JPH0744936A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a malfunction in searching by detecting running speed of a tape from a reel rotation signal generator and surely judging kind of a marker when envelope detection and label section at the time of starting the searching exist. CONSTITUTION:A signal recorded on a tape is read by a reproducing head 1, and is amplified by a reproducing amplifier 2, and envelope component is extracted by an envelope detection circuit 3. The period of the output signal of the reel rotation signal generator 4 is measured by a period measuring means 5 to be stored in a period holding means 6. By a first tape speed detection means 7, the output of the period measuring means 5 is compared with the output of the period holding means 6, and the running speed of the tape is obtained. By a second tape speed detection means 8, the running speed of the tape is obtained from the output of the envelope detection circuit 3. By a time constant setting means 9, any one side output of the first tape speed detection means 7 and the second tape speed detection means 8 is selected, and the time constant of the envelope detection circuit 3 is set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for detecting an envelope waveform of a signal intermittently recorded on an auxiliary track of a tape and performing a search.

[0002]

2. Description of the Related Art In recent years, a PCM signal recording / reproducing apparatus called DCC (Digital Compact Cassette Tape Recorder) has been developed which records an audio signal in a digital system by using a mechanism of a compact cassette tape recorder which has been widely spread. By the signal recorded intermittently on the auxiliary track, by measuring the running time of the tape, changing the cycle of the signal recorded intermittently, and using it as a marker at the start point of the song or a marker to invert the tape, It is possible to search at high speed.

A conventional magnetic recording / reproducing apparatus will be described below with reference to the drawings. FIG. 3 is a block diagram of a conventional magnetic recording / reproducing apparatus. In FIG. 3, 1 is a reproducing head for reproducing the signal recorded on the tape, 2 is a reproducing amplifier for amplifying the output signal of the reproducing head 1, and 3 is an envelope for detecting the output signal of the reproducing amplifier 2 and outputting an envelope signal. Detection circuit, 15 is search speed setting means, 14
Is a motor drive circuit for driving the reel motor 13 at the speed set by the search speed setting means 15, and 9 sets the time constant of the envelope detection circuit 3 based on the speed set by the search speed setting means 15. Time constant setting means, 16
Is a label length detecting means for measuring the time when the output signal of the envelope detection circuit 3 is at a high level and obtaining the label length based on the speed set by the search speed setting means 15.

FIG. 4 is a diagram showing a signal waveform of an auxiliary track of a tape at the time of search. (1) is a normal recording portion, and a portion with a signal and a portion without a signal are periodically repeated (hereinafter referred to as normal). Called a frame). (2) is a portion in which a marker is recorded (hereinafter referred to as a label section). At the beginning of the song, a continuous signal, which is called a start marker and has a length 64 times that of a normal frame, is recorded. At the end of the A side of the tape, a continuous signal called a reverse marker having a length 128 times that of a normal frame is recorded. In the DCC search, the length of the label section is measured and the tape running control is performed.

The operation of the magnetic recording / reproducing apparatus configured as described above will be described below. In FIG. 3, the motor drive circuit 14 drives the reel motor 13 at the speed set by the search speed setting means 15 to run the tape at high speed. On the other hand, the signal read from the tape by the reproducing head 1 is amplified by the reproducing amplifier 2 and only the amplitude component thereof is detected by the envelope detecting circuit 3, and the label length detecting means 16
Then, the time in the high level section of the envelope signal is measured, the label length is obtained based on the speed set by the search speed setting means 15, and the marker type is determined. The characteristic of the envelope detection circuit 3 is the search speed setting means 15
It is determined by the time constant setting means 9 based on the speed set in.

[0006]

However, in the above-mentioned conventional configuration, since the tape traveling speed is not known during acceleration such as at the start of the search, the characteristic of the envelope detection circuit 3 is set by the time constant setting means 9. The optimum value could not be set for the current traveling speed, and the envelope waveform could be erroneously detected. Furthermore, even if there is a label section during acceleration, since the traveling speed changes, there is a problem that the label length cannot be obtained from the time of the high level section of the envelope signal to determine the marker type. It was

The present invention solves the above-mentioned problems of the prior art. The envelope detection at the start of search and the determination of the marker type when there is a label section during acceleration are performed reliably, and the search operation is performed without malfunction. It is an object of the present invention to provide a magnetic recording / reproducing device that can be used.

[0008]

According to a first aspect of the present invention, there is provided a magnetic recording / reproducing apparatus including a reproducing head for reading a signal recorded on a tape, a reproducing amplifier for amplifying the signal of the reproducing head, and an output of the reproducing amplifier. An envelope detection circuit for extracting an envelope component from the signal, a reel rotation signal generator for generating a signal according to the number of rotations of the reel, a cycle measuring means for detecting a cycle from an output signal of the reel rotation signal generator, From the output of the envelope detection circuit, the cycle holding means for holding the cycle detected by the cycle measuring means, the first tape speed detecting means for comparing the outputs of the cycle measuring means and the cycle holding means to detect the running speed of the tape. Second tape speed detecting means for detecting the running speed of the tape;
And a time constant setting means for setting the time constant of the envelope detection circuit from the output of either one of the second tape speed detecting means.

According to another aspect of the magnetic recording / reproducing apparatus of the present invention, the counter for counting the output signal of the reel rotation signal generator while the output signal of the envelope detection circuit is at a high level, the output of the cycle holding means and the counter. The first label length detecting means for detecting the label length from the output and the second label length detecting means for detecting the label length from the output of the envelope detection circuit are provided.

[0010]

The magnetic recording / reproducing apparatus of the present invention travels at a constant speed before shifting to the search operation, finds the cycle of the reel rotation signal generator by the cycle measuring means, and stores the value in the cycle holding means. Next, during the search operation and during acceleration, the cycle of the reel rotation signal generator measured by the cycle measuring means is compared with the cycle stored in the cycle holding means, and the tape speed is obtained by the first tape speed detecting means. This makes it possible to reliably perform envelope detection even during acceleration. Also,
When the tape speed is stable, the tape speed is obtained from the output signal of the envelope detection circuit by the second tape speed detection means, and the time constant of the envelope detection circuit is set by the time constant setting means, so that the envelope detection is surely performed. It is possible.

Further, during acceleration, while the envelope signal is at a high level, the number of output signals of the reel rotation signal generator is counted by the reel rotation signal generator counter, and the cycle holding means is provided by the first label length detecting means. By obtaining the label length by multiplying it by the cycle stored in, it is possible to accurately determine the marker type even during acceleration. If the tape speed is stable, the second label length detecting means compares the period of the envelope signal before the label section with the time of the label section from the output signal of the envelope detection circuit to obtain the label length, thereby obtaining the marker length. It is possible to accurately determine the type of.

[0012]

1 is a block diagram showing the structure of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention. In the figure, the reproducing head 1, the reproducing amplifier 2, the envelope detecting circuit 3, and the time constant setting means 9 are the same as those in the conventional example, and the description of those parts will be omitted. The reel rotation signal generator 4 generates a signal according to the number of rotations of the reel, and the cycle measuring means 5 measures the cycle of the reel rotation signal generator 4. The cycle holding means 6 stores the cycle measured by the cycle measuring means 5. The first tape speed detecting means 7 compares the output of the cycle measuring means 5 and the output of the cycle holding means 6 to obtain the running speed of the tape. The second tape speed detecting means 8 obtains the tape running speed from the output of the envelope detection circuit 3. The time constant setting means 9 may be the first tape speed detecting means 7 or the second tape speed detecting means 7.
The time constant of the envelope detection circuit 3 is set by the output of the tape speed detection means 8.

The operation of the magnetic recording / reproducing apparatus configured as described above will be described below. Before shifting to the search operation, the tape is run at a constant tape running speed, for example, the tape running speed during reproduction, and the period measuring means 5 measures the time between the rising edge or the falling edge of the output signal of the reel rotation signal generator 4. The number of times is measured, and the measured value is stored in the cycle holding means 6.

Next, after shifting to the search operation, the period measuring means 5 measures the time between the same number of edges as the period is measured at a constant traveling speed, and compares it with the period stored in the period holding means 6. To do. Since the tape position is almost the same before and after the shift of the search operation, the tape winding diameter is almost the same, and the cycle ratio of the cycle holding means 6 and the cycle measuring means 5 after the shift of the search operation becomes the speed ratio. If the speed before shifting to the operation is the speed at the time of reproduction, the period ratio obtained above becomes the tape running speed immediately after shifting to the search operation.

The time constant of the envelope detection circuit 3 is set by the time constant setting means 9 from the speed obtained by the first tape speed detecting means 7. Since the speed changes greatly during the tape acceleration, the above operation is repeated and the envelope detection circuit 3 is operated by the time constant setting means 9 so that the envelope detection circuit 3 always operates in an optimum state with respect to the running speed. Set the time constant of.

After the change in the measured value of the period measuring means 5 is reduced to be within a certain range and the tape running speed is stabilized, the period is measured from the output signal of the envelope detection circuit 3. The cycle of the envelope at the time of reproduction is a constant value, the tape running speed is obtained by the second tape speed detecting means 8 from the cycle ratio at the time of reproducing and after the tape running is stabilized, and the time constant setting means 9 is used for the envelope detection circuit 3. Set the time constant.

As described above, according to this embodiment, the cycle measuring means 5 travels at a constant speed before shifting to the search operation.
Then, the cycle of the reel rotation signal generator 4 is obtained, the value is stored in the cycle holding means 6, and the cycle of the reel rotation signal generator 4 measured by the cycle measuring means 5 and the cycle are held during the search operation and acceleration. The tape speed is calculated by the first tape speed detecting means 7 by comparing with the cycle stored in the means 6, and when the tape speed is stabilized, the tape is detected by the second tape speed detecting means 8 from the output signal of the envelope detection circuit 3. By obtaining the speed and setting the time constant of the envelope detection circuit 3 by the time constant setting means 9, it is possible to reliably perform envelope detection even during acceleration.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing the configuration of a magnetic recording / reproducing apparatus according to the second embodiment of the present invention. In the figure, a reproducing head 1, a reproducing amplifier 2,
The envelope detection circuit 3, the reel rotation signal generator 4, the cycle measuring means 5, the cycle holding means 6, the first tape speed detecting means 7, the second tape speed detecting means 8 and the time constant setting means 9 are the first Same as the embodiment. The counter 10 counts the output signal of the reel rotation signal generator 4 while the output signal of the envelope detection circuit 3 is at a high level. First
The label length detecting means 11 determines the label length from the output of the cycle holding means 6 and the output of the counter 10. The second label length detecting means 12 obtains the label length from the output of the envelope detection circuit 3. The cycle change determining means 7 outputs a signal when the cycle change measured by the cycle measuring means 5 falls within a certain range. The label length detection means 18 is a cycle determination means 17
Of the first label length detecting means 11 and the second label length detecting means 11
Either one of the label length detecting means 12 is selected.

The operation of the magnetic recording / reproducing apparatus configured as described above will be described below. Description of the same parts as those in the first embodiment will be omitted, and only different points will be described. While the tape is accelerating, the output signal of the reel rotation signal generator 4 is counted by the counter 10 while the output signal of the envelope detection circuit 3 is at the high level, and the first label length detecting means 11 measures the counter 10. The label length is obtained by multiplying the value by the period stored in the period holding means 6. When the tape speed is stable, the second label length detecting means 12 compares the period of the envelope signal before the label section with the time of the label section from the output signal of the envelope detection circuit 3 to obtain the label length.

That is, while the tape is accelerating, the first label length detecting means 11 multiplies the cycle stored in the cycle holding means 6 when traveling at a constant traveling speed by the measured value of the counter 10, The label length is obtained by obtaining the time of the label section and dividing it by the reference period of the envelope signal during traveling at a constant traveling speed. If the tape speed becomes stable, the second label length detecting means 12 measures the length of the high section of the output signal of the envelope detection circuit 3, and the label of the two consecutive envelope signals is labeled by the ratio of the periods of the high section. Seeking the length.

As described above, according to this embodiment, the output signal of the reel rotation signal generator 4 is counted by the counter 10 and the first label length is detected while the envelope signal is at the high level during acceleration. The label length is obtained by multiplying the label stored in the period holding unit 6 by the unit 11,
When the tape speed stabilizes, the second label length detecting means 12 compares the period of the envelope signal before the label section with the time of the label section from the output signal of the envelope detection circuit 3 to obtain the label length, thereby accelerating. Even inside, it is possible to accurately determine the type of marker.

[0022]

According to the magnetic recording / reproducing apparatus of the present invention,
The cycle of the reel rotation signal generator obtained by traveling at a constant speed before shifting to the search operation is stored in the cycle holding means, and during the acceleration when shifting to the search operation, the current cycle of the reel rotation signal generator. And the cycle stored in the cycle holding means to obtain the tape speed, and if the tape speed stabilizes, the tape speed is obtained from the output signal of the envelope detection circuit,
By setting the time constant of the envelope detection circuit to the optimum value by the time constant setting means, the envelope detection can be reliably performed.

Further, while the envelope signal is at a high level during the acceleration of the search, the output signal of the reel rotation signal generator is counted and multiplied by the period stored in the period holding means to obtain the label length. If the tape speed is stable, the marker length can be accurately determined by comparing the period of the envelope signal before the label section with the time of the label section from the output signal of the envelope detection circuit to obtain the label length. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional magnetic recording / reproducing apparatus.

FIG. 4 is a signal waveform diagram of an auxiliary track on a tape during a search.

[Explanation of symbols]

 3 Envelope Detection Circuit 4 Reel Rotation Signal Generator 5 Cycle Measuring Means 6 Cycle Holding Means 7 First Tape Speed Detecting Means 8 Second Tape Speed Detecting Means 9 Time Constant Setting Means 10 Counter 11 First Label Length Detecting Means 12 Second label length detecting means

Claims (2)

[Claims] 1. A reproducing head for reading a signal recorded on a tape, a reproducing amplifier for amplifying the signal of the reproducing head, an envelope detection circuit for extracting an envelope component from an output signal of the reproducing amplifier, and a rotation of a reel. A reel rotation signal generator for generating a signal according to the number, a cycle measuring means for detecting a cycle from an output signal of the reel rotation signal generator, a cycle holding means for holding the cycle detected by the cycle measuring means, A first tape speed detecting means for comparing the outputs of the cycle measuring means and the cycle holding means to detect the running speed of the tape, and a second tape speed detecting means for detecting the running speed of the tape from the output of the envelope detection circuit. Means for setting the time constant of the envelope detection circuit from the output of any one of the first and second tape speed detecting means. Magnetic recording and reproducing apparatus comprising a number setting unit. 2. A counter for counting the output signal of the reel rotation signal generator while the output signal of the envelope detection circuit is at a high level, a first for detecting the label length from the output of the cycle holding means and the output of the counter. The magnetic recording / reproducing apparatus according to claim 1, further comprising label length detecting means and second label length detecting means for detecting a label length from the output of the envelope detection circuit.