JPH0433593Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a magnetic reproducing device for reproducing address code signals recorded on a magnetic tape.

[Technical background of the invention]

Recently, the Japan Electronics Industries Association has standardized the address codes used in consumer compact cassette tape recorders.

The address code system is constructed in such a way that the code signal can be read out prior to each audio signal portion to which it corresponds, without interfering with the reproduction of the audio signal, and in both the playback state and the fast-winding state. The fundamental frequency of the code signal is 10 Hz, and the code signal is recorded on the tape so that the L channel and R channel are in opposite phases. Information on the code signal is expressed by the presence or absence of the fundamental frequency (10 Hz), and is recorded in order from address code 1 on each side.

One set of code signals is composed of 13 cycles at 10 Hz, a logic "1" is represented by one cycle of 10 Hz, and a logic "0" is represented by a no-signal portion of one cycle of 10 Hz.
An example of a code signal is shown in FIG. 5, and the code signal in this case represents address A-7 (the beginning of the seventh track on side A). Note that position 1 in the figure is the first code signal read out during reproduction.

Both sides A and B of the compact cassette start from 1.
It consists of codes for addresses up to 30 and codes for uses other than addresses from 31 to 35, of which code 35 (A-35, B-35) is used as an end code. Further, the instructions for the A side and the B side are made depending on whether the logic of position 4 is "0" or "1". The above-mentioned code signal is placed in a no-signal portion between songs (audio signal portions).

Positions 1 to 3 and positions 11 to 13 of the code signal are called preamble positions, and are used to identify whether the signal generated by playing the magnetic tape is an address code signal or another signal, and to set the preamble position. It is used to recognize the following code, but how to detect the preamble position signal is left up to each manufacturer.

[Purpose of invention]

In view of the above-mentioned points, an object of the present invention is to provide a magnetic reproducing device that can process preamble position signals in the same way regardless of the running direction and running speed of the magnetic tape and can recognize address codes. It is said that

[Summary of the idea]

A digital signal consisting of a pulse train is obtained by shaping the reproduction signal of the magnetic tape, and the H level time and L level time of three successive pulses are compared with each other, and the preamble pulse can be detected and recognized based on the comparison result. By doing this, the address code can be reproduced by the same signal processing regardless of the magnetic tape running direction and speed.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing an embodiment of a magnetic reproducing apparatus according to the present invention. In the figure, 1 is a magnetic tape, and address code signals are recorded in the non-signal portions between songs. 2 is the playback head, 3
4 is a reproducing circuit, 4 is an analog-to-digital (A-D) converter that shapes the waveform of the signal sent from the reproducing circuit 3 and converts it into a digital signal consisting of a pulse train, and 5 is a signal sent from the A-D converter 4. A code analysis device detects and analyzes an address code based on an incoming digital signal, and 7 is a display device that displays the contents of the code analyzed by the code analysis device 6.

With the above configuration, when the magnetic tape 1 on which the address code signal is recorded is played back, queued or reviewed, the signal on the magnetic tape 1 is played back by the playback head 2 and the playback circuit 3, and the playback signal is converted into the A- The signal is converted into a digital signal by the D converter 4 and input to the code analysis circuit 5. The code analysis circuit 5 analyzes the input digital signal and detects and recognizes the preamble pulse of the address code.

Assuming that an address code as shown in FIG. 5 is recorded on the magnetic tape 1, when the magnetic tape is played back or queued, a digital signal as shown in FIG. 2a is output from the A-D converter 4. The code analysis device 5 analyzes these signals.

As is clear from Figure 2 a and b, the address code corresponds to positions 1 to 3 when the magnetic tape is run in the playback or queue state, and to positions 13 to 11 when it is run in the review state. By detecting and recognizing the leading preamble pulse, the subsequent code body between positions 4 to 10 can be analyzed.

By the way, the parts of the preamble pulse that are effective for detection and recognition, corresponding to positions 1 to 3, are the times t ₁ and 2 of the H and L levels of the first and second waves and the H level of the third wave. t ₁ ′, t ₂ ,
t ₂ ' and t ₃ , and for those corresponding to positions 13 to 11, the H level of the first wave and the H and L level times of the second and third waves T ₁ , T ₂ , T ₂ ', _T3 ,
T ₃ ′. Therefore, the preamble pulse can be detected and recognized by measuring and comparing these times and determining whether a predetermined relationship is established between these times.

FIG. 3 shows a specific example of the code analysis device 5, in which 5a is a timer counter circuit that measures the connection time and pulse interval of three successive pulses of the digital signal from the A-D converter 4. , 5b is a timer counter circuit 5
5c is a comparison calculation device which performs a comparison operation on the duration and pulse interval of three successive pulses stored in the time count storage circuit 5b; 5d is a comparison calculation device 5c is a display output circuit that outputs the result to the display device 6.

The operation of the code analysis device 5 described above with reference to FIG. 3 to detect and recognize a preamble pulse will be explained with reference to the flowchart of FIG. 4.

The flowchart starts, for example, with the start of the playback operation in the song selection mode, and first, in the first step _S1 , the H level time _t1 of the first wave is measured by the timer counter circuit 5a, and the measurement result is used in the next step. At _S2 , it is stored in the time count storage circuit 5b. In the following step _S3 , the L level time _t1 ' of the first wave is measured by the timer counter circuit 5a, and the result is stored in the time count storage circuit 5b in the next step _S4 .
Then, in the next step _S5 , the H level time _t2 of the second wave is measured by the timer counter circuit 5a, and the result is stored in the time count storage circuit 5b in step _S6 .

In step _S6 above, the H level time of the second wave
After t ₂ is stored, the comparison calculation device 5c calculates -t ₁ -t ₂ - and xt ₁ /100 based on this data t ₂ and data t ₁ stored in step S ₂ .
In step _S7 , it is determined whether -t ₁ -t ₂ -≦xt ₁ /100 or not. Here, x is the allowable error between the H level times of adjacent pulses expressed in %, and is _arbitrarily set depending on the performance of the playback device mechanism _. We are checking whether the absolute value of the difference in t ₂ is within the allowable error range.

Generally, if the first wave and the second wave are not preamble pulses of the address code, the values of times _t1 and _t2 are significantly different, and the determination in step _S7 is NO, and the process proceeds to step _S8 . In step _S8 , the second wave data _t2 is converted into first wave data _t1 , and then the process returns to step _S2 to store this data. Then, in the following step _S3 , the second
The L level time of the first wave is the L level time of the first wave.
After measuring this as _t1 ' and storing this in step _S4 , the H level time of the third wave is measured as the input in step _S5 as the H level time of the second wave _t2 , and this is stored in step S4. Remember in ₆ .

Thereafter, a predetermined determination is made again in step _S7 based on the data stored by executing steps _S2 and _S6 for the second time. Even if the second and third waves as input are not preamble pulses, times t ₁ and t ₂ may fall within the range of error x by chance, and in such a case, the determination in step S ₇ is YES.
becomes.

If the judgment in step S ₇ is YES, step S ₉
Then, as an input, the L level time of the third wave is measured as the L level time t ₂ ' of the second wave, and this is stored in the next step _S10 . After that, 2
Data stored by executing step _S4 for the second time
t ₁ ′ and the data stored by executing step S ₁₀
Based on t ₂ ′, in step S ₁₁ −t ₁ ′−
Determine t ₂ ′-≦xt ₁ ′/100.

Now, if the judgment in step _S11 is NO,
In step _S12 , data t ₂ ′ is changed to t ₁ ′ and data t ₂
Convert each data to t ₁ , then step
In _S13 , the converted data _t1 is stored, and the process returns to step _S4 . In step _S4 , t ₁ ' obtained by data conversion is stored.

Thereafter, in step _S5 , the H level time of the fourth wave is input as the H level time of the second wave _t2.
is measured and stored in step _S6 . Then, in step _S7 , the third
Compare the H level time of the first wave and the fourth wave. If the next step _S7 is YES, step _S9
As an input, the L level time of the fourth wave is measured as the L level time t ₂ ' of the second wave, and this is stored in step _S10 . And step S ₁₁
As input, the L of the third and fourth waves is
Compare level times.

Now, if the determination in step _S11 is YES, that is, if the H and L level times of the third and fourth waves as input are within the allowable error range, the process advances to step _S14 . As an input, the H level time of the fifth wave is measured as the H level time _t3 of the third wave, and this is stored in step _S15 . Then, in the next step _S16 ,
Based on the data stored in steps _S6 and _S15 , it is determined that _-t2 - _t3- ≦ _xt2 /100. If the judgment in step _S16 is NO, step _S17
After data conversion from data t ₃ to t ₁ in step S ₂
Returning to step S18, if the determination is YES, the process proceeds to step _S18 , where it is assumed that a preamble pulse has been detected and recognized, and subsequent pulses are analyzed and the address code is decoded. The address code decoding result is sent to the display device 6 via the display output circuit 5d and displayed.

In short, among the three successive pulses, the timer counter circuit 5a successively measures the H level time _t1 , the L level time _t1 ', and the H level time _t2 , and records the measured data at any time. The count is stored in the count storage circuit 5b. After measuring up to H level time t ₂ , compare t ₁ and t ₂ ,
It is determined whether t ₂ is within ±xt ₁ % of t ₁ , and if it is not, the first wave is not regarded as a preamble pulse. Therefore, the data at t ₁ and t ₂ ' are erased, and the t ₂ data is not regarded as a preamble pulse. Therefore, the data at t ₁ and t ₁ ' are erased, the t ₂ data is converted to new data at t ₁ , and the next L level time is stored as t ₁ '. below
The same steps are executed until the comparison between _t1 and _t2 , and the loop passing through step _S8 is repeated until the first determination becomes YES.

When the first judgment above becomes YES, exit from the above loop, measure and memorize t ₂ ′, and calculate t 1 ′ and t ₁ ′.
Compare t ₂ ′ in the same way as above. Determine whether a predetermined relationship is satisfied by this comparison,
If the determination is NO, t ₁ and t ₁ ' are deleted, t ₂ and t ₂ ' are converted to new _t 1 and t ₁ ', and the process returns to the measurement of t ₂ in the previous loop. The same steps are executed until the comparison between t ₁ ' and t ₂ ', and the loop passing through steps S ₁₂ and S ₁₃ is repeated until the second determination becomes YES.

When the second determination becomes YES, the loop is exited, t ₃ is measured and stored, and t ₂ and t ₃ are compared in the same manner as described above. This comparison determines whether a predetermined relationship is satisfied, and this third
If the determination is NO, t ₁ , t ₁ ′, t ₂ , t ₂ ′ are deleted, t ₃ is converted to new t ₁ data, and then the process returns to the measurement of t ₁ ′. Thereafter, until the comparison between _t2 and _t3, the loop passing through step _S17 is repeated until the third determination becomes YES.

After exiting the last loop, the three successive pulses are recognized as preamble pulses, the preamble pulse detection and recognition step is completed, and the process proceeds to the next step.

Note that although the above example shows the detection and recognition of preamble pulses for signals during playback driving, detection and recognition of preamble pulses can also be performed during queue and review driving by executing the same flowchart. I can do it.

Further, in the above embodiment, the address code analysis result is displayed on the display device, but
The analysis results may be input to a mechanism control device that controls the tape transport system to an arbitrary state.

Furthermore, in the above example, since the address code is recognized by the leading preamble pulse, there is a risk that a signal other than a preamble pulse may be detected and recognized as a preamble pulse if the same period continues for three or more waves. However, it is possible to determine whether this is true or false by analyzing the signals after this pseudo signal.

As an example, when a preamble pulse is detected, the average period of three preamble pulses is calculated, and the address code is configured such that there is 7 bits of data between each of the three preamble pulses before and after the preamble pulse. If the subsequent preamble pulse is not recognized even after 7 x 〒 time has elapsed, it is assumed that the detected and recognized preamble pulse is a pseudo signal and not the address code, and the decoded address code is used. Make sure to reset it.

〔effect〕

As explained above, according to the present invention, since the preamble pulse is detected and recognized by mutually comparing the H level time and L level time of three successive pulses, the speed and direction of tape running are not affected. It is possible to detect and recognize preamble pulses without any interference, and to recognize address codes through the same signal processing in any of the playback, queue, and review states.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the basic configuration of the magnetic reproducing device according to the present invention, Figure 2 is a waveform diagram showing the output waveform of the A-D converter in Figure 1, and Figure 3 is an analysis of the code in Figure 1. FIG. 4 is a block diagram showing a specific example of the configuration of the device, FIG. 4 is a flowchart showing the operation of the circuit of FIG. 3, and FIG. 5 is a waveform diagram showing an example of an address code signal. 1...magnetic tape, 2...playback head, 4...
A-D changer, 5...Code analysis device, 5a...
Timer counter circuit, 5b... Time count storage circuit, 5c... Comparison calculation device.

Claims (1)

[Scope of Claim for Utility Model Registration] A means for reproducing a magnetic tape, a means for shaping the reproduced signal obtained by the reproducing means and converting it into a digital signal consisting of a pulse train, and a method for sequentially inputting and analyzing the digital signal to generate a preamble. and a means for detecting and recognizing pulses, the preamble pulse detection and recognition means comprising: H level time and L level time of three successive pulses.
means for measuring the level time; means for sequentially storing data measured by the measuring means; and mutual comparison of the H level time and L level time of three successive pulses based on the data stored in the storing means. What is claimed is: 1. A magnetic reproducing device, comprising: a comparison means for performing a preamble pulse, and detects and recognizes a preamble pulse based on a comparison result by the comparison means.