JPH04373379A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To surely drive out the noise, which is generated at the time of reproducing a still picture, to the vertical blanking period. CONSTITUTION:The magnetic recording and reproducing device where the video signal recorded on a magnetic tape is reproduced as a still picture and the stopped magnetic tape is driven at a low speed in a prescribed direction to drive out the noise to the vertical blanking period is provided with a frequency generator(FG) 8 attached to a capstan motor 7 and a counting circuit 10 which counts a prescribed number of output pulses of the FG 8, and the extent of driving at a low speed is controlled based on the counted value of the counting circuit 10 to always try to feed the tape by a certain extent, thus surely driving out the noise to the vertical blanking period.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus designed to force noise generated during still image reproduction into a vertical blanking period or its vicinity.

0002

2. Description of the Related Art In a helical scan VTR that forms a recording track that is inclined with respect to the longitudinal direction of a tape, one field of video signal is formed on one recording track, so playback is output while the tape is stopped. can be obtained. In this still image reproduction, the noise band generated due to the scanning locus being different from the recording can be forced into the vertical blanking period by changing the tape stop position. That is, it is possible to prevent noise from occurring in the still image reproduction image.

One method for eliminating this noise is to drive the tape at low speed, and when the timing of the noise during playback and the pulse indicating the vertical blanking period coincides,
There is something that stops the tape from running. (For example, see Japanese Patent Application Laid-open No. 104282/1982).

In this method, when driving the noise into the vertical blanking period, a certain amount of drive pulses are output,
A configuration is adopted in which the magnetic tape is driven at low speed.

[0005]

However, in the case of the above-mentioned configuration, when the load applied to the capstan motor is always constant, the amount of drive to drive the magnetic tape is approximately constant, and stable low-speed drive is achieved. When the load changes due to variations in the capstan motor, tape type, humidity, etc., the amount of drive will not be constant, causing problems such as the magnetic tape being fed too much or not being fed at all. Vertical blanking eliminates noise. There is a risk that it takes too much time to fill in the vertical blanking period, or that the noise cannot be correctly pushed into the vertical blanking period, resulting in noise remaining on the playback screen.

[0006]

[Means for Solving the Problems] Therefore, in the present invention, a frequency generator (hereinafter referred to as FG) attached to a capstan motor and a counting means for counting a predetermined number of output pulses of the FG (hereinafter referred to as FG pulses) are provided. The driving amount when driving the magnetic tape at low speed is controlled based on the count value of the FG pulse.

[0007]

[Operation] Therefore, according to the present invention, since the drive amount when driving the magnetic tape at low speed is controlled based on the count value of the FG pulse, it is possible to try to feed the tape at a substantially constant rate regardless of load fluctuations. can.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram of the embodiment, and FIG. 2 is a waveform diagram of each part for explaining the operation.

In FIG. 1, 1 is an input terminal to which a reproduced video signal b is connected, 2 is an input terminal to which a head switching (RF.SW) signal c having a predetermined phase relationship with the reproduced video signal is connected, and 3 is an input terminal to which a head switching (RF.SW) signal c having a predetermined phase relationship with the reproduced video signal is connected. This is a noise detection circuit that detects noise from a reproduced video signal and outputs a detection pulse d having a predetermined pulse width. 4 is a reference pulse generating circuit which outputs a pulse e having a predetermined width corresponding to the vertical blanking period from the falling timing of the head switching signal.

A comparison circuit 5 detects that the timings of the output of the noise detection circuit 3 and the output of the reference pulse generation circuit 4 do not match, and outputs a mismatch detection signal f. 6 is a drive pulse generation circuit that generates a drive pulse to drive the capstan motor 7 at low speed only when the mismatch signal f is input from the comparator circuit 5;
A driving pulse g is generated in synchronization with the rising edge of , and the generation period of the driving pulse is controlled by the output i of a counting circuit, which will be described later.

Reference numeral 8 denotes an FG that is attached to the capstan motor 7 and outputs FG pulses in accordance with the rotation of the capstan motor 7. Reference numeral 9 indicates that the above-mentioned
This is a gate circuit that supplies G pulse h. A counting circuit 10 counts the FG pulses immediately after the drive pulse of the drive pulse generation circuit 6 is input, and supplies a reset signal i to the drive pulse generation circuit 6 when the FG pulse reaches a predetermined value.

Next, the noise drawing operation will be explained based on FIG. 2. When still image reproduction is instructed during reproduction of the VTR, the still image reproduction start signal a rises to the H level, and tape running is temporarily stopped (not shown). At this time, the positional relationship between the recorded tracks on the magnetic tape and the rotary head is arbitrary, and therefore the noise in the reproduced video signal also has an arbitrary phase positional relationship, as shown in FIG. 2b.

In this case, the noise d detected by the noise detection circuit 3 does not match the signal e in the vertical blanking period output from the reference pulse generation circuit 4, and therefore the comparison circuit 5 outputs a mismatch signal f. do. As a result, a drive command is given to the drive pulse generation circuit 6, and the drive pulse generation circuit 6 generates the drive pulse g in synchronization with the rise of the head switching signal. This driving pulse g drives the capstan motor 7 at a low speed, sets one side of the gate circuit 9 to H level, and resets the count value of the counting circuit 10.

Therefore, the FG pulse h is output from the FG 8 attached to the capstan motor 7 and is supplied to the counting circuit 10 via the gate circuit 9. Counting circuit 1
0, this FG pulse h is counted, and when it reaches a predetermined value set in advance, a reset signal i is supplied to the drive pulse generation circuit 6.

Upon receiving this reset signal i, the drive pulse generation circuit 6 stops generating the drive pulse g, and stops the capstan motor 7. As a result, the magnetic tape is always driven at a low speed by a certain amount. Therefore, the positional relationship between the tracks on the magnetic tape and the rotating head changes slightly,
The position of noise in the reproduced video signal b also changes slightly. At this time, the noise detected by the noise detection circuit 3 has a positional relationship as shown in FIG.
Since the discrepancy signal f is outputted from , the magnetic tape is driven at a lower speed.

When the position of the noise in the reproduced video signal b is successively moved by repeating the above operations and reaches the position shown in FIG. The discrepancy signal f is not output, and the magnetic tape remains stopped at this position. At this time, the noise d'' does not appear in the reproduced image because it is in the vertical blanking period.

In this embodiment, noise is detected by the noise detection circuit 3 and the noise is automatically pushed into the vertical blanking period. It may be configured so that the period is forced into the vertical blanking period.

[0018]

Therefore, according to the present invention, since the drive amount during low-speed drive is controlled based on the count value of FG pulses, variations in the capstan motor, tape type,
Approximately constant tape feeding can be attempted regardless of load fluctuations caused by humidity, etc., thereby making it possible to reliably drive noise into the vertical blanking period at a desired time.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram of each part showing the operation of the embodiment.

[Explanation of symbols]

3 Noise detection circuit 4 Reference pulse creation circuit 5 Comparison circuit 6 Drive pulse generation circuit 9 Gate circuit 10 Counting circuit

Claims (1)

[Claims] 1. A magnetic recording and reproducing apparatus that reproduces a still image from a video signal recorded on a magnetic tape and drives the stopped magnetic tape at low speed in a predetermined direction to drive noise into a vertical blanking period, comprising: a capstan motor; and a counting means for counting a predetermined number of output pulses of the frequency generator, and controlling the amount of drive during the low-speed drive based on the counted value. Magnetic recording and reproducing device.