Dynamic magnetic information storage or retrieval – Record editing
Patent
1988-03-28
1991-03-26
Richardson, Robert L.
Dynamic magnetic information storage or retrieval
Record editing
360 103, 360 7712, H04N 5782
Patent
active
050034065
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
This invention relates to a video image picture reproducing apparatus for eliminating a noise bar by employing a field memory.
BACKGROUND OF THE ART
As an example of a conventional video image reproducing apparatus, a high speed reproducing operation of a video tape recorder employing a field memory (hereinafter referred to as a VTR) will be described with reference to even multiplied speed reproduction such as reproducing at four times the recorded speed. An odd multiplied speed is generally selected in the high speed reproducing. This is because the odd multiplied speed reproducing has such a characteristic that a noise bar is locked since a noise position is identical in each field. On the other hand, a width of a noise bar can be made narrow, in some cases, by employing a memory. This is because the even multiplied speed reproducing has such a characteristic that a noise position and a signal position occur alternately.
FIG. 1 is a block diagram showing the high speed reproducing system of the above described conventional VTR. In FIG. 1, reference numeral (1) is a recorded video tape. A reproducing signal is fed to a preamplifier (3) through video heads (2a) and (2b). Thereafter, the reproducing signal is applied to a video signal processing circuit (4). Reference numeral (5) is an envelope detecting circuit which picks out an envelope of the reproducing signal from an output of the preamplifier (3). An output signal of the envelope detecting circuit (5) is applied to a comparator (6) to be compared with a given constant level signal.
Reference numeral (7) is a memory control circuit which receives the output signal of the comparator (6) and generates a timing signal and an address signal for writing an output signal from the video signal processing circuit (4) on a field memory (8) in response to the output of the comparator (6). The video signal processing circuit (4) produces a synchronizing signal to the memory control circuit (7).
The field memory (8) is a dual-port memory (not shown in the drawing) having a random output and a serial output as an output port. Writing and reading operations can be performed asynchronously by using the serial port. In this case, a reading operation for reading a content of the field memory (8) is carried out asynchronously by the use of the signal port, while the reproducing signal from the video signal processing circuit (4) is written to the field memory (8).
Reference numeral (9) is a control head. A servo circuit (10) controls a capstan motor (11) and a reel motor (12) based on an output signal of the control head (9) to thereby control the running of the tape in each mode.
An operation of the video image reproducing apparatus constructed above will be described hereinbelow.
The video tape (1) is played back in a reverse direction at a high speed (of four times the recorded speed, for instance). FIGS. 2 and 3 are explanatory diagrams of the operation when the video tape (1) is played back in the reverse direction at four times the recorded speed. In FIG. 2, reference numeral (50) is a video track and reference characters (A) and (B) designate azimuth recording, respectively. The video head (2a) moves along the azimuth (A) whereas the video head (2b) moves along the azimuth (B).
When the video head (2a) traces along the azimuth shown by broken lines (d) in FIG. 2, the reproducing signal of the preamplifier (3) is as shown in FIG. (3a) due to the azimuth recording. However, the video head (2a) and the video head (2b) are used both in a first mode and a second mode in which a tape feeding speed is slower than that of the first mode. A head width is narrower than a tracking pitch in the first mode.
When the video head (2b) traces a locus indicated by broken lines (e) of FIG. 2, an output signal of the video head (2b) is as shown in FIG. 3(b). The contents of the two fields of FIG. 3(a) and (b) are interpolated with each other on a time base, so that one field image is obtained as shown in FIG. 3(c). The one field image is stored in the field me
REFERENCES:
patent: 4811130 (1989-03-01), Takayama
Hatanaka Keiji
Itoga Masami
Nakajima Yoshimitsu
Mitsubishi Denki & Kabushiki Kaisha
Richardson Robert L.
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