JPH04311882A - Digital vtr - Google Patents

Abstract

PURPOSE:To secure the confidence of a recorded content by recording a password on the subcord of digital data and deshuffling processing when the word is watched with a password recorded on a magnetic tape. CONSTITUTION:When a recording is operated by utilizing a password, the password is inputted by operating the password input switch of a VTR, encoded at a subcord generating circuit and recorded on a video tape with an image data. When the password is included in a subcord extracted from regenerated data at a subcord extracting circuit 41 at the time of regeneration, the word and the word inputted by the above-mentioned switch are compared at a password comparing circuit 44 and only when they are matched, control instruction for executing deshuffling operation is supplied to a deshuffling circuit 27 by a deshuffling control circuit 45.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a digital VT system that converts a video signal into digital data, records it on a magnetic tape, and plays it back.
Regarding R.

0002

[Prior Art] A helical scan type rotary head device transmits video signals and the like onto a magnetic tape once every unit time.
2. Description of the Related Art Digital VTRs have been put into practical use, which record and reproduce diagonal tracks by digitizing video signals. This is because digitalization allows for high-quality recording and playback.

By the way, in the past, as long as the VTR was of the same standard, even if the videotape was recorded on another VTR,
Recorded video can now be played back correctly, ensuring compatibility. This is a digital VTR,
The same applies to any analog VTR.

0004

[Problems to be Solved by the Invention] However, since any VTR can reproduce the data, it has been difficult to maintain the confidentiality of the recorded contents. In other words, it is impossible to make a videotape playable only by a specific person, and even though the recorded contents must be kept confidential, if this videotape can be obtained, it can be played by an unspecified number of people. People can watch it.

[0005] In view of this point, it is an object of the present invention to provide a digital VTR that can maintain the confidentiality of recorded contents.

[0006]

[Means for Solving the Problems] The present invention provides a digital VTR that converts a video signal into digital data, performs predetermined shuffling, and records and plays back on a magnetic tape.
A password is added to the subcode of digital data and recorded, and when the password input during playback matches the password recorded on the magnetic tape, deshuffling corresponding to shuffling is performed.

[0007]

[Operation] By doing this, only those who know the password can reproduce the data recorded on the magnetic tape, and the recorded contents can be kept confidential.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

This example is applied to a digital VTR that records digital video signals, and the recording system circuit is configured as shown in FIG. That is, in FIG. 1, 1Y, 1U, 1V
For example, a digital luminance signal Y and digital color difference signals U and V formed from three primary color signals R, G, and B from a color video camera are supplied to the input terminals respectively indicated by . In this case, the clock rate of each signal is the same as the frequency of each component signal of the D1 format of the digital VTR. That is, each sampling frequency is 13.5MH
z and 6.75 MHz, and the number of bits per sample is 8 bits. Therefore, the data amount of the signals supplied to the input terminals 1Y, 1U, and 1V is approximately 216 Mbps. The effective information extraction circuit 2 removes the data in the blanking period from this signal and extracts only the information in the effective area, and the amount of data is approximately 167.
Compressed to Mbps. Among the outputs of the effective information extraction circuit 2, the luminance signal Y is supplied to the frequency conversion circuit 3, and the sampling frequency is converted from 13.5 MHz to 3/4 thereof. For example, a thinning filter is used as the frequency conversion circuit 3 to prevent aliasing distortion from occurring. The output signal of the frequency conversion circuit 3 is supplied to the blocking circuit 5, and the order of luminance data is converted into the order of blocks. The blocking circuit 5 is provided for the block encoding circuit 8 provided at the subsequent stage.

Furthermore, among the outputs of the effective information extraction circuit 2,
Two color difference signals U and V are supplied to a sub-sampling and sub-line circuit 4, each having a sampling frequency of 6.7.
After being converted from 5 MHz to half that, the two digital color difference signals are alternately selected line by line and combined into one channel of data. Therefore, a line-sequential digital color difference signal is obtained from this sub-sampling and sub-line circuit 4.

The line sequential output signal of the sub-sampling and sub-line circuit 4 is supplied to a blocking circuit 6. In the blocking circuit 6, similarly to the blocking circuit 5, color difference data in the scanning order of the television signal is converted into data in the block order. This blocking circuit 6 converts into a block structure similar to that of the blocking circuit 5. The output signals of the blocking circuits 5 and 6 are supplied to a combining circuit 7.

In the synthesis circuit 7, the luminance signal and color difference signal converted into the block order are converted into one-channel data, and the output signal of the synthesis circuit 7 is sent to the block encoding circuit 8.
is supplied to This block encoding circuit 8 is an encoding circuit (
ADRC), DCT (Discrete C
(osine Transform) circuit, etc. can be applied. The output signal of the block encoding circuit 8 is then supplied to a shuffling circuit 9, where shuffling is performed. The shuffling process in the shuffling circuit 9 is performed in order to disperse the error over the entire screen and make it less noticeable when a burst error occurs due to a dropout during playback. Change the arrangement of data. In this case, in this example, the shuffling method is changed depending on the presence or absence of a password, which will be described later.

The output of the shuffling circuit 9 is then supplied to a framing circuit 10, where it is converted into frame-structured data. In this framing circuit 10, switching between the image system clock and the recording system clock is performed.

Further, 11 indicates a subcode generation circuit,
Various data to be recorded along with the image data to be recorded are supplied to this subcode generation circuit 11 and converted into subcode data according to the recording format, and this generated subcode data is supplied to the frame generation circuit 10. ,
Converted to a frame structure similar to image data. In this case, when a password is input to the subcode generation circuit 11, this password is added to the subcode.

Although not shown, audio data synchronized with the video is also supplied to the framing circuit 10 and converted into a frame structure.

The output signal of the framing circuit 10 is then supplied to an error correction code parity generation circuit 12 to generate the parity of the error correction code. The output signal of the parity generation circuit 12 is supplied to a channel encoder 13, and channel coding is performed to reduce the low frequency portion of the recorded data. Channel encoder 13
The output signal of is supplied to the mixing circuit 14. Mixing circuit 14
is supplied with a pilot signal for ATF (Automatic Track Following Control). This pilot signal is a low-frequency signal that can be frequency-separated from the recorded data. The output signal of the mixing circuit 14 is sent to the magnetic heads 17a and 17a via recording amplifiers 16a and 16b and a rotary transformer (not shown).
17b and recorded on the magnetic tape.

Next, the configuration on the playback side will be explained with reference to FIG. 2.

In FIG. 2, reproduced data from magnetic heads 17a and 17b is supplied to a channel decoder 22 and an ATF circuit 23 via a rotary transformer (not shown) and reproduction amplifiers 21a and 21b, respectively. In the channel decoder 22, channel coding is demodulated, and the output signal of the channel decoder 22 is supplied to a TBC circuit (time base correction circuit) 24. In this TBC circuit 24, time axis fluctuation components of the reproduced signal are removed. The ATF circuit 23 generates a tracking error signal from the level of the beat component of the reproduced pilot signal, and this tracking error signal is supplied to, for example, a phase servo circuit of a capstan servo.

The reproduced data from the TBC circuit 24 is ECC
The signal is supplied to a circuit 25, where error correction and correction using an error correction code are performed. The output signal of the ECC circuit 25 is supplied to a frame decomposition circuit 26.

The frame decomposition circuit 26 separates each component of the block encoded data of the image data, and also switches from the recording system clock to the image system clock. Each piece of data separated by the frame decomposition circuit 26 is supplied to a deshuffling circuit 27, where the shuffled data is demodulated into the original data. That is, by the deshuffling process in the deshuffling circuit 27, the shuffled data is shuffled by changing the arrangement of the block data at the time of recording.
Restore the original array. In this case, the method of deshuffling in the deshuffling circuit 27 is controlled by a control command from a deshuffling control circuit 45, which will be described later.

Further, the data separated by the frame decomposition circuit 26 is supplied to a subcode extraction circuit 41, and the subcode extraction circuit 41 extracts the subcode contained in the reproduced data. The extracted subcode is supplied from the output terminal 42 to a system controller (not shown) that controls the operation of the entire VTR, and is also supplied to the password comparison circuit 44.

The password comparison circuit 44 is a circuit that compares the password supplied from the password input terminal 43 with the password included in the subcode extracted by the subcode extraction circuit 41. Here, input terminal 43
The password supplied to the VTR is data generated by operating a password input switch (not shown) provided on this VTR, and the password input by the playback operator operating this password input switch and the playback data It is determined whether the password included in the subcode matches the password. Then, the comparison result is sent to the deshuffling control circuit 4.
Supply to 5. The deshuffling control circuit 45 supplies the deshuffling circuit 27 with a control command to correctly deshuffle the reproduced image data when the subcode included in the reproduced data matches the input subcode. In addition, if there is no password in the subcode of the reproduced data (that is, if there is no password recorded), the deshuffling circuit sends a control command to always correctly deshuffle the reproduced image data regardless of the password input operation. Supply to 27. However, when deshuffling is performed by matching passwords,
There are control commands for deshuffling in different ways depending on the case where deshuffling is performed due to no password being recorded. Furthermore, since the subcode recording area is not shuffled, deshuffling is not performed either.

The playback data deshuffled by the deshuffling circuit 27 is then sent to the block decoding circuit 28.
The original data and the corresponding restored data are decoded for each block. Decoded image data from the block decoding circuit 28 is supplied to a distribution circuit 29 . This distribution circuit 29 separates the decoded data into a luminance signal and a color difference signal. The luminance signal and color difference signal are sent to the block decomposition circuit 3.
0 and 31, respectively. The block decomposition circuits 30 and 31 convert the decoded data in the order of blocks into the order of raster scanning, contrary to the blocking circuits 5 and 6 on the transmission side.

The decoded luminance signal from the block decomposition circuit 30 is supplied to an interpolation filter 31 . In the interpolation filter 31, the sampling rate of the luminance signal is 3fs to 4fs.
(4fs=13.5MHz). Digital luminance signal Y from interpolation filter 31 is taken out to output terminal 32Y.

On the other hand, the digital color difference signals from the block decomposition circuit 33 are supplied to the distribution circuit 34, and the line sequential digital color difference signals U and V are separated into digital color difference signals U and V, respectively. The digital color difference signals U and V from the distribution circuit 34 are supplied to an interpolation circuit 35 and interpolated respectively. The interpolation circuit 35 interpolates the thinned out line and pixel data using the restored pixel data, and the interpolation circuit 35 obtains digital color difference signals U and V with a sampling rate of 4 fs and outputs them. They are taken out to terminals 32U and 32V, respectively.

Next, the track pattern on the video tape of data recorded and reproduced using the configurations shown in FIGS. 1 and 2 will be explained with reference to FIG.

FIG. 3A shows the arrangement of data recorded on one track (or one segment). In the figure, the left end of the track is the head entry side, and the right end is the head separation side. Furthermore, the shaded area is a margin or IBG (interblock gap) where no data is recorded. For example, a pulse signal having a frequency equal to the bit frequency of data is recorded in the preamble or postamble to facilitate locking of a PLL provided on the reproduction side for bit clock extraction.

[0028] ATF at the end of one track on the head entry side.
The pilot signal for The encoded video data and audio data are recorded in the next section. Furthermore, a recording section for only audio data is provided after this video and audio section. Then, sub-data is recorded in the recording section closest to the head separation side.

The video and audio sections consist of a number of sync blocks, and a more detailed data arrangement of the sync blocks is shown in FIG. 3B. At the beginning, a block synchronization signal indicating the start of a block is located, followed by a sync block SB for identifying the block, and then an ADR.
A threshold value THR for determining the number of bits allocated to C is located. The subsequent block address BA is for the address on the screen. Furthermore, NEXT is
Indicates the length of the block. The encoded data generated by ADRC includes dynamic range DR', minimum value MIN
', a group BPL of code signals corresponding to each pixel. Furthermore, audio data is inserted into a section separate from image data within this section. The parity of the error correction code is placed at the end of the sync block. The arrangement of the sync blocks shown in FIG. 3B is an example, and in consideration of the amount of video data, the amount of audio data, and the amount of parity data, sync blocks with a data arrangement not shown are also used.

The recording section for only audio data and the recording section for sub-data also have the same data arrangement as described above. FIG. 3C shows the data arrangement of the sync block in the sub-data section.

At the beginning, a block synchronization signal indicating the start of a block is located, followed by an ID signal, and then subdata (subcode). The sub data includes a password recording section, and when a password is recorded, it is recorded in this password recording section. The parity of the error correction code is placed at the end of the sync block. The ID signal includes a code for identifying the sub-data area, a start ID, a frame ID, a track address,
It includes a skip ID, program number, block number, etc. This ID signal is required not only during normal playback but also when restoring an image using playback data during high-speed playback.

Next, the operation of the VTR constructed in this manner when recording and reproducing data using a password will be explained. First, when a password is used during recording, the password is input by operating a password input switch (not shown) of the VTR, and the input password is converted into a subcode by the subcode generation circuit 11. This password can be any combination of letters and numbers as long as it is data that can be recorded in the password recording section of the subcode (see FIG. 3C). and,
A subcode containing this password is recorded on the videotape together with the image data. Then, when recording this password, the shuffling circuit 9 performs recording shuffling in a different way from the usual method.

[0033] When playing back a videotape on which a password has been recorded in this manner, normal playback cannot be performed unless the same subcode as the one entered at the time of recording is input. That is, if a password is included in the subcode extracted from the reproduced data by the subcode extraction circuit 41 during reproduction, the password comparison is performed by comparing the reproduced password with the password input using the password input switch. This is done in circuit 44. Then, only if the passwords match as a result of this comparison, the deshuffling control circuit 45 causes the deshuffling circuit 27 to supply a control command for executing deshuffling. Therefore, when the password input with the password input switch does not match the recorded password, deshuffling is not performed in the deshuffling circuit 27, and the image data output from the deshuffling circuit 27 remains shuffled. Even if the image data output from the output terminals 32Y, 32U, and 32V is supplied to a monitor receiver, a correct reproduced image cannot be obtained.

On the other hand, when the password input with the password input switch matches the recorded password, a control command is supplied to the deshuffling circuit 27 to perform deshuffling, and the password is matched to the recorded data. The reproduced data that has been deshuffled is output from the output terminals 32Y, 32U, and 32V.

Furthermore, when a video tape on which no password is recorded is played back, the deshuffling control circuit 45 issues a control command to the deshuffling circuit 27 to perform deshuffling without having to input a password by operating the password input switch. is supplied, and the playback data that has been correctly deshuffled is output to output terminal 3.
Output from 2Y, 32U, 32V. However, this deshuffling when no password is recorded is performed in a different manner from the deshuffling of a playback signal from a videotape on which a password is recorded. For this reason, even if you play a videotape with a password recorded on a VTR without a password function, deshuffling corresponding to the videotape recorded with this password will not be possible, correct playback data will not be obtained, and the password will be lost. The recorded videotape content cannot be played back without the password.

As described above, according to the VTR of this example, by recording a password, correct playback cannot be performed unless the password is entered during playback, and only a specific person who knows the password can view the recorded content. is possible,
Records can be kept confidential. In this case, in this example, when a burst error occurs due to a dropout during playback, shuffling processing is used to disperse the error across the screen and make it less noticeable. Since the content is kept confidential, there is no need for a dedicated shuffling circuit to maintain confidentiality, only a circuit that compares the played password with the input password and determines whether to deshuffle it or not. This can be achieved with a simple configuration. In addition, since the shuffling method is different from the usual one, even if a video tape with a password recorded is played back on a VTR without a password function, correct deshuffling will not be performed. Good confidentiality is maintained.

[0037]

According to the present invention, only a person who knows the password can reproduce the data recorded on the magnetic tape, and the recorded contents can be kept confidential with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a recording system circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a reproduction system circuit according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a data structure according to one embodiment.

[Explanation of symbols]

11 Subcode generation circuit 41 Subcode extraction circuit 43 Password input terminal 44 Password comparison circuit 45 Deshuffle control circuit

Claims (1)

[Claims] [Claim 1] In a digital VTR that converts a video signal into digital data, performs predetermined shuffling, and records and plays back on a magnetic tape, a password is added to the subcode of the digital data and recorded, and the password is inputted during playback. A digital VTR characterized in that when a password matches a password recorded on the magnetic tape, deshuffling corresponding to the shuffling is performed.