JPS62146405A - Detecting system for incorrect dubbing tape - Google Patents

Abstract

PURPOSE:To detect an incorrect dubbing tape by comparing a time difference between both information reproduced from the 1st and 2nd parts on the same inclined track with a reference time and detecting the presence/absence of dubbing protection data for a PCM information signal. CONSTITUTION:A video signal and an FM signal to be a multiplex signal of an FM sound signal is recorded on the 1st part on each inclined track of a tape and a PCM sound signal having the same contents as the FM sound signal is recorded on the 2nd part following the 1st part. A signal reproduced by the 1st part is demodulated by a video/sound reproducing circuit 4 and a signal reproduced by the 2nd part is demodulated by a PCM sound signal processing circuit 7. Output signals from the circuits 4, 7 are outputted through a muting switch circuit 8 and supplied to a time difference comparator 12. The output signal of the circuit 7 is also supplied to a decision data detecting circuit 13. When incorrect dubbing data are detected by the compared result of the time difference with the reference time and the presence/absence of the dubbing protection data, the circuit 8 is turned off through an AND circuit 14.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for detecting unauthorized dubbing tapes.

[Summary of the invention]

The present invention reproduces a tape in which an information signal is recorded in a first part of the same inclined track and the same information signal converted into PCM is recorded in a second part, and the tape is reproduced from the first and second parts. The results of comparing the time difference between the two information signals with the reference time and the PCM ti! By detecting whether or not a tape has been illegally dubbed based on the presence or absence of dubbing protection data in the multiplier signal, it is possible to easily and reliably detect whether or not a tape has been illegally dubbed. This is what I did to get it.

[Conventional technology]

A soft tape manufacturer uses a printer (VTR) to reproduce a number of slave tapes from the mask tape.

On the other hand, those who wish to create illegal dubbing tapes (pirate tapes) usually copy a large number of pirate tapes from this genuine slave tape.

[Problem that the invention seeks to solve]

Such pirated tapes are difficult to clearly distinguish from genuine tapes, except for signal deterioration.

In view of this, the present invention proposes a method for detecting illegally dubbed tapes that can easily and reliably detect whether or not a tape has been illegally dubbed.

[Means for solving problems]

The present invention reproduces a tape in which an information signal is recorded in the first part of the same oblique track and the same information signal converted into PCM is recorded in the second part, and This system detects whether or not the tape has been illegally dubbed based on the result of comparing the time difference between the two reproduced information signals with a reference time and the presence or absence of dubbing protection data in the PCM information signal. Such an information signal is
Any of audio signals, video signals, data signals, etc. may be used.

[Effect]

According to the present invention, the time difference between both information signals reproduced from the first and second portions of the same inclined track on the tape is compared with a reference time, and the presence or absence of dubbing protection data in the PCM information signal is detected. If the time difference between the two information signals is greater than or equal to the reference time, and dubbing protection data is detected from the PCM information signal, the tape is determined to be an unauthorized dubbing tape; otherwise, it is a genuine tape, a self-made tape, or a dubbing tape thereof. I judge that.

〔Example〕

Prior to detailed description of the present invention, first, with reference to FIG. 2,
Recording and playback of a VTR called 8mm video will be explained. In this VTR, signals are recorded and reproduced by a pair of rotating magnetic heads arranged at an angle of 180 degrees so as to alternately form inclined tracks.

and the first part of one inclined track (rotation '1t
180 degrees of the f1% head), a multiplexed signal of one field's worth of video signals and the associated FM audio signal is FM-modulated and recorded (if the video signal is a color video signal, A low frequency converted carrier color signal is further multiplexed onto this FM multiplexed signal, but this is omitted here for simplicity.)
At the same time, a PCM audio signal (compressed signal) related to the video signal is recorded in a second portion (36 degrees of the rotating magnetic head) following the first portion.

FIG. 2A shows the input audio signal to be recorded on tape. Figure 2 B and C show a pair of rotating magnetic nodules Ha and Hb, respectively.
indicates the recording signal to be recorded on the tape, and the multiplex signal (V+
It consists of the FM signal of A) and the PCM audio signal (PCM). This PCM audio signal (PCM) is recorded on the tape with a delay of less than one field period compared to the FM audio signal (A). The second diagram and E show reproduction signals reproduced from the tape by a pair of rotating magnetic heads Ha, , Hb, respectively. FIG. 2F shows a switching pulse of one frame period for switching the recording and reproduction signals of the pair of rotating magnetic nodes Ha and Hb. Figure 3 G shows the final output video/audio signal (multiple signal) (V+A)
FM signal is shown. Figure 2H shows the output PCM signal,
FIG. 2 (■) shows the output audio signal obtained by demodulating this.

This output audio signal is obtained with a time delay of less than one field period from the PCM audio signal.

Thus, by dubbing the tape once, P
It can be seen that the CM audio signal is delayed by a period of a little less than two fields (between the first and second field periods) with respect to the FM audio signal (video signal).

By the way, the data for one field of the digital audio signal of a VTR called 8mm video consists of 1050 words of digital audio data, 6 words of discrimination word data, parity, and CRC code ( (See Japanese Patent Application Laid-open No. 199409/1983).

Next, the 6-word discrimination word data will be explained with reference to FIG. In this diagram, ■Do~■
D5 is composed of 8-bit bit data Bo to B7, respectively. Among these, ■D.

~rD is utility code word data, and ■Do is mode code word data, TDI-I
D4 is data code word data. Then, depending on the data IDoO value, data ID, ~ID,
By: Tape counter; Program number I; Recording year, month, day, day of the week, recording hour, minute, second, frame;
Program number ■; Table of contents; Discrimination code for multi-PCM is displayed.

ID5 is control word data, and various control data are expressed by the value of each bit data.

First, when bit data B7 is 1, it indicates dubbing protection (dubbing protection for digital signals as they are).

The bit data B5 and B6 represent the recording start and end points and the recording period according to their values. Bit data B3 and B4 are respectively assigned to channel 1 by these values.
(CHl), indicates whether the channel 2 (CH2) is audio or other information. Bit data B1, B2
is expressed as monaural, stereo, bilingual, or other depending on its value. Bit data BO is 1
．． 0 indicates whether other bit data B, ~B, are valid or invalid.

The present invention has been made in consideration of the above points.

Next, an embodiment in which the present invention is applied to a VTR called 8 mm video will be described in detail with reference to FIG.

First, the record will be explained.

Each slanted track on the tape has a first section containing a multiplex signal of a video signal and an associated FM audio signal.
An M signal is recorded, and a PCM audio signal having the same content as the FM audio signal is recorded in the second portion following this. If this tape is a genuine tape or its dubbing tape,
Discrimination word data included in the PCM audio signal ■Do
~■ Bit data B7 of control word data ID5 of D5 is set to 1. Incidentally, bit data B7 of data ID5 of the homemade tape is, of course, 0.

Next, the reproduction system will be explained with reference to FIG.

Ha and Hb are a pair of rotating magnetic heads, and their respective reproduction signals are supplied to a video/audio reproduction circuit (4) and an equalizer (5) through head changeover switches (2) and (3).

The video/audio reproduction circuit (4) demodulates the FM signal of the multiplexed video signal and FM audio signal reproduced from the first portion of the above-mentioned inclined track to obtain the original video signal and audio signal. , are output to output terminals (9) and (10) via muting switch circuits (8), respectively.

The output of the equalizer (5) is sent to the PC via the limiter (6).
The M audio signal is supplied to the processing circuit (7). This processing circuit (7) demodulates the PCM audio signal to obtain the original audio signal, which is output to the output terminal (11) via the muting switch circuit (8).

The FM demodulated audio signal from the reproduction circuit (4) and the PCM demodulated audio signal from the processing circuit (7) are supplied to a time difference comparison circuit (12) to detect the time difference, and also to detect the time difference. is compared to a reference time (eg, a predetermined time between the 1st and 2nd field periods). Note that this time difference is determined by relatively delaying both audio signals so that their signal timings match, and from the relative delay time at that time. Then, the obtained time difference is compared with a reference time to detect whether dubbing has been performed for the second time or later. Alternatively, the relative delay amount of both audio signals is set to a predetermined value, and the second
It may also be possible to detect whether or not dubbing has been performed since the first time.

In addition, here, the first dubbing is, speaking of true tape,
This is the case when making slave tape from mask tape. This number of dubbings also applies to self-made tapes.

Further, the PCM audio signal from the processing circuit (7) is supplied to the discrimination data detection circuit (13), where it is determined whether the bit data B7 of the control word data ID5 is 1 or not.
0 is detected.

The outputs of the comparison circuit (12) and the detection circuit (13) are supplied to an AND circuit (14), and the muting switch circuit (8) is controlled by the output.

Therefore, if the reproduced tape is a fraudulent tape, that is, a dubbing tape of a genuine tape, the time difference between both audio signals is equal to or greater than the reference time, and bit data B7 of discrimination word data ID5 from the PCM audio signal is 1. Therefore, both the comparator circuit (12) and the detection circuit (13) output a logic value of 1, and therefore the output of the AND circuit (14) also becomes a logic value of 1, and the switch (8) is turned off. , the reproduction of the video signal and audio signal is no longer performed.

In other cases, i.e., when playing genuine tapes, handmade tapes, or dubbing tapes made from handmade tapes,
Switch (8) is on.

〔Effect of the invention〕

According to the present invention described above, there is provided a method for detecting an illegally dubbed tape that can easily and reliably detect whether or not a tape has been illegally dubbed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart for explaining the same, and FIG. 3 is an explanatory diagram of discrimination data of digital audio data.

Claims (1)

[Claims] an information signal is recorded on a first portion of the same inclined track;
Reproducing the tape on which the PCM information signal is recorded in the second part, and comparing the time difference between the information signals reproduced from the first and second parts with the reference time and the PCM information signal. A method for detecting an unauthorized dubbing tape, characterized in that it is detected whether or not the tape has been illegally dubbed based on the presence or absence of dubbing protection data in the tape.