JP2696861B2 - Video signal processing device - Google Patents

Description

The present invention relates to a method for displaying digital RGB data on a CRT display device using a digital-analog converter.
The present invention relates to a video signal processing device that converts a video signal into a composite video signal (for example, the NTSC format). [Related Art] In recent years, in the field of personal computers or microcomputer systems, the display functions of CRT display devices have become important due to the diversification and diversification of game software or word processing software. On the other hand, in the case of computers intended for widespread use at home, in order to construct a system at low cost, a conventional television receiver must be used.
It is essential that the system can be used as a CRT display device. Therefore, the computer system must use a signal format that can be received by a conventional television receiver (NTSC system in Japan,
PAL format in European countries). In addition, in order to realize an inexpensive computer system as described above, at present, it is necessary to integrate as many circuit components as possible on a large-scale integrated circuit. Further, in order to improve the degree of integration, the circuit must be realized by a MOS digital circuit. However, in both the NTSC system and the PAL system, since analog signals are very complicated and high precision, high-quality composite video signals cannot be handled by MOS digital circuits. [Problems to be Solved by the Invention] Conventionally, in such a video signal processing device, when digital RGB data is converted into a composite video signal such as the NTSC system, it is difficult to faithfully reproduce color information. It was difficult. The present invention converts a luminance signal and two color difference signals obtained based on digital RGB data into a high-quality composite video signal using a circuit configuration that can be easily realized by a MOS digital circuit, and faithfully converts color information. It is an object of the present invention to provide a video signal processing device capable of reproducing. [Means for Solving the Problems] A video signal processing apparatus according to the present invention is a video signal processing apparatus for obtaining a composite video signal, wherein a first digital-analog converting a luminance signal represented by a digital value into an analog value is performed. Converting means, adding means for adding a color burst signal to one of the two color difference signals represented by digital values and outputting a first signal represented by digital values, and balancing the first signal Balanced modulating means for modulating, second digital-analog converting means for converting the modulated signal output from the balanced modulating means and represented by a digital value to an analog value, and the other of the balanced and modulated represented by the digital value A third digital-to-analog converting means for converting the color difference signal into an analog value; and a composite video by combining the outputs of the first, second and third digital-to-analog converting means. Synthesizing means for obtaining a signal, wherein the color burst signal comprises:
It is characterized by being added to the one color difference signal before balanced modulation. [Embodiment] FIG. 1 shows a first embodiment of the present invention and is a block diagram of a video signal processing apparatus for generating a composite video signal of the NTSC system. 2, 3, 4 are input terminals for digital RGB data,
1 is a synchronization signal input terminal. Reference numeral 6 denotes a matrix conversion circuit, which converts digital RGB data input from 2, 3, and 4 into digital values, such as a luminance signal (digital Y signal), a red color difference signal (digital R-Y signal), and a blue color difference signal. Signal (digital BY signal). 8 is digital Y signal, 9 is digital RY signal, 10 is digital BY
Signal. Reference numerals 11 and 12 denote balanced modulation circuits, which are color subcarriers having different phase angles and balance-modulate the digital RY signal and the digital BY signal output from the matrix conversion circuit. The control signal generation circuit 7 generates 21 digital color burst signals.
In 22 digital adders, the digital adder is added to 10 digital BY signals and input to 12 balanced modulators. 7
The control signal generating circuit supplies a control signal to the 11 'and 12 balanced modulation circuits by using a synchronization signal and a reference clock. Reference numeral 13 denotes a digital-analog converter, which is the digital Y signal, the balanced modulated digital RY signal,
Three digital signals that are balanced-modulated by adding a digital color burst signal to a digital BY signal are converted to analog signals by independent digital-analog converters. Further, a synchronizing signal is also input to the digital-to-analog converter for the Y signal, and the output signal is a Y signal including the synchronizing signal. A composite video signal synthesizing circuit 17 synthesizes the Y signal 14, the RY signal 15, and the BY signal + burst signal 16 which have been converted into analog values, and outputs a composite video signal. . FIG. 2 shows a specific circuit example of the composite video signal synthesizing circuit 17 shown in FIG. A Y signal converted to the analog value,
Inputting the RY signal, BY signal + burst signal,
The composite video signal is output to the terminal of 34. FIG. 3 is a block diagram of a video signal processing device for generating a PAL composite video signal according to a second embodiment of the present invention. FIG. 4 is a diagram showing a color burst in the PAL system and a phase relationship between two axes. In the PAL system, the phase of the color burst is selected to be ± 135 ° from the BY axis as shown in FIG. 4 corresponding to the switching of the phase of the color subcarrier of the RY signal. In the embodiment, two axes A and B shown in FIG. 4 are set as the modulation axes instead of the BY axis and the RY axis. Therefore, in the matrix conversion circuit 40 in FIG.
The G and B data are converted into three digital data of Y, A and B. Reference numerals 41 and 42 denote balanced modulation circuits, which are color subcarriers having different phase angles and balance-modulate the 48 digital A signals and the 49 digital B signals output from the matrix conversion circuit. From the 44 control signal generation circuits,
A digital color burst signal is generated, and in accordance with the switching of the phase of the chrominance subcarrier of the RY signal, 45 digital color burst signal changeover switches operate, and the A of 48 is used.
The signal or the B signal of 49 is added through digital adding circuits of 46 and 47. The color bust on the A axis in FIG. 4 indicates a state in which the digital color burst signal is added to the 48 digital A signals through the 46 digital addition circuits in FIG. . The control signal generation circuit 44 supplies the color modulation sub-carriers 41 and 42 with the color sub-carriers having a phase difference of 90 ° according to the switching of the phase of the color sub-carrier of the RY signal. 13
Is a digital-to-analog converter, which converts the digital Y signal, the balanced modulated digital A signal + burst signal (or A signal), and the balanced modulated digital B signal (or B signal + burst signal). The three are converted into analog signals by independent digital-analog converters. Further, a synchronizing signal is also input to the digital-to-analog converter for the Y signal, and the output signal is a Y signal including the synchronizing signal. Reference numeral 43 denotes a composite video signal synthesizing circuit, which synthesizes a Y signal 14, an A signal + burst signal (or A signal) 52, and a B signal (or B signal + burst signal) 53 which have been converted into analog values. Then, a composite video signal is output. According to the configuration described above, in the NTSC system, the Y signal, the RY signal, the BY signal + the burst signal are each subjected to digital-to-analog conversion independently to have a phase angle of 90 °. In addition, the RY axis and the BY axis can be obtained, and the BY axis delayed by 180 ° with respect to the phase of the color burst signal can be obtained accurately. Is obtained. Similarly, in the PAL system, the Y signal, A
The signal + burst signal (or A signal) and the B signal (or B signal + burst signal) are digital-to-analog converted independently to have a 90 ° phase angle.
The A-axis and the B-axis can be obtained, and the A-axis (or the B-axis) delayed by 180 ° with respect to the phase of the color burst signal can be obtained accurately, and a high-quality composite video signal can be obtained. By synthesizing three analog signals and adjusting each resistance value in the configuration shown in FIG. 2, the phase and amplitude of each signal can be adjusted independently.
It is possible to adjust and correct the color tone on the T display. [Effects of the Invention] A video signal processing apparatus according to the present invention is a video signal processing apparatus for obtaining a composite video signal, comprising: a first digital-analog conversion unit for converting a luminance signal represented by a digital value into an analog value; Adding means for adding a color burst signal to one of the two color difference signals represented by values and outputting a first signal represented by a digital value; and balanced modulation means for performing balanced modulation of the first signal A second digital-analog converting means for converting the modulated signal output from the balanced modulation means and represented by a digital value into an analog value; and converting the other color difference signal represented by the digital value and subjected to balanced modulation into an analog value. A third digital-to-analog converting means for converting the output from the first digital-to-analog converting means into a composite video signal And the color burst signal comprises:
Since it is added to the one color difference signal before the balanced modulation, the phase of the two color difference signals with respect to the phase of the color burst signal, that is, the setting of the color difference signal axis can be made accurate, and the color information can be faithfully reproduced. Because of digital processing, it can be easily realized with MOS digital circuits. Further, since the addition means for adding the color burst signal is placed before the balanced modulation, the addition means can be small in circuit scale. Therefore, even when obtaining a PAL composite video signal, the addition means is not required. Addition to any of the color difference signals according to the switching of the phase of the subcarrier can be easily performed in terms of a circuit. Therefore, by mounting the video signal processing apparatus of the present invention on a computer intended for widespread use in homes, a television receiver of any system (NTSC system, PAL system, etc.) can be equipped with an advanced Thus, a complex composite video signal can be obtained, and a composite video signal faithful to color information can be reproduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a video signal processing apparatus showing a first embodiment of the present invention, and FIG. 2 is a circuit example of a composite video signal synthesizing circuit shown in FIG. It is a circuit diagram. FIG. 3 is a block diagram of a video signal processing apparatus according to a second embodiment of the present invention. FIG. 4 is a block diagram of the PAL system according to the second embodiment.
FIG. 3 is a diagram illustrating a color burst and a phase relationship between two axes. 1 ... Synchronization signal input terminal 2 ... Digital R color data input terminal 3 ... Digital G color data input terminal 4 ... Digital B color data input terminal 5 ... Clock signal input terminal 6 ... Matrix conversion circuit 7 ... Control signal generation circuit 8 Digital Y signal 9 Digital RY signal 10 Digital BY signal 11 Digital balanced modulation circuit 12 Digital balanced modulation circuit 13 Digital-analog converter 14 … Analog Y signal 15… Analog RY signal 16… Analog BY signal + analog color burst signal 17… Composite video signal synthesizing circuit 18… Composite video signal output terminal 19… R-Y balanced modulated carrier Signal 20: BY + burst balanced modulation carrier signal 21: Digital burst signal 22: Digital addition circuit 31: Analog Y data input terminal 32: Analog RY data Input terminal 33: Analog BY data + analog burst data input terminal 34: Composite video signal output terminal 35: Resistive element 36: Capacitive element 37: npn-type bipolar transistor 40: Matrix conversion circuit 41: Digital balance modulation circuit 42 Digital balance modulation circuit 43 Composite video signal synthesis circuit 44 Control signal generation circuit 45 Digital color burst signal changeover switch 46 Digital addition circuit 47 Digital addition circuit 48 ... Digital A signal 49 ... Digital B signal 50 ... A + burst (or A) balanced modulation carrier signal 51 ... B (or B + burst) balanced modulation carrier signal 52 ... Analog A signal + analog color burst signal (or analog) A signal) 53: Analog B signal (or analog B signal + analog color burst signal)

Claims (1)

(57) [Claims] A video signal processing apparatus for obtaining a composite video signal, comprising: first digital-analog conversion means for converting a luminance signal represented by a digital value into an analog value; and one color difference signal of two color difference signals represented by a digital value Adding a color burst signal to the first signal, and outputting a first signal represented by a digital value; balanced modulation means for performing balanced modulation on the first signal; A second digital-analog converting means for converting the modulated signal into an analog value; a third digital-analog converting means for converting the other color difference signal represented by the digital value and balanced-modulated into an analog value; Synthesizing means for synthesizing the outputs of the first, second and third digital-analog converting means to obtain a composite video signal; A video signal processing device, wherein a signal is added to the one color difference signal before balanced modulation. 2. 2. The video signal processing device according to claim 1, wherein the one color difference signal is a red difference signal or a blue difference signal. 3. The one color difference signal is +
2. The video signal processing apparatus according to claim 1, wherein the color difference signals are phases shifted by 135 degrees or -135 degrees.