JPS59158179A - Still picture reproducing device - Google Patents

Abstract

PURPOSE:To decide on a noiseless state extremely stably and accurately and to obtain a still reproduction screen having no noise bar by feeding a tape at a slow speed after a pause button is operated, and stopping the tape by the output of a state detecting circuit. CONSTITUTION:The output of a head B is supplied to a noise detecting circuit 10 through a head amplifier 4 and an noise pulse is detected on the basis of a reproduced envelope. A gate pulse and the noise pulse are supplied to an AND gate 12 to detect a time coincidence between the both. When a coincidence output is generated by the AND Gate 12, a flip-flop 13 is set by the output and its output is supplied as a control signal (s) to a capstan motor control circuit 9. Thus, a slow or intermittent driving signal supplied from a control circuit 9 to a capstan motor is stopped to stop the tape. Then, noiseless still reproduction is performed until the pause button 8 is released.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a still image reproduction device.

BACKGROUND ART AND PROBLEMS In a rotating head type video tape recorder, the angle between the scanning locus of the head and the track differs when repopulating a still image, so a scanning state that crosses the track occurs, resulting in a striped pattern on the screen. A noise bar is generated. For this reason, a so-called noiseless still control is performed in which the tape is stopped at a position where it does not cross the track, thereby obtaining a still reproduced image in which no noise bar appears.

Noiseless still control is a method that stops the tape in synchronization with the playback control signal and determines the positional relationship between the track and the head without noise bars appearing.
A method is known in which a noiseless state is determined while the tape is played back slowly or intermittently, and based on the determination result, the tape is stopped and still playback is performed. Although the former method is simple, it has the problem that the timing of tape stop control is likely to go awry due to changes over time, and it also requires an expensive motor with good braking characteristics.

In Ago-Nagisa's method, since the tape enters a slow feed state before still playback, problems are unlikely to occur in timing control of the tape stop position. To determine the noiseless still state using this method, the noise signal in the reproduced signal that causes the noise bar is detected, and the point where the noise bar is hidden at the top of the screen is compared to the noise signal and the reference signal (vertical synchronization signal). A method is known in which detection is performed based on the phase relationship with the rotational phase signal of the head drum.

However, the noise signal to be detected is perceived as a lowered envelope portion of the reproduced signal or a missing portion of the reproduced signal. Furthermore, the point in time when the noise bar is in a position hidden at the top of the screen is a state in which the noise signal exists within the vertical blanking section. However, since no reproduced signal originally exists within this vertical blanking section, it is difficult to detect a noise signal, and therefore, it is actually impossible to determine a noiseless still state. Therefore, in general, the state is determined by detecting the limit point at which a noise bar appears on the screen based on the phase relationship between the noise signal and the reference signal, and after detection, the tape is advanced by a small step (for example, % track pitch). This performs tape stop control to obtain a noiseless still playback state.

Therefore, with respect to tape feeding at % track pitch, the tape stop position may be deviated due to temperature characteristics of the control circuit, changes over time of the tape drive device, etc. Also, if the tape goes too far beyond the correct stop position when feeding the tape at % track pitch, the noise signal representing the noise bar has already disappeared within the vertical blanking section, so there is no way to correct the overshoot by returning the tape. There is an inconvenience. Furthermore, the detection of the noise position immediately before the tape feed of the % track pitch is performed in the vicinity of the head switching position of the two rotating heads, so the detection is unstable and if there is a level difference between the outputs of the two heads. , causing false positives.

OBJECTS OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to determine a noiseless state extremely stably and accurately, and to obtain a still raw screen 7j without noise bars.

Summary of the Invention The still playback device of the present invention is a playback device that obtains still playback images by continuously playing back one of tracks alternately formed on a tape with first and second azimuths. , a pair of rotating heads (A, A') approximately 180° apart having the same azimuth as the first azimuth, and a pair of rotating heads (A, A') having the same azimuth as the second azimuth or different rotational phases with respect to the pair of heads. a sixth rotary head CB) having a sixth rotary head; a noise detection circuit (10) for obtaining a noise noise corresponding to a bar noise position on the screen based on the output of the sixth rotary head; A state detection circuit ((1υ(121+131)
Embodiments The present invention will be described below with reference to embodiments.

FIG. 1 is a schematic plan view of a rotary head device for a video table recorder to which the present invention is applied. The rotary head drum (11) is equipped with an auxiliary A' head in addition to the normal A head and B head. The head and the B head have gap azimuths in different directions, thereby performing so-called azimuth recording in which there is no card band between adjacent tracks.A'
The head is, for example, 1.25H (H is the drum half circumference length '1
It is provided close to the B head at an interval of 262.5 (length divided by 262.5) and has the same azimuth as the A head.

FIG. 2 is a block diagram of the main parts of a VTR including a tape stop control device showing an embodiment of the present invention, and FIG. 6 is a pattern diagram and signal waveform showing the phase relationship between the track and the head during still playback. FIG. 4 is a time chart showing the operation of the control device shown in FIG. 2.

In FIG. 2, when the pause button (8) is operated during playback, the capstan motor is controlled by the capstan motor control circuit (9), and the tape is fed slowly or intermittently. In this state, A head and B head (A'
The scanning locus of the head] is tla, 1lbf in Figure 6 A and B.
As shown here, tracks a1, bl, a2, b2...
. . ., there is a tilt error of approximately one track pitch, and reproduction is substantially performed over two tracks.

Track (al, a2, song... A head for the bend (
The "portrait" state of the A' head is best in the case shown in section τ2 in Figure 3, and the tape is stopped at this position and the A and A' heads alternately scan track a1. If the signal is scanned, a good reproduction pattern (envelope waveform) as shown in the τ2 section of FIG. 3C can be obtained. In this state, bar noise does not occur on the screen,
You can get a noiseless still screen.

On the other hand, in the section indicated by τ1 or τ3 in FIG.

6" of the head against the track is poor, A/A
'The envelope of the signal generated by the head is τ in Figure 6C.
1 or τ6, and bar noise occurs on the screen in a portion where there is substantially no reproduced signal.

To stop the tape at a “hit” or good τ2 position,
Conventionally, as described above, the noise pulse shown in Figure 3 representing the bar noise position is extracted from the reproduction envelope waveform (Fig. 6C), and this noise pulse and the pulse representing the head rotation phase (for example, Figure 6) are extracted. The state was determined by comparing the G head switching pulse R1''-8W), but in reality, there is no noise pulse in the area where the hit is good, as shown in the τ2 section of the sixth diagram, and therefore, τ1(
Alternatively, after determining the state of τ3), the tape is shifted by a small amount to shift to the state of τ2. The disadvantages of this method are as mentioned above.

Therefore, in this embodiment, A head (or A head) at τ2 is used.
'Head] is the best hit, or the portrait for B head is Figure 5B (or Figure 3E:A/
The tape stop position is controlled by paying attention to the fact that, as shown in the reproduction envelope of the B head, the worst case occurs, and a necessary noise pulse is generated as shown in FIG. 6F.

In Fig. 2, the output of each head A, A', B is transmitted through a head switching circuit (5) via a head amplifier (21+31(4)).
), the A head and the A' head (or the A head and the B head) are alternately selected according to the head switching pulse RF-8W, and are taken out as a video output through the reproduction circuit (6).

On the other hand, the noiseless still state determination circuit is configured as follows. In other words, the output of the B head is the head amplifier (
4) to the noise detection circuit QQI, and the noise pulse shown in FIG. 4C is detected based on the reproduction envelope. In addition, the head switching pulse 1%F- shown in FIG. 4A
8W is completely supplied to the gate pulse generation circuit θυ, and the gate pulse shown in FIG. 4B is formed approximately in the center of the high level B head section. This Kate pulse is the 6th
This corresponds to the noise pulse position of the B head output when the B head is in the best condition, as shown in the τ2 interval in the figure.

What is gate pulse and noise pulse? AND gate (121
is given, and a temporal coincidence between the two is detected.

When a matching output is obtained from the AND gate (121), the flip-flop (■3) is set by this output,
The output thereof is given as a control signal S to the capstan motor control circuit (9). As a result, the slow or intermittent drive signal applied to the capstan motor from the control circuit (9) is stopped, and the tape is stopped. After this, noiseless still playback is performed until the pause button (8) is released. Note that the flip-flop (13) is reset by a reset signal r generated when the pause button (8) is released.

In FIG. 2, during the slow playback period from when the pause button (8) is operated until the start of still playback, field slow playback may be performed using the A head and A' head. Frame playback may be performed using the head, and at the time of still playback, switching may be made to field still playback using the A/A' head. In the latter case, the output of the flip-flop is supplied to the head switching circuit (53) as a switching control signal. Note that there are only two transmission channels between the rotating drum and the stationary side, and therefore the A' head When switching between the A/B head and the B head is performed on a rotating drum, the A/B head is switched during slow playback before still playback.
The B head is used, and the A/A' head is used during still playback. In this case, the noise detection circuit (101 is a reproduction circuit (101)
0), and is configured to extract noise pulses based on the envelope of the B channel output of the head switching circuit (5).

Although the present invention has been described above based on embodiments, the present invention can be applied to, for example, a four-rotation head type VTR. In other words, if a sixth head is provided that differs in either rotational phase or azimuth from the A/A' head, noise pulses are detected based on the output of the third head and the noiseless still position is determined. It is possible to distinguish between

Note that if the rotational phase of the sixth head is different, even if it has the same azimuth as the A/A/head, the A/A/
8. When noiseless playback fails for the head,
Since a noise pulse corresponding to bar noise is generated in the sixth head output, the tape stop position can be controlled based on this noise pulse.

Effects of the Invention Since the present invention is configured as described above, it is possible to obtain a noise pulse corresponding to bar noise even in a noiseless still playback state, and based on this noise pulse, the tape can be stopped in a noiseless still state. Therefore, a noiseless still position can be obtained extremely stably and reliably.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of a rotary head device of a video table recorder to which the present invention is applied, and FIG. 2 is a block diagram of main parts including a tape stop control device showing an embodiment of the present invention. FIG. 6 is a pattern diagram showing the phase relationship between the track and the head during still playback, and a waveform diagram showing the signal waveform.
FIG. 4 is a time chart showing the operation of the control device shown in FIG. In addition, in the symbols used in the drawings, (1)・・・・・・・・・・・・Rotating head drum (5)・・・・・・・・・・・・Head switching circuit (6)・・・・・・・・・・・・・・・Reproduction circuit (8)・・・・・・・・・・・・・・・Pause button (9)・・・・・・・・・・・・・・・・・・・Capstan motor control circuit (10)・・・・・・・・・・・・・・・
・・・・・・Noise detection circuit aυ・・・・・・・・・
......Gate pulse generation circuit 02...
・・・・・・・・・・・・・・・And Gate Makoto・－・・
...Song...Flip-flop A, A',
B... 4. Rotating head. Agent Masaru Ueya〃 Yoshio Tsunekako〃 Toshiki Sugiura 45

Claims (1)

[Claims] In a reproducing apparatus that obtains a still reproduced image by continuously reproducing one of tracks alternately formed on a tape with first and second azimuths, the reproducing apparatus has approximately iao' having the same azimuth as the first azimuth. a pair of rotary heads spaced apart from each other, a third rotary head having the same azimuth as the second azimuth or a different rotational phase with respect to the pair of heads, and a third rotary head based on the output of the sixth rotary head. a noise detection circuit that obtains a noise pulse corresponding to the bar noise position on the screen; and a noise detection circuit that detects, based on the noise pulse, a state in which no bar noise appears on the screen when the first azimuth track is scanned with the pair of heads. A still image playback device comprising: a state detection circuit that moves the tape slowly after a pause button is operated, and then stops the tape according to an output of the state detection circuit.