JPS62295592A - Video encoder circuit - Google Patents

Abstract

PURPOSE:To obtain a circuit capable of varying the depth of a color on a small circuit scale by providing an amplitude setting means for setting the amplitude of a color burst superimposed during the burst period in an optional value. CONSTITUTION:A luminance signal component generation section 13 converts a color luminance signal (EY) by color information S0-S14 into binary data. Further, a color difference signal component generating section 14 converts two kinds of color difference signals (ER-EY, EB-EY) by color information S0-S14 into binary data. Then a modulation section 15 uses the two kinds of color difference signal components outputted from the section 14 to apply balanced modulation to chrominance subcarriers whose phase differs by 90 deg. thereby outputting a chrominance carrier component. A color burst component is outputted from the modulation section 15 during the output period of the burst flag signal BF. The color burst component is outputted as binary data corresponding to the amplitude set for the burst generation section 16 by an amplitude set section 17. The depth of color is adjusted by varying the amplitude of the color burst at the section 17.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a video encoder that converts digital color signals output from a display controller into video signals, for example. Regarding circuits.

(Prior art) In videotex systems, teletext systems, etc., characters, figures, etc. are stored as digital data in an image memory 1, as shown in FIG. The image is read out and displayed at a timing synchronized with . In these systems, color information data for one image is usually output in the form of a digital waveform, so a dedicated monitor capable of inputting digital RGB is required. Therefore, in order to connect to a popular type television capable of video input, a video encoder circuit 3 is required to generate a video signal, which is an analog signal, from a color signal of a digital value.

(Problems to be Solved by the Invention) Conventionally, this video encoder circuit does not have a function to adjust the intensity and saturation of one color, and the intensity is always constant. However, 1
Since it is desirable to make one color darker or lighter depending on the surrounding parent frame conditions or the viewer's preferences, adjustments were made on the television receiver side.

In this case, not only the video signal from the video encoder circuit, but also the saturation level of the video signal detected by the TV receiver changes, so 1. When watching a normal TV program, the saturation level must be readjusted. .

Furthermore, in order to change the color density in the video encoder circuit itself, it is conceivable to make the amplitude value of the chroma component variable. However, since it is necessary to keep the relative ratio of the chroma components of each color constant and to vary the amplitude value of the chroma components, the scale of one circuit increases.

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the above-mentioned problems, and an object of the present invention is to provide a video encoder circuit that can vary the color density with a small circuit scale.

[Structure of the invention]

(Means for solving problems) The present invention relates to a video encoder circuit.

The present invention is characterized in that an amplitude setting means is provided which can set the amplitude value of the color burst superimposed on the burst period to an arbitrary value.

(Function) The chroma component of the video signal is demodulated and amplified by the color signal reproducing circuit of the television receiver: the primary color signal or color difference chroma component is sent to the picture tube.
It is added in the form of No. 8. At this time.

An ACC circuit in the color signal reproducing circuit detects the size of the color burst and adjusts the gain of the band amplification circuit.

The color density on the screen is set to be constant. Therefore,
If the amplitude value of the color burst superimposed on the video signal is increased by the amplitude setting means, the amplitude value of the chroma component becomes relatively small, so the color density becomes lighter due to the above function. Conversely, if the amplitude value of the color burst superimposed on the video signal is reduced, the amplitude value of the chroma component becomes relatively large, and the color density becomes deeper.

(Embodiment) An embodiment of the video encoder circuit of the present invention will be described in detail below with reference to one section.

In FIG. 1 showing an embodiment of the present invention, a latch 11 receives a red signal R11, a color signal G, and a blue signal B, which are output from a display controller or the like in synchronization with raster scanning.
, the luminance signal Y, the composite synchronization signal SY, and the burst flag signal BP indicating the superimposition position of the color burst. The signals R, G, B, Y and sy sampled by this latch circuit 11 are converted into corresponding color information 80-814 by a 0 color decoder 12 and outputted.

The luminance signal component generating section 13 converts the luminance signal (Ey) of the color indicated by the color information 80-814 into binary value data.

Further, the one color difference signal component generating section 14 similarly includes color information SO~
Two types of color difference signals (ER-By) of the color indicated by 814.

DB -FiY) into binary value data. and,
The modulator 15 balance-modulates the two types of color difference signal components outputted from the color difference signal component generator 14 and the color subcarriers having phases different from each other by 90e', and outputs a carrier color signal component. Note that during the output period of the burst 72 signal BP, the color burst component is output from the modulation section 15. This color burst component is the burst generating part 1
6 is output as binary value data corresponding to the amplitude value set by the amplitude setting section 17. By varying the amplitude of the color burst using the amplitude setting section 17, it becomes possible to adjust the color density.

The digital low-pass filter 18 and the digital band-pass filter 19 perform filtering on the luminance signal component and carrier color signal component, respectively, to suppress mutual interference. The filtered luminance signal component and carrier color signal component are added by an adder 20 and combined into a digital video signal component. This video signal component is once latched by a latch 21 to match the timing, and a D/A converter converts it into an analog video signal. High frequency components of this analog video signal are cut by a low-pass filter, and a video signal VD is output.

Next, the operation of this embodiment configured as described above will be explained.

The digital signals R, G, B, Y, SY and BP output from the display controller are 4/s.
Latch 11 with c (/sc: color subcarrier frequency) clock
sampled. Among these signals, signal 几.

Since G, B, and Y indicate color information of eight colors and two gradations, the one-color decoder 12 converts them into corresponding color information SO~814. The circuit configuration of this color decoder 120 is shown in FIG. 2, and the operating state is shown in FIG. 3. In Figure 2, Nantes Gate 1
21-1 to 121-8 decode which of the eight colors the signal, G, and B are, and then perform the orgame) 122-
Two gradations (full brightness and half brightness) corresponding to the signal Y are selected from 1 to 122-14. That is, for 15 colors of 8 colors and 2 gradations (however, black does not have 2 gradations), only one signal of 8O-J314 is decoded to the @L'' level. When the signal is at L'' level, that is, during the composite synchronization signal period, all signals 80 to 814 are converted to ``H'' level to facilitate subsequent processing.

By the way, for the three primary color signals ER, BG, ``B'', the luminance signal EY of each color and the two color difference signals ER-BY, EB
-EY can be expressed by the following mixing ratios.

By-0,30Ba+0.5(JEG+0.ttEn
...(1) BR-BY=0.70EB-0,5
9BG -0,11EB...(2)EB-Ey
=-0,30 to -0,59BG+0.89EB ・
...(3) Furthermore, in order to prevent overmodulation, one color difference signal E
,-BY.

The amplitude of EB -BY is 1/1.14.1/2.03 respectively.
limited to.

Therefore, for the 15 colors of 8 colors and 2 gradations decoded by the 1-color decoder 12, the luminance signal BY and the color difference signal
Y)/1.14. The relative values of (EB-BY)/2.03 are shown in FIG. 4, respectively. The relative amplitude value of the color par signal is shown in FIG. 5 using this value. Here, the ratio of full brightness to half brightness is set to 2:1, but it may also be a value subjected to r correction.

Luminance signal component EY for each color decoded by the color decoder 12, that is, 15 colors of 8 colors and 2 gradations, and a synchronization signal
and color difference signal component (ER-BY)/1.14. (EB
-EY)/2.03 is generated as binary value data □ as shown in FIG. In this embodiment, in order to simplify the subsequent digital processing, the value shown in FIG. 5 above is multiplied by 100, and the value of the "L" level of the synchronizing signal is set to 01. However, negative numbers are expressed in two's complement.

The luminance signal component Ey is generated by a luminance signal component generating section 13 whose details are shown in FIG. That is.

The color information SO~814 from the color decoder 12 is decoded by the NAND games 13-0~13-7 to output 8-bit signals Eyo~7. In addition, in the case of the synchronization signal, since the one-color information SO~814 are all at the ``H'' level, the signal B
For YO to 7, @θ'' is output.

Similarly, the above color difference signal component (ER-EY)/1.14
.

(DB-FIY) /2.03 is 1 color difference signal component generation unit 14 generates color information 81 to 812 (So, 813.81
4, it is "0" and therefore unnecessary) is decoded and output as 7-bit signals Ryo-e, l3yo-6.

By the way, in a video signal, two color difference signal components (ER-EY)/1.14. (EB-B
Y)/2.03, and the color subcarriers have a phase difference of 90° from each other.

In other words, (2) 2πf set , m 2π/ set
The carrier color signal Cy is created by performing balanced modulation.

Video signal ==a By + CY...
(4) This cos2g Ct and m2x Haat are periodic waveforms whose phases differ by 90 degrees as shown in FIGS. 8(a) and (b), so to perform balanced modulation digitally,
The color difference signal component of each color (ER-E
Y)/1.14 and (BB-Ex)/2.03
It is sufficient to switch between the value of and the value obtained by multiplying it by ``''-1''. That is, eos 2* /act and sin 9
The sampling point of /sct is t;□・n (n=0.1, 2, 3...)
...(6) If 7sc is selected, the above carrier color signal Cy is (BR-BY)/1
．． 14°(BB-BY)/2.03. -(ER-EY)
/1.14. -(Fin-Ey)/2.03°... is obtained. Therefore, the signals RYo~6. Switch BYo~6 and R
Yo~6. BYo~s, -RYO~6. -BYO~
If it is output in the order J [of e, ・-, it will be balanced modulation.

Here, for the above-mentioned balanced modulation, the amplitude values of two types of color difference signals are positive values and negative values (here, the value multiplied by *-1m).
Therefore, in this embodiment, the color difference signal component generating section 14 is configured as follows to simplify the process.

There is a complementary color relationship in color signals, and the ER-EY axis and EB-
They have a positive and negative relationship with respect to the EY axis. In other words.

When the B, -Ey acid component of a certain color has a positive amplitude value.

Its complementary color has a negative amplitude value. The same applies to the BB-HY acid component. Therefore, the color difference signal component ER of a certain color
-BY, EB When performing balanced modulation of the color subcarrier with -BY, if a color is converted to its complementary color at the timing when a negative value of that component is required, the amplitude value of the color difference signal component of that color can be changed. You can get negative values of .

Therefore, when modulating a color subcarrier with a color difference signal of a certain color, the complementary color conversion unit 140 of the one color difference signal component generation unit 14 modulates the color subcarrier at the timing when that component becomes a negative value (a value multiplied by @-1'). Switch the color information of a color to color information in a complementary color relationship.

The above timing is "/278C,"/ in Figure 8 above.
4D. The timing is right. In FIG. 9, details of this complementary color conversion section 140 are shown.

At the timing of 0*1/478C in FIG. 8, the pulses -cos and -gavl, details of which will be described later, are both
Since the level is L'', the color information 81 to 812 is selectively output from the switch group 140-3 as complementary color information 01 to C12 by the NOR gate 140-1 and inverter 140-2, resulting in a normal color state. / 3
/s. At the timing of 2fsc, 4/, either pulse -cos or -sin is "
H" level, the complementary color states of the color information 81 to 812 are transmitted from the switch group 140-3 as complementary color information c1 to 0, respectively.
Appears 12 years old.

Complementary color information 01 to C output from the complementary color conversion section 140
12 and eER-EY generating section 141°EB-
[FIY generating section] 42 are color difference signal components (En - Ey
)/1.14. (BB-EY)/2.03 is output as a 7-bit signal RYo~6°BYO~6. 1st
EFL-1 on figure 0! As shown in the details of the y generating section 141, it may be configured to output only one of the positive and negative amplitude values of one color difference signal component.

As described above, in order to perform balanced modulation of the color subcarrier with the color difference signal component created by complementary color conversion at a predetermined timing, the above (
6) Select the sampling points shown in Eq.

Signal RYO~6. BYO~, RYo~a, BYO
~e, 几Yo-e, BYo~a.

All you have to do is switch in the order of... This balanced modulation is performed by the /sc modulation section 151 which performs a switch operation.

Switch pulse cos, sin required for SO switch.

-cos, -5in is performed by the modulation unit 15, which includes a Sln*Cos generation unit 152 that generates -cos and -5in, and outputs carrier color signal components CYo~6. The above Sin a C
As shown in FIG.
It is configured as a four-stage ring counter using FIG. 12a) as a clock pulse. The switch pulse cos, sin generated by this sin e cos generation section 152
, -cos, -5In (FIGS. 14b to 14e), the two color difference signal components are switched in the 7sc modulation section 151.

However, since a color burst is superimposed on the video signal during the burst period as shown in FIG. 5, it is necessary to output the color burst instead of the two color difference signal components during this period. The relative amplitude value of this color burst is 0.2 (20 in this embodiment), and the phase is in an opposite phase relation to the color difference signal component EB -EY. Therefore, the signal BO~6 indicating the EB-BY axis component of the color burst
．． -BO to 6 are always outputted by the BP generating section 16, and when the burst flag signal BP is at the IILI11 level,
As shown in FIG.
Boss, “0”.

-Bo~6. You just need to switch in this order and output.

In this embodiment, in order to make it possible to arbitrarily set the amplitude value of the color burst and adjust the color density, the BP generator 16 uses the 7-bit binary amplitude value Ao~ set by the amplitude setting unit 17. 6, respectively, 7-bit positive and negative signals BO to 6. -BO~6 is generated.

The details are shown in FIG. 14, and the 7-bit amplitude value A
0 to 6 are output as they are as signals BO to 6.

Further, after each pit is inverted in the 1 inverting unit 161, the adder 1
@1" is added at 61 and output as signals -Bo~6. In other words, the signal -BO is added as the two's complement of signals BO~6.
~6 is obtained. Since the amplitude values Ao~6 are 7 pins, the amplitude setting section 17 can set the amplitude values of the color burst from IO''~@63''. In other words, it is possible to obtain an amplitude value approximately three times larger than the vR@value@20'' of one normal color burst.

The carrier color signal components CYo~6 and luminance signal components 11Yo~7 obtained in the above manner need to have their low frequency components and high frequency components removed, respectively, in order to prevent mutual interference when combined into a video signal. There is. In this example, a digital low-pass filter (
D-LPF) 18 performs calculations with low-pass characteristics that filter out high frequency components. On the other hand, the carrier color signal component CY
Digital band pass filter (D-B
PF) 19 performs calculations with bandpass characteristics that cut low frequency components.

The amplitude characteristics of the filters 18 and 19 are shown in FIGS. 15 and 16, respectively.

The adder 20 adds the digitally filtered luminance signal component and the carrier color signal component to synthesize the digital video signal VYo~7 shown by the above equation (4), and the latch 21 uses 4/sc as a clock. Latch.

That is, the latch 21 outputs a binary digital value that matches the amplitude value of the desired video signal at a period of 4/sc. These digital values VYo~7 are converted into analog values by a D/A converter η, high frequency components are captured by a low pass filter n, and output as an analog video signal VD.

As explained above, in this embodiment, the amplitude value of the color burst superimposed on the video signal is made variable, and the magnitude of the amplitude value of the 4-major signal is relatively made variable. Therefore, a system that can vary the density of one color according to observation conditions and the viewer's preference can be obtained with a simple hardware configuration. Also,
In this embodiment, when the amplitude value of the color burst is increased and the amplitude of the chroma signal is relatively decreased, the noise component superimposed on the chroma signal is also decreased. Therefore,
Compared to simply reducing the amplitude of the chroma signal for noise of the same amplitude, this method also has the advantage of producing a video signal with a better S/N ratio.

Furthermore, in this embodiment, from the digital waveform color signal output from the display controller.

Since analog waveform video signals are generated through digital processing, analog peripheral components such as resistors, capacitors, inductors, and delay lines are no longer required. Therefore, the influence of deterioration of resistance etc. is eliminated.

Consistency can be maintained. Furthermore, since adjustment of two peripheral parts is not necessary, the workability of one assembly is significantly improved.

Note that the present invention is not limited to digital video encoders, but may also be analog encoders.

〔Effect of the invention〕

According to the present invention, it is possible to provide a video encoder circuit that can vary the color depth on a small circuit scale.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the video encoder circuit of the present invention, FIGS. 2, 7, 9 to 12.
14 are circuit diagrams showing details of each part of the embodiment shown in FIG. 1, and FIGS. 3 to 6. FIG. 8, FIG. 13, FIG. 15, and FIG. 16 are explanatory diagrams for explaining the operation of the embodiment, and FIG. 17 is a block diagram for explaining the outline of the video encoder circuit. 12... Color decoder, 13... Luminance signal component generation section. 14... Color difference signal component generation section, 15... Modulation section. 16... Burst generation section, 17... Amplitude setting section. Agent Patent attorney Nori Ken Yudo Yuyama L/l C/l Ll'l CI'+ no ψsu+
tl+ u+ li+ v+ u+ I/+ u+
uro 0 0+3
Figure 13
S. Tf@”: 'Bln LA2.
B2ay-AB3 Fixed A4, , B4 Subcommittee 1B5], 161. 6286 1: -1:InJP-A-RUG2-295592(9) 111 Stomach 1. )■: Figure 17

Claims (1)

[Claims] In a video encoder circuit that creates an analog waveform video signal from a plurality of color signals supplied in the form of digital waveforms and a burst flag signal indicating the superimposition position of the color burst, the amplitude value of the color burst is set. What is claimed is: 1. A video encoder circuit comprising: an amplitude setting means for setting the amplitude; and a color burst generating means for generating a color burst with an amplitude corresponding to the amplitude value set by the amplitude setting means.