JPH03189964A - data playback device - Google Patents

Abstract

PURPOSE:To obtain the data reproducing device capable of securely reproducing information even under the state of variable tape speed by providing a tape speed detecting means and a demodulating means for changing demodulating conditions at the time of demodulating a regenerative signal from a tape based on a bit of tape speed information. CONSTITUTION:The tape speed is detected by measuring a rotational period of a reel, whereas the demodulating means is provided for changing its demodulating condition based on the above information at the time of demodulating a regenerative signal from the tape, and the tape speed detcting means is equipped with a reel rotational period detecting part 109 and a tape speed calculating part 110, while an envelope demodulating part 108 is provided with a run length measuring part 503, thus constituting the subject device. Then, since a run length measured by the tape speed is corrected, even when the tape speed is changed during a high speed search, a search mark can securely be detected. By this method, the data reproducing device capable of securely reproducing information even under the state of variable tape speed can thus be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a recording and reproducing apparatus such as a 5-DAT (fixed head digital audio tape recorder), and in particular to a data recording and reproducing apparatus such as a 5-DAT (fixed head digital audio tape recorder). The present invention relates to a playback device.

Conventional Technology 5 - Fixed head type digital recording/reproducing devices such as DAT do not require a rotating cylinder unlike rotating head types, so the mechanism can be made smaller. However, unlike the rotating head type recording/reproducing apparatus, the bit rate of the reproduced signal increases in proportion to the tape speed, making it difficult to read control data during high-speed searches.

For example, 5-DAT can record 20 tracks, and main data and sub data are recorded in these 20 tracks. The main data area mainly records audio data and the like, and the sub data area mainly records control data for high-speed search and the like. The modulation method adopts the 8-10 modulation method, which equalizes the waveform of the reproduced signal during demodulation, extracts the reproduced clock from the reproduced signal after waveform equalization, and converts the reproduced signal after waveform equalization using the reproduced clock. , and then enters 8-10 demodulation processing. Note that 5-DAT is explained on pages 159 to 166 of "Digital Audio Dictionary" published by the Japan Audio Association on July 25, 1989.

With the tape running at high speed for high-speed search,
In order to read the control data, a PLL (Phase Lo
cked loop) circuit needed to exhibit sufficient performance even when the bit rate of the recovered clock changed significantly.

Therefore, in conventional fixed head type recording and reproducing apparatuses, such as 5-DAT, this has been dealt with by switching the waveform equalization characteristics or the capture range of the PLL depending on the tape speed.

Problems to be Solved by the Invention However, the fixed head type recording and reproducing apparatus as described above has problems such as being susceptible to rapid changes in bit rate and increasing manufacturing costs.

The present invention solves the conventional problems described in 1. It performs low-frequency envelope modulation on the recording signal of auxiliary data, demodulates the envelope-modulated playback signal during high-speed search, and measures the run length and tape speed. However, it is an object of the present invention to provide a data reproducing device that can reliably reproduce information even when the tape speed is changing by correcting the change in run length due to the tape speed.

Means for Solving the Problems In order to achieve the above object, the data reproducing device of the present invention comprises:
A tape speed detecting means for obtaining tape speed information by measuring a rotation period of a reel, and a demodulating means for changing demodulation conditions when demodulating a reproduced signal from the tape based on the tape speed information, The speed detection means includes a reel rotation period detection section and a tape speed calculation section, and the demodulation section includes a run length measurement section.

Operation With the above configuration, the data reproducing device of the present invention applies low frequency envelope modulation to the recording signal of auxiliary data, demodulates the envelope modulated reproduction signal during high-speed search, measures the run length, and reproduces information. do. moreover,
By measuring tape speed and correcting changes in run length due to tape speed, information can be reliably reproduced even when the tape speed is changing.

Embodiments Hereinafter, embodiments of the data reproducing apparatus of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a recording and reproducing apparatus including a data reproducing apparatus of the present invention.

In FIG. 1, 101 is a cassette storing a magnetic tape, 102 is a mechanism control unit that controls the running of the magnetic tape according to instructions from a system control unit 105, and 103
is a recording and reproducing head that performs recording and reproducing on a magnetic tape. The recording head is composed of nine heads, one head records auxiliary data such as control data used for reproduction control, and the remaining eight heads record main data such as audio data. The playback head consists of nine heads, one head outputs an auxiliary channel playback signal including control data used for playback control, and the remaining eight heads output a main channel playback signal including audio data, etc. Output. In this embodiment, the magnetic tape is divided into two areas, upper and lower.
One is used for forward direction recording and the other is used for reverse direction recording. To reverse the running direction, rotate the head 180 degrees.

FIG. 2 is a diagram showing a recording track pattern on a tape recorded by a recording head in an embodiment of the present invention.

104 adds an error correction code to the input audio data, and 8-
10 modulation and output as a main channel recording signal to eight recording heads for main channel recording in the recording/reproducing head 103, and an error correction code is added to the auxiliary data used for travel control etc. given from the system control unit 105. is added, modulated, and supplied to the envelope modulation section 107 as auxiliary channel recording data, and also demodulates the reproduction signal reproduced by the eight main channel reproduction reproduction heads of the recording and reproduction head 103 to eliminate errors. It performs correction and outputs output audio data, and also demodulates the auxiliary channel playback data reproduced by one of the playback heads for auxiliary channel playback in the recording/playback head 103, performs error correction, and outputs auxiliary data. It is also a recording and reproducing unit that sends out data to the system control unit 105. 105 instructs the mechanism control unit 102 to select a running mode, and the recording/reproducing unit 104
The recording mode, playback mode, etc. are instructed to the envelope modulation section 107, and the start ID is sent to the envelope modulation section 107.

Provide search mark information such as lead-out area ID,
This is a system control unit that receives run length information of the auxiliary data demodulated from the envelope demodulation unit 108 and detects search mark information.

The system control unit 105 can be realized by a microprocessor or the like. Reference numeral 106 denotes a recording/reproduction mode setting unit for the user to give commands to the system control unit 105.

The user uses a recording/reproducing mode setting unit 106 configured by Sui-Sochi, etc. to instruct the general operation mode such as recording, reproduction, or repeated reproduction.

In this embodiment, the input/output of the recording/reproducing device is audio data, but other data such as image data may be used, so auxiliary data used for control is generally referred to as main data. 107 modulates the auxiliary channel recording data output from the recording and reproducing section based on search mark information such as a start ID flag and a lead-out area ID flag supplied from the system control section 105, and modulates the auxiliary channel recording data output from the recording and reproducing section 103. This is an envelope modulation section that outputs to a recording head for recording one auxiliary channel.

Here, the start ID flag is a flag that requests recording of the start ID, and the lead-out area ID flag is a flag that requests recording of the lead-out area ID.

Furthermore, the start ID is information indicating the beginning position of a song used when recording audio or the like as main data. When searching at high speed, use this start ■D as a landmark to find the beginning of a song.

Further, the lead-out area ID is information indicating the end of the recording area. The reason why it is necessary to record the lead-out area ID is as follows.

(1) Use it as a mark when recording a link.

(2) Mark the final point of the valid area.

In particular, the lead-out area is necessary when overriding is performed on a tape that has been previously recorded and the end point of the previous recording is later than the end point of the latest recording. This is because the ending point of the latest recording is connected to the area of the previous recording, so it is impossible to determine where the ending point is. (-When recording on tape, it is possible to detect the unrecorded portion and find the end point of the recording.
If the lead-out area is used for recording, it is possible to find the end point of the recording more quickly and reliably. This is because when determining the end point in a non-recorded part, it is necessary to check the non-recorded state for several frames in order to reliably determine that it is a non-recorded part, rather than a burst error due to a dropout. This is because if an out area is recorded, it can be determined that the end point is reached immediately upon detection.

For example, in an R-DAT (rotating head digital audio tape recorder), the lead-out area is 30 mm.
When 0 or more frames are recorded and a lead-out area ID is detected during end search, tape running is stopped, several frames are rewound, and a standby state is entered for splice recording. Continuous recording is to record a frame that has already been recorded so that the -110- phase, etc. of the frame is continuous.

Therefore, before splicing recording, it is necessary to check the recording position of the already recorded frames and read the time code, frame number, etc. Also, it is necessary to keep the tape speed constant before recording starts. A run-up for several frames is required.

For this purpose, after detecting the lead-out area ID, the program rewinds several frames and waits.

In addition, in the case of R-DAT, a frame refers to a pair of a plus azimuth track recorded with a plus azimuth head and a minus azimuth track recorded with a minus azimuth head, and is the smallest unit that can be independently recorded and reproduced. .

Note that R-DAT is explained on pages 142 to 158 of the aforementioned "Digital Audio Dictionary".

As mentioned above, the lead-out area ID is used for end searches and the like, so it needs to be reliably readable even during high-speed searches. Furthermore, it is necessary to distinguish between the start ID and lead-out area ID during high-speed search. This is because if the start ID and lead-out area ID cannot be distinguished during high-speed search, it is necessary to stop tape running and check in normal playback mode.
This is because the search operation becomes slow.

Next, the operation of envelope modulation section 107 will be explained below.

FIG. 3 is a block diagram showing the configuration of envelope modulation section 107, and FIG. 4 is a timing chart showing its operation.

In FIG. 3, 301 is a normal modulation signal generating section that generates a normal modulation signal NSG which is a clock with a high period of 8 seconds and a low period of 8 seconds.

NSC in FIG. 4 indicates a normal modulation signal NSC.

302 is a star ID modulation signal generator that outputs a high level for two cycles of the normal modulation signal NSG based on the normal modulation signal NSG when the start ID flag 5IDF supplied from the system control unit 105 becomes valid. Department. 5IDF in FIG. 4 indicates a start ID flag, and SSG indicates a start ID modulation signal. 303 is the system control unit 1
Lead-out area ID flag LI supplied from 05
This is a lead-out area ID modulation signal generating section that outputs a high level in an interval corresponding to 10 cycles of the normal modulation signal NSC based on the normal modulation signal NSC when the DF becomes effective. LIDF in FIG. 4 indicates a lead-out area D flag, and LSG indicates a lead-out area ID modulation signal.

304 is a normal modulation signal NSC generated by the normal modulation signal generation section 301 and a start ID modulation signal generation section 3.
This is an OR gate that takes the logical sum of the star) ID modulation signal SS color generated by 02 and the lead-out area ID modulation signal LSG generated by the lead-out area ID modulation signal generation section 303.

As a result, the run length of the output signal of the OR gate when the start ID is valid, that is, the high level duration is 58 seconds, and the run length of the output signal of the OR gate when the lead-out area ID is valid is 218 seconds. become. OSG in FIG. 4 shows the output signal of the or game 1-304. 305 is the auxiliary channel recording data supplied from the recording/reproducing section 104 and the output signal O8 of the OR gate 304;
This is an AND gate that performs the logical product of G. AUX in Figure 4
RDT indicates auxiliary channel recording data, AUXR8G
indicates the auxiliary channel recording signal which is the output signal of AND gate 305. The auxiliary channel recording data AUXRDT is 8-10 modulated auxiliary data generated by the recording/reproducing section 104, but the 8-10 modulated auxiliary data is
Since it is difficult to read during high-speed searches when the tape speed changes, start ID and lead-out area ID are
Data that cannot be read erroneously, such as data, is envelope-modulated so that it can be reliably read even during high-speed searches.

Also, the auxiliary channel recording signal AUXR8G is in the form of a masked part of the auxiliary channel recording data AUXRDT, but since the same data is written twice at a cycle of S seconds, it is 8-10 modulated. Any auxiliary data created will not be lost.

As described above, the envelope modulation section 107 performs envelope modulation with a run length of 5S seconds based on the search mark information supplied from the system control section 105 when the start ID flag 5IDF is enabled, and performs the envelope modulation with a run length of 5S seconds. When the area ID flag LIDF is enabled, envelope modulation is performed with a run length of 21 seconds, and when the start ID flag 5 IDF & lead-out area ID flag LIDF are disabled, the run length is 8 seconds.
Performs envelope modulation of seconds.

Reference numeral 108 denotes an envelope demodulation unit that demodulates the auxiliary channel reproduction signal reproduced by one of the reproduction heads for auxiliary channel reproduction in the recording/reproduction head 103, measures the run length, and supplies it to the system control unit 105. .

Next, the operation of envelope demodulation section 108 will be explained below.

FIG. 5 is a block diagram showing the configuration of envelope demodulation section 108.

In FIG. 5, 501 is a low-pass filter that removes high-frequency components of the auxiliary channel reproduction signal.

502 is a comparator that determines the output signal level of the low-pass filter 502. Reference numeral 503 denotes a run length measurement unit that measures the continuous high level section of the output signal of the comparator 502 and sends run length information to the system control unit.

The envelope demodulator 108 has the above-described configuration, extracts the low frequency component of the auxiliary data, measures the duration of the high level, and outputs it to the system controller 105 as run length information.

Reference numeral 109 is a reel rotation period detection unit that detects the rotation period of the reel. A common method for detecting the rotation period of the reel is to use a frequency generator (FG) as described below.

The rotation period of the reel is measured by shining light onto a striped pattern written on a reel stand fixed to the shaft that drives the cassette reel, and converting the reflected light into an electrical signal using a light receiving element. For example, when two striped patterns are written on the reel stand, the period of the electrical signal output from the photodetector is T.
In this case, the rotation period T of the reel is expressed as shown below.

T,=T @P...(
1) 16-110 is a tape speed calculation unit that calculates the tape speed.

A method of calculating the tape speed using the reel rotation period Tr will be explained below.

FIG. 6 is a diagram showing the tape wound around the reel.

In FIG. 6, r is the radius of the reel, RI is the radius of the winding of the supply reel, R2 is the radius of the winding of the take-up reel, and Vt is the tape speed.

When the rotation period of the supply reel is T1 and the rotation period of the take-up reel is T2, the product LH of the tape thickness H and tape length is expressed by the following equation.

LH=π(RI2-r2)+yr(R22-r2)
-(2) Also, the tape speed Vt is expressed by the following formula.

Vt” 2 πR+/ T+= 2 yr R1!/
T2 - (3) From formulas (2) and (3), Vt = C/ (TI2 + T22) ” ・
...(4) However, C=(4xLmH+2yrr")"2 "(5) If the constant C is known, use equation (4) to calculate the rotation period T of the supply reel and the take-up reel. The tape speed Vt can be determined from the rotation period T2.

The constant C can be determined by measuring the rotation period of the supply reel and the rotation period of the take-up reel while the tape speed is known.

The tape speed during normal recording and playback is ve, the rotation period of the supply reel is T19, and the rotation period of the take-up reel is T2.
11, the constant C is expressed by the following equation.

C=VII(T+g"+Tag2)"2-(8) Using the method explained above, the tape speed calculation section 110 calculates the tape speed from the rotation period of the reel, and supplies the tape speed information to the system control section 105. .

Next, search mark information extraction processing performed by the system control unit 105 will be described.

Envelope modulation Hastert I with run length of 5S seconds
An envelope modulation with a run length of 218 seconds indicates a lead-out area ID, and an envelope modulation with a run length of 8 seconds indicates a section in which neither a star 7) ID nor a lead-out area ID is set.

If the tape speed is the same as when recording, run length L.
When L satisfies the following formula, the lead-out area ID
is determined to be valid.

10S<LL...(7) When run length LL satisfies the following formula, star) I
D is determined to be valid.

2.58≦LL≦1O8 (8) At the time of high-speed search, the run length is corrected using the tape speed information V sent from the tape speed detection section 110. Letting the corrected run length be a corrected run length CL, CL is expressed by the following equation.

CL=Vt-CC* (9) At this time, when the run length LL satisfies the condition of the following equation, it is determined that the lead-out area ID is valid.

10S<CL...(10)
When run length LL satisfies the condition of the following equation, =19=star) ID is determined to be effective.

2.58≦CL≦1O8 (11) Tape speed Since detection is performed using the reel FG, detection may be delayed by a time equivalent to one cycle of the reel FG. Therefore, a detection error may occur in the tape speed Vt. In the above-described search mark detection method, if the error in tape speed Vt is suppressed within 0.5 times to 2 times, erroneous detection will not occur.

This is because the run length of the lead-out area ID is 2.
Since it is 18 seconds, due to the error in tape speed Vt,
．． The time can range from 5*21S=10.5S seconds to 2*21S=42S seconds, which satisfies equation (10). Note that the * mark indicates multiplication. Also, the run length of the start ID is 5.
Since it is 8 seconds, table speed FVt (D error Niyotte, 0
．． The time can range from 5*5S=2.5S seconds to 2*5S=10S seconds, which satisfies equation (11). Since the run length of the section where both lead-out area ID and star) ID are invalid is 8 seconds, the error of tape speed V, causes 0.5*
It can take from S=0 0.5S seconds to 2*5=2S seconds, but (10
) and (II) are not satisfied.

Through the procedure described above, the data reproducing apparatus of the present invention can reliably detect search marks such as start ID, lead-out area ID, etc. even when the tape speed is changing during high-speed search.

Effects of the Invention The data reproducing apparatus of the present invention includes a tape speed detecting means that obtains tape speed information by measuring the rotation period of a reel, and a demodulating means for demodulating a reproduced signal from the tape based on the tape speed information. The tape speed detecting means includes a reel rotation period detecting section and a tape speed calculating section, and the demodulating section includes a run length measuring section. Since the measured run length can be corrected, search marks such as the start ID and lead-out area can be reliably detected even when the tape speed is changing during high-speed search.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a recording and reproducing apparatus including a data reproducing apparatus of the present invention, FIG. 2 is a diagram of a recording track pattern on a tape recorded by a recording head in an embodiment of the present invention, and FIG. A block diagram showing the configuration of the envelope modulation section, FIG. 4 is a timing chart showing the operation of the envelope modulation section, FIG. 5 is a block diagram showing the configuration of the envelope demodulation section, and FIG. 6 is a diagram showing the tape wound around a reel. It is. 101... Cassette, 102... Mechanism control unit, 103... Recording and reproducing head, 104...
...recording and reproducing section, 105...system control section, 1
0f3...recording/playback mode setting section, 107...
Envelope modulation section, 108... Envelope demodulation section, 109... Reel rotation period detection section, 110
... Tape speed calculation section.

Claims (3)

[Claims] (1) A tape speed detection means that obtains tape speed information by measuring the rotation period of a reel, and a demodulation means that changes demodulation conditions when demodulating a playback signal from the tape based on the tape speed information. A data reproducing device characterized by: (2) The tape speed detection means includes a reel rotation period detection section that detects the rotation period of the reel, and a tape speed calculation section that calculates the tape speed based on the reel rotation period detected by the reel rotation period detection section. Equipped with
2. The demodulation means includes a run length measurement section that demodulates an envelope from a reproduced signal from a tape recorded with envelope modulation and detects a run length of the tape by measuring the period of the envelope. 1. The data reproducing device according to 1. (3) The data reproducing apparatus according to claim 1, wherein the demodulating means demodulates the control data based on the product of tape speed and run length.