JPS637548A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the detection of the program searching of a first music, by detecting the end of a period where no recording signal exists by an envelope detection circuit, after detecting a bit of sub-code information by a sub-code detection circuit, and detecting the start position of a music. CONSTITUTION:The output of a reproducing amplifier 6 detects a start ID signal through a sub-code extraction circuit 11, and a start ID signal extraction circuit 12, etc., and is supplied to a microcomputer 14. Meanwhile, an envelope detection circuit 13 envelope-detects the output signal of the reproducing amplifier 6, and also, supplies a signal to the computer 14 only for a period where no recording of a digital signal is performed on a magnetic tape 2. The output of the reproducing amplifier 6 is processed at the envelope detection circuit 13, and is changed to a signal having a waveform which goes to an 'L' level only for a period where no recording signal exists, and it is supplied to the computer 14, and after detecting the start ID signal, it detects the trailing edge of the output signal from the envelope signal detection circuit 13. In this way, a control signal is outputted to a mechanism control circuit 15, then the program searching of the first music can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a magnetic recording and reproducing device, and particularly to a digital audio tape recorder (hereinafter simply abbreviated as DAT).
It is used for etc.

(Prior Art) Conventionally, when recording PCM signals on magnetic tape,
There is a method of combining a video tape recorder (VTR) and a PCM adapter. With this method, no special signal is recorded to determine the beginning of a song, so for example, the beginning of a song can be found while rewinding a magnetic tape.
It is extremely difficult to stop at that part or to play from the starting part.

For this reason, DAT records "1" as star ID information in a part of the subcode area during recording for a certain period of time immediately after the start of one song, and records "0" for other periods. It is suggested that you keep it. With this method, accurate cueing is possible by detecting the start ID signal, but in this case, it is necessary to clearly distinguish between the "1" part and the r01 part of the start ID signal. .

(Problem to be Solved by the Invention) However, at the beginning of the recording (i.e., the first track), before the star ID signal is recorded, the unrecorded part of the digital signal, that is, the clear start ID signal ( There is a so-called noise part where there is no =rOJ) part,
For this reason, there was a problem in that accurate cueing could not be performed.

In this case, prior to the start of recording of the first song, Star 4 ID
One possible method is to pre-record an information area with a signal of "0" (so-called zero track) on a magnetic tape, but in order to create such a magnetic tape, a high-speed winding tape is required before the recording of the first track starts. It is necessary to record the so-called zero track for a sufficient period of time so that it can be detected even when returning, which creates a new problem of impairing the speed of the recording operation.

(Means for Solving the Problems) A magnetic recording/reproducing apparatus according to the present invention records information by forming tracks on a magnetic tape using a magnetic head, or reproduces recorded information. The apparatus records subcode information indicating that it is the beginning of a song for a certain period of time after the start of the song in the subcode ID information recording area of each of the trunks, and also performs subcode detection for detecting this subcode information. circuit, and an envelope detection circuit for detecting whether or not a recording signal exists, and after the subcode detection circuit detects subcode information, the envelope detection circuit detects a period in which a recording signal is not present. The starting position of the song is detected by detecting the end of the song.

(Function) Before starting the recording of the first song, the start ID signal is
When rewinding and reproducing a magnetic tape on which no information has been recorded, even if the subcode detection circuit only obtains a signal in which the falling edge of the waveform is not detected, the subcode detection circuit detects the rising edge of the signal. Thereafter, by detecting the end of the period in which no recording signal exists using the envelope detection circuit, it becomes possible to detect the beginning of the first song.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the circuit configuration of a magnetic recording/reproducing apparatus according to the present invention.

In the figure, la and lb are magnetic heads, 2 is a magnetic tape, 3 and 4 are reels, 5 is a switch circuit, 6 is a reproduction amplifier, 7 is an equalizer circuit, 8 is a comparison circuit, 9 is a demodulation circuit, and 10 is a parity circuit. 11 is a subcode extraction circuit, 12 is a start ID signal extraction circuit, 13 is an envelope detection circuit, 14 is a microcomputer, and 15 is a mechanism control circuit.

During reproduction, the reproduction outputs from the magnetic heads la and lb are alternately switched by the switching operation of the switch circuit 5 based on the head switching signal, and are supplied to the reproduction amplifier 6. In other words, during the period when the magnetic head 1a is in contact with the magnetic tape 2,
The switch circuit 5 is switched to the a contact side, and the magnetic herad 1
During the period when b is in contact with the magnetic tape 2, the switch circuit 5
is switched to the b contact side.

The outputs of the reproduction amplifier 6 obtained in this way are output to the equalizer circuit 7 and the envelope detection circuit 13, respectively. The output of the reproduction amplifier 6 that is output to the equalizer circuit 7 is further passed through a comparator circuit 8, a demodulation circuit 9, a parity check circuit 10, a subcode extraction circuit 11, and a start ID signal extraction circuit 12, and a star ID signal is detected. and is supplied to the microcomputer 14, which is a system controller.

On the other hand, the envelope detection circuit 13 performs envelope detection on the output signal of the reproduction amplifier 6, and also performs envelope detection on the output signal of the reproduction amplifier 6.
A signal is supplied to the microcomputer 14 only during a period when no digital signal is recorded. The microcomputer 14 detects the start position of the song on the magnetic tape 2 based on the start ID signal and the signal from the envelope detection circuit 13, and controls the mechanism control circuit 15.
I? B.

Next, the operation of the magnetic recording/reproducing apparatus having the above configuration will be explained with reference to FIGS. 2 and 3.

When the playback WW mode is, for example, rewind mode, the trajectory of the magnetic helix la and lb is indicated by arrow A in FIG.

The trajectory will be as shown in B. In the figure, the arrow H indicates the rotation direction of the magnetic heads la and lb, and the arrow mark indicates the magnetic tape 2.
It shows the direction of travel. Here, TR indicates a track on the magnetic head, SC,.

SCz indicates a subcode information area.

In this way, when the magnetic healds la and lb scan the track TR on the magnetic tape 2, the output of the reproduction amplifier 6 has a signal waveform as shown in FIG. 3 (al), and the output of the reproduction amplifier 6 Parity check circuit 10 obtained by processing
The output has the waveform shown in FIG. 3(b). At this time, a star appears on the magnetic tape 2 before the recording of the first song begins)
When the information area where the ID signal is "0" (hereinafter referred to as zero track) is not recorded, the output of the start ID signal extraction circuit 12 will be a waveform with no falling edge detected as shown in FIG. 3 (dl). Signal output is microcomputer 1
4.

On the other hand, the output of the reproduction amplifier 6 supplied to the envelope detection circuit 13 is processed here to become a signal with the waveform shown in FIG. Output is microcomputer 1
4.

After the microcomputer 14 detects the start ID signal (see FIG. 3(d)), the mechanism control circuit detects the fall of the output signal from the envelope detection circuit 13 (see FIG. 3(Q)). A control signal is output to 15 to cue the beginning of the first song.

The waveform shown in FIG. 3(e) is the start ID after the second track on the magnetic tape 2, or when the zeroth track is recorded before the start of recording of the first track.
Showing a signal.

A specific circuit configuration of the envelope detection circuit 13 described above is shown in FIG. Further, FIG. 5 is an operation waveform diagram of the circuit shown in FIG. 4.

, FIG. 4, an amplified rewind playback signal S, (see FIG. 5 (al)) is input to an input terminal 30, and this signal Sl passes through a low-pass filter 16 and an amplitude detection circuit 17. This results in a signal S2 with a waveform shown in FIGS.
It becomes 3. - On the other hand, the input terminal 31 receives a head switching signal S4 for switching the switch circuit 5 (see FIG. 1).
(Fig. 5 (see [1]) is input, and this head switching signal S4 passes through the delay circuit 21 and the exclusive OR circuit 22 and is formed into the signal S with the pulse waveform shown in Fig. 5 (g). , this pulse signal S, integrator 19°23
is being initialized.

The step-like output signal Sh shown in FIG. 5 (dl) integrated by the integrator 19 is waveform-shaped by the comparator 20 based on the voltage Tb to obtain a signal S7 having the waveform shown in FIG. 5+81.

This signal S is input to the data input terminal of the D-flip-flop 25. - side, the fifth integrated by the integrator 23
The sawtooth wave output signal S shown in FIG.
A signal S9 having a waveform shown in is obtained. This signal S9 is input to the clock terminal CK of the D-flip-flop 25.

In the D-flip-flop 25, at the rising edge of the output signal S of the comparator 24, the output signal S of the comparator 20 is
The output of the envelope detection circuit 13 is obtained as the Q output S1 (see FIG. 5).

(Effects of the Invention) As described above, according to the magnetic recording/reproducing apparatus of the present invention, by using the envelope detection circuit for the reproduction output, high-speed cue reproduction based on the start ID information G can be performed. In particular, even if the first and earlier tracks on the magnetic tape are unrecorded and the start ID information cannot be detected accurately, high-speed cue playback can be easily performed. Therefore, in a digital audio tape recorder, etc., the start I before recording the first song on the magnetic tape.
It is not necessary to record signals including D information, and quick recording operations can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the main parts of the magnetic recording and reproducing apparatus of the present invention, FIG. 2 is a diagram showing tracks on a magnetic tape and an example of the locus of a rotary head during high-speed rewinding and reproducing, and FIG. FIG. 1 is an operational waveform diagram of the main parts of the circuit, FIG. 4 is a schematic block diagram showing an example of the configuration of the envelope detection circuit, and FIG.
This figure is an operation waveform diagram of the envelope detection circuit shown in FIG. 4. la, lb...magnetic head 5...switch circuit 6...playback amplifier 7...equalizer circuit 8...
・Comparison circuit 9...Demodulation circuit 10...Parity check circuit 11...Sub code extraction circuit 12...Star) ID signal extraction circuit 13...Envelope" detection port! 14...Micro Computer 15...mechanism control circuit Fig. 3 (e-no--7++-

Claims (1)

[Claims] 1) A magnetic recording/reproducing device that uses a magnetic head to form a track on a magnetic tape to record information or to reproduce recorded information, and the track remains at the beginning of a song for a certain period of time after the start of the song. Subcode information indicating this is recorded in the subcode ID information recording area of each track, a subcode detection circuit for detecting this subcode information, and an envelope detection circuit for detecting whether or not a recording signal exists. circuit, and after the subcode detection circuit detects subcode information, the envelope detection circuit detects the end of a period in which no recording signal exists to detect the start position of the song. Features of magnetic recording and reproducing device.