JPS5937792A - Digitizing device of component video signal - Google Patents

Abstract

PURPOSE:To widen the band of a luminance signal to be transmitted by sampling three luminance signals and one chrominance signal during the digitization of a component video signal. CONSTITUTION:When three luminance signals Y are sampled at horizontal sampling intervals Px, a color difference signal U or V is sampled at the next sampling point. The color difference signal U is sampled on either of adjacent scanning lines in the same field and the color difference signal V is sampled on the other. After the sampling, component which is present at an origin and has a coefficient of 12 is the DC component of an original luminance signal. The next sampling point is thinned successively by three times, so a higher harmonic component having a coefficient of 4 and coefficients of + or -4i is generated. The level of the higher harmonic components is one third as high as the original signal and the degree of distortion is less.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a digitizing device for component encoding of color video signals.

[Background art and its problems - 1 As a method for digitizing color video signals, there are two methods: composite coding, in which a composite color video signal is quantized and coded, and a luminance signal and two color difference signals are each quantized. , component encoding is known. Component encoding, compared to composite encoding, uses two-television systems (NTSC,
PAL method.

It has the advantage that it is less affected by differences in SECAM systems and can be standardized worldwide.

In component encoding, luminance signal Y1 color difference signal U,
For example, as the sampling frequency for each of
4 MHz (Y), 3.5 MHz (U, V) are used. Based on the ratio of sampling frequencies for each component, this encoding is called the (4°1.1) method. There are also (4,4,4) method and (4,2,2) method. Further, the above-mentioned sampling frequency is also used in a digital VTR that records a digital color video signal on a magnetic tape using a rotating head. However, when creating a compact, lightweight digital VTR that can be used for ENG, etc., using the sampling frequency related to the luminance signal as described above would result in a large amount of data and a transmission bit rate that would become too high, making recording difficult. Furthermore, since the circuit scale becomes large, it is conceivable to use the (2, 1, 1) method.

However, in the (2,1,1) system, the sampling frequency for the luminance signal is low, and the band of the luminance signal that can be transmitted is insufficient. Therefore, the (3,41,0) method has been proposed. This means that the luminance signal is sampled at a frequency of 3
The color difference signals U and V are sampled at the sampling frequency Js, and the color difference signals are sampled at the sampling frequency Js. As for the color difference signal, even if it is processed in this way, it is possible to transmit optical information. This method has the advantage that a sufficient band for the luminance signal can be secured and the amount of data to be transmitted does not increase.
I'R makes it easy to record.

By the way, devices that perform various processing on digital 1° digital brightness counterfeit signals, such as noise reducers and special effect devices such as enlargement and reduction, are designed on the premise of a 4fs sampling frequency. many. Therefore, if the sampling frequency of the luminance signal reproduced from the digital V'rR is 3fs, the sampling frequency should be changed to 4fs. This conversion of the sampling frequency from 3fs to 4fs is to form 4-sample data from 3-sample data. Moreover, it requires buffer memory for its processing.

"Objective of the Invention" The present invention realizes a component video signal digitization device that is capable of transmitting a sufficient band as a luminance signal and can operate only with a sampling frequency of 4 fs and a corresponding clock. The purpose is to

1-Summary of the Invention j This invention provides a system in which the sample ratio of the luminance signal and the color signal is (3:
1), and different color signals are sampled sequentially for every 12 inputs. The data is dot-sequentially processed so that three luminance signals are sampled and one color signal is sampled one time.

Embodiment FIG. 1 shows sampling points in an embodiment of the present invention. The same applies to the following explanation, but the horizontal scanning line shown as a solid line and the horizontal line shown as a broken line represent those belonging to different fields, the white dots are sampling points for the luminance signal Y, and the black dots are the color difference signals U or ■. These sampling points are located in a grid pattern.

As can be understood from FIG. 1, when the luminance signal Y is sampled three times in succession at the sampling interval Px in the horizontal direction, the color difference signal is sampled at the next sampling point. The color difference signal U is sampled on one side of adjacent scanning lines of the same field, and the color difference signal V is sampled on the other side. In the same field, the sampling points of the color difference signals are not at the same position in the vertical direction, but in different fields, the sampling points of the color difference signals are shifted by 2 Px. py indicates the sampling interval in the vertical direction.

The horizontal sampling interval Px corresponds to a sampling frequency of 4 fs. This sample has a frequency of 7s. What are the specific numbers? , 13.5M)□2.4 fs
c (fsc * Cassie subcarrier frequency), '12
8fhCfh: horizontal scanning frequency).

FIG. 2 shows the spatial frequency spectrum of the DC component of the luminance signal and its harmonic components when the above-mentioned sampling is performed. In FIG. 2, the direct current component of the original luminance signal is located at the origin and has a coefficient of 12, and the remaining components are harmonic components. If the sampling process of the luminance signal were always repeated at intervals of Px, only harmonic components having 12 coefficients and located in a grid pattern would appear in FIG.

On the other hand, in the present invention, the sampling point next to the three sampling points is thinned out, so in FIG. A harmonic component having a coefficient is generated.

For simplicity, FIG. 2 shows only the DC component.

If we draw the spectrum corresponding to 4-5 MHz in Fig. 2, it is represented by a dashed line centered at the origin, which is a radius of about π 2 - It becomes a circular shape with .

Px 3 Therefore, the harmonic component that breaks the coefficient of 12 is 1)
It can be removed by a post filter (low pass filter) provided after the /A converter. On the other hand, 4
The harmonic components that have a high coefficient or number cannot be removed by the post filter, resulting in aliasing distortion. However, the level of the harmonic components that cause aliasing distortion is as low as - of the original signal, and the aliasing distortion occurs only in high-frequency components, so the degree of this distortion is small. small.

In FIG. 3, 1, 2.3 each represent an analog switch, and 2. An analog luminance signal Sy is supplied to the analog switch 1 from an input terminal 4, an analog color difference signal Su is supplied to the analog switch 2 from an input terminal 5, and an analog color difference signal Su is supplied to the analog switch 3 from an input terminal 6.

These analog switches 1, 2.3 are connected to terminals 7.8.
Control pulses P11P2 supplied from each of
, ps. Tsumashi, this control pal 22, P2. While P3 is 0 (low level), the analog r edges 1, 2.3 are on, and while P3 is 1 (high level), they are off. Analog switch 1, 2.3
The outputs of the A1) are commonly supplied to the converter 10.

This 8/'I) converter 10 also operates based on the clock pulse supplied from the terminal 11, converting 8 bits to 1?
Sample digital data is generated. this person/'
The output of the D-converter 10 is fed to a demultiplexer 12, and with a timing pulse from terminal 13
The signal is divided into channels and taken out to output terminals 14 and 15, respectively. These two channels of data are recorded on the C magnetic tape as two parallel tracks by a rotating head for each field.

FIG. 4A shows a clock pulse with a frequency of 4fs,
In synchronization with this clock pulse, control pulses P1, Ps, and Ps shown in FIG. 4B are formed. The illustrated control pulse is in the horizontal period during which the color difference signal U is sampled. Therefore, the control pulse P3 is always set to 1, and the analog switch 3 is off. Furthermore, since the analog switch 1 is turned on during the period when the control pulse P1 is O, and the analog switch 2 is turned on during the period when the control pulse pg is 0, the signal obtained by combining the outputs of the analog switches 1 and 2.3 is the fourth The result is shown in Figure C.

This analog signal is supplied to the A/D converter 0 to form data in which the digital luminance signal Dy and the color difference signal Du are made sequential. The demultiplexer 12 is operated by a pulse signal shown in FIG. 4E, and as shown in FIG.
A digital signal divided into channels and having a data rate of 1 is produced at each of the output terminals 14,15.

In addition, in the horizontal period during which the color difference signal Su is sampled,
The relationship between control pulses PI and Ps is reversed.

As shown in FIG. 3, the digitization circuit in one embodiment of the present invention has three signals (Y, tJ, V).
Since only one A/D converter can be provided for each circuit, a sample and hold circuit is not required, the circuit configuration can be simplified, and power consumption can be reduced.

Although not shown, the two-channel data reproduced from the magnetic tape is returned to one-channel data by a multiplexer, and is further divided into a luminance signal and a color difference signal. In this luminance signal, a position that is not sampled is subjected to average value interpolation using, for example, two data located before and after the position. The color difference signals are also subjected to interpolation processing, and sample data of the luminance signal Y and the color difference signals U and (2) are finally formed for all sampling points located in a grid pattern at intervals of KPx and py. In one embodiment of the present invention, as is clear from FIG. 1, the sample points of the color difference signal are shifted between adjacent horizontal scanning lines, so that the drop in color resolution due to interpolation processing is greatly reduced. There is.

The hairstyle of the sampling method according to the present invention will be explained with reference to FIG. 5 and subsequent figures. these are.

The sample points of the color difference signals are different in phase.

The sampling method shown in FIG. 5 is such that sample points related to color difference signals are shifted by two sample intervals between two consecutive horizontal scanning lines of the same field. In the case of this method, the spatial frequency spectrum of the DC component of the luminance signal and its harmonic components is as shown in FIG.

The sampling method shown in FIG.
The sample points are shifted in a predetermined direction by one sample interval between the horizontal scanning lines of the book. FIG. 8 shows the spatial frequency spectrum of the DC component and its harmonic components of the luminance signal in this method.

The 9th sampling method is similar to the sampling method shown in FIG. 7, but differs in the direction in which the sample points are shifted.
As shown in the figure. FIG. 10 shows the spatial frequency spectrum of the DC component of the luminance signal and its harmonic components in this method.

[Effects of the Invention] According to the present invention, the sampling frequency r for the luminance signal can be increased compared to the (2, i, 1) method, and the band of the luminance signal to be transmitted can be made wider. In this invention,
It is fine to use one system of clock pulses, but (4,
Matching with a video signal processing device using a sampling frequency Me of 4fs such as 4,4) or (4,2°2) can be easily performed.

[Brief explanation of drawings]

FIG. 1 is a wr diagram showing sampling points in an embodiment of this invention, FIG. 2 is a diagram showing a spatial frequency spectrum of the DC component of a luminance signal in an embodiment of this invention, and FIGS. 3 and 4 5 is a block diagram showing the configuration of an embodiment of the present invention and a time chart used for its operation theory 131j.
6 and 6 are route maps showing sampling points in other embodiments of the present invention and their spatial frequency spectra, and FIGS. 7 and 8 are route maps showing sampling points γ in still other embodiments of the present invention. Figures 9 and 10 do not show the sampling points of other better embodiments of the present invention, but the route map and the spatial frequency spectra in that case do not show the sampling points of the better embodiment of the present invention.
” is the frequency spectrum. 1. 2, 3...'j7'' log su r nochi, 4. Song... Input terminal of Teru's information signal, 5, 6...
・Envelopment difference signal input terminal, 10...A/
D converter. Agent Tadashi Sugiura Tomo 482 Figure 5 U Figure 6 Figure 7 5-*-◆-÷→〜÷-◆-0-÷-*-◆-10-o-
υ Figure 8

Claims (1)

[Claims] In a device for digitizing a component video signal consisting of a luminance signal and two types of color signals, different color signals are digitized line by line in a point-sequential manner such that the sample ratio of the luminance signal and the color signal is (3:1). A component video signal digitizing device characterized in that the component video signals are sampled sequentially.