JP3042440B2 - Video signal processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a CRT using digital-to-analog converters for converting digital RGB data.
A composite video signal (for example, NT) for displaying on a display device
(SC system). 2. Description of the Related Art In recent years, in the field of personal computers or microcomputer systems, game software or word processing software has become multifunctional and diversified.
The display function of a CRT display device has become important. On the other hand, in the case of a computer intended to be widely used for home use, it is indispensable that a conventional television receiver can be used as a CRT display device in order to construct a system at low cost. Signal formats that can be received by television receivers (NTSC system in Japan, PAL system in European countries)
Must be output. 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. In order to improve the degree of integration, MO
The circuit must be realized with an S digital circuit. However, in both the NTSC system and the PAL system, a high-quality composite video signal cannot be handled by a MOS digital circuit because it is a very complicated and highly accurate analog signal. Conventionally, in such a video signal processing apparatus, digital RGB data is
When converting to a composite video signal such as the TSC system, it has been difficult to faithfully reproduce color information. The present invention
A digital color difference signal based on digital RGB data using a circuit configuration that can be easily realized by a MOS digital circuit,
It is an object of the present invention to provide a video signal processing device capable of converting a luminance signal into a high-quality composite video signal and faithfully reproducing color information. A video signal processing apparatus according to the present invention is a video signal processing apparatus for obtaining a composite video signal.
First 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 performing balanced modulation on the first signal A first balanced modulating means, a first digital-to-analog converting means for converting a modulated signal output from the first balanced modulating means and represented by a digital value into an analog value, and represented by the digital value A second adding means for adding a color burst signal to the other color difference signal and outputting a second signal represented by a digital value; a second balanced modulation means for performing balanced modulation on the second signal; A second digital-to-analog converter for converting a modulated signal output from the second balanced modulator and expressed in a digital value into an analog value, and a third digital-to-analog converter for converting a luminance signal expressed in a digital value into an analog value. Digital-to-analog converting means, synthesizing means for synthesizing outputs of the first, second and third digital-to-analog converting means to obtain a composite video signal, and combining the color burst signal with the first adding means or the Switching means for switching to a second addition means, wherein the color burst signal is added to the color difference signal before balanced modulation based on switching of the phase of the color subcarrier of the color difference signal. I do. 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 digital R
The GB data input terminal 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 (devital BY signal). 8 is a digital Y signal, 9 is a digital RY signal, and 10 is a digital BY signal. 11, 12
Is a balanced modulation circuit, with color subcarriers of different phase angles,
The digital RY signal and the digital BY signal output from the matrix conversion circuit are balanced-modulated. The control signal generation circuit 7 generates 21 digital color burst signals, and this signal is added to 10 digital BY signals in a 22 digital addition circuit and input to 12 balanced modulation circuits. Is done. Further, the control signal generation circuit of 7 is configured to control the above-described 1 by using a synchronization signal and a reference clock.
Control signals are supplied to the balanced modulation circuits 1 and 12. 13
Is a digital-to-analog converter, which converts the digital Y signal, the balanced modulated digital RY signal, and the balanced modulated digital signal by adding a digital color burst signal to the digital BY signal, Independent digital-to-analog converters convert to analog signals. 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 17 denotes a composite video signal synthesizing circuit, which 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. The Y signal, RY signal, BY signal + burst signal converted to the analog value are input, and are synthesized by 35 resistance elements and 37 transistors. Is output. FIG. 3 shows a second embodiment of the present invention.
FIG. 3 is a block diagram of a video signal processing device that generates a composite video signal of the AL system. FIG. 4 is a diagram showing a color burst in the PAL system and a phase relationship between two axes. P
In the AL system, the phase of the color burst is selected to be ± 135 ° from the B-Y axis as shown in FIG. 4 corresponding to the switching of the phase of the chrominance subcarrier of the RY signal.
In this embodiment, two axes A and B shown in FIG. 4 are set as the modulation axes instead of the B-Y axis and the R-Y axis. Therefore, the matrix conversion circuit 40 in FIG. 3 converts three digital R, G, and B data 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 are provided with the 48 digital A signals output from the matrix conversion image path and the 4
Nine digital B signals are balanced-modulated. A digital color burst signal is generated from the control signal generation circuit of 44, and the digital color burst signal changeover switch of 45 operates in accordance with the switching of the phase of the color subcarrier of the RY signal, and the A signal of 48 Alternatively, the signal is added to the B signal of 49 through digital adding circuits of 46 and 47. In FIG. 4, the color burst is on the A axis because the digital color burst signal is shown in FIG.
The figure shows a state where the digital A signal is added to the 48 digital A signals through the 46 digital adding circuits. In the control signal generation circuit 44, the color subcarriers having a phase difference of 90 ° according to the switching of the color subcarriers of the RY signal are supplied to the balanced modulation circuits 41 and 42. Reference numeral 13 denotes a digital-to-analog converter, which includes a digital Y signal, a balanced digital A signal + burst signal (or A signal), a balanced modulated digital B signal (or B signal + burst signal), Are converted into analog signals by independent digital-to-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 converts the Y signal 14 and the A signal +
The burst signal (or A signal) 52 and the B signal (or B signal + burst signal) 53 are combined to output a composite video signal. According to the configuration described above, in the NTSC system, the Y signal, the RY signal, the BY signal + the burst signal are each converted into a digital-to-analog signal independently to form a 90 ° phase. The R-Y and B-Y axes with angles can be obtained.
It is possible to accurately obtain the BY axis with a phase delay of 80 °,
A high-quality composite video signal can be obtained. Similarly, in the PAL system, the Y signal, the A signal + burst signal (or the A signal), and the B signal (or the B signal + burst signal) are each independently subjected to digital-to-analog conversion.
A axis and B axis having a phase angle of 0 ° can be obtained, and A is delayed by 180 ° from the phase of the color burst signal.
The axis (or B axis) can be accurately obtained, and a high-quality composite video signal can be obtained. In addition, by synthesizing three analog signals and adjusting each resistance value in the configuration as 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 display. As described above, according to the present invention, the MOS
Using a circuit configuration that can be easily implemented by a digital circuit, a luminance signal, a signal obtained by digitally adding one of the two color difference signals and a color burst signal represented by a digital value, and the other color difference signal , 3 independent each
By performing digital-to-analog conversion and synthesizing the digital-to-analog by an adjustable means (for example, a resistor) to obtain a composite video signal, a high-quality composite video signal can be obtained. Further, by adding the color burst signal to one of the two color difference signals, the setting of the two color difference signal axes for the color burst can be performed accurately. Further, the color tone can be adjusted and corrected, and the color information can be faithfully reproduced. In particular, a video signal processing apparatus according to the present invention is a video signal processing apparatus for obtaining a composite video signal, in which a color burst signal is added to one of two color difference signals represented by digital values and represented by a digital value. First adding means for outputting the obtained first signal, first balanced modulation means for performing balanced modulation on the first signal, and modulation output from the first balanced modulation means and represented by a digital value. First digital-analog converting means for converting a signal into an analog value, and a second means for adding a color burst signal to the other color difference signal represented by the digital value and outputting a second signal represented by a digital value Adding means, a second balanced modulation means for performing balanced modulation on the second signal, and a second means for converting a modulated signal output from the second balanced modulation means and represented by a digital value into an analog value. Digital-to-analog conversion means, third digital-to-analog conversion means for converting a luminance signal represented by a digital value into an analog value, and outputs of the first, second and third digital-to-analog conversion means And a switching means for switching the color burst signal to the first addition means or the second addition means, wherein the color burst signal is a color subcarrier of a color difference signal. Is added to the chrominance signal before the balanced modulation based on the switching of the phase of the color burst signal. Is added, and an appropriate composite video signal can be automatically obtained regardless of the signal system of the NTSC system or the PAL system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a video signal processing apparatus according to a first embodiment of the present invention. FIG. 2 is a circuit diagram of a circuit example of a composite video signal synthesizing circuit 17 of FIG. 1; FIG. 3 is a block diagram of a video signal processing device according to a second embodiment of the present invention. FIG. 4 is a diagram showing a color burst and a phase relationship between two axes in the PAL system according to the second embodiment. [Description of Signs] 1 ... Sync 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, 12 Digital balanced modulation Circuit 13: Digital-to-analog converter 14: Analog Y signal 15: Analog RY signal 16: Analog BY signal + analog color burst signal 17, 43: Composite video signal synthesis Circuits 18, 34: composite video signal output mizuko 19: RY balanced modulated carrier signal 20: BY + burst balanced modulated carrier signal 21: digital burst signal 22, 46, 47 ... digital addition circuit 31 ... analog Y data input terminal 32 ... analog RY data input terminal 33 ... analog BY data + analog burst data input terminal 35 ... Resistance element 36 Capacitance element 37 NPN-type bipolar transistor 40 Matrix conversion circuits 41 and 42 Digital balance modulation circuit 44 Control signal generation circuit 45 Digital color burst signal Switch 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)

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/64-9/78

Claims (1)

(57) [Claims] In a video signal processing apparatus for obtaining a composite video signal, a first addition for adding a color burst signal to one color difference signal of two color difference signals represented by digital values and outputting a first signal represented by digital values Means, first balanced modulation means for performing balanced modulation on the first signal, and first digital-analog for converting a modulated signal output from the first balanced modulation means and represented by a digital value into an analog value. Conversion means; second addition means for adding a color burst signal to the other color difference signal represented by the digital value and outputting a second signal represented by the digital value; and balanced modulation of the second signal A second balanced modulating means, a second digital-analog converting means for converting a modulated signal output from the second balanced modulating means and represented by a digital value into an analog value, Third digital-to-analog converting means for converting the luminance signal represented by the formula (1) into an analog value; Switching means for switching the color burst signal to the first addition means or the second addition means, wherein the color burst signal is balanced based on the switching of the phase of the color subcarrier of the color difference signal. A video signal processing device characterized by being added to the color difference signal before modulation.