JPH0766590B2 - Magnetic recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording / reproducing apparatus, and more specifically,
Four kinds of pilot signals having different frequencies in sequence,
The present invention relates to a magnetic recording / reproducing apparatus capable of performing both standard mode and long-time mode in which recording is performed on a magnetic tape by sequentially switching each field and tracking control is performed by the pilot signal during reproduction.

(Prior Art) In a conventional magnetic recording / reproducing apparatus of this type, for example, an 8 mm video tape recorder, in a standard mode (hereinafter referred to as SP mode), a video tape is run at a standard speed and an SP having a wide head width is used. The rotary magnetic head for mode records and reproduces video signals, and in the long-time mode (hereinafter referred to as LP mode), the video tape is run at a low speed and the video is recorded by the rotary magnetic head for LP mode with a narrow head width. Record and play back signals.

With an 8 mm video tape recorder capable of both SP and LP modes, if the playback mode and the recording mode do not match, tracking control cannot be performed and noise appears on the playback screen. , It disappears as a normal screen. For this reason, it is necessary to determine whether the mode at the time of recording and the mode at the time of reproducing match, and if they do not match, it is necessary to switch the mode. It takes a relatively long period of 4 to 8 fields, and during that time, there is a problem that the playback screen is disturbed.

(Object of the Invention) The present invention has been made in view of the above circumstances, and magnetic recording capable of promptly determining whether or not the reproduction mode and the recording mode match. An object is to provide a reproducing device.

(Structure of the Invention) In order to achieve such an object, the present invention is a magnetic recording / reproducing apparatus capable of both a standard mode and a long time mode in which tracking control is performed by four types of pilot signals having different frequencies in sequence. In the first to fourth filters, each of the four types of pilot signals reproduced by the rotary magnetic head for recording and reproduction is passed, and the first to fourth detection circuits for detecting the reproduction pilot signals from each filter, respectively. The first to fourth sample and hold circuits that sample and hold the outputs of the respective detection circuits in the field cycle, and the outputs of the respective sample and hold circuits,
An A / D converter that binarizes each at a predetermined threshold value, and a determination means that determines whether or not the reproduction mode matches the recording mode based on the output of the A / D converter. It has and.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a block diagram of an embodiment of the present invention. In this embodiment, an azimuth recording type helical scan type 8 mm video tape recorder will be described. This 8 mm video tape recorder is composed of first and second rotary magnetic heads 1a and 1b for SP mode with wide head width and third and fourth rotary magnetic heads 2a and 2 for LP mode with narrow head width.
equipped with b. Incidentally, in FIG. 1, only one of the pair of rotary magnetic heads is shown for simplification.

The recording signal of the video tape T used in this embodiment is
As shown in FIG. 2, it comprises four kinds of pilot signals f _{1 to} f ₄ having different frequencies in sequence, a low frequency conversion chroma signal S1 and an FM modulated luminance signal component S2 for recording a color video signal on a video tape. , The four types of pilot signals
f ₁ ~f ₄ is recorded with cyclic every field.
The shaded portion S3 in the FM-modulated luminance signal component S2 is the FM carrier frequency shift portion corresponding to the tip of the synchronization signal and the white peak. Further, the pilot signals f ₁ and f
_As shown in FIG. 3, the frequencies of ₂ , f ₃ and f ₄ are 6.5f ₀ ,
It is set to 7.5f ₀ , 10.5f ₀ , 9.5f ₀ (f ₀ is the horizontal synchronizing frequency), and the pilot signal recorded on a track and the pilot signals recorded on both sides adjacent to each other are The frequency difference is f ₀ (16kHz), 3f ₀ (46kHz).

Next, the tracking control in the normal reproduction by the four types of pilot signals f _{1 to} f ₄ when the modes at the time of reproduction and at the time of recording are the same will be described. The reproduction outputs from the first and second rotary magnetic heads 1a and 1b or the third and fourth rotary magnetic heads 2a and 2b are amplified by the first and second head amplifiers 3 and 4, respectively, and the low-pass filter 5 produces four types. Pilot signal of
Only f _{1 to} f ₄ are taken out and given to the mixer 6. To the mixer 6, the four reference pilot signals f ₁ ~f ₄ respectively corresponding to the four kinds of pilot signals f ₁ ~f ₄ are sequentially provided from the reference pilot signal generating means 7. The mixer 6 mixes both pilot signals and forms and outputs a beat signal having a frequency difference between the two signals. Of these, the frequency f _0,3
Two types of beat signals of f ₀ have two band pass fills 8,9
Are taken out respectively.

Both beat signals are signals of a frequency difference between a pilot signal recorded on a certain video track and pilot signals recorded on adjacent video tracks on both sides of the video track. For example, as shown in FIG. 4, a pilot signal f having a frequency of 6.5f ₀ is recorded on a video track traced by the first and second rotary magnetic heads 1a and 1b or the third and fourth rotary magnetic heads 2a and 2b. _{When 1} is recorded, the video tracks adjacent to both sides of it are 7.
Since the pilot signals f ₂ and f ₄ having frequencies of 5f ₀ and 9.5f ₀ are recorded, the frequencies of both beat signals are f ₀ and 3f, respectively.
It becomes ₀ .

Both beat signals from both band pass filters 8 and 9 are given to the switching circuit 10. Since both beat signals have the opposite phases of advance and polarity of sending in each field, the switching circuit 10 outputs the polarities alternately in response to the head switching pulse for each field. The output from the switching circuit 10 is rectified by the first and second rectifying circuits 11 and 12 and given to the comparator 13.

If the output levels of the first and second rectifier circuits 11 and 12 are equal, then the first
1, 2nd or 3rd, 4th rotating magnetic heads 1a, 1b or 2a, 2b
Are tracing the video track correctly, and if they are not equal they are not. The output of the comparator 13 corresponding to this tracking state is given to a servo circuit (not shown) and tracking control is performed so that the output levels become equal. Such tracking control is similar to the conventional one.

The 8 mm video tape recorder of this embodiment is configured as follows in order to determine whether or not the reproduction mode matches the recording mode.

That is, the reproduced four types of pilot signals f ₁ to
First to fourth bandpass filters that respectively pass f ₄
14 ₁ to 14 _4, the reproduced pilot signal f ₁ first to fourth detection circuit for detecting ~f ₄ respectively 15 _{1-15 4} from each band-pass filter 14 ₁ to 14 _4, the detection circuits 15 ₁ ~ First to fourth sample and hold circuits 16 _{1 to} 16 _{4 which} sample and hold the output of 15 ₄ at predetermined timings in response to gate pulses.
And the A / D converter 18 ₁ that converts the output of each sample and hold circuit 16 _{1 to} 16 ₄ into a digital signal, and the playback mode based on the output of this A / D converter 18 ₁ It is provided with a discriminating means 19 ₁ for discriminating whether or not they match with each other in a field unit as described later.

Each detection circuit 15 ₁ to 15 ₄ is connected to each bandpass filter 14 _{1 to} 14 ₄
Each of the reproduced pilot signals f _{1 to} f _{4 from} is rectified and peak-detected to obtain a DC voltage. Each sample-hold circuit 16 _{1 to} 16 ₄ uses a gate pulse corresponding to the central timing in one field period to detect each detection circuit.
Sample and hold the outputs of 15 ₁ to 15 ₄ . A / D
The converter 18 ₁ converts the analog signal from each of the sample and hold circuits 16 _{1 to} 16 ₄ into a digital signal in response to the head switching pulse. The discriminating means 19 ₁ to which the output of the A / D converter 18 ₁ is given is composed of, for example, a microcomputer. Based on the digital signal from the A / D converter 18 ₁ , the discrimination means 19 ₁ discriminates in field units whether or not the reproduction mode matches the recording mode, as will be described later. Output a discrimination signal.

Next, the operation of the 8 mm video tape recorder having the above configuration will be described.

First, the operation when the reproduction mode and the recording mode match will be described with reference to FIGS. 5 and 6. FIG. 5 shows the case where the signal recorded in the LP mode is reproduced in the LP mode.

5 (A) is a tape pattern, FIG. 5 (B) is a head switching pulse, and FIGS. 5 (C) to (F) are reproductions output from the _first to fourth band pass filters 14 _{1 to} 14 _4. The pilot signals f _{1 to} f ₄ and FIG. 5 (G) show the outputs of the A / D converter 18 ₁ , respectively, and FIG. 6 shows the detection circuits 15 ₁
15 ₄ and a waveform diagram for explaining the operation of the sample-and-hold circuits _161-164, in the FIG. 6, is representatively shown for the first pilot signal f _1, FIG. 6 (A ) is reproduced pilot signal output from the Figure 5 (C) the first identical bandpass filters 14 ₁ described above, FIG. 6 (B) is first output of the detection circuit 15 _1, FIG. 6 (C) Is the first
The outputs of the sample and hold circuit 16 ₁ are shown.

In the tape pattern of FIG. 5 (A), the horizontal axis represents time, the vertical axis represents the amount of tape movement (distance), and the shaded area represents the locus of the head.

The third and fourth rotary magnetic heads 2a and 2b for LP mode corresponding to the respective channels (ch-1 and ch-2) are alternately switched in response to the head switching pulse to perform reproduction. If the playback mode and the recording mode match, the pilot signal is f ₁ → f ₂ → f ₃ → f ₄ → f ₁
→ f ₂ ... are played in order. At this time, from the bandpass filter 14 ₁ to 14 ₄ are respectively output as shown in reproduced pilot signal f ₁ ~f ₄ is FIG. 5 (C) ~ (F), for example, FIG. 6 (A) The reproduction pilot signal f ₁ from the _first bandpass filter 14 ₁ shown in FIG. 5 (C) is detected by the first detection circuit 15 ₁ as shown in FIG. 6 (B), Further, the sample and hold is performed as shown in FIG. 6C at the timing corresponding to the center of the field. The output of the first sample hold circuit 16 ₁ is converted into a digital signal by the A / D converter 18 ₁ with the level L as the reference conversion level. Other bandpass filters
14 _{2-14 4} reproduced pilot signal f ₂ ~f ₄ from also processed in the same manner, respectively.

In this way, when the reproduction mode and the recording mode match, the output of the A / D converter 18 ₁ in each field, that is, the four modes, as shown in FIG. One of the parallel data is always "1".

Next, the operation when the reproduction mode and the recording mode do not match will be described with reference to FIGS. 7 and 8.

FIGS. 7 (A) to (F) correspond to FIGS. 5 (A) to (F), respectively, and FIGS. 8 (A) to (C) correspond to FIG. 6 (A).
To (C) respectively.

FIGS. 7 and 8 show the case where the signal recorded in the LP mode is reproduced in the SP mode. In this case, if the width of the video track is narrow, the head width is wide.
Tracing is performed by the first and second rotating magnetic heads 1a and 1b for SP mode. Therefore, each bandpass filter 14 ₁
It reproduced pilot signal f ₁ ~f ₄ from to 14 ₄ become as shown in FIG. 7 (C) ~ (F), for example, FIG. 8 (A) (FIG. 7 (C) the same as) reproduced pilot signal f ₁ from the first band-pass filter 14 ₁ shown in is detected as shown in FIG. 8 (B), further, is sampled and held as shown in FIG. 8 (C) . The output of the sample hold circuit 16 ₁ is converted into a digital signal by the A / D converter 18 ₁ with the level L as the reference conversion level. Reproduced pilot signals f _{2 to} f ₄ from the other band pass filters 14 _{2 to} 14 ₄ are processed in the same manner.

When the mode at the time of reproduction does not match the mode at the time of recording as described above, the output of the A / D converter 18 ₁ in each field, that is, the four modes as shown in FIG. 7 (G). Two of the parallel data are always "1".

Therefore, as is clear from FIG. 5 (G) and FIG. 7 (G), the determination means is based on the output of the A / D converter 18 _1.
In 19 _1, in a short period of every field, so that you can determine whether or not the mode at the time of reproduction it is matched to the mode at the time of recording. If the result of the determination is that they do not match, the mode is immediately switched to match.

In the above-described embodiment, the case where the signal recorded in the LP mode is reproduced in the SP mode has been described, but it is needless to say that the same judgment can be made when the signal recorded in the SP mode is reproduced in the LP mode. .

As described above, according to the present invention, in the magnetic recording / reproducing apparatus capable of both the standard mode and the long time mode in which the tracking control is performed by the four kinds of pilot signals having different frequencies in sequence, the recording / reproducing is performed. First to fourth filters for respectively passing the respective four types of pilot signals reproduced by the rotary magnetic head for use in the same, first to fourth detection circuits for respectively detecting reproduced pilot signals from the respective filters, and respective detections First to fourth sample-and-hold circuits that sample and hold the output of each circuit in the field cycle, an A / D converter that binarizes the output of each sample-and-hold circuit with a predetermined threshold, and this A / D converter Since it is provided with a discriminating means for discriminating whether or not the reproduction mode matches the recording mode based on the output of the D converter,
Whether or not the mode at the time of reproduction and the mode at the time of recording match can be determined in an extremely short period of a field unit.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a frequency distribution of a recording signal, and FIG. 3 is a pilot signal f ₁
Fig. 4 shows the frequency distribution of ~ f ₄ , Fig. 4 shows the trace state of the rotary magnetic head, and Fig. 5 shows the tape pattern and signal waveforms when the reproduction mode and the recording mode match. 6 and 6 are signal waveform diagrams when the reproduction mode and the recording mode match, and FIG. 7 shows the tape pattern when the reproduction mode and the recording mode do not match. FIG. 8 is a signal waveform diagram when the reproduction mode and the recording mode do not match. 14 _{1 to} 14 ₄ ... 1st to 4th bandpass filters, 15 ₁ to 15 ₄
...... First to fourth detection circuits, 16 _{1 to} 16 ₄ ...... First to fourth sample and hold circuits, 18 ₁ ...... A / D converter, 19 ₁ ...... Discrimination means.

Claims (1)

[Claims] 1. A magnetic recording / reproducing apparatus capable of performing both a standard mode and a long-time mode in which tracking control is performed by four kinds of pilot signals having different frequencies in sequence, wherein the reproducing is performed by a rotary magnetic head for recording / reproducing. First to fourth filters that pass each of the four types of pilot signals, first to fourth detection circuits that detect the reproduced pilot signals from each filter, and sample and hold of the outputs of each detection circuit at field periods First to do
A fourth sample-and-hold circuit, an A / D converter that binarizes the output of each sample-and-hold circuit with a predetermined threshold value, and a playback mode is recorded based on the output of this A / D converter. And a discriminating means for discriminating whether or not the time mode matches.