JPH10210493A - Color signal adjustment method for video encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a dot crawl phenomenon and a dot disturbance phenomenon inconspicuous in a visual sense and to allow a television receiver side to recognize a reference burst signal. SOLUTION: A digital chrominance signal C and a digital luminance signal Y are generated independently, the digital chrominance signal C is converted into an analog chrominance signal C a through a 1st D/A converter 54, the digital luminance signal Y is converted into an analog luminance signal Y by a 2nd D/A converter 55, and the analog chrominance signal C and the analog luminance signal Y are composited by an analog adder 58 to generate a composite signal. Then the 1st D/A converter 54 decides a maximum amplitude of the chrominance signal C, based on a reference voltage Vref , while a reference burst signal is generated and decides the maximum amplitude of the chrominance signal C based on an adjustment voltage Vs1 , while the reference burst signal is not generated so as to decrease a voltage of the chrominance signal C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal adjusting method for a video encoding device.

[0002]

2. Description of the Related Art Conventionally, when an RGB signal output from a personal computer or the like is output to a television, the RGB signal is converted to NTSC by a video encoding device.
The video signal is converted to a video signal conforming to the standard.
FIG. 2 is a block diagram of a conventional video encoding device.

In the figure, reference numeral 11 denotes a matrix circuit, 1
2, 13 are modulation circuits, 14 and 15 are D / A converters,
18 is an analog adder, 19 and 20 are video amplifiers, 2
1 is a control unit, 22 is a synchronization control unit, 23 is a phase shifter, 24 is a delay circuit, 26 and 27 are reference voltage sources, 31 is a composite video terminal, 32 is an S video terminal, and 33 and 34 are adders. In the control unit 21, the horizontal synchronizing signal H
SYNC and the vertical synchronization signal VSYNC are input, a clock DACCLK is generated, and sent to the D / A converters 14 and 15. The D / A converter 1
Reference voltage sources 26 and 27 are connected to 4 and 15, respectively, and the amplitude of the converted analog signal is determined according to the voltage value of the reference voltage.

The matrix circuit 11 receives digital RGB signals, that is, an R signal, a G signal, and a B signal. The matrix circuit 11 converts the R, G, and B signals into a luminance signal Y and a chrominance signal Cr. , Cb. The R, G, and B signals and the luminance signal Y and the chrominance signals Cr, Cb have the relationship shown in the following equations, and conversion is performed according to each equation.

Y = 0.30R + 0.59G + 0.11B Cr = 0.70R−0.59G−0.11B Cb = −0.30R−0.59G + 0.89B The color difference signals Cr and Cb are modulated by the modulation circuits 12 and 13. Is modulated by a 3.58 [MHz] color-specific carrier (subcarrier) and added by an adder 33 to become a color signal C. The color signal C is subjected to digital / analog conversion by a D / A converter 14. Video amplifier 1
9 and output from the S-video terminal 32. In this case, the modulation circuit 13 receives the 0-degree synchronization signal from the synchronization control unit 22, and the modulation circuit 12
The color difference signals Cr and Cb are modulated with a phase shift of 90 degrees from each other since they receive the synchronizing signal of degrees. Therefore, the color signal C is represented by the following equation.

[0006] _{C = Cr (cos2πf sc t)} /1.14
+ Cb (sin2πf _sc t) /2.03 The luminance signal Y, is delayed in the delay circuit 24 is synchronized with the color signal C, the composite synchronizing signal from the synchronization control unit 22 in the adder 34 is added Later, D / A
The digital / analog conversion is performed by the converter 15, amplified by the video amplifier 20, and output from the S video terminal 32.

In this manner, the separated luminance signal Y and chrominance signal C are output from the S video terminal 32, and a television having a YC separation input terminal (not shown) is connected to the S video terminal 32. By doing so, an image can be displayed on the screen of the television. On the other hand, a composite signal can be generated by synthesizing the luminance signal Y and the chrominance signal C by the analog adder 18 and output from the composite video terminal 31.

FIG. 3 is a waveform diagram of a composite signal, FIG. 4 is a waveform diagram of a luminance signal, FIG. 5 is a waveform diagram of a chrominance signal, and FIG. 6 is a detailed diagram of a reference burst signal. As shown in FIG. 3, the cycle T _L of the composite signal for one line is 63.5 [μ].
s], and the maximum amplitude W is 1.0 [V _PP ]. SG1 is a sine wave signal. The luminance is represented by the amplitude of the luminance signal Y shown in FIG. 4. For the color, the hue is represented by the phase difference of each of the sine wave signals SG2 to SG7 in the color signal C shown in FIG. Represents the saturation.

The composite signal is obtained by synthesizing the luminance signal Y and the chrominance signal C, and the chrominance signal C enters the band of the luminance signal Y (about 4.2 [MHz]). Then, when the composite signal is output to a television to display an image, the luminance signal Y and the chrominance signal C are separated on the television side. The width of the horizontal synchronization signal HSYNC of the reference burst signal shown in FIG.
The back porch TB after the rise of the horizontal synchronizing signal HSYNC is set to 4.7 [μs], and the back porch TB generates a sine wave signal SG1 of 3.58 [MHz] and 9 cycles. .

[0010]

However, in the conventional video encoding apparatus, when an attempt is made to output a composite signal to a television and display an image, the television separates the luminance signal Y and the chrominance signal C from each other. However, since the color signal C enters the band of the luminance signal Y, the luminance signal Y and the color signal C cannot be completely separated. Therefore, the color signal C becomes the luminance signal Y
, A dot crawling phenomenon in which vertical edges flow jagged, a dot obstruction phenomenon in which horizontal edges flow jagged, and the like occur. The dot crawl phenomenon and the dot obstruction phenomenon are significant when the edge of an image is sharp and the color phase changes rapidly.

Therefore, it is necessary to store the image data for one screen in the memory, and to perform a complementing process between the image data of the previous screen and the image data of the current screen. I will. Further, when the voltage of the color signal C is low, the dot crawling phenomenon and the dot disturbance phenomenon become visually inconspicuous, so it is conceivable to lower the voltage of the color signal C. In this case, the voltage of the reference burst signal itself is considered. Will also be lower. In this case, the reference burst signal cannot be recognized on the television side, and the image quality deteriorates.

The present invention solves the above-mentioned problems of the conventional video encoding apparatus, and when a composite signal is output to a television and an image is displayed, a dot crawling phenomenon and a dot are visually observed on a television screen. It is an object of the present invention to provide a color signal adjusting method for a video encoding device that can make a disturbance phenomenon inconspicuous and recognize a reference burst signal on a television side.

[0013]

Therefore, in the color signal adjusting method of the video encoding apparatus according to the present invention, a digital color signal and a digital luminance signal are generated independently, and the digital color signal is converted to a first color signal. , The digital luminance signal is converted into an analog luminance signal by a second D / A converter, and the analog color signal and the analog luminance signal are added to an analog signal. To generate a composite signal.

[0014] The first D / A converter includes:
While the reference burst signal is being generated, the maximum amplitude of the color signal is determined based on the reference voltage, and while the reference burst signal is not being generated, the maximum amplitude of the color signal is determined based on the adjustment voltage. To lower the voltage of the color signal C.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of a main part of a video encoding device according to the first embodiment of the present invention, and FIG. 7 is a time chart showing an operation of the video encoding device according to the first embodiment of the present invention. The operation until the color signal C is generated by the adder 33 (see FIG. 2) and the operation until the composite synchronizing signal is added to the luminance signal Y by the adder 34 are the same as those of the conventional video encoding device. Since this is the same, the description of FIG.

In the figure, 54 and 55 are first and second D
/ A converter, 66 and 67 are reference voltage sources, 68 is a voltage source for adjustment, and 69 is a reference voltage V of the reference voltage source 66.
An analog switch for selecting one of _ref and the adjustment voltage V _S1 of the adjustment voltage source 68 and outputting it as a reference voltage V _OUT , 70 is a switching control unit, and 72 and 73 connect a television (not shown) to the video encoding device. A video amplifier used as a current / voltage buffer at this time, R1 and R2 are resistors, 58 is an analog adder, and 81 is a composite video terminal. The first D / A converter 54 receives the color signal C sent from the adder 33 in FIG.
The converter 55 receives the luminance signal Y sent from the adder 34 in FIG. 2.

The switching control section 70 comprises a flip-flop 75 and a counter 76. Next, the operation of the video encoding device having the above configuration will be described. First, when a digital color signal C is input to the first D / A converter 54, the first D / A converter 54 performs digital / analog conversion in accordance with the reference voltage V _OUT from the analog switch 69, and performs analog / digital conversion. Is output. In this case, the analog switch 69 selects one of the reference voltage _Vref of the reference voltage source 66 and the adjustment voltage V _S1 of the adjustment voltage source 68 based on the control signal VSEL from the flip-flop 75, and Voltage V
Output as _OUT . Here, the reference voltage V _ref of the reference voltage source 66 and 4.0 [V], when the adjustment voltage V _S1 of the adjustment voltage source 68 and 4.2 V, the control signal VS
Based on EL, a reference voltage V _{OUT of} 4.0 [V] or 4.2 [V] is selected and output to the first D / A converter 54.

Then, for example, a first D / A converter
The amplitude of the output voltage of reference voltage V _OUTAnd power supply voltage V_CC
Assuming that_OUT= 4.0 [V] V_CC = 5.0 [V] of the output voltage of the first D / A converter 54
The maximum amplitude becomes 1.0 [V]. Also, V_OUT= 4.2 [V] V_CC = 5.0 [V] of the output voltage of the first D / A converter 54
The maximum amplitude is 0.8 [V].

As described above, by changing the reference voltage V _OUT , the maximum amplitude of the output voltage of the first D / A converter 54 can be suppressed, and the voltage of the color signal C can be reduced. Then, a composite signal can be generated by synthesizing the luminance signal Y and the chrominance signal C by the analog adder 58, and can be output from the composite video terminal 81. Also, each video amplifier 72,
By connecting an S terminal (not shown) to 73, outputting a luminance signal Y and a chrominance signal C separated from the S terminal, and connecting a television having a YC separation input terminal (not shown) to the S terminal, An image can also be displayed on the screen of the television.

As shown in FIG. 5, the chrominance signal C is represented by the phase difference and the amplitude of each of the sine wave signals SG2 to SG7 with respect to the sine wave signal SG1 of the reference burst signal. It must always be constant. Therefore, while the reference burst signal is being generated, the reference voltage V _ref of the reference voltage source 66 is used as it is as the reference voltage V _OUT, and after the generation of the reference burst signal ends, the reference voltage V _ref and the adjustment voltage V _{S1 Is set} as the reference voltage V _OUT .

For this purpose, the switching control unit 70
The flip-flop 75 sets the output signal VST (Q output) to low level in synchronization with the falling of the horizontal synchronization signal HSYNC, resets the counter 76, and sets the control signal VSEL (/ Q output) to low level. as the reference voltage a reference voltage V _ref of the reference voltage source 66 V _{OU T}
And Then, the counter 76 receives the clock DACCL.
K is counted, and when the count value reaches the set value, the reference burst signal generation end signal RST is set to low level, and the flip-flop 75 is reset. As a result, the output signal VST and the control signal VSEL goes high, the adjustment voltage V _S1 to the reference voltage V _OUT.

[0022] In this way, when the count value of the counter 76 reaches the set value, the change of the reference voltage V _{OU T} is performed, by setting the set value as appropriate, a reference burst signal are then generated During this period, the color signal C having a normal voltage is output from the first D / A converter 54, and while the reference burst signal is not generated, the color signal C is output.
Is lowered.

As described above, by lowering the voltage of the color signal C, when a composite signal is output to a television and an image is displayed, a dot crawling phenomenon and a dot disturbance phenomenon are visually recognized on the television screen. It can be less noticeable. While the reference burst signal is being generated, the first D / A converter 54 outputs the color signal C having a normal voltage.
The reference burst signal can be recognized on the television side.

Next, a second embodiment of the present invention will be described. FIG. 8 is a main block diagram of a video encoding device according to the second embodiment of the present invention. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. In the figure, reference numeral 91 denotes an adjusting voltage generating means for generating an adjusting voltage V _S2 , which is connected to the resistors R3 and R4 connected in parallel to the reference voltage source 66 and the voltage division at a predetermined position of the resistor R3. It comprises a terminal 82 for taking out.

In this embodiment, the reference voltage V _ref of the reference voltage source 66 is set to 4.0 [V], and the adjustment voltage V _S2 generated by the adjustment voltage generating means 91 is set to 4.0 to 5.0. 0 [V]. The analog switch 6
9 is a control signal VSE from the flip-flop 75
Based L, and selects one of the adjustment voltage V _S2 of the reference voltage V _ref and the adjustment voltage generating means 91 of the reference voltage source 66, is output as the reference voltage V _OUT. And, for example,
Assuming that the amplitude of the output voltage of the first D / A converter 54 is determined by the reference voltage V _OUT and the power supply voltage V _CC , V _OUT = 4.0 [V] V _CC = 5.0 [V] The maximum amplitude of the output voltage of the first D / A converter 54 becomes 1.0 [V]. The maximum amplitude of the output voltage of the first D / A converter 54 when it is V _OUT = 4.0 to 5.0 [V] V _CC = 5.0 [V] corresponds to the reference voltage V _{OU T} And change.

Therefore, while the reference burst signal is being generated, the color signal C having a normal voltage is output from the first D / A converter 54. While the reference burst signal is not being generated, the color signal C is being output. The voltage of the signal C is the adjustment voltage V
_Lowered corresponding to _S2 . As described above, by lowering the voltage of the color signal C, when the composite signal is output to the television and an image is displayed, the dot crawling phenomenon and the dot disturbance phenomenon are visually inconspicuous on the television screen. be able to. While the reference burst signal is being generated, the first D / A converter 54 outputs the color signal C having a normal voltage, so that the television recognizes the reference burst signal. be able to.

Further, the voltage of the color signal C can be adjusted without providing the adjusting voltage source 68. next,
A third embodiment of the present invention will be described. FIG. 9 is a main block diagram of a video encoding device according to the third embodiment of the present invention. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

In the drawing, reference numeral 85 denotes an adjusting voltage generating means for generating an adjusting voltage V _S3 , and the adjusting voltage generating means 85 comprises an analog multiplexer 86 and adjusting voltage sources w1, w2,. , Each adjustment voltage source w
, Wn, the voltages V1, V2,..., Vn
Are the input terminals MU of the analog multiplexer 86, respectively.
X1, MUX2, ..., MUXn. And
The analog multiplexer 86 supplies selection signals s1 and s
, Sn, and the selection signals s1, s2,.
One of the adjustment voltage sources w1, w2,..., wn is selected by sn, and any corresponding voltage is output to the analog switch 69 as the adjustment voltage V _S3 .

If the video encoding device includes a processor (not shown), a register (not shown)
The selection signals s1, s2,..., Sn can be set by software by the / O command. If the video encoding device does not include a processor, a DI (not shown)
It can be operated from outside the video encoding device using a P switch or the like.

In this case, the adjustment voltage sources w1, w2,.
With wn, the voltage of the color signal C can be adjusted to a plurality of levels. It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, in a color signal adjusting method for a video encoding device, a digital color signal and a digital luminance signal are generated independently, and the digital color signal is generated. The signal to the first D / A
The converter converts the digital luminance signal into an analog color signal, converts the digital luminance signal into an analog luminance signal with a second D / A converter, and combines the analog color signal and the analog luminance signal with an analog adder. To generate a composite signal.

And, the first D / A converter is:
While the reference burst signal is being generated, the maximum amplitude of the color signal is determined based on the reference voltage, and while the reference burst signal is not being generated, the maximum amplitude of the color signal is determined based on the adjustment voltage. To lower the voltage of the color signal. In this case, a digital color signal and a digital luminance signal are independently generated, the digital color signal is converted to an analog color signal by a first D / A converter, and the digital luminance signal is converted to a second luminance signal. Is converted into an analog luminance signal by the D / A converter, and the analog color signal and the analog luminance signal are combined by an analog adder to generate a composite signal.

While the reference burst signal is being generated, the maximum amplitude of the color signal is determined based on the reference voltage. While the reference burst signal is not being generated, the maximum amplitude of the color signal is determined based on the adjustment voltage. The maximum amplitude is determined, and the voltage of the color signal is reduced. As described above, when the composite signal is output to the television and an image is displayed by lowering the voltage of the color signal, the dot crawl phenomenon and the dot disturbance phenomenon are visually inconspicuous on the television screen. Can be. Also, while the reference burst signal is being generated, the first D / A converter outputs a color signal of a normal voltage, so that the television can recognize the reference burst signal. it can.

[Brief description of the drawings]

FIG. 1 is a main block diagram of a video encoding device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a conventional video encoding device.

FIG. 3 is a waveform diagram of a composite signal.

FIG. 4 is a waveform diagram of a luminance signal.

FIG. 5 is a waveform diagram of a color signal.

FIG. 6 is a detailed diagram of a reference burst signal.

FIG. 7 is a time chart illustrating an operation of the video encoding device according to the first embodiment of the present invention.

FIG. 8 is a main block diagram of a video encoding device according to a second embodiment of the present invention.

FIG. 9 is a main block diagram of a video encoding device according to a third embodiment of the present invention.

[Explanation of symbols]

54 first D / A converter 55 second D / A converter 58 analog adder V _ref , V _OUT reference voltage V _{S1 to} V _S3 adjustment voltage C color signal Y luminance signal

Claims (1)

[Claims] 1. A digital color signal and a digital luminance signal are independently generated. (B) The digital color signal is converted into an analog color signal by a first D / A converter. c) converting the digital luminance signal into an analog luminance signal by a second D / A converter; and (d) synthesizing the analog color signal and the analog luminance signal by an analog adder to generate a composite signal. And (e) the first D / A converter is configured to generate the reference burst signal while
The maximum amplitude of the color signal is determined based on the reference voltage, and while the reference burst signal is not generated, the maximum amplitude of the color signal is determined based on the adjustment voltage to lower the voltage of the color signal. A color signal adjustment method for a video encoding device.