Dynamic magnetic information storage or retrieval – Record editing
Patent
1987-05-08
1989-06-20
McElheny, Jr., Donald
Dynamic magnetic information storage or retrieval
Record editing
H04N 5782
Patent
active
048413810
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a still reproduction controlling circuit in a helical scan video tape recorder (VTR).
BACKGROUND ART
As the picture signals of one field are formed in one record track in a helical scan VTR for forming the record track inclined with respect to the tape longitudinal direction, thereby to obtain the reproduction output with the tape running being stopped. Also, in the still reproduction, the noise band to be caused due to the different scanning track during the recording may be driven into the vertical blanking period by means of changing the tape stop position.
Namely, it is possible to prevent the noises from being caused on the still reproduction images.
One of the noise driving methods is to stop the running operation of the tape when the noises of the reproduction output have conformed to the timing of the pulse showing the vertical blanking period through the driving operation of the tape at the low speed (for example, see Japanese Laid-Open Patent Publication Tokkaisho No. 60-12881). This method adopts the construction of detecting the envelope fall of the reproduction signal to detect the noise position.
In the helical scan VTR, normally the recording and reproducing is performed by the use of two heads which are opposite by 180.degree.. And the reproducing output from two heads is rendered continuous by the switching operation, but the head switching time-point is a portion where the head starts its contact with the tape or finishes its contact, so that the reproducing output may become unstable. When the reproducing output has been lowered in the head switching portion of the output being unstable, the error detection as the noise band is performed so that the noise driving operation may not be performed correctly. Namely, in the arrangement where the tape feeding is stopped through the coincidence with the vertical blanking period when the envelope fall portion is discriminated as the noise band, the output fall portions except for the noise bands may be detected as noise bands so that the correct noise driving operation may not be performed.
SUMMARY OF THE INVENTION
Accordingly, in the present invention, an error operation preventing means is provided, which is adapted to detect the existence of the other noises to release the tape stop, when the noises have conformed to the vertical blanking period, to cause the tape to run.
As the noise band is provided in the other portion of the reproduction output when the output fall portions except for the noise bands have been mistaken as noise bands to come to a stop if a still reproduction control circuit composed of such construction as described hereinabove is employed, the noise bands are detected to release the tape stop, the tape is again driven so that the noises may be correctly driven.
BRIEF DESCRIPTION OF THE DRAWINGS
The embodiment of the present invention will be described in accordance with the drawings.
FIG. 1 is a circuit diagram showing the embodiment of a still reproduction controlling circuit of the present invention.
FIG. 2 is a wave form chart for illustrating the circuit operation of FIG. 1.
FIG. 3 is an illustrating view showing the condition of the still reproduction of the circuit of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, (1) is an input terminal upon which the AGC control voltage of the FM brilliance signal system is applied, (2) is an input terminal of a head change-over (RFSW) signal, (3) is an output terminal of a motor driving signal to be applied onto the drive controlling circuit of the capstan motor, (4) is an input terminal of a still reproduction start signal.
(5) is a noise detection portion which receives an input of the AGC control voltage to detect the reproduction output fall portion to output the detection pulse of a given pulse width. (6) is a reference pulse making portion which outputs the pulse of given width corresponding to the vertical blanking period from the falling timing of the head change-over sig
REFERENCES:
patent: 4280146 (1981-07-01), Misaki et al.
patent: 4306255 (1981-12-01), Misaki et al.
patent: 4338631 (1982-07-01), Ota
patent: 4342053 (1982-07-01), Hirota
patent: 4495525 (1985-01-01), Uchida et al.
patent: 4531162 (1985-07-01), Tokumitsu
patent: 4611252 (1986-09-01), Igata et al.
patent: 4649439 (1987-03-01), Tanaka
McElheny Jr. Donald
Sanyo Electric Co,. Ltd.
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