JPH06217341A - Chrominance luminance separate circuit for scanning line conversion - Google Patents

Abstract

PURPOSE:To effectively utilize a line memory for Y/C separation and to attain effective scanning line conversion by utilizing the Y/C separation processing as a pre-stage filter for scanning line conversion. CONSTITUTION:When a CIF picture of 5/6 line conversion is generated from an NTSC television signal, chrominance luminance separate circuits 2-12 use a comb-line filter to generate a chrominance signal C and a luminance signal Y and they are inputted to scanning line conversion sections 13-30. On the other hand, when a QCIF picture of 5/3 line conversion is generated, the luminance signal Y is generated by adding a time 2H to the television signal by a line memory LM2, then the characteristic of the QCIF luminance signal is equivalent to that through a low pass filter in the vertical direction in comparison with the CIF luminance signal at a Y/C separation output. Then the CY signal is fed to a scanning line conversion section to obtain a scanning line being a half to that of the CIF signal. The changeover of the CIF and QCIF system is executed by using a mode control section 10. Thus, the Y/C separation processing is used for a pre-stage filter for scanning line conversion and effective scanning line conversion is attained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a device for separating a television signal into a color signal and a luminance signal and further converting the number of scanning lines. In particular, the television signal is divided into a plurality of different intermediate formats (for example, CIF: Common Intermediate). Format, QCIF: Qua
The present invention relates to a color / luminance separation circuit for scanning line conversion that selectively switches to rter CIF) for processing.

[0002]

2. Description of the Related Art In a television signal (NTSC composite signal), a color signal (C signal) is located within a band of a luminance signal (Y signal). For this reason, a method (Y
/ C separation) is required. Y / C which is said to have good characteristics
As a separation method, there is a method using a comb filter. This method is a method that uses the fact that the phase of the color signal is inverted line by line and the similarity of the lines before and after. Y / C using 1 line memory (LM) in Fig. 2 (a) (b)
A block diagram of the separation circuit is briefly shown.

The creation of color signals will be described first. A television signal (NTSC composite signal) input from the NTSC input port 1 is subtracted by a subtractor 3 from a signal delayed by 1 line by the 1-line memory 2. As described above, the phase of the color signal is shifted by 180 degrees for each line,
Due to the nature of television signals, where adjacent lines are highly similar, the color signals are separated by subtracting adjacent lines. This will be briefly described using mathematical expressions. First, NTSC
The signal can be expressed as follows. En = Eyn + Ein ・ sin (ωt) + Eqn ・ cos (ωt) where n = 0,2,4, ..... En = Eyn + Ein ・ (-sin (ωt)) + Eqn ・ (-cos (ωt)) where n = 1,3,5, ..... where En: NTSC signal of the nth line Eyn: Luminance signal of the nth line Ein: Color I signal of the nth line Eqn: Color Q signal on the n-th line ω: Color signal frequency.

Subtracting adjacent lines (for example, 2 and 3 lines) is performed by E2-E3 = (Ey2-Ey3) + (Ei2 + Ei3) sin (ωt) + (Eq2 + Eq3) cos (ωt) Become. Considering the similarity of adjacent lines, Ey2 = Ey3 Ei2 = Ei3 Eq2 = Eq3, and the previous equation becomes E2-E3 = 2 ・ Ei2 ・ sin (ωt) + 2 ・ Eq2 ・ cos (ωt), Separated into color signals only.

Furthermore, since the color signal is modulated at 3.58 MHz, a more accurate color signal can be obtained by passing it through the bandpass filter 5. With respect to the color signal, the color demodulator 9 creates color difference signals Cb and Cr.

Next, the generation of the luminance signal will be described.
As described above, the NTSC signal is a signal in which a chrominance signal is multiplexed with a luminance signal. That is, a luminance signal is obtained by subtracting the color signal from the NTSC signal (FIG. 2 (a)). Further, as shown in FIG. 2B, it is also possible to create a luminance signal using a 1-line memory. Input NTSC signal,
In this method, a luminance signal is obtained by adding the signal delayed by one line time. Explaining using the formula shown above, adding two adjacent lines is E2 + E3 = (Ey2 + Ey3) + (Ei2-Ei3) sin (ωt) + (Eq2-Eq3) cos (ωt ). Considering the similarity of adjacent lines, E2 + E3 = 2 · Ey2, which is the luminance signal. The delay 11 in FIG. 2 is a circuit for adjusting the time of the color signal and the luminance signal passing through the color demodulator.

Now, the difference between FIGS. 2A and 2B will be described. In FIG. 2A, the resolution in the line direction (vertical direction) is completely guaranteed, while in FIG.
In (b), since a calculation is performed with a plurality of lines, the resolution is obtained by applying a low-pass filter in the line direction.

In recent years, a system requiring the conversion of the number of scanning lines of a television signal has appeared. For example, in the field of image transmission used for videophones, videoconferences, and the like. In the field of image transmission, the transmission rate is from 64 kbps to 1.
International standard H.261 of 5Mbps was decided. Image transmission needs to enable international transmission. However, at present, PAL
The image format differs between the NTSC and NTSC areas. Therefore, for the purpose of enabling mutual communication, a common intermediate format (CI
F) has been decided. The effective scanning line of one field of NTSC signal is 240 lines, and the effective scanning line of CIF is 288.
It is a line. Therefore, it is necessary to generate 6 lines from 5 lines of NTSC to create a CIF image. Also, H.2
At 61, the image format is 1/4 the size of CIF (QCIF)
Has been decided. That is, in QCIF, 5 lines of NTSC must be converted into 3 lines. Conventionally, this CIF and QCI
To generate the F image, as shown in FIG. 3, CIF and QC
The filter coefficient (c1 c2 c3 y1y2 y3) is calculated for the data output from the line memory for IF conversion, and CIF image, QCIF
Generating an image.

The processing of the luminance signal (Y) in FIG. 3A will be specifically described as an example. First, in the case of 5/6 conversion, while 6 lines of the input luminance signal (Y) are input,
Output of CIF luminance signal (CIF_Y) is required. Therefore, a memory (FIFO 14) for absorbing this time difference is required. The output signal from the FIFO reads one line out of five lines twice as shown in FIG. In the example of FIG. 3C, the first line is read twice. F
The luminance signal output from the IFO 14 is input to the arithmetic unit 22 as it is, and input to the line memory 17 to 1
The signal is delayed by the line time, and is further input to the line memory 18 and is delayed by 2 line times. The filter coefficients (Y1, Y2, Y3) of the respective signals are calculated by the calculators (22, 23, 24). The calculation results of each line are added by an adder (26) to generate a CIF luminance output (). In Fig. 3 (b), NTSC5
The relationship of generating a CIF6 line from a line is shown.

In the case of 5/3 conversion, 5/6 conversion may be subsampled in the line direction (sampling every other line). Therefore, the coefficient (Y1, Y2, Y3) of the filter calculation needs to be different from that of the 5/6 conversion (to ensure frequency characteristics without folding).

[0011]

In the above prior art, since the color / luminance separation and the scanning line conversion are independent, the line memory used for the color / luminance separation is irrelevant to the scanning line conversion.
For this reason, the Y / C separated line memory cannot be effectively used in scanning line conversion. In addition, line number conversion (5/6
When switching (conversion, 5/3 conversion), it is necessary to change the filter coefficient for line conversion to handle it.
An object of the present invention is to change the Y / C separation method by scanning line conversion (5/6 conversion, 5/3 conversion) and use the line memory for Y / C separation also for scanning line conversion. It is in.

[0012]

In order to achieve the above object, a scanning line conversion color / luminance separation circuit of the present invention is provided with a line memory (2) for temporarily recording an NTSC signal input from an input port. ), And a first adder (3) for subtracting the NTSC signal and the output from the line memory to obtain a color signal.
A second adder (4) for adding the NTSC signal and the output from the line memory to obtain a luminance signal, and selectively outputting the output from the second adder and the NTSC signal. Output to
1 selector (6), a second selector (7) for selectively outputting the output of the first adder and the 0 signal, and adding the second selector output and the first selector output Third adder
(8) Y / C separation circuit section (1-12),
A scanning line conversion unit (13 to 30) that performs scanning line conversion for the two outputs (Y / C) of the C separation circuit unit, and the first, second, and third selectors according to the format of the output signal. And a mode control unit for controlling the coefficients of the coefficient adders (19, 20, 21, 22, 23, 24) inside the scanning line conversion unit. In the present invention, in the H.261 standard, when a CIF and QCIF image is generated by using one-line comb Y / C separation, the Y / C separation method is switched between CIF and QCIF. The mode control unit controls as it does. When generating a CIF, a color signal and a luminance signal are created in a normal line comb shape as shown in FIG.
As shown in (b), the luminance signal is controlled to be generated from the sum of a plurality of lines.

[0013]

By doing so, the color / luminance separation can be utilized as a filter in the preceding stage of scanning line conversion. For this reason,
The line memory used for Y / C separation is also used for scanning line conversion.

That is, the scanning line conversion can be performed by the construction of a transversal type filter which is developed into Y / C separation and original scanning line conversion. Therefore, more effective scanning line conversion can be performed with a small number of line memories.

In addition, when CIF is created (5/6 conversion) and QCIF
It is possible to make the filter coefficient for scanning line conversion the same at the time of creation (at the time of 5/3 conversion).

[0016]

FIG. 1 shows an embodiment of the present invention. This example
This is an example in which two types of Y / C separation are performed by scanning line conversion (5/6 conversion when creating a CIF image and 5/3 conversion when creating a QCIF image) based on the conventional 1-line comb Y / C separation. First,
The operation of creating a CIF image with the circuit of the present invention (FIG. 1) will be described. FIG. 4 is a block diagram of a path selected when a CIF image is created by the circuit of the present invention. The TV signal (NTSC composite) input to the input port 1 is stored in the line memory 2 for one line time (63.5μ).
s) The color signal (C) is generated by subtracting the delayed signal and passing it through the bandpass filter 5 centered at 3.58 MHz. The luminance signal (Y) is generated by subtracting this color signal from the input television signal. The color signals are converted into color difference signals (Cb, Cr) through the demodulator 12 and input to the scanning line conversion circuit.

The signal separated into the luminance signal and the color signal by the Y / C separation circuit is input to the scanning line conversion circuit. When creating a CIF image from an NTSC image, it is necessary to generate 5 to 6 lines of NTSC. The separated luminance signal and chrominance signal are respectively input to the FIFO (13, 14). This FIFO, as described in the prior art,
It is necessary to absorb the time of scan line conversion, and one line of the NTSC 5 lines is read twice to create a scan line time of 6 lines. The output signal from the FIFO is subjected to a vertical (line direction) filter operation, so that the line memory (L
M, 15-18), and a signal delayed by 1 line and delayed by 2 lines is created. The output from the line memory is
The integrators (19 to 24) perform vertical direction filter calculation for CIF image creation. The calculation at this time is NTSC
Since this is an operation for interpolating from 5 lines to 6 lines, the filter coefficients (Y1, Y2, Y3, C1, C2, C3) need to be switched for each line.

Next, the operation of the circuit of the present invention when creating a QCIF image will be described. With the circuit of the present invention, QCIF
When creating an image, a block diagram of the route as shown in FIG. 5 is used. Color signals are generated similar to CIF,
As for the luminance signal, the fact that the phase of the color signal is inverted line by line is used to generate a luminance signal by adding two lines. By using such Y / C separation, the QCIF luminance signal at the time of Y / C separation output has a characteristic of being passed through a low-pass filter in the vertical direction as compared with the CIF luminance signal.

The luminance signal and the color signal separated by the Y / C separation circuit are input to the scanning line conversion circuit. The number of scan lines in QCIF is 1/2 that in CIF. That is, the CIF scan line is 2: 1
If thinned out, it becomes a QCIF scan line. In the method of the present invention,
Even if the configuration of the vertical filter in the scan line conversion circuit is the same as that of the CIF conversion, QC is performed at the time of Y / C separation.
In the case of IF conversion, since it has a low-pass filter characteristic, scanning line conversion is possible only by thinning out (2: 1) in the line direction from the CIF image. In addition, even when a vertical filter that performs QCIF conversion is provided with the characteristics of a low-pass filter and the thinning-out method is used with a frequency characteristic with less aliasing, the Y / C separation acts as a front-stage filter. The number of taps (number of coefficients (Y1, C1, etc.) to be calculated) can be reduced. This makes it possible to reduce the line memory due to the circuit configuration, which is effective for the development of LSI and the like.

In QCIF, the number of pixels on one line is 1/2 that of CIF. Therefore, a filter in the horizontal direction (pixel direction) is also required. In FIG. 5, the LPF (27, 28) is the horizontal low-pass filter. In the block configuration of FIG. 5, the circuit of the present invention operates so as to perform scan line conversion in the vertical direction, further pass a low pass filter in the horizontal direction, and create a thinned QCIF image in a ratio of 2: 1 in the horizontal and vertical directions.

As described above, the Y / C separation circuit of the present invention is characterized in that its system changes according to the conversion of the image format, and is equipped with the mode controller 10 for controlling this switching. That is the circuit of the present invention. That is, in the circuit of the present invention, the Y / C separation method is changed for the conversion of the image format, and the Y / C separation is made to act as a filter in the preceding stage of the scanning line conversion.

FIG. 6 shows an application example of the present invention. In the example of FIG. 1, the one-line comb Y / C separation is used as the Y / C separation. However, since the present invention is to change the Y / C separation method according to the scan line conversion, The same can be applied to the two-line comb Y / C separation as shown in FIG.

A case of creating a CIF image will be described. NTSC signal (N0) input from input port 101
Is a signal delayed by 1 line (N1) and a signal delayed by 2 lines (N
2) and the following calculation is performed, and further, by passing through the band pass filter 106 centered at 3.58 MHz,
A color signal is created. Color signal = ―1/4 ・ N0 + 1/2 ・ N1 -1/4 ・ N2 Luminance signal is created by subtracting this luminance signal from the input NTSC signal.

A case of creating a QCIF image will be described. The color signals are the same as when creating the CIF. At the time of creating the luminance signal, the following calculation is performed, and the filter action in the vertical direction is performed by Y / C separation. Luminance signal = 1/4 · N0 + 1/2 · N1 + 1/4 · N2 For scanning line conversion, the case where the number of taps of the vertical filter for scanning line conversion is increased compared to Fig. 1 is shown. .
The advantage of increasing the number of taps is that the characteristics of the vertical filter are improved. Another drawback is the increase in the number of line memories.

[0025]

According to the present invention, since Y / C separation can be used as a filter in the preceding stage of scanning line conversion, effective scanning line conversion can be performed with a small amount of line memory.

[Brief description of drawings]

FIG. 1 is a block diagram of a color / luminance separation circuit for scanning line conversion, which is an example of the present invention.

FIG. 2 is an example of a color / luminance separation circuit using a 1-line memory.

FIG. 3 is 1 of scanning line conversion (5 lines / 6 lines conversion)
Example.

FIG. 4 is a block diagram illustrating a case where 5/6 conversion is performed in the present invention.

FIG. 5 is a block diagram illustrating a case where 5/3 conversion is performed in the present invention.

FIG. 6 is a block diagram showing an application example of the present invention.

[Explanation of symbols]

1 ... TV signal input port, 2 ... Line memory, 3 ... Subtractor, 4 ... Adder, 5 ... Bandpass filter, 6 ... Selector, 7 ... Selector, 8 ... Subtractor, 9 ... Color demodulator, 10 ... mode controller, 11 ... delay circuit, 12 ... selector, 13 ... F
IFO memory, 14 ... FIFO memory, 15 ... Line memory, 16 ... Line memory, 17 ... Line memory, 18
... line memory, 19 ... multiplier, 20 ... multiplier, 2
1 ... Multiplier, 22 ... Multiplier, 23 ... Multiplier, 24
... multiplier, 25 ... adder, 26 ... adder, 27 ... horizontal low-pass filter, 28 ... horizontal low-pass filter, 29
... selector, 30 ... selector, 31 ... CIF color signal output port, 32 ... CIF luminance signal output port, 101 ... TV signal input port, 102 ... line memory, 103 ... line memory, 104 ... adder / subtractor, 105 ... addition Bowl, 106 ...
Bandpass filter, 107 ... Selector, 108 ... Selector, 109 ... Subtractor, 110 ... Color demodulator, 111 ... Mode controller, 112 ... Delay circuit, 113 ... Selector, 114
... FIFO memory, 115 ... FIFO memory, 116 ...
Line memory, 117 ... Line memory, 118 ... Line memory, 118 ... Line memory, 119 ... Line memory, 120 ... Line memory, 121 ... Line memory, 1
22 ... Line memory, 123 ... Line memory, 124 ...
Adder, 125 ... Adder, 126 ... CIF color signal output port, 127 ... CIF luminance signal output port.

Claims (2)

[Claims] 1. A color / luminance separation circuit for scanning line conversion, characterized in that a color / luminance separation method of a television signal is changed in accordance with scanning line conversion, wherein an NTSC signal input from an input port is temporarily changed. Line memory for recording, a first adder for obtaining the color signal by subtracting the NTSC signal and the output from the line memory, and the NTSC signal and the output from the line memory And a second adder for obtaining a luminance signal, a first selector for selectively outputting the output from the second adder and the NTSC signal, and the output of the first adder A second selector that selectively outputs the 0 signal;
A Y / C separation circuit section comprising a second adder output and a third adder for adding the first selector output, and the Y / C separation circuit section.
A scanning line conversion unit that performs scanning line conversion for the two outputs (Y / C) of the separation circuit unit, and the first, second and third selectors and the scanning line conversion unit according to the format of the output signal. A color luminance separation circuit for scanning line conversion, comprising: a mode control unit for controlling the coefficient of an internal coefficient adder. 2. The mode control unit uses a CIF (common intermediate format: an image format used in image transmission such as H.261) from an NTSC television signal or QCIF (CIF 1).
/ 4 image format), when performing 5 line / 6 line conversion (when creating CIF), create color signals by multi-line calculation and subtract luminance signals from television signals. 2. When performing 5 line / 3 line conversion (when creating QCIF), the color signal and the luminance signal are controlled so as to be created from the calculation of a plurality of lines. A color-brightness separation circuit for scanning line conversion described.