JPH03178291A - Recording and reproducing method for video signal - Google Patents

Abstract

PURPOSE:To prevent picture quality from being deteriorated by applying frequency conversion to a high frequency component into a low frequency and applying line sequential processing to the result, recording it with time division multiplex. CONSTITUTION:A low frequency component is extracted from a luminance signal at a low pass filter 2 and fed to a memory 10 via an A/D converter 9. Moreover, the low frequency component is fed to a subtractor 4. Thus, a high frequency component of the luminance signal is extracted at the output of the subtractor 4 and converted into a low frequency by a frequency converter 6 and fed and stored in a memory 8 via an A/D converter 7. The output signal of the memory 10 and the output signal of the memory 8 are subjected to time division multiplex and the result is fed to a D/A converter 12 and the output signal of the D/A converter 12 subjected to time compression is FM-modulated by an FM modulator 13 and recorded on a magnetic tape 15. At reproduction the signal FM-demodulated by an FM demodulator 17 is fed to the A/D converter 18 and a high frequency component of the luminance signal is inputted to the memory 20 by a switch 19 and subjected to time axis expansion. Thus, picture quality deterioration is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording method for an apparatus for recording video signals on a recording medium, such as a video tape recorder.

Conventional Technology The frequency band of a high-definition television signal such as high-definition television is about four times that of a conventional television signal such as NTSC. When such a wide range signal is recorded on a home video tape recorder, etc., the recordable time per cassette is shorter than that of conventional television signals, so it is not possible to obtain sufficient recording time. becomes difficult. Therefore, in a home video tape recorder where it is essential that the tape cassette be small, one-sided recording is possible by reducing the frequency bandwidth within a permissible range.

As a frequency bandwidth reduction method suitable for analog transmission, a method of transmitting high frequency components of video signals line-sequentially has been reported (for example, at the IEICE General National Conference, 1983).
-7).

Figure 4 shows the signal shape at this time. When the low frequency component of the luminance signal is YL and the high frequency component of the luminance signal is 11, the l line transmits YL-tY□, and the next f transmits YL. death,
In order to equalize the frequency bands used, the time of the YL-only line is compressed to two-thirds.

Using this method, Y, is 0 to l0M1lz, Y□ is 1
0 to 20 MHz, and considering that only the luminance signal is transmitted, the YL+Y11 line is time-expanded by 4/3, and the YL line is time-compressed by 2/3, as shown in Figure 5. A continuous signal with a band of 15 MH2 can be obtained, and the frequency bandwidth can be reduced to three quarters.

The relationship between the horizontal frequency and vertical frequency when the high frequency components of the video signal are transmitted line-sequentially is 20M as shown in Figure 6.
When a Hz signal is band-limited to 10M1lz for each line, the result is as shown in FIGS. 7(a) to 7(d), and the oblique resolution is degraded. However, it is known from the 1985 Institute of Electronics and Communication Engineers General National Conference, 5-57 high-frequency signal line sequential transmission system of high-definition television that deterioration of diagonal resolution does not cause a large deterioration of image quality.

Problems to be Solved by the Invention However, when converting the high-frequency components of a video signal into line-sequential lines, performing angle modulation on the signal shown in FIG. 5, and recording the signal on a video tape recorder, the following problems arise. When the amplitude characteristics of the recording/reproducing system change depending on the frequency, the reproduced and restored video signal has amplitude characteristics in the mid-range frequency band that change line by line, as shown in FIG. Also, 81
2. Even if the phase characteristics of the recording/reproducing system are not linear with respect to frequency, the phase of the mid-range frequency band will similarly differ from line to line. In any of these cases, the brightness of the vertical line portion on the screen changes line by line, resulting in significant image quality deterioration.

The present invention solves the problems described above.

Means for Solving the Problems The present invention frequency-divides an input video signal into a high-frequency component and a low-frequency component, converts the high-frequency component to a low frequency, and converts it to line sequential. The frequency components and the high-frequency components of the line-sequential input video signal are time-division multiplexed by time-axis conversion, where at least the low-frequency components are equal, and are recorded on a recording medium, and when played back, the line-sequential human input video signal is recorded. It is characterized in that the high frequency components of the video signal are synchronized and frequency-converted back to the original frequency, and the low frequency components and high frequency components of the reproduced video signal are added to obtain a reproduced video signal.

Function Therefore, in the present invention, since the same frequency components of the human video signal base line are recorded and reproduced at the same frequency,
Even if amplitude and phase frequency distortion occurs in the recording/reproduction system, the video signals of each line are equally distorted, and unlike the conventional system, there is no significant deterioration in image quality.

Example An embodiment of the present invention will be described in detail below.

An embodiment in which the present invention is implemented in a video tape recorder is shown in FIG. ■ is the luminance signal input terminal, 2 is 10M
A low-pass filter that passes low-frequency components up to 1lz; 3 is a delay line with a delay time equal to that of low-pass filter 2;
4 is a subtracter, 5 is a L OM Hz oscillator, 16 is a frequency converter, 7 is an A-D converter, 8 is a memory, 9 is an A-D
Converter, 10 is memory, 11 is switch, 12 is D-A
Converter, 13 is an FM modulator, 14 is a magnetic head, 15 is an R-air tape, 16 is a magnetic head, 17 is an FM demodulator,
18 is an A-D converter, 19 is a switch, 20 is a memory,
21 is a DA converter, 22 is a frequency converter, 23 is a memory, 24 is a DA converter H, 25 is an adder, and 26 is a luminance signal output terminal.

The operation will be explained below. The luminance signal input from input terminal 1 is filtered by low-pass filter 2 to extract low frequency components and
It is supplied to the memory 10 via the D converter 9. Further, the low frequency component is supplied to a subtracter 4.

Therefore, as shown in FIG. 2(C), the high frequency component of the luminance signal is extracted from the output of the subtracter 4, and the frequency change IAi
! If6, the frequency is converted to the lower frequency side as shown in FIG. 2(e). The frequency-converted output signal is supplied to a memory 8 via an A-D converter 7 and stored therein. memory 10
The output signal of the memory 8 and the output signal of the memory 8 are time-division multiplexed by a switch 11 and supplied to a DA converter 12. These time relationships are shown in Figures 3(a) to (F!5), where the high frequency components of the luminance signal are thinned out every l lines, and
The line becomes a signal whose time is compressed to two-thirds. The output signal of the DA converter 12 is FM modulated by an FM modulator 13 and recorded on a magnetic tape 15.

During playback, the FM demodulated signal in the FM demodulator 17 is
-D converter 18 and stored in memories 20 and 23 via switch 19. These time relationships are shown in FIGS. 3(a) to 3(a). The high frequency component of the luminance signal is input to the memory 20 by the switch 19, and the output signal is expanded in time by three times as much as 2. The same signal is repeatedly output between lines.The low frequency component of the luminance signal is manually input to the memory 23, expanded on the time axis as shown in FIG. 3, and output.

The output signal of the memory 21 is supplied to a frequency converter 22,
The frequency converter 22 converts the signal into a sum frequency with the output signal of the oscillator 5, and returns it to the original frequency as shown in FIG. 2(f). The adder 25 includes a frequency converter 22 . The output signal of the DA converter and the output signal of the DA converter IA device 24 are added. Therefore, the high frequency components are transmitted line-sequentially to the output terminal 26, and a synchronized luminance signal is output.

In the embodiment described above, the low frequency components of the luminance signal to be recorded are recorded and reproduced with equal time axis compression performed between each line, so the frequency characteristics do not change from line to line as in the conventional method. It's good.

Further, the present invention is applicable not only to luminance signals but also to color difference signals.

Effects of the Invention The recording/playback method of the present invention is particularly effective in the case of wideband signals and can reduce the recording bandwidth, thereby increasing the recordable time per cassette in the case of video tape recorders, and Even if distortion occurs in the frequency characteristics of the recording/reproducing system as in the case of the above-mentioned method, the distortion does not vary from line to line, so there is no significant deterioration in image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment in which the present invention is implemented in a video tape recorder, FIGS. 2 and 3 are explanatory diagrams of the embodiment shown in FIG. 1, FIGS. 4, 5, 6, FIG. 7 is an explanatory diagram of the conventional method. ■...Video signal input terminal, 2...Low pass filter, 4...Subtraction circuit, 6.22...
...Frequency converter, 8. l0120.23...
・Memory, 122], 24...D-A converter,
7,9.18...A-D converter, 25...
... Adder, 26... Output terminal.

Claims (1)

[Claims] The input video signal is frequency-divided into high-frequency components and low-frequency components, and the high-frequency components are frequency-converted to a low frequency and line-sequentialized, and the low-frequency components of the frequency-divided input video signal and the line-sequentialized input are combined. The high-frequency components of the video signal and the low-frequency components are time-division multiplexed using equal time-axis conversion and recorded on a recording medium, and during playback, the reverse time-axis conversion to that during recording is performed to generate line-sequential input video. A video signal recording and reproducing method characterized in that a high frequency component of the signal is frequency-converted and returned to the original frequency, and the same is added to a low frequency component of a reproduced video signal to obtain a reproduced video signal.