JPS61269483A - Processing circuit for digital color video signal - Google Patents

Abstract

PURPOSE:To eliminate a disturbance to a luminance signal and to improve the picture quality of a color video signal by arraying plural digital reduced chrominance signals in one time series signal having a period 1/2fSC and adding a delay signal whose horizontal scanning period is delayed by an integral multiple, and thus generating digital modulated chrominance signals. CONSTITUTION:Digital reduced signals (a) and (b) are made into one time series signal (c) by a multiplexer 11. This time series signal G is passed through a 1H (one horizontal scanning period) delay circuit 12 and an adder 13 to remove components having no vertical correlation and then added by an adder 15 to the luminance signal Y as modulated signal which is inverted in polarity. A signal which has no vertical correlation and becomes in-phase during modulation is removed by the reduced chrominance component correlating circuit composed of the 1H delay circuit 12 and adder 13 to remove effectively the disturbance of the interleaved modulated chrominance signals from the luminance signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to a digital color video signal processing circuit suitable for digitally processing a low frequency converted color signal obtained from a video camera or the like. .

[Technical Background of the Invention] In Japan's NTSC broadcasting system, the phase of a modulated color signal in a composite video signal is a half-cycle for each scanning line. Therefore, as seen in the energy distribution of the color television signal of the above system shown in FIG. 4, the color signal spectrum and A are the luminance signal spectra.

A frequency interleaving method is used that is inserted between the mouths. However, in the figure, "," indicates the low frequency C4 Shingetsu subcarrier frequency, and "C" indicates the horizontal scanning frequency.

In this frequency interleaving method, the polarity of the modulated color signal is reversed between scanning lines, fields, and frames, so the modulated signal is visually canceled, and the modulated color signal interferes with the luminance signal. ＜＞It is like this. FIG. 5 shows (111) of the modulated color signal, and between the scanning lines (n,
n-4-1...etc.) and between the frames (
~ Gender is reversed.

However, the modulated color signal that is applied to the general image contains components that are not affected by the visual reduction effect against the above-mentioned disturbances during modulation. One of them is a component that is folded back to the high frequency signal or low frequency signal side during modulation when the band of the modulated color signal is not wide.

Even if the polarity of the signal is reversed between scanning lines, this aliasing component is detected by the human eye as line pairing (stripes between lines) because the frequency band is too low, degrading the image quality. Cause. Normally, such image quality deterioration is avoided [
To achieve this, the modulated color signal is subjected to sufficient band-limiting processing to remove high-frequency signals before modulation.

Until now, on the receiver side that reproduces TV signals, the modulation center frequency (=J) band components near J are used as color signals, and the other low-frequency components are used as brightness signals. However, with one means of concavity for Y and C as described above,
The luminance signal band was limited by the chrominance signal band and could not be made sufficiently wide, resulting in a decrease in horizontal resolution.
If the limited band of the band-limiting filter applied to the modulated color signal is too wide, as in 7B (previous), aliasing interference will occur, and conversely, if it is too narrow, the resolution of the color signal will deteriorate. 6
Due to this problem, it has recently become necessary to perform Y-C separation using a comb-shaped filter that utilizes the polarity of the modulated color signal shown in Figure 5. I-ko.

Figure 6 shows an example of a Y-C minute 1fiii type filter.
A signal extracted from the combined signal Y-1-C (of 3° luminance signal and color value) by a bandpass filter (1) of the modulation frequency, and a signal extracted by the bandpass filter (1) of the modulation frequency and the delay line (2) and the gain for one horizontal scanning period (11-1). The signal that has been subtracted from the signal passed through the gain control roller (3) is the color signal C, and the luminance signal is the signal obtained by subtracting the color signal from the first Y10 signal that has passed through the gain control roller (4). As Y, go ahead Y-C minutes.

[Problems with the previous technique] By the way, the color signal components include components that cannot be separated by the above-mentioned means.

= 3- Now consider the case where there is no vertical correlation in the images. Figure 7 (
A) shows one frame's worth of low-frequency modulated color signals without vertical correlation. Such a signal may occur when there is no vertical correlation in the image, and as shown in FIG. 7(B), all the modulated color signals are folded back into in-phase components. Therefore, for such a signal, it is no longer possible to expect an interference reduction effect on the luminance signal of the modulated color signal visually, and such a modulated color signal cannot be handled by the comb-shaped filter shown in FIG. It becomes impossible to separate. For this reason, interference to the luminance signal included in the modulated color signal appears visually as aliasing interference to the luminance signal, as typified by dot crawl, which has the disadvantage of causing deterioration in image quality, especially in the vertical resolution of the luminance signal. there were.

[Object of the Invention] In view of the above-mentioned drawbacks, an object of the present invention is to provide a digital color video signal processing circuit that supplies a high-quality color television signal with almost no interference with the luminance signal caused by the modulated color signal. is.

[Summary of the invention] The present invention converts a plurality of digital low-pass color signals into 1/2 fS (:
After adding this time series signal and a delayed signal delayed by an integer multiple of the horizontal scanning period of the television signal, this tightening signal is
The above object is achieved by creating a digital color video signal by switching the polarity each time a digitally modulated color signal is created, and adding a digital luminance signal to this digitally modulated color signal to create a digital color video signal.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing one embodiment of the digital color video signal processing circuit of the present invention. Band limit filter 7.8
The high-frequency components are removed from the two digital color signals R-Y and B-Y, and the digital low-frequency color signals a and b, which have passed through gain controllers (9, 10), are sent to the multiplexer 11.

The multiplexer 11 is 1. The low frequency color signals a and b are alternately selected in the cycle of '2 fsc, and the delay circuit 12 between horizontal and vertical lines is used as one 1/2 fsc period l and '1 series transmission C.
and output to adder 13. 1 horizontal scanning law interpolation circuit 12 and adder 13 refine the low frequency color signal vertical correlation circuit (
), 11. '1 series signal 8 Remove the vertically correlated 4 signals from c and use it as 1 logical OR circuit 14
is supplied to one input end of the The input terminal of this JJI alistic OR circuit 1A has "(J, , '18M 1
-1 y) No. 18 C is manually generated and the time series signal d IJ, f,. The high level 11 is inverted to "■" and output to the adder 15.

f3. : At 1-1-level, time series signal 8d is J
, is output to the cylinder 15. The adder 15 adds the ti time-series signal tone 'SC to the brightness signal Y as a carry signal and outputs it as Yl-C (i number (e). In order to reverse the polarity of a digital word that takes the number d, it is necessary to add 1 to the lowest bits 1 to 1 of the inverted data.For this reason, the adder 15 adds the luminance signal to the signal d. When adding Y, 1 is added to the inverted data at the high level of f, . to realize a -C polarity inversion circuit.
The portion excluding the vertical correlation circuit constitutes a modulation circuit.

Next, the operation of this embodiment will be explained. First, the two types of digital low-IFI color signals R-Y and B-Y are band-limited by the band-limiting filter 7.8, and the gain controllers 1 to 1-
The gains are multiplied by α and β by α and β, respectively, as shown in Figure 2 (
As shown by a), ([)>, the digital low-frequency signals a, [) are obtained. These digital bass signals? 3a and 3b become one time-series signal C as shown in FIG. 2(C) by multiple breakout. At this time □Sequence signal c l; 1: 1
After components with no vertical correlation are removed by the horizontal scanning period delay circuit 12.7 Ifl latitude 13, the time series signal d shown in FIG. 2(d) is obtained. This time series signal @d is added to the luminance signal Y by an exclusive OR 14 and an adder 15 as a modulated color signal whose polarity has been inverted.

According to this embodiment, before modulation, the band ili! +limiting filter 7
．． 8 limits the bands of the low-frequency conversion color signals R-Y and B-Y, so that the phenomenon of folding back of high-frequency signals to low-frequency signals is prevented, and image quality deterioration due to this phenomenon does not occur. In addition, signals with no vertical correlation that are in phase during modulation are removed by a low frequency color signal vertical correlation circuit including a 1-horizontal scanning period delay circuit 12 and an adder 13-7, and the luminance signal of the modulated color signal by the incremental method is removed. interference is effectively removed. This means that in the process of adding signals between lines by the adder 13, if a sudden change in polarity occurs between lines of the time-series signal C as shown in FIG. As shown in Fig. 3(e), the polarity change of the time-series signal (d) is made to have stages, as shown in Fig. 3(e). This means reducing the occurrence of aliasing interference components.

Furthermore, since the low frequency color signal vertical correlation circuit is combined in the low frequency color signal modulation circuit, it is possible to improve the efficiency of signal processing and reduce the circuit scale.

Note that if a vertical correlation circuit is installed after complete modulation of the low-range color signal, depending on the image, it may not be possible to tell whether the signal was originally a luminance signal or a aliased signal of the color signal. In the embodiment, such a situation can be prevented. This vertical correlation processing circuit also improves the S/N of the color signal; in other words, when passing through this circuit, the signal component doubles, or the noise component (15 times the noise component).
After all, it is possible to improve the S/N by t, Jl 3 d B in two-line correlation, and by =1 dB in three-line correlation. Further, since the vertical correlation processing of the signal applied to the vertical correlation processing circuit also blurs the color in the vertical direction, it is possible to alleviate the influence of vertical false signals generated in a single-chip color camera.

Note that although the above embodiment describes the processing of two types of digital low-range color signals, it is also possible to perform similar processing using several types of low-range color signals. This is useful when the situation arises.

[Effects of the Invention] As described above, according to the digital color video signal processing circuit of the present invention, a plurality of digital low-frequency color signals can be processed at 1/2 fs.
After adding a delayed signal obtained by arranging the time series signal into one time series signal having a period of c and delaying this time series signal by an integral multiple of the horizontal scanning period of the television signal and the original time series signal, this added signal is processed at 172 fsc. A digitally modulated color signal is created by switching the polarity each time, and a digital luminance signal is added to this digitally modulated color signal to create a digital color video signal. This has the effect of eliminating interference and improving the image quality of color video signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the digital color video signal processing circuit of the present invention, FIG. 2 is a diagram showing an example of the digital signal processed in FIG. 1, and FIG. A diagram showing the signal processing process when there is a sudden polarity change between the lines of the low-range color signal processed by the circuit. Figure 4 is a diagram showing the energy component 15 of the color video signal. Figure 5 is a diagram showing the energy component 15 of the color video signal. Figure 6 shows an example of polarity change of a modulated color signal. Figure 6 is a block diagram showing an example of a general comb circuit. Figure 7 shows an example of a modulated low-frequency modulated color signal for one frame. FIG. 3 is a diagram showing a polarity change process. 7.8... Band limit filter 9.10... Gain controller 11... Multiplexer 12... 1 Horizontal scanning period storage circuit 13, 15... Constrictor 10... Exclusive OR Circuit agent Patent attorney Kensuke Chika (and 1 other person) Figure 5 Figure 6 (A) Hiresashi CB) Figure 7

Claims (1)

[Claims] 1) Multiple types of digital low-frequency color signals created from the output signals of an image sensor such as a color video camera at a frequency of f_s
modulated by the color signal subcarrier of __c to obtain a modulated color signal;
In a digital color video signal processing circuit that adds a digital luminance signal generated from the image sensor to this modulated color signal to create a digital color video signal, the plurality of types of digital low-pass color signals are selected at a cycle of 1/2 f_s_c. a signal arraying means for producing one digital time series signal by delaying the digital time series signal by an integral multiple of the horizontal scanning period of the television, and adding the delayed signal and the original digital time series signal to produce a digital time series signal; a color signal vertical correlation means for producing an addition signal; a polarity inversion means for inverting the polarity of the digital addition signal at a period of 1/2f_s_c to produce a digitally modulated color signal; 1. A digital color video signal processing circuit comprising: signal addition means for adding signals.