JPH01106384A - Reproducing position detecting device - Google Patents

Abstract

PURPOSE:To detect the absolute address of each frame as a frame number from a reference position by executing a position detecting using a counting output as well as the pulse width of a control pulse which is pulse-width- modulated with a code signal. CONSTITUTION:A control pulse Pc from a reproducing amplifier 13 is supplied to a counter 1 and a pulse width detecting circuit 2. The counter 1 counts the positive polarity pulse of the pulse Pc and supplies the counting output S1 to a reproducing position detecting circuit 3. Further, the initialization and the resetting of the counter 1 are executed by a counter control signal S2 supplied from the reproducing position detecting circuit 3. On the other hand, the pulse width detecting circuit 2 detects the pulse width between the positive polarity and the negative polarity of the pulse Pc, discriminates whether the control pulse is '0' or '1', supplies the control pulse to the reproducing position detecting circuit 3, and decodes the address data or the index data from the combination of '0' and '1' of a detecting output S3. Thus, an accurate random access and a high-accuracy edition can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a playback position detection device for a VTR (video tape recorder).

(Prior Art) Generally, when editing or random accessing a recorded magnetic tape on which video and audio signals have been recorded using a VTR, it is necessary to know the positional information of the recorded contents, especially the absolute address.

And, as a VTR that can know this absolute address, the United States (7) SMPTE (Society of Mo
tion P 1ture and Te1evi
A device is known in which a fixed head forms a dedicated time code track to record and reproduce an SMPTE time code signal defined based on the E. Nineeers standard.

This SMPTE time code signal is a code signal that determines the tape address in a 24-hour system of hours, minutes, seconds, and frames, with the TV frame as the minimum unit.By recording and reproducing this time code signal, it can be accurately recorded on the magnetic tape. It is now possible to know the absolute address of the recording/reproducing position.

However, the above-mentioned SMPTE time code signal consists of an 80-bit signal that is phase-modulated per frame, and consists of a 64-bit data area and a 16-bit fixed pattern sync word that indicates the frame division. Furthermore, the data area is a complex coded signal in which time code bits and user's bits are arranged in a comb shape every four bits.

For this reason, such SMPTE time code is useful for broadcast VTRs that require highly accurate editing functions, but it is expensive because the time code generator and time code reader are extremely complex. It was particularly unsuitable for consumer VTRs, which require low prices.

Therefore, as a conventional VTR that has been able to obtain an absolute address with a simple configuration, a control pulse whose pulse width is modulated by a time code signal indicating an absolute address is recorded on a control track of a magnetic tape, and when playing back, from this control pulse. It is also known to demodulate and separate a time code signal to obtain an absolute address.

Incidentally, such a VTR is described in detail in Japanese Utility Model Publication No. 57-34633.

(Problems to be Solved by the Invention) As described above, the pulse width of the control pulse is modulated with a time code signal and recorded, although it can be constructed at low cost, it is not possible to obtain the absolute address of each frame. Therefore, it was not possible to perform highly accurate editing.

(Means for solving the problems) The present invention has been made in view of the above-mentioned circumstances,
It is an object of the present invention to provide a four-main position detection device capable of obtaining an absolute address for each frame.

In order to achieve this object, the present invention, as shown in FIG. A reproduction position detection device for detecting the absolute address of each frame in a television signal recorded on the magnetic tape Tp using a count number, the magnetic head HC for reproducing the control pulse Pc.
A counter 1 that counts the control pulse Pc reproduced by the magnetic head)-1c, and a pulse width detection circuit 2 that detects the pulse width of the control pulse Pc.
The absolute address of the reference position on the magnetic tape Tp is obtained from the detection output S3 of the pulse width detection circuit 2, and the number of frames from the reference position is detected by the count output S1 of the counter 1, and the absolute address of each frame is obtained. The present invention provides a playback position detection device characterized by comprising a playback position detection circuit 3 for obtaining an address.

(Function) According to the playback position detection device configured as described above, the absolute address of each frame is detected by detecting the position using not only the pulse width of the control pulse whose pulse width is modulated by the code signal but also the count output. can be detected as the number of frames from the target position.

This enables accurate random access and highly accurate editing.

(Embodiment) Hereinafter, a preferred embodiment of the playback position detection device according to the present invention will be described in detail with reference to FIGS. 1 to 4.

FIG. 1 is a block diagram showing the electrical configuration of an embodiment in which the present invention is applied to a general VTR. The magnetic tape Tp used in this VTR has an audio track TA and a video track as shown in FIG. A track TV and a control track TC are each formed.

One control pulse pc per frame is recorded on the control track Tc in correspondence with the video track TV.

In addition, as shown in Fig. 3, this control pulse PC is a pulse width modulated pulse with a duty ratio of 50%, and when the duty ratio is 60±5%, it shows rOJ, and the duty ratio is 27.5±2. .5% is "1"
This shows that.

Then, as shown in FIG. 2, a plurality of control pulses pc indicating "0" and "1" depending on the pulse width are used to locate reference positions A on the magnetic tape Tp at predetermined intervals (for example, every 10 seconds). It is designed to represent the absolute address of .

That is, the address data representing this absolute address is 11 each.
It consists of four bit headers 1-16 and 16-bit address data □a inserted between these headers 86, and the header Hd has a 2-bit value of the most significant bit MSB and the least significant bit LSB. is "0", and the values of the remaining 9 bits from the second bit to the tenth bit are "1".

Further, next to each header Hd, 4-bit x 4-digit address data Oa indicating the address of the reference position HA is arranged, and each digit of this data [)a is "1000" or "100 J r A 4-bit numerical value in the tens Jr-J digit is expressed in a BCD code.

Note that the three pieces of address data Da between each header 86 have the same content, and the same data is repeatedly recorded three times.

Further, as shown in FIG. 4, such address data is arranged on the magnetic tape Tp at regular intervals (for example, every 10 seconds), and a second address data is placed at any position other than this address data.
Index data D as shown by the dotted chain line in the figure is recorded.

The value of the most significant bit and the least significant bit of this index data ID is "0", and the value of the remaining 61 bits is "1".
This is 63-bit fixed pattern data, and this index data ID can be set to any position, such as a position where a specific person appears or a position where a frame still is recorded, by operating the operation unit 4 of the device, which will be described later. recorded.

In addition, the duty ratio of the control pulse other than the part where the above address data and index data are recorded is 50.
%.

Recording of address data as described above is automatically performed during various types of recording and photographing.

That is, as shown in FIG. 1, for example, during recording, the synchronization separation circuit 6 extracts vertical synchronization signals y and 5ync from the video signal STV supplied via the input terminal 5, and the pulse generation circuit 7 extracts the vertical synchronization signals y and 5ync. Generate a clock pulse synchronized with y, 5sync.

And this clock pulse is an S-R type flip 7
The signal is supplied to the set terminal S of the zero-tube FF8 to set it, and is also supplied to the reproduction position detection circuit 3. The reproduction position detection circuit 3 supplies the reset terminal R of the flip-flop circuit 8 with a reset pulse delayed from the clock pulse by a predetermined time according to the header Hd and address data D^.

As a result, the correct output of the flip-flop circuit 8 becomes a control pulse Pc with a duty ratio (60±5% or 21.5±2.5%) corresponding to the delay time, as shown in FIG.

This control pulse pc is transmitted to the servo circuit 9,
The signal is supplied to the control head Hc via the first switch circuit 10, the recording amplifier 11, and the second switch circuit 12, and is recorded on the control track TC of the magnetic tape Tp.

In addition, the above 1. The second switch circuits 10 and 12 are automatically switched between recording and reproduction by switch signals respectively supplied from the reproduction position detection circuit 3.

Further, the index data ID is arbitrarily recorded not only during recording but also when shooting with a video camera or by operating the operation unit 4 of the m-device while viewing a reproduced image.

That is, when operating this operating section 4 to record index data summer, the reproduction position detection circuit 3 outputs a clock pulse Pc of a predetermined duty ratio for 63 bits as shown in FIG. This clock pulse Pc is applied to the first switch circuit 10. Recording amplifier 11 and second
The control head H via the switch circuit 12 of
It is supplied to C and recorded.

Note that this index data ID is recorded as a flag in the part of the screen where a specific person appears, or as a flag in the part where a frame still is recorded when transporting the camera, etc. The position of the first control pulse is defined as a reference position A.

On the other hand, the control pulse pc recorded on the magnetic tape Tp as described above is reproduced by the control head HC as shown in FIG. 1, and is supplied to the reproduction amplifier 13 via the second switch circuit 12.

Here, as shown in FIG. 3, the control pulse pc during recording is a square wave, but the reproduced control pulse pc is differentiated by the differential characteristics of the control head Ha, etc., and is recorded. When the control pulse pc rises, it becomes a positive polarity pulse, and when it falls, it becomes a negative polarity pulse.

Such control pulses Pc are supplied to the servo circuit 9 via the reproduction amplifier 13, and the servo circuit 9 uses only the positive pulses to drive the capstan motor and the magnetic tape Tp. 0
- respectively controlling the rotational speed and phase of the drum motor for rotating the guide drum to which the tally head is attached;

Further, the control pulse pc outputted from the reproduction amplifier 13 is supplied to the counter 1 and the pulse width detection circuit 2, respectively.

The counter 1 counts the positive polarity pulses of the control pulse pc, and supplies the count output S1 to the reproduction position detection circuit 3. The initial value setting and resetting of the counter 1 is performed by the counter control signal S2 supplied from the reproduction position detection circuit 3.

On the other hand, the pulse width detection circuit 2 detects the control pulse p
Detect the interval between the positive and negative pulses of c, that is, the pulse width, and determine whether the control pulse is "0" or "1".
Determine whether

The detection output S3, which is the result of this determination, is supplied to the reproduction position detection circuit 3, and the reproduction position detection circuit 3 determines what the combination of "0" and "1" of the supplied detection output S3 represents. decipher.

That is, this playback position detection circuit 3 outputs the detection output S
3 represents address data or index data ID, and decodes the address data DA or index data 10.

As a result, the playback position detection circuit 3 uses the decoded address data DA or index data ID and the count output $1 to determine the absolute address of the playback position, for example, the 100th frame, frame, or frame within the address ro010J. It can be designated as the 150th frame in the index, which is displayed on display 14.

On the other hand, the playback position detection circuit 3 can be switched between an address designation mode and an index designation mode by operating the operation section 4.

The operation unit 4 is designed to specify an absolute address or index data (number) by operating a numeric keypad, for example, and the playback position detection circuit 3 is configured to specify the address data or index data (number) decoded as described above. The number of frames in the address or index is compared with the absolute address specified by the numeric keypad, and a tape drive mechanism (not shown) is controlled so that the portion at the specified absolute address is reproduced.

That is, when set to addressing mode,
When it is confirmed by the detection output S3 that the address data has been reproduced, that is, when 92-bit address data as shown in FIG. 2 has been reproduced, the counter 1 is reset and its initial value is set to 92.

This makes it possible to detect which frame within each address is being reproduced, that is, the absolute address of the position being reproduced.

In this state, the magnetic tape Tp is controlled for running tII so that the absolute address designated by the operation of the operating section 4 matches the absolute address detected as described above.

Therefore, the part at the desired absolute address can be immediately found and reproduced, and furthermore, the reproduced image can be printed out using the printer 15. A reproduced video signal is supplied to this printer 15 through an input terminal 16, and a frame portion of the video signal designated by the above-mentioned absolute address is recorded in a frame memory and printed out.

On the other hand, when set to index specification mode,
When it is confirmed that the index data ID has been reproduced by the detection output S3, that is, 63 as shown in FIG.
When the bit index data is reproduced, the counter 1 is reset and the initial value is set to 63.

Thereby, it is possible to detect which frame in the index is being reproduced as an absolute address.

Then, in this state, the running of the magnetic tape TO is controlled so that the specified absolute address and the detected absolute address match, and a desired absolute address can be found.

In addition, since the control pulse pc is 301-1z (in the case of NTSC), the count number of this pulse can be converted into time, so the absolute address detected as described above can be displayed on the display device 14 as time data. 1/30
It can also be displayed in seconds (frames).

As described above, according to the playback position detection according to the present embodiment, absolute addresses can be obtained on a frame-by-frame basis, allowing accurate random access and highly accurate editing.

Furthermore, by indicating that frame still recording is being performed using the index data ID and the number of frames in this index data when photographing with a camera, accurate frame still reproduction can be performed during reproduction.

Furthermore, since the playback position can be detected in units of frames, the recording or playback time can be displayed in units of 1/30 seconds (frame period).

(Effects of the Invention) As is clear from the above description, according to the present invention, by using the count output obtained by counting control pulses, it is possible to obtain an absolute address in frame units, so that accurate random access is possible. and can be edited.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the playback position detecting device according to the present invention, FIG. 2 is a diagram schematically showing the recording format of address data and index data on a magnetic tape, and FIG. 3 is a diagram during recording. FIG. 4 is a waveform diagram showing the control pulses of 1 and 2 and the control pulses during reproduction, respectively. FIG. 4 is a diagram schematically showing the recording format of address data and index data on the control track. 1...Counter 2...Pulse width detection circuit 3...Reproduction position detection circuit HC...Magnetic head (control head).

Claims (1)

[Claims] A television recorded on the magnetic tape using the pulse width and count number of a control pulse that is pulse width modulated by a predetermined time code signal and specifies the absolute address of a reference position on the magnetic tape. a reproduction position detection device for detecting the absolute address of each frame in a John signal, comprising: a magnetic head for reproducing the control pulse; a counter for counting the control pulses reproduced by the magnetic head; and a pulse of the control pulse. A pulse width detection circuit detects the width, and the absolute address of the reference position on the magnetic tape is obtained from the detection output of this pulse width detection circuit, and the number of frames from the reference position is detected by the counting output of the counter. A playback position detection device comprising: a playback position detection circuit that obtains the absolute address of each frame.