JPS61293081A - Magnetic recording and reproducing method for still-picture signal - Google Patents

Abstract

PURPOSE:To maintain the brightness of pictures constant by controlling the gain of a reproducing amplifier to make the reproduction level of a standard level signal constant when reproduced and thereby to correct the difference in sensitivity of the magnetic tape. CONSTITUTION:A recording accumulated in such as a magnetic tape not shown in the figure is read sequentially by a head 8, and a picture signal is amplified by the amp. 9 whose gain is controllable. In this case, the standard level signal is first reproduced provided that the amp. 9 executes auto-gain-control because an analog switch 10 controlled by a controller 2 is being on, and that the gain of the amp. 9 is set so that the output level becomes constant. The switch 10, thereafter, is turned off by the control of the controller 2, and the gain of the amplifier 9 is fixed at the current value. Accordingly, the picture signal is reproduced at a fixed level regardless of the sensitivity of the magnetic tape.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to recording digital still image signals stored in a memory onto a magnetic recording medium such as a magnetic tape, and recording the still image signals for reproducing the recording. The present invention relates to a magnetic recording and reproducing method.

[Prior art]

There are different types of image recording methods in which a still image signal that has been A/D converted and stored in memory is converted to analog by a D/A converter, and this is directly recorded on a magnetic recording medium such as a magnetic tape. When a magnetic tape or the like is used as a magnetic recording medium, if there is a sensitivity difference in the magnetic tape, there will be a difference in the output level during reproduction, so there is a problem that the brightness of the image will differ depending on the type of magnetic tape.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned conventional problems, and the present invention has been made in view of the above-mentioned problems of the prior art. This book aims to provide a method for magnetically recording and reproducing image signals.

(Structure of the Invention) The method for magnetically recording and reproducing still image signals according to the present invention performs D/A conversion on a digital still image signal read out from a memory, and first selects and records a standard level signal output from a controller. After that, the analog still image signal is recorded on a magnetic recording medium, and upon reproduction, the gain of the reproduction amplifier is controlled so that the reproduction level of the standard level signal is constant, and the gain is fixed as it is, and the image signal is reproduced. Accordingly, the reproduced image signal is set to a level unrelated to the sensitivity of the magnetic tape so that the brightness of the image is kept constant.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 and 2.

FIG. 1 is a block diagram for implementing the present invention, and shows an A/D
A memory 1 that stores the converted still image signal, a controller 2 that controls timing of writing and reading from the memory 1, and a controller 2 that performs D/A conversion on the digital still image signal read from the memory 1. A still image signal converted into an analog signal by the D/A converter 3 is converted to a level corresponding to the brightness of each pixel. It further includes a selection switch 4 for first selecting and recording the standard level signal output from the controller 2 and then adding an analog still image signal passed through the D/A converter 3 to the standard level signal; It has a recording equalizer 5, a recording driver 6, and a recording head 7. In addition, in order to reproduce recorded data from a magnetic recording medium such as a magnetic tape and store it in the memory 1, it is equipped with a read head 8 and an amplifier 9 having an auto gain control function, which is turned on when a standard level signal is reproduced. an analog switch 10 that operates the amplifier 9 and sets a gain so that the output level is constant; an integrator 11; It has an A/D converter 12 for writing.

Next, a recording and reproducing method using the above magnetic recording and reproducing apparatus will be explained with reference to FIG.

When a standard level signal having the waveform shown in FIG. 2(1) is applied from the controller 2 to the selection switch 4, the selection switch 4 selects the standard level signal and outputs it to the recording equalizer 5. After that, the digital still image signal stored in the memory 1 is controlled by the controller 2 and is read out one pixel at a time starting from the first pixel,
The D/A converter 3 converts the signal into an analog still image signal having a level corresponding to each brightness, thereby obtaining a waveform signal as shown in FIG. 2(2). When this analog still image signal is applied to the selection switch 4, the selection switch 4 selects this waveform signal, so the recording equalizer 5
The output signal to has a waveform as shown in FIG. 2 (3). The waveform analog still image signal thus formed is output to the recording head 7 via the recording equalizer 5 and the recording driver 6, and is recorded on a magnetic recording medium such as a magnetic tape (not shown). In each diagram in FIG. 2, the vertical axis represents the signal level, and the horizontal axis represents time.

Next, when reproducing the magnetic recording, the following reproducing operation is performed.

First, records stored on a magnetic tape (not shown) are sequentially read by a read head 8, and an image signal is amplified by an amplifier 9 whose gain can be controlled.

In this case, the standard level signal is first reproduced, and at this time, the analog switch 10 controlled by the controller 2 is on, and the amplifier 9 operates with automatic gain control, so that the output level of the amplifier 9 is kept constant. Gain is set. Thereafter, the analog switch 10 is turned off under the control of the controller 2, and the gain of the amplifier 9 is fixed at the same value, so that the image signal is reproduced at a predetermined level regardless of the sensitivity of the magnetic tape. The reproduced signal thus obtained has the waveform shown in FIG. 2 (4). When this waveform signal further passes through the integrator 11, a reproduced signal as shown in FIG. 2 (5) is obtained. The output of the read head 8 is a differential value of the recorded still image signal, and by integrating this with an integrator 11, a reproduced still image signal as shown in FIG. 2 (5) can be obtained. be. This reproduced still image signal is applied to the A/D converter 12 at read timing, digitized, and then written to the memory I.

〔Effect of the invention〕

As described above, the method for magnetic recording and reproducing of still image signals according to the present invention performs D/A conversion on a digital still image signal read out from a memory, and when recording this image signal directly on a magnetic tape or the like, it converts the digital still image signal into an analog still image signal. Before recording the image signal, a standard level signal is recorded, and during playback, the gain of the playback amplifier is controlled so that the playback level of the standard level signal is constant, and then the gain is fixed and the image signal is played back. This is what I decided to do. Therefore, the level of the reproduced image signal is not affected by the sensitivity of the magnetic tape, etc., and can be set independently. Even when using different magnetic tapes with different sensitivities, the level of the reproduced image signal can be set independently. Since the brightness of the image can be kept constant through correction, it is possible to ignore the influence of sensitivity differences between magnetic tapes, which is a disadvantage of direct recording.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a still image signal magnetic recording and reproducing method according to the present invention, and FIGS. 2 (1) to (5) are waveform diagrams of output signals from each part in FIG. 1, respectively. 1 is memory, 2 is controller, 3 is D/A converter, 4
is a selection switch, 9 is an amplifier with auto gain control function, 10 is an analog switch, 11 is an integrator, 1
2 is an A/D converter.

Claims (1)

[Claims] 1. D/D digital still image signal read from memory
A conversion is performed, and the standard level signal output from the controller is first selected and recorded, and then the analog still image signal is recorded on a magnetic recording medium, and during playback, the standard level signal is played back so that the playback level is constant. A method for magnetic recording and reproducing a still image signal, characterized in that after controlling the gain of an amplifier, the gain is fixed as it is and the image signal is reproduced.