JPH0731879B2 - PCM signal recording / reproducing apparatus - Google Patents

Description

The present invention relates to, for example, an apparatus for converting an audio signal into a PCM signal and recording / reproducing with a rotary head, and particularly index data for detecting a desired recording track. Of reading and driving.

[Outline of Invention]

The present invention provides an audio signal whose time axis is shortened by a rotary head, as seen in, for example, an 8 mm video recording / reproducing apparatus.
In a device that converts to a PCM signal and records / reproduces it, it is possible to reliably detect the index signal that is driven to find the track on which the PCM signal is recorded. The present invention provides a useful detection means for discriminating the index signal driven by after recording.

[Conventional technology]

The method of recording / reproducing the video signal and the audio signal by the helical scan method on the 8 mm video tape is the so-called 8 m
It has been standardized as m-video and has already been commercialized.

FIG. 8 shows an example of such an 8 mm video rotary head device, and FIG. 9 shows the tape format.

In these figures, H _A and H _B indicate rotary heads for recording and reproduction, 1 is a rotary drum, 2 is a rotary drum 1 wound in a range of 180 ° + α with respect to the rotary drum 1, and a direction of an arrow 3T is shown. It is a magnetic tape running on.

The two rotary heads H _A and H _B are configured so that the azimuth angles of the magnetic gaps are different from each other, and are attached so as to slightly project from the rotary drum 1 at an angular interval of 180 °.

Then, at the frame frequency (30Hz) of the video signal, the arrow 3H
Is rotating in the direction of.

Therefore, in the recording tracks of the magnetic tape 2 formed by such a rotary head device, as shown in FIG. 9, tracks 4A and 4B having different azimuths are alternately formed in the oblique direction of the magnetic tape 2.

Normally, in the area AV corresponding to the 180 ° angle of the tracks 4A and 4B,
The video signal is recorded, and in the area AP of α angle (≈36 °), the audio signal is shortened on the time axis, and PCM (Pulse Code Modulatio
The n) signal can be sequentially recorded for each field.

(In 8 mm video, the audio signal is not limited to the area AP described above, and the frequency of the audio signal may be frequency-modulated and supplied to the rotary heads H _A and H _B , and the audio signal may be superposed and recorded in the area AV of the video signal. ) In this way, the 8mm video recording / playback system has a function to record / playback audio signals with the rotary heads H _A and H _B , so recording / playback of extremely high quality audio signals is possible. Playback can be performed.

In addition, in such a normal recording / reproducing mode, a time-axis-compressed audio signal is recorded in the area AV in which the video signal is recorded.
It can also be used as a multi-PCM mode that records channels.

FIG. 10 shows a recording format in the multi-PCM mode when audio PCM data for 5 channels is recorded in the area AV of the track where the video signal is recorded.

As described above, in the multi-PCM mode, a total of 6 channels of audio PCM data are formed on one track.

The 8 mm video track format as described above will be described in more detail. The signal format is as shown in FIG.

That is, in one recording track, from the area where the rotary head is in contact with the tape 2, first, the protrusion angle is 5 degrees at the head angle.
11 and 2.06 degrees (video signal
In the period (corresponding to 3H)), the preamble section 12 becomes the part of the clock line synchronized with the PCM data.

Following this preamble section 12, a PCM data section 13 for converting the time-axis-compressed audio signal into PCM data and recording it is 26.3
It is provided twice. The 2.06 degree (3H) period following the PCM data section 13 is the postamble section 14, and the subsequent 2.62 degree is the guard section 15 indicating the boundary between the video signal and the PCM data section.

The video signal recording area 16 is formed following the guard portion 15, and as described above, the video signal for one field is recorded over 180 degrees, and at the same time, the pilot signal for tracking is superposed on this portion. .

At the end, a separating portion 17 for about 5 degrees is provided.

Further, FIG. 12 shows the recording format in the multi-PCM mode in which the PCM audio signal is recorded in the video signal recording area 16 as described above. The signal arrangement of the divided tracks of each PCM audio signal is shown in FIG. Similar to the PCM audio area, a rush section 21, a preamble section 22, a PCM data section 23, a postamble section 24, and a guard section 25 are provided so that a total of 6 such signals can be recorded.

PCM data is a binary signal, for example, logic "1"
The part of is a signal of frequency 5.8MHz, the part of logic "0" is 2.9M
It is recommended to record with the signal of Hz being FM modulated. And preamble part 12, (22), and postamble part 1
Data “1” is entered in 4, (24).

By the way, according to the invention previously proposed by the applicant, in order to find a predetermined recording track at the time of reproducing such a normal reproduction mode of 8 mm video or multi-PCM mode, For example, a method has been proposed in which an index signal is recorded in the postamble part 14 or 24 and the index signal is read to detect a desired track. (Japanese Patent Application No. 60-64554) According to the previously proposed invention, the index signal can be recorded in the postamble portion 14 or 24 of FIG. 11 or 12 by the rotary head. When the index signal is detected by a picture search or the like, the cue control is performed.

In addition, only the index signal can be input or erased later.

[Problems to be solved by the invention]

Incidentally, in the case of the prior invention described above, the specified signal of the index signal area, two rotary heads H _A, switching signal H _B, i.e., the rotary head H _A, the pulse generator showing the absolute rotational phase of H _B It is formed based on (PG generator).

That is, as a 13 referenced to the rising or falling point T of the switching signal of the head which is formed in synchronism with the PG signal or PG signal as shown in FIG, the index area specifying signal Pi after a predetermined time T _0, for example, It is formed so as to output for 1.5H period, and the index signal IS (2.
8 MH) is supplied to the rotary head to form a recording track Ti with an index.

However, when the audio PCM signal is after-recorded on the tape on which the index signal IS is recorded as described above, it is preferable that the audio PCM signal is always recorded from the above-mentioned reference point T. The plunging part 11 of the rotary head may be displaced by an angle E degree due to a slight difference between the error and the head height, and the writing pattern of the PCM data at that time is as shown in T _WL in FIG. 13, and vice versa. When you have advanced by an angle of E degrees, PC
The M data write pattern is recorded as shown in T _WF . (Such an error is within the permissible range of ± 1.5H even in the standard.) Then, in the case of the recording track T _WL afterafter recording, the index signal IS that was originally recorded is erased as shown in T _RL. But T _{RF for} T _WF
First recorded index signal IS as shown in
Will remain, and the index signal I remaining during playback will remain.
S'may cause malfunction. That is, at the time of cueing, the tape is cueed by the remaining index signal IS ', and there is a problem that an unexpected screen or music is switched to a reproduction state. Further, in this after recording, when the index signal IS ″ is driven in as shown by the dotted line, there are two index signals.

The present invention has been made in order to solve such a problem. A first object of the present invention is not to detect an unerased index signal which originally existed when reproducing an after-recorded tape. The object to be added is to provide a recording / reproducing apparatus for a PCM signal that can easily specify the recording area when the index signal is input or erased. It is in.

[Means for solving problems]

A postamble detection means for detecting the postamble part in the PCM recording area, and an area designation signal for generating a window pulse capable of extracting at least the area where the index signal exists by the signal output from the postamble detection means. Providing generating means,
The window pulse obtained from the area designating signal generating means fetches only the index signal output during the period when the gate is opened.

[Action]

In the area where the audio PCM signal is recorded, a preamble part whose logical level is “1” is provided after the inrush part for 3H, and the logical level is also set to “1” after the PCM data. A postamble section is provided. Then, the index signal IS is added to the latter half of the postamble portion if desired.
In the present invention, first, the preamble portion is detected to form the area designating signal indicating the area in which the index signal exists. Therefore, when the area designating signal is used to detect the index signal, for example, The index signal left unerased during after recording can be prevented from being erroneously detected.

Also, when recording or erasing the index signal, the index area can be designated by a simple circuit.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention for an 8 mm video device.

In this figure, 31 is a recording / re-selection switch for connecting recording amplifiers 41A, 41B for supplying recording signals to the rotary heads H _A , H _B or reproducing amplifiers 42A, 42B for outputting reproducing signals, and 32A.
Is a first head changeover switch for supplying a recording signal to the two rotary heads H _A and H _B only for a predetermined period, similarly 32B is a second head changeover switch for changing and outputting a reproduction signal, and 33 is a recording / re-changing switch. A gate circuit for supplying a signal, 34 is an RF switch pulse generator for generating a head switching signal in a normal reproduction mode, and 35 is a shift circuit for generating a head switching signal in the above-mentioned multi-mode.

The RF switch pulse generator 34 is normally controlled by the PG signal indicating the rotation reference phase of the drum, and when the output of the shift circuit 35 is selected by the mode switch 36, the multi-PCM signal is generated.
In the mode, the recording track format of FIG. 9 described above is converted into the recording track format of FIG. 10 together with the signal of the system controller.

Reference numeral 37 denotes a switch to which data related to PCM audio is supplied, and by switching the switch, an index signal or an erase signal can be supplied as described later.

Reference numeral 40 denotes a video signal processing block that performs various signal processing on the recorded video signal and the reproduced video signal.
It includes circuits for separation, demodulation circuit, frequency conversion, synchronization signal processing, etc. Then, the video signal input to the terminal 43 is subjected to signal conversion and supplied to the head changeover switch 32A,
The reproduced video signal will be output from the terminal 44.

Reference numeral 50 denotes an audio system PCM signal processing block. The input audio signal is converted into a PCM signal after compressing the time axis and divided into 132 blocks for each field as shown in FIG. P parity and Q parity are added, and a CRC code is also added to each block. Then, it is supplied to the head changeover switch 32A through the switch 37, and the above-mentioned PCM recording area AP
Recorded in.

One block of digital data in the PCM audio data is, for example, as shown in FIG. 2, a 3-bit synchronizing signal SYNC, an 8-bit address signal ADRS, and an 8-bit word signal W _{0 to} W _7, and Parity P, Q, and 16-bit C
It consists of RC code CRC.

And "1" of these data is 5.8MHz, and "0" of the data is
It is FM digital data that is modulated by a signal with a frequency of 29 MHz.

Reference numeral 51 is an equalizer that equalizes the signal from the head changeover switch 32B output during reproduction, 52 is a limiter circuit, 53 is a PLL circuit for forming a clock signal, 54 is a D-flip-flop, The PLL recorded by the signal recorded in the added preamble section 12
The circuit 53 is pulled to the clock frequency, and the D-flip-flop 54 is triggered by this clock frequency to detect the FM digital data indicating "1" and "0", which is input to the PCM audio signal processing block 50. Then, error detection, error correction, etc. are performed, and the time axis is expanded to demodulate into a stereo audio signal.

Reference numeral 60 indicated by a one-dot chain line is an index detection section showing a main part of the present invention.

The FM digital data, the clock signal CLK, and the area signal P _AR indicating the recording area AP of the audio PCM are input to the index detection unit 60.

Reference numeral 61 is a demodulation circuit for converting FM digital data (FMDT) into NRZ data indicating "1" and "0" at a binary DC level, and 62 is for detecting that a "0" level signal has been input / output for a predetermined period of time. 0 "detection unit, 63 is a" 1 "detection unit that detects that a" 1 "level signal has been input for a predetermined period, 64 is a delay circuit that delays the PCM recording area designation signal P _AR for a predetermined time, and 65 is an AND A gate, 66 is an SR-flip-flop, 67 is a monostable multivibrator, and 68 is an AND gate.

Since one embodiment of the present invention is configured as described above, in the normal recording mode, the head changeover switch 32
A and 32B are alternately switched by the output of the RF switch pulse generator 34, a video signal for one field is supplied from the video signal processing block 40 in synchronization with the switching timing, and the PCM audio signal processing block 50 When the rotary heads H _A and H _B are controlled to output PCM audio data when in contact with the PCM recording area AP,
Video signals and PCM audio signals are recorded in the recording format shown in FIG.

Further, in the multi-PCM mode, the phase-shifted RF switching pulse output from the shift circuit 35 is supplied to the head changeover switches 32A and 32B, and the PCM audio data is supplied to the rotary heads H _A and H _B at a predetermined timing. By doing so, multi-channel PCM audio data as shown in FIG. 10 can be recorded.

It is also possible to switch the switch 37 during this recording and record the index signal IS in the latter half of the postamble parts 12 and 24, for example.

The switching timing of the switch 37 is the “PCM signal recording / reproducing apparatus” filed by the applicant earlier (Japanese Patent Application No. 60-150428).
No.), the control can be performed using the address data of the PCM data as a reference.

When the signal input from the gate circuit 33 at the time of recording becomes “0”, for example, the recording / reproducing switch 31 is switched to the reproducing side (PB), and the signals reproduced from the rotary heads H _A and H _B are switched to the head. It is supplied to the video signal processing block 40 and the PCM audio signal processing block 50 via the switch 32B.

One of the features of the present invention is that the index signal IS
To accurately detect.

That is, if the part of the PCM audio signal is rewritten by after-recording on the tape on which the index signal IS has been imprinted together with the video signal and the PCM audio signal during normal recording, the first index as described in FIG. 13 above. Although the signal IS may remain or may disappear, the PCM signal recording / reproducing apparatus of the present invention can always detect only the index signal by the after recording.

Hereinafter, this point will be described with reference to the waveform chart of FIG.

PC for the RF switching pulse RFSW for head switching
The area signal P _AR indicating the M audio area AP has a phase relationship as shown in the figure. When this area AP is enlarged, all “1” data is recorded in the preamble section 12 as shown in FMDT. Then, PCM data is recorded in the PCM data section 13 and all “1” is recorded in the postamble section 14. However, when the index signal IS is driven in, the latter half (about All “0” in 1.5H period)
Is recorded. When the preamble portion 14 'indicating the remaining portion to be erased is added to this portion as described above, an index detection error is generated in this portion.

Therefore, in the present invention, first, the area signal P _AR indicating the PCM audio area is input to the delay circuit 64 and delayed by τ to form the _first window pulse W ₁ .

By inputting the FM digital data FMDT and the clock signal CLK input to the index detection unit 60 to the demodulation circuit 61, the "1" portion of the data is set to H level and the "0" portion is set to L level NRZ The data is output. ("1", "0"
The mixed areas of are shown by diagonal lines.) This NRZ data is for "0" detector 62 and "1" detector 6 respectively.
Input to 3 and, for example, if "1" continues for τ for ₁ hour, 1 detection signal S
_When a pulse is output to ₁ and 0 continues for τ ₀ period, 0 detection signal S
_A pulse is output at ₀ .

In this case, 1 detection signal S ₁ detected by the preamble section 11
SR is the pulse P ₁ is not outputted for the other input of the AND gate 65 is 0 level, the pulse P ₂ of the detected postamble portion 14 1 detection signals S ₁ passes through the AND gate 65
Inverting the flip-flop 66 and raising its Q output causes the monostable multivibrator 67 to output a second window pulse P _M of τ _M.

When the index signal IS added by the after recording exists, the pulse P ₄ of the signal S ₀ output from the “0” detector 62 is output from the AND gate 68. However, the output of the AND gate 68 is 0 when the index signal is not added.

After this, the SR-flip-flop 66 is reset by the fall of the delayed area signal (first window pulse W ₁ ), and the AND gate 65 is closed until the PCM audio data to be reproduced next is input. .

The pulse width tau _M serving as the second window pulse P _M, the period of postamble portion 14 when T, the set such that _{T + τ 0> τ 1 +} τ M> T. (T is set to 3H for NTSC and 3.8H for PAL) By setting in this way, even if the unerased index signal IS 'is output from the "0" detector 62 as pulse P ₅ after τ ₁ hour. The detection pulse P _{5 at} this time cannot pass through the AND gate 68, and erroneous detection of the index signal can be prevented.

That is, the index detection unit 60 adopted by the present invention.
Then, only the latest after-recorded index signal is always output as P _N.

Note that continuous "1" or "0" level detection period τ ₁ or τ
₀ may be set to at least a time (eg, 64 bits) corresponding to the number of bits that are not output in the PCM data.

In the above-described embodiment, the “0” detection unit 62 and the “1” detection unit 63 may be composed of either digital circuits or analog circuits.

FIG. 4 is a block diagram in the case where a "0" or "1" detection unit is constituted by a digital circuit, 70 is a counter for counting the clock signal CLK, and 71 is a clock pulse generator.

Since the counter 70 receives the data as the NRZ signal in the demodulation circuit 61 at the reset terminal R, when the counter 70 is reset to "0", it counts clock pulses until it is reset to "0". Therefore, when a carry signal is output during this counting period τ ₁ , all 1s are output.
Similarly, when it is reset by "1", the counting operation is performed when 0 is input, so when the carry signal is output after τ ₀ , it becomes an all 0 detector. The detection period τ ₁ (τ ₀ ) is determined by the cycle T _{C of the} clock CLK and Qn, and τ ₀ (τ ₁ ) = 2nT _C.

In the case of PCM data of this system, for example, by selecting a 64-bit period as the detection period τ ₁ (τ ₀ ), it is possible to reliably detect all 1 periods or all 0 periods in the postamble or index signal.

FIG. 5 shows a case where the “0” or “1” detection section is configured by an analog circuit. 72 is a bandpass filter, 73 is an envelope detector, 74 is a comparator, and 75 is a trigger pulse generator. .

In this embodiment, FM digital data FMDT is directly input to the bandpass filter 72. And bandpass filter 72
When the center frequency of 2.9MHz is 2.9MHz, it becomes a "0" detector, and when it is 5.8MHz, it becomes a "1" detector.

The detection periods τ ₀ and τ ₁ can be set by the value of the reference power source E of the comparator 74.

In the above-mentioned embodiment, the data of all "0" is set as the index signal IS in the latter half of the postamble, but the tape count value, the playing time, etc. are written by coding this index signal. You can

Even in the case of such a coding index, as described above, a ghost index may be generated due to the accuracy of the angle E of the plunging portion 11 and erroneous data may be detected. There is an effect that the probability of erroneous reading of can be reduced.

FIG. 6 is a block diagram of an index detector useful for detecting a coding index, and the same reference numerals in FIG. 1 indicate the same parts.

In the case of this embodiment, the detection of the coded index signal IC is detected by the AND gate 68 by the second window pulse P _M output from the monostable multivibrator 67.
Is output during the open period, and the output coding index IC is detected by the detection circuit 69 to determine whether there is an error. Then, when there is no error, it is output as an index signal.

The detection circuit 69 may be provided on the input side of the AND gate 68 as shown by 69A.

By the way, index detection is often requested especially at high speed search.

In this case, as shown in FIG. 7, the scanning locus of the rotary head H _A (H _B ) should intersect the recording tracks 4A and 4B as shown by the arrow X in the normal recording / reproducing tape format. become.

However, if the intersecting angle Δθ is within a certain range, there is an opportunity to perform scanning without departing from the postamble part 14, (24) of the PCM audio area AP as shown in FIG. A window pulse can be formed by the index detection method and the index signal IS or the coding index IC can be read.

By the way, in the 8mm video recording format, the crossing angle Δθ at the time of 30x picture search is 0 ° 36'76 ″ in the case of NTSC system and 0 ° 17'12.6 ″ in the long play mode (long-time recording mode). , The postamble part 14, (24) does not deviate from the track. (PAL
In the case of the system, SP is 0 ° 53'43.3 ", LP is 0 ° 24'32.
It is 8 ″, and there is no problem.) The detection of the index signal when the PCM audio area is after-recorded has been described in detail above. However, in the PCM signal recording / reproducing apparatus of the present invention, the window output from the index detection unit is used. It is also possible to specify the recording area of the index by the pulse and drive and erase the index signal.

That is, in the embodiment of FIG. 1, as shown by the dotted line,
While inputting the PCM audio signal and the area signal P _AR , the block 70 generates an index pulse of a predetermined width, which is obtained from the AND gate 68 and is delayed by a predetermined time with the rising edge of the window pulse as a reference point. Supply switching index signal (29MHz) or erase signal (5.8MH).

In the read mode, the index pulse is used to switch to the recording mode, and the index signal or the erase signal of the index signal is output during playback.
It can be supplied to H _A and H _B.

In this case, the method of detecting the address of the PCM signal proposed by the present applicant and designating the index area as described above is also useful, but this method detects the address signal and further designates the index area. There is a drawback that the circuit of becomes complicated. However, the use of the index signal detection section employed in the PCM signal recording / reproducing apparatus of the present invention has the effect of simplifying the circuit configuration.

〔The invention's effect〕

As described above, the PCM signal recording / reproducing apparatus of the present invention has a means for detecting the preamble portion formed in the area where the PCM signal is recorded, and an area where the index signal should exist by the detection of the preamble portion. Since a means for outputting a window pulse for specifying is added, even when a drive error occurs on the tape of the index signal (or code) due to a difference in model or variation in adjustment, that error is If it is within the standards, there is an effect that an effective index can be surely detected.

In addition, there is an advantage that the index driving area can be designated by a simplified circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing the outline of a PCM signal recording / reproducing apparatus of the present invention, and FIG. 2 is an explanatory diagram showing the contents of PCM data.
FIG. 3 is an explanatory waveform diagram for performing index detection,
4 and 5 are block diagrams showing specific examples of the “0” detection unit and the “1” detection unit, FIG. 6 is a block diagram of the detection unit that can be used for the coding index, and FIG. 7 is at the time of picture search. 8 is an explanatory diagram of index detection in FIG.
Explanatory diagram showing the correlation between the rotating head of 8mm video and the tape,
Fig. 9 is a tape format diagram for normal 8mm video, Fig. 1
Figure 0 shows the tape format in multi-PCM mode,
FIG. 11 is a track format in the normal mode of 8 mm video, FIG. 12 is a track format in the multi-PCM mode of 8 mm video, and FIG. 13 is an explanatory diagram of the recording of the index signal and the after-recording thereof. In the figure, 60 is an index detection unit, 61 is a data demodulation circuit, 62 is a "0" detection unit, 63 is a "1" detection unit, 64 is a delay circuit,
67 indicates a monostable multivibrator.

Claims (3)

[Claims] 1. A detection circuit for recording an audio PCM signal on a track formed in a diagonal direction of a magnetic tape by a rotary head, adding an index signal following the audio PCM signal, and detecting the index signal. In the PCM signal recording / reproducing apparatus, the index signal detecting circuit is
A delay circuit (64) for delaying an area signal (P _AR ) indicating a signal recording area for at least a time longer than a preamble data reproduction time, and a continuous data “1” recorded in the audio PCM signal area are integrated, A first detection circuit (63) that outputs a signal with a predetermined integrated value, and is set when the logical product of the output signal of the first detection circuit and the area signal output from the delay circuit is established, A bistable circuit reset at the trailing edge of the area signal, and pulse generating means (65, 66, for outputting a window signal (P _M ) having a predetermined pulse width (τ _M ) during the set operation of the bistable circuit. 67) and a second detection circuit for extracting an index signal from the data reproduced within the period in which the window signal is being output. Recording / playback device. 2. The second detection circuit is a continuous data "0".
Circuit that integrates and outputs a signal with a predetermined integrated value (62)
The PCM signal recording / reproducing apparatus according to claim 1, characterized in that 3. The PCM signal recording / reproducing apparatus according to claim 1, wherein the second detection circuit is composed of a circuit (69) for detecting a coded index signal. .