JPS6310374A - Recording and reproducing method for digital data - Google Patents

Abstract

PURPOSE:To simplify the constitution of a read processing system by adding a reference signal of 'zero' or 'one' to the top of digital data whose pulse position is modulated, detecting the frequency of the reference signal at the time of reproducing, setting the frequency to the reference and deciding respective bit pulses in subsequent digital data to be 'zero' or 'one'. CONSTITUTION:For recording in a recording area, the reference signal RS is recorded before the first bit pulse MSB of an address signal. Here, the reference signal RS is of 'zero' bit, and has the frequency T, but it can be a reference signal of 'one' bit and has the frequency 2T. For reproducing recorded digital data, the frequency of the reference signal RS is detected, and compared with those of respective bit pulses of subsequent digital data, whereby respective bit pulses are decided to the 'zero' or 'one'. Thus, digital data is easily and accurately decided to the 'zero' or 'one', irrespective of the speed of a magnetic tape.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a method for recording and reproducing digital data.
In particular, the present invention relates to a technique for recording pulse position modulated digital data on a magnetic tape using a magnetic head and for reproducing the recorded digital data.

(Prior Art) In recent years, systems have been put into practical use that control other devices using signals recorded on magnetic tape. An example of this type of system is a synchronous tape recorder that controls a video floppy player.

For example, a video floppy player can store up to 50 still images.
It is configured to be able to play back a magnetic sheet (video floppy) with a diameter of about 2 inches that can record up to 2 discs, but it does not have an audio playback function.

Therefore, in the synchronous tape recorder, a magnetic tape called a so-called C-cassette having a two-channel recording area is used, and audio related to the video recorded on the magnetic sheet is recorded on one channel. .

In the other channel of the C-cassette, a track feed signal for switching the video being played back on the video floppy player is recorded so that the video floppy player can be controlled. This track feed signal usually uses a burst signal with a constant frequency.

The recording of data on the magnetic tape and its reproduction will be explained below with reference to FIG.

FIG. 3 is an explanatory diagram showing the recording area of the magnetic tape.

The magnetic tape 1 includes two signal recording areas: a first channel recording area CH1 and a second channel recording area CH2. An audio signal is recorded in the first channel recording area CHI, and a trunk sending signal is recorded in the second channel recording area CH2. The areas in which audio signals are recorded are indicated by hatched areas 2a to 2C, and the recording areas for track feed signals are indicated by shaded areas 3a to 3c, respectively. Note that 4 is a magnetic head for recording and reproducing in the first channel recording area CHI, and 5 is a second channel recording area C.
This figure shows an I2 magnetic head for recording and reproducing.

Suppose now that the magnetic tape 1 is traveling in the direction indicated by the arrow. Then, the first channel description t1 area CHI
The audio signal recorded on is reproduced by the magnetic head 4,
After being processed by an audio processing circuit (not shown), it is output to a speaker (not shown) or the like. On the other hand, the trunk signal recorded in the second channel recording area CH2 is transmitted to the magnetic head 5.
After being played back, the data is processed by a system controller (not shown), etc., and the l-rank forwarding operation of the video floppy player is controlled.

By the way, there are cases where the user may want to issue a command from another device to select a desired video from among the plurality of still images recorded on the magnetic sheet and view the selected video. Operations like this (
The cueing operation) is performed as follows. First, a desired trunk number for cueing is designated from another device, and the difference between this cueing track number and the current track number is calculated.

Then, as the magnetic tape is played in fast forward, the second
The track feed signals recorded in the channel recording area CH2 are counted. The point where the count value becomes equal to the difference between the track numbers obtained by the above calculation is the designated cue track.

However, since the track feed signal recorded in the second channel record t39M area CH2 is a burst-like signal with a constant frequency, it is possible that only a specific trunk feed signal is recorded.
It is not possible to know the trunk number. That is, in order to know the current track number, it is necessary to count the track feed signals in order from the beginning of the magnetic tape. Therefore, when you first use a video floppy player and a synchronized tape recorder, set the magnetic sheet that records the video to the outermost track 1, and set the magnetic tape that records the audio signal to the starting position. Initial setting operations such as rewinding until the end are required.

Since such initial setting operations are troublesome, in order to avoid this, a method has been proposed in which an address signal corresponding to a track number is recorded instead of a track signal (Japanese Patent Application No. 68028/1982). .

For example, when identifying up to 50 images (that is, 50 tracks) recorded on a magnetic sheet, 50 types of address signals are required, so the address signal consists of at least 6 bits.

At this time, the address signal when specifying trunk No. 7 becomes '0OOIIIJ. Such an address signal is pulse position modulated and recorded in the second channel recording area CH2 of the magnetic tape.

FIG. 4 shows the waveform of the address signal modulated by one pulse. The “0” bit of the address signal has a period T
The '14 bits are modulated into a pulse with a period of 2T, and the least significant bit (LSB
) is provided with a pulse/stop pulse SP for determining the cycle.

During reproduction, the time t from when the first pulse of the address signal rises to when the next pulse rises.
is detected, and this time t is T-Tm≦t≦T+Tm
If -. Here, Tm indicates a read margin determined according to fluctuations in magnetic tape temperature.

However, there are two modes for reproducing signals recorded on a magnetic tape: a normal reproduction mode and a fast-forward reproduction mode for cueing. Fast-forward playback mode is performed at a tape speed that is 10 to 20 times faster than normal playback mode. Therefore, since the period of each bit pulse of the reproduced address signal is significantly different depending on the two modes, the address signal cannot be decoded unless the above-mentioned equations (1) and (2) are set for each mode. Therefore, according to the above-described method, a problem arises in that a program for determining rQj and rll from Fil)IJI of the bit pulse of the address signal must be prepared separately for each reproduction mode.

Furthermore, even if a program is prepared for each playback mode, there is a difference in tape speed between the start and end of winding of the magnetic tape in the same mode, and this difference is particularly noticeable in fast-forward playback mode. Therefore, the variation in the period between the bit pulses of each address signal becomes large, so it is necessary to set the read margin large.

However, if the read margin is set large, the boundary area for OJ and IJ judgment (between T+Tm and 2T-Tm in the above 0.0 formula) becomes narrower, so the influence of wow and fluff in the tape running system becomes narrower. OJ,'
Another problem arises in that errors in IJ determination are likely to occur.

(Object of the Invention) The present invention has been made in view of the above circumstances, and it is possible to easily determine the 'OJ' and 'IJ' of digital data recorded on a magnetic tape, regardless of the playback speed of the magnetic tape. The aim is to do so accurately and precisely.

(Structure of the Invention) In order to achieve the above object, the present invention has the following structure.

That is, the present invention provides a digital data recording and reproducing method for recording and reproducing pulse position modulated digital data on a magnetic tape using a magnetic head, and when recording digital data on a magnetic tape, the digital A reference signal of "0" or "11" is added to the beginning of the data, and when reproducing the recorded digital data, the period of the reference signal is detected, and this period and each bit pulse of the following digital data are "0" and "1" of each bit pulse are determined by comparing the period with the period.
It is characterized by making judgments.

Next, the above invention will be explained in detail.

When the reproduction speed of the magnetic tape changes, the period of the reference signal and the period of each bit pulse of the digital data change in the same way. Therefore, before making 'OJ and 'IJ judgments on digital data, if the cycle of the reference signal is detected and compared with the cycle of each bit pulse of the subsequent digital data using this cycle as a reference, the magnetic tape speed It is possible to easily and accurately determine 'OJ' and 'IJ' of digital data regardless of the situation.

(Example) Hereinafter, an example of the present invention shown in the drawings will be described in detail based on the drawings.

FIG. 1 shows a waveform diagram of a signal recorded on magnetic tape using one embodiment of the present invention.

That is, the address signal as pulse position modulated digital data is transmitted to the second magnetic tape shown in FIG. 3, for example.
When recording in the channel recording area CH2, the reference signal R3 is recorded before the first bit pulse (MSB) of the address signal.

The reference signal R3 shown in FIG. 1 is an 'OJ bit,
Although it has a period T, this may be used as a reference signal for the 'IJ bit with a period 2T.

A method of reproducing the address signal to which the reference signal R5 has been added in this manner will be explained with reference to FIG.

When the step mini playback operation starts, the reference signal is first read and the period T of the reference signal, that is, the time from the rising edge of the reference signal to the rising edge of the MSB is detected.

Step b: For example, if the address signal is composed of 6 bits,
Set "6" to the B register among the registers.

Step C: Next, the process enters the stage of reading the address signal following the reference signal, and first detects the period t of the MSB.

Step d: Determine whether or not this period t is within the range of 3T/4≦t≦5T/4 .

Step e: If the bit pulse is within the range ■, the bit pulse is determined to be "0", and "0" is placed in the least significant bit of the A register.

Step f: If it is not within the range ■, it is determined whether the period t is within the range 7T/4≦t≦9T/4. If it is not within this range,
As a reading error, return to step a and read the reference signal R3.
Start over again from reading.

Step g: If it is within the above range ■, set "IJ" to the least significant bit of the A register.

Step h: Subtract 1 from the value of the B register (B).

Step 1: It is determined whether (B)-1 is 0 or not.

If it is 0, it means that all the data has been read, so the address signal reading process ends.

If step jj(B)-] is not 0, the contents of the A register are shifted by 1 bit to the upper bit 1-example, and the process returns to step C to read the next data.

When the processing described above is completed, the address of the magnetic tape can be known from the contents of the A register at that time.

In addition, in formulas ■ and ■, data reading merge -11= was set to T/4, but this is set by selecting an appropriate value depending on the wow and flutter of the tape running system and speed changes. .

Further, in the above embodiments, the digital data recorded on the magnetic tape is described as an address signal, but the digital data is not necessarily limited to an address signal, and the present invention can be applied to any pulse position modulated digital signal. It can be applied to recording and reproducing data.

(Effects of the Invention) As is clear from the above description, the digital data recording/reproducing method according to the present invention adds a reference signal of 'OJ or '1' to the beginning of pulse position modulated digital data, During playback, the cycle of this reference signal is detected, and each beat pulse of subsequent digital data is set to "0" using this cycle as a reference.

'IJ is being judged.

Therefore, according to the present invention, the "OJ" of digital data is independent of the running speed of the magnetic tape.

1 can be performed, there is no need to provide separate determination programs for normal playback mode and fast-forward playback mode as in the conventional method, and the configuration of the digital data reading processing system can be simplified. Can be done.

In addition, even if there is a speed difference in the magnetic tape between the start and end of the magnetic tape, the time width of the reference signal changes accordingly, so changes in the running speed of the magnetic tape are taken into account as in the conventional method. There is no need to set a large reading margin. Therefore, according to the present invention, since the reading margin can be set smaller than in the conventional method, the boundaries of 'OJI' and IJ determination of digital data are expanded accordingly, and the determination can be performed with higher accuracy.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, in which a waveform diagram of a pulse position modulated address signal recorded on a magnetic tape,
FIG. 2 is a flowchart showing address signal reading processing. 3 and 4 are explanatory diagrams of a conventional example, where FIG. 3 is an explanatory diagram of a recording area of a magnetic tape, and FIG. 4 is an explanatory diagram of a recording area of a magnetic tape. FIG. 3 is a waveform diagram of a pulse position modulated address signal. 1... Magnetic tape, 2a to 2c audio signal recording area,
3a to 3d...Track signal or address signal recording area, CHI...first channel recording area, CH2.
...Second channel recording area, R3...Reference signal.

Claims (2)

[Claims] (1) A digital data recording and reproducing method in which pulse position modulated digital data is recorded and reproduced on a magnetic tape using a magnetic head, and when recording digital data on a magnetic tape, the beginning of the digital data is When reproducing the recorded digital data, the period of the reference signal is detected, and this period is compared with the period of each bit pulse of the following digital data. By comparing the ``0'' and ``1'' of each bit pulse,
A method for recording and reproducing digital data, characterized by making a determination. (2) The digital data recording/reproducing method according to claim 1, wherein the digital data is an address signal corresponding to a position on a magnetic tape.