signals. . As described above, a multi-VCR (hereinafter referred to as NTSC / PAL-M multi-VCR) that uses both NTSC and PAL-M methods is generally designed to perform signal processing using the PAL-M method. Therefore, if the signal reproduced from the videotape is a PAL-M signal, the signal processing may be performed as it is. If the reproduced signal is an NTSC signal, signal processing must be performed after converting the signal to a PAL-M system signal. Accordingly, the NTSC / PAL-M multi VCR includes a conversion circuit for converting an NTSC signal into a PAL-M signal, and can switch between the NTSC method and the PAL-M method.

At this time, the broadcasting method is switched by the user's selection. Typically, a user has recognized a wrong broadcast method when a normal playback screen is not output by viewing a playback screen, and has manually selected a broadcast method different from the currently selected broadcast method. If the user selects the NTSC method, the playback signal is converted into a PAL-M signal through a conversion circuit and then signal processed. On the other hand, if the PAL-M method is selected, the playback signal is processed without any conversion circuit. Accordingly, when the user selects a broadcast method different from the broadcast method of the signal recorded on the video tape, the normal playback screen cannot be viewed. Therefore, the user could select the NTSC method or PAL-M method correctly according to the broadcast method of the signal recorded on the videotape to be reproduced, so that the normal playback picture could be viewed.

As described above, in order to watch a normal playback picture, there is a inconvenience in that a user must select a broadcast method of a multi VCR according to a broadcast method of a signal recorded on a video tape to be reproduced each time. In addition, if the user does not know how to select the broadcast method has a problem that can not watch the normal playback screen.

Accordingly, an object of the present invention is to provide a broadcast type automatic switching circuit capable of automatically switching the broadcast type according to a signal reproduced from a video tape.

1 is a block diagram of a broadcast type automatic switching circuit according to an embodiment of the present invention;

2 is a processing flowchart of a microcomputer according to an embodiment of the present invention;

3 is an operation timing diagram of the present invention.

In order to achieve the above object, the present invention compares a phase of a color burst signal included in a signal reproduced from a videotape with a chroma sub-carrier signal of a currently selected broadcast method and is out of phase. When an error pulse signal is generated and the number of pulses of the error pulse signal is more than the set number during a predetermined test time, the method is switched to another broadcasting method.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the annexed drawings, numerous specific details are set forth in order to provide a more thorough understanding of the present invention, such as specific signals, processing flows, and the like. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. Detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted, and for convenience, the present invention will be described as an example by applying the present invention to the NTSC / PAL-M multi-VCR as described above.

Referring now to FIG. 1, which shows a block diagram of a broadcast type automatic switching circuit according to an embodiment of the present invention, a signal reproduced from a video tape is applied to one input terminal of a switch 106 via a conversion circuit 100. At the same time it is applied to the color phase inversion furnace (102). The conversion circuit 100 is a circuit for converting an NTSC signal into a PAL-M signal as described above, and the output signal of the conversion circuit 100 is applied to the other input terminal of the switch 106. The switch 106 selects one of a reproduction signal not passed through the conversion circuit 100 and a reproduction signal converted by the conversion circuit 100 to the signal processor 108 by the control of the microcomputer 104. The signal processing unit 108 reconstructs and outputs the video and audio signals before signal processing the playback signal as it is or according to the output of the switch 106 or before processing and recording the playback signal converted by the conversion circuit 100. The signal thus output is applied to a television receiver or a monitor and output as a reproduction screen. The signal processor 108 is the same as the conventional signal processor provided in the NTSC / PAL-M multi-VCR. The signal processor 108 includes a color synchronization circuit for generating a color carrier signal, which is a carrier wave necessary for image demodulation, from a reproduction signal. The color synchronization circuit generates a color carrier signal having a frequency and a phase exactly the same as the color burst signal included in the reproduction signal. At this time, the frequency of the color carrier signal is different depending on the broadcasting method, which is 3.579545MHz for the NTSC method and 3.575611MHz for the PAL-M method. Therefore, the signal processor 108 generates the color carrier according to the broadcasting method under the control of the microcomputer 104.

As described above, the color processor carrier signal used for image demodulation in the signal processor 108 is used to determine a broadcast method of a reproduction signal. Looking at this in more detail, the color phase inversion path 102 compares the phase of the color burst signal included in the reproduction signal with the color carrier signal generated by the control of the microcomputer 104. At this time, the color carrier signal has the frequency and phase of the currently selected broadcast method of the NTSC method and PAL-M method as described above. Therefore, when the broadcast method of the reproduction signal and the color carrier signal are the same, the phases of the two signals are matched, but when they are different, the phases of the two signals are not matched. At this time, the color phase inversion circuit 102 generates an error pulse signal as shown in FIG. 3 in which a pulse appears or does not appear depending on whether two phases coincide with each other. The pulses of the error pulse signal of FIG. 3 are output when the phases of the two signals inputted to the color phase comparator 102 are not in phase, and when the phases are not in phase, the pulses are not output. This color phase inversion circuit 102 is typically included as part of the APC type color synchronization circuit provided in the signal processing section of the VCR. That is, when the color synchronization circuit provided in the signal processing unit 108 adopts the APC method, the APC which is the output to the color phase comparison circuit included in the APC system color synchronization circuit without the need to use the color phase comparison circuit 102 separately. The error pulse signal may be used as it is.

In the above state, the microcomputer 104 determines whether the broadcast method matches the broadcast method from the number of pulses of the error pulse signal input from the color phase comparator 102 during the preset inspection time, and switches to the same broadcast method as the playback signal. At this time, the microcomputer 104 switches the switch 106 and changes the frequency of the color carrier signal of the color phase inversion channel 102. The microcomputer 104 programs and uses a function according to the flowchart of FIG. 2 in a microcomputer that is typically provided as a control unit in a multi-VCR.

2 is a flowchart illustrating the processing of the microcomputer 104 according to an exemplary embodiment of the present invention. When the count value counting the number of pulses of an error pulse signal during a predetermined test time is greater than or equal to a set number, a predetermined number of times occurs. It shows the process of switching the broadcasting method. 2 is periodically performed by the microcomputer 104 every time set to be shorter than the inspection time.

Referring now to Figures 1 to 3 an operation example of the present invention will be described in detail. First, the microcomputer 104 is interrupted every time the pulse of the error pulse signal as shown in FIG. 3 is input during the above-described inspection time, and counts down the error counter by one from the initial value. The error counter is a software counter for counting the number of pulses of the error pulse signal. As described above, the error counter is used to detect a phase mismatch when the reproduction signal and the color carrier signal are different from each other. If the broadcast time is correct, the inspection time is set longer than the time required for phase synchronization between the reproduction signal and the color carrier signal in the color phase comparator 102, and the error counter is larger than the number of pulses of the error pulse signal that may occur. Set it. In addition, even if the broadcast method is correct, the phase of the playback signal may be temporarily unstable due to factors such as noise. In this case, the broadcast method may be incorrectly determined to be incorrect, so a debounce counter, which is a software counter, may be set to check the number of errors. 2 shows an example in which the inspection time is set to 200 ms, the initial value of the error counter is set to 6, and the debounce counter is set to 2.

If the user reproduces the video tape on which the NTSC or PAL-M signal is recorded by the NTSC / PAL-M multi-VCR including the circuit of Fig. 1, the microcomputer 104 generates an error as shown in FIG. Each time a pulse of a pulse signal is input, the signal is interrupted and the error counter is decremented by one, and the operation according to the flowchart of FIG. 2 is performed periodically, for example, every 10 ms. First, the microcomputer 104 checks whether the inspection time, that is, 200 ms has elapsed in step 200, and terminates as it is. On the other hand, when the inspection time has elapsed, the microcomputer 104 checks the number of pulses of the error pulse signal generated during the inspection time to determine whether the broadcasting scheme is matched and to control the switch 106 accordingly (202) to (214). Follow the steps. In step (202), if the microcomputer 104 checks the count value of the error counter and does not become 0, the microcomputer 104 resets the debounce counter, the error counter, and the test time to 2, respectively, in steps 210 and 214, respectively. Set to 6, 200Hz and exit. That is, if the error counter is not 0, it is determined that the currently selected broadcast method is correct.

On the contrary, if the error counter becomes 0 in step 202, the microcomputer 104 counts the debounce counter by one decrement in step 204 and then checks the count value of the debounce counter in step 206. FIG. At this time, if the count value of the debounce counter does not become 0, the error counter and the test time are set again to 6, 200 ms, respectively, in steps (212) to (214), and then ends. This is to decrement only the debounce counter to check again, and to check for errors during the next inspection time if the debounce counter is not zero, although it may be temporary as described above even if an error occurs. On the contrary, if the debounce counter becomes 0 in step 206, the microcomputer 104 determines that the current broadcast method does not match in step 208 and switches to another broadcast method. At this time, the microcomputer 104 switches the switch 106 and changes the frequency of the color subcarrier signal of the color phase inversion channel 102 to a frequency different from that of the present broadcast. That is, if the currently selected broadcast method is NTSC, the method is changed to PAL-M. Therefore, a broadcast method matching the broadcast method of the signal reproduced from the video tape is automatically selected. After that, the microcomputer 104 sets the debounce counter, the error counter, and the inspection time to initial values of 2, 6, and 200 ms again in steps 210 to 214, and ends.

By repeating the above process, even if the user does not select the broadcasting method of the multi VCR according to the broadcasting method of the signal recorded on the video tape to be played every day or if the user does not know how to select the broadcasting method, the broadcasting method is automatically adjusted. As a result, the normal playback screen can be always viewed.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications can be made without departing from the scope of the present invention. In particular, although the embodiment of the present invention shows an example of applying the present invention to NTSC / PAL-M multi-VCR, the same applies to the multi-VCR which uses two other broadcasting methods. Therefore, the scope of the invention should not be defined by the described embodiments, but should be defined by the equivalents of the claims and the claims.

As described above, the present invention automatically adjusts the broadcasting method, so that the user does not need to select the broadcasting method of the multi VCR according to the broadcasting method of the signals recorded on the video tape to be played every day, and always does not know how to select the broadcasting method. The advantage is that you can watch the normal playback screen.

Claims (8)

In the broadcasting system switching device of the video cassette recorder which uses two broadcasting systems, When the phase is out of phase by comparing the color burst signal included in the signal reproduced from the video tape with the color carrier signal of the currently selected broadcast method, the error pulse signal is generated, and the number of pulses of the error pulse signal is constant. Broadcasting method automatic switching circuit, characterized in that switching over to the current broadcasting method if more than the set number during the inspection time. 2. The broadcasting method of claim 1, wherein the error pulse signal is generated from a color phase comparator included in a color synchronization circuit of a signal processing unit of the video cassette recorder. The automatic switching circuit of claim 2, wherein the two broadcasting schemes are NTSC scheme and PAL-M scheme. In the broadcasting system switching device of the video cassette recorder which uses two broadcasting systems, A color phase comparison circuit configured to compare the color burst signal included in the signal reproduced from the videotape with the color carrier signal of the currently selected broadcast method, and generate an error pulse signal when the phase is out of phase; A conversion circuit for converting the reproduction signal into a signal of one broadcasting method preset among the broadcasting methods; A switch for selecting one of the playback signal and the converted playback signal and applying it to a signal processor; And a control unit for switching the switch and changing the frequency of the color carrier signal to a broadcasting system different from the current one when the number of pulses of the error pulse signal is greater than or equal to a predetermined number during a predetermined test time. 5. The automatic broadcast switching circuit of claim 4, wherein the two broadcasting schemes are NTSC scheme and PAL-M scheme. 6. The broadcasting method automatic switching circuit according to claim 5, wherein the conversion circuit converts an NTSC signal into a PAL-M signal. The method according to claim 6, wherein the control unit switches the switch when the count value is generated every time the interruption is interrupted by the pulse of the error pulse signal during the inspection time and the count value is greater than or equal to the set number. Broadcasting method automatic switching circuit, characterized in that for changing the frequency of. 8. The broadcasting method according to claim 7, wherein the color phase comparator is included in an APC color synchronization circuit of the signal processor.