JPS622383B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the position of a cassette tape mainly applied to a two-track cassette tape for audio.

Conventionally, the following method is known as a method for detecting the position of an audio cassette tape. First, for example, the audio signal shown in Figure 1A is put into a limiter amplifier and detected, thereby creating the signal shown in Figure 1B, and this signal remains at L (low) level for a predetermined period of time or longer. In this method, the tape position is detected by regarding the position as a break in the audio signal and counting the number of breaks. Part 2 is the pulse signal shown in Figure 1C by integrating the signal shown in Figure 1B,
This method detects the tape position by counting the number of pulse signals.

However, in the case of these methods, if there is a silent part in the audio signal for more than a certain period of time, this may be regarded as a break in the audio signal, or
This is not a desirable method because if there is noise at the delimitation of the audio signal, it may be assumed that it is not a delimitation.

By the way, there is a method of recording an audio signal on the first track of the two tracks of a cassette tape, and recording information regarding the tape position on the second track. In this method, for example, a 1KHz AC signal (numbers 1 and 2 in Figure 2) is placed on the second track corresponding to the audio signal on the first track (numbers 1 and 2 in Figure 2).
4), detecting and rectifying this AC signal to convert it into a pulse signal (FIG. 2B), and detecting the track position by counting this pulse signal.

However, this method has the disadvantage that if the pulse signal count deviates for some reason, the tape must be returned to its initial position and then counted again.
It also had the drawback of not being able to write information (related to audio signals).

In view of these circumstances, the present invention provides a method for detecting the position of a cassette tape in which information regarding the tape position is recorded on the second track, which allows a desired tape position to be detected at all times, and also enables writing of various information on the second track. Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3A is a diagram showing an audio signal being recorded on the first track of the tape. here,
A series of audio signals indicated by symbols A ₁ to _{A 6} is referred to as an audio signal unit, and a set of audio signal units indicated by symbols B ₁ to _{B 3} is referred to as an audio signal block. In this case, the audio signal unit does not correspond to a so-called sentence, but is a unit equivalent to a sentence. Therefore, the audio signal units A ₁ to _{A 6} naturally include portions where the audio is interrupted. Furthermore, the audio signal units A ₁ -A ₆ and the audio signal blocks B ₁ -B ₃ are each arbitrarily set by the producer of this tape.

FIG. 3B is a diagram showing various information recorded on the second track in response to the audio signal shown in FIG. 3B. In this figure, H ₁ and H ₂ are discrimination signals, and a 1 KHz AC signal is written for 300 msec (in the "PLAY" state of the tape). In addition, the information areas BS ₂ and BS ₃ contain the block numbers of the audio signal blocks B ₂ and B ₃ , respectively, and the audio signal unit A ₁ included in each audio signal block B ₂ and B ₃ .
~A ₆ numbers are written, information area AS ₁ ~ _{AS 6}
The unit numbers of the audio signal units A ₁ to A ₆ are respectively written in the . In this case, the information areas AS ₁ to AS ₆ are located corresponding to the audio signal units A ₁ to A ₆ , and the discrimination signal H ₁ and the information area BS ₂ are located corresponding to the audio signal blocks B ₁
and _B2 , the discrimination signal _H2 and the information area _BS3 are located between the audio signal blocks _B2 and _B3 . The tapes shown in Figure 3 A and B are as follows:
When in "PLAY" and when fast forwarding, the arrow shown in the figure
It feeds in the Y ₁ direction, and when rewinding, it feeds in the Y ₂ direction.

Next, the code format of the information (block number, unit number, etc.) recorded in the information areas BS ₂ , BS ₃ and AS ₁ to _{AS 6} will be explained.

FIG. 4 is a diagram showing the above code format. As shown in the figure, in this format, both the "1" signal and the "0" signal are expressed as a set of H (high) level and L (low) level. It can be done. However, in the case of a "1" signal, the ratio of the H level time t ₁ to the L level time t ₂ is 2:1, and in the case of a "0" signal, the ratio of the H level time t ₃ to the L level time t The ratio with ₄ is 1:2. Note that t ₁ = t ₄ and t ₂ = t ₃ . Further, in FIG. 4, the tape advances in _{the three} directions of arrow Y (at the time of "PLAY"). Furthermore, when the signal shown in FIG. 4 is actually written on the tape, a 1 KHz AC signal is written when the signal is at H level, and no signal is written when it is at L level.

Further, the time t ₂ (=t ₃ ) is 10 msec (in the “PLAY” state). This is because when the signal shown in FIG. 4 is read out and processed by, for example, a microcomputer, it is desirable that the signal has a time width of at least 5 to 10 msec.

When reading a signal written in such a format, first count up the time _t1 using an up/down counter, and
Next, after counting down the time _t2 and resetting the counter at the rising edge of time _t3 ,
The time _t3 is counted up, the time _t4 is counted down, the counter is reset at the rising edge of the time _t5 , and the time is counted up, and so on. If the count output immediately before resetting the counter is positive, it is determined to be a "1" signal, and if it is negative, it is determined to be a "0" signal.

In this way, according to this code format, a "1" signal or a "0" signal is determined based on the time ratio, so there is no need for a clock signal, and even if the tape speed changes, there is no error. The advantage is that the signal can be detected. In addition, time t ₁ and
The ratio with t ₂ or the ratio between times t ₄ and t ₃ does not necessarily have to be 2:1. In short, it is sufficient to obtain a certain discrimination ratio according to the degree of redundancy of reading. However, 2:
By setting it to 1, it is possible to sufficiently cope with changes in speed of the tape.

Here, an example of application of this code format other than magnetic tape will be explained. For example, information such as characters and figures may be printed on the front side of a paper roll, and data corresponding to the information on the front side may be recorded on the back side using a "black, white" code. Figure 6 shows an example of data recorded on the back side in this case.
In this figure, the shaded areas are filled in black and correspond to the H level signals shown in FIG. 4, and the white areas correspond to the L level signals. and,
Data is detected by reading the data written in these "black and white" tones using a reflective phototube or the like. In this case, attention should be paid to the start bit (symbol S in FIG. 6) and the end bit (symbol E). That is, according to this format, the start bit indicating the start position of the block is "black": "white".
A code with a ratio of 5:1 is used, and as an end bit indicating the end position of the block,
A code with a "black":"white" ratio of 1:5 is used. Note that the ratio is 1:2 or 2:1 except for the start bit and end bit. This provides the following advantages.

You can easily detect the length of the black part or the length of the white part by comparing it with those of other data, without having to take the trouble to enter a start signal or an end signal at the start position and end position of the data block. . Therefore, for example, when detecting the start position of a data block from the middle of the same data block, it can be easily detected.

If you want to stop the paper roll at a certain distance from the end position (separation of information on the surface of the paper roll), if you stop the paper roll after a certain time from the end position,
Depending on the speed of the paper roll, it may not stop at the desired position. Therefore, in this case, the length of each bit must be changed according to the length of the information on the surface of the paper roll (length of paper), thereby making the length of the information on the front side match the length of the data on the back side. It won't happen. However, according to this code format, the above-mentioned problem can be solved by extending the length of the white part of the end bit to the information section on the front surface.

Next, a position detection circuit for detecting the position of the tape shown in FIG. 3 will be explained.

FIG. 5 is a block diagram showing the configuration of the above-mentioned position detection circuit. In this figure, reference numeral 11 is a magnetic head for reading out the first track signal, and reference numeral 12 is a magnetic head for reading out the second track signal. be. For example, suppose that the audio signal shown in FIG. 15. After being detected here, the waveform is shaped by the waveform shaping circuit 16 into the waveform shown in FIG. On the other hand, the signal on the second track shown in FIG.
2 and supplied to a detection circuit 20 via an equalizer circuit 18 and a buffer and limiter amplifier 19. After being detected here, the signal is integrated by an integrating circuit 21 having a time constant of approximately 1 msec, and is supplied to a waveform shaping circuit 22.
The waveform shaping circuit 22 shapes the output of the integrating circuit 21 and supplies it to the CPU 17 as a waveform shown in FIG. 3D. The waveforms shown in FIG. 3C and D are both when the tape is in the "PLAY" state.

Next, the tape position detection operation of the circuit configured as described above will be explained. First, the operation when fast forwarding the tape will be explained. Normally, when fast forwarding or rewinding a tape, the tape speed is 10 to 30 times the speed during "PLAY", and as a result, the time t ₂ or t ₃ (=
10msec) is 0.33msec to 1msec. Therefore, the signal of the second track read in the fast-forward state is integrated by the integrating circuit 21 and further shaped by the shaping circuit 22, resulting in the signal shown in FIG. 3(E). In other words, in the fast forward state, the pulse interval of the waveform shown in Figure 3 D is 0.33 msec.
~1 msec, and this waveform is integrated by the integrating circuit 21 to become a continuous waveform. This results in
A single pulse signal is obtained corresponding to each of the information areas BS ₂ , BS ₃ , AS ₁ to _{AS 6} .

Then, the CPU 17 detects the tape position by counting the pulse signal (output of the shaping circuit 22) shown in FIG. That is, for example, when you want to read audio signal block _B3 , the third
Stop the tape when the pulse _P1 shown in Figure E is counted. Next, the tape is put into the "PLAY" state, and the pulse signal P ₂ (information area BS ₃
The tape position is confirmed by reading the block number (stored in the block number). In this case, if the tape position is deviated, the tape is fast-forwarded or rewound based on the read block number to search for the correct tape position.

Next, the operation for detecting the tape position while rewinding the tape will be described. In this case, as mentioned above, the tape speed is 10 to 10 when the tape speed is "PLAY".
Therefore, the signal shown in FIG. 3E is supplied from the waveform shaping circuit 22 to the CPU 17. Now, for example, if we want to read audio signal block _B2 , we will count the pulse signals shown in FIG. 3E while rewinding the tape. Then, when the pulse _P5 is counted, the tape is stopped, and then the tape is placed in the "PLAY" state, and the pulse signal _P4 (block number stored in the information area _BS2 ) shown in FIG. 3D is read. Check the tape position. If the tape position is deviated, the correct tape position is searched again based on the read block number.

If you want to search for audio signal units A ₁ to _{A 6} , first search for audio signal blocks B ₁ to _{B 2} using the method described above, and then fast forward to search for audio signal units A ₁ to _{A 6} . good.

By the way, in the case of the position detection method described above, the number of audio signal units A ₁ to _{A 6} included in each audio signal block B ₁ to _{B 3} is stored in advance in a storage circuit (not shown) attached to the CPU 17. Must be remembered. However, by using the signal obtained from the first track (output of the waveform shaping circuit 16; see FIG. 3C), such inconvenience can be eliminated. That is, as is clear from FIG. 3, the discrimination signals H ₁ , H ₂ and the information areas BS ₂ , BS ₃
At the time when the pulses P ₃ , P ₁ , P ₅ , and P ₆ (FIG. 3 E) respectively corresponding to are output, the audio signal shown in FIG. 3 A is not output, and the output of the waveform shaping circuit 16 is It is a “0” signal. On the other hand, _among the pulses shown in _FIG . The output becomes H level. Therefore, among the pulses shown in FIG. Even if the number of audio signal units within _B3 is not known, it is possible to detect a desired audio signal block _.

Further, in this case, the discrimination signals H ₁ and H ₂ are useful. That is, when detecting the audio signal block _B3 by rewinding, for example, it is sufficient to stop the tape when the pulse _P6 is counted, and therefore the discrimination signal _H2 (pulse _P1 ) is not necessary. On the other hand, for example by fast forwarding, the audio signal block B ₃
To detect this, assuming that there is no pulse _P1 , the tape must be stopped when pulse _P6 is counted, rewound again, and then pulse signal _P2 must be read out. But if there is a pulse P ₁ , then this pulse P ₁
Just stop the tape when you have counted .

It is also conceivable that the CPU 17 directly reads the pulse signal shown in FIG. 3D and detects the tape position based on the pulse signal shown in FIG. 3D, without creating the signal shown in FIG. 3E. However, in this case, the following problem occurs. In other words, as mentioned above, CPU1
In order for 7 to read the pulse signal shown in FIG. 3D, the pulse interval of the pulse signal needs to be approximately 10 msec. On the other hand, the maximum speed when rewinding or fast forwarding the tape is about 30 times that of the "PLAY" state. Therefore, in order for the CPU 17 to read the pulse signal shown in FIG.
(at the time of "PLAY"), and the amount of information that can be written becomes extremely small.

In addition, in FIG. 5, the time constant of the integrating circuit 21 is 1 msec as described above, and therefore, when the tape is in the "PLAY" state, it has an adverse effect on the signal obtained from the second track (FIG. 3 D). (The minimum pulse interval of the signal shown in Figure 3 D is
It is 10msec. ).

Further, if the width of the data (unit number) written in the information area AS ₁ etc. is shorter than the width of the information area AS ₁ etc., a "0" signal is written in the remaining part.

Further, the method according to the present invention
Of course, this can be applied even when B ₁ to _{B 3} are not divided into audio signal units.

As explained above, according to the present invention, block information is recorded at the position of the second track corresponding to each audio signal block recorded on the first track, and when the tape is fast-forwarded or rewound, the block information is By integrating the information, each pulse becomes a single pulse, and by counting this pulse, the tape position is detected.
The advantage is that a desired tape position can always be detected and various information can be written on the second track.

[Brief explanation of the drawing]

1 and 2 are waveform diagrams for explaining the conventional tape position detection method, FIG. 3 is a waveform diagram for explaining the method according to the present invention, and FIG. 4 is a waveform diagram for explaining the method according to the present invention. FIG. 5 is a block diagram showing the configuration of the position detection circuit in the same embodiment. FIG. 6 is a diagram showing an example of application of the code format shown in FIG. 4. 12...Magnetic head, 17...Processing unit (CPU), 21...Integrator circuit, _B1 to _B3 ...Audio signal block.

Claims (1)

[Claims] 1. A method for detecting a position of a cassette tape, in which a signal is recorded on a second track corresponding to an audio signal recorded on a first track, and a tape position is detected based on the signal recorded on the second track. Block information is recorded at the second track position corresponding to each audio signal block of one track, and when fast forwarding or rewinding the tape, each block information read by the magnetic head is integrated. A method for detecting the position of a cassette tape, characterized in that the position of the tape is detected by counting the number of pulses.