JPH0537963A - Color television signal transmitting system - Google Patents

Abstract

PURPOSE:To prevent picture quality from being deteriorated even when the band of a chrominance signal is <=1/5 the band of a luminance signal. CONSTITUTION:A transmitting chrominance signal generating circuit 5 fetches a color difference signal and outputs a color difference signal based upon the color difference signal in the case of a picture element having high brightness or outputs a signal obtained by dividing the color difference signal by the luminance signal in the case of a picture element having low brightness. Low pass filter circuits 6a, 6b limit the bands of the signals outputted from the circuit 5 and transmit the band-limited signals as chrominance signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television signal transmission system which prevents deterioration of image quality even if the transmission signal band is narrowed.

SUMMARY OF THE INVENTION The present invention relates to a color signal transmission system in a color television system, in which a non-linear process using luminance signal information is applied to a color signal so that a pixel having high luminance becomes a color difference signal. In addition, by forming a transmission color signal that becomes a chromaticity signal in a pixel having low luminance, it is possible to maintain high image quality even in a narrower color signal band.

[0003]

2. Description of the Related Art As one of band compression methods for a color television signal, a conventional RGB three primary color signal and a luminance signal are used.
A method of converting into one color signal and limiting the color signal to a narrow band for transmission is often used.

For example, in the studio standard or the like, 4: 2:
Two methods are standardized.

At this time, the color signals are RY and B-.
A color difference signal such as Y is used, and the color signal directly corresponds to the chromaticity (hue, saturation) of the subject.
-Y) / Y, (B-Y) / Y, and other methods have been proposed in which a chromaticity signal representing chromaticity is used as a transmission color signal ("Color Television" edited by NHK, P. 199, published by Nippon Broadcasting Corporation). Association, 1961).

[0006]

From the human visual characteristics, the required band of the chromaticity information of the image is "1" as compared with the luminance.
It is said to be / 5 "or less.

However, in the color difference signal which is widely used at present, since the chromaticity of the object does not directly correspond to the signal value, in order to maintain high image quality, "1 /" of the luminance signal band is maintained.
More than 3 "is needed.

Therefore, the above-mentioned chromaticity signal has also been proposed, but it has not been put into practical use because a division circuit is required to create the chromaticity signal and the analog circuit is unstable.

However, although such technical problems can be solved by the digital technology which has been developed in recent years, when actually tested, another problem is that the chromaticity signal (RY) / Y, Since it is necessary to multiply the luminance signal by the chromaticity signal in the process of restoring (BY) / Y and the like to the three primary color signals on the image receiving side, an image with high luminance ringing of the filter for band limiting the chromaticity signal. It was found that the received image was greatly amplified due to the amplification in the part.

For the same reason, the quantization error and noise on the transmission line are also amplified, which also causes a large deterioration in image quality.

In view of the above circumstances, the present invention provides a color television signal transmission system capable of preventing the image quality from deteriorating even if the color signal band is equal to or less than "1/5" of the luminance signal band. It is an object.

[0012]

In order to achieve the above object, a color television signal transmission system according to the present invention comprises:
In a television system that converts a three-primary-color signal into a luminance signal and two-color signals and transmits the signals, the color-difference signal is captured and a color-difference signal is output to a pixel with high luminance and a pixel with low luminance is output A transmission color signal generation circuit that divides the color difference signal by a luminance signal and outputs the color difference signal, and a low-pass filter circuit that limits the band of the signal output from the transmission color signal generation circuit, and the output of the low-pass filter circuit is the color signal. It is characterized by transmitting as.

[0013]

In the above structure, the color difference signal is fetched by the transmission color signal generation circuit, the color difference signal is output to the pixel having high luminance based on the color difference signal, and the luminance signal is outputted to the pixel having low luminance. The color-difference signal is divided and output by the low-pass filter circuit, and the signal output from the transmission color signal generation circuit is band-limited by the low-pass filter circuit, which is transmitted as a color signal.

[0014]

1 is a block diagram showing an example of a television system to which an embodiment of a color television signal transmission system according to the present invention is applied.

The television system shown in this figure is provided with an encoder 1 provided on the image transmitting side and a decoder 2 provided on the image receiving side, and transmits R'G'B 'signals obtained by a television camera or the like. The luminance signal Y and the color signals C1 and C2 are taken in, transmitted, and transmitted to the encoder 2 provided on the image receiving side for decoding.
The Rr'Gr'Br 'signal corresponding to the B'signal is reproduced.

As shown in FIG. 2, the encoder 1 includes three inverse gamma correction circuits 3a to 3c, a matrix circuit 4, a transmission color signal generation circuit 5, and two low pass filter circuits 6.
a and 6b are provided, and the R'G'B 'signal obtained by a television camera or the like is taken in to generate a luminance signal Y and narrow band color signals C1 and C2, and this is sent out on the transmission path. Then, the data is transmitted to the encoder 2 provided on the image receiving side.

Each of the inverse gamma correction circuits 3a to 3c takes in each R'G'B 'signal obtained by a television camera or the like and inverse-gamma-corrects the R'G'B' signal to generate a linear RGB signal and generate it. It is supplied to the matrix circuit 4.

The matrix circuit 4 takes in the RGB signals output from each of the inverse gamma correction circuits 3a to 3c and performs a matrix process on the RGB signals to perform a luminance signal Y.
After generating the two color difference signals RY and BY, the luminance signal Y is transmitted to the decoder 2 provided on the image receiving side, and the luminance signal Y and the two color difference signals RY,
BY is supplied to the transmission color signal generation circuit 5.

The transmission color signal generation circuit 5 takes in the luminance signal Y and converts it into a signal F (Y) having a preset characteristic, and the non-linear level conversion circuit 7 outputs the non-linear level conversion circuit 7. Two color difference signals R- output from the matrix circuit 4 by the signal F (Y).
Two division circuits 8a and 8b for dividing Y and BY respectively.
And the luminance signal Y is fetched and converted into a signal F (Y) having a preset characteristic, and the color difference signals R-Y, B are generated by the signal F (Y).
-Y is divided respectively to obtain signals (RY) / F (Y), (B
-Y) / F (Y) is calculated and supplied to the low-pass filter circuits 6a and 6b, respectively. The above-mentioned nonlinear level conversion circuit 7 will be described in detail later.

The low-pass filter circuits 6a and 6b output the respective signals (RY) output from the transmission color signal generation circuit 5.
/ F (Y), (BY) / F (Y) is taken in, and the high frequency components of these signals (RY) / F (Y) and (BY) / F (Y) are cut. For the band of the luminance signal Y,
Each signal (RY) / F (Y), (BY) / F
The color signal C1 in which the band of (Y) is limited to about "1/5",
C2 is generated and this is transmitted to the decoder 2 provided on the image receiving side.

As shown in FIG. 3, the decoder 2 includes two low-pass filter circuits 10a and 10b, a transmission color signal restoration circuit 11, an inverse matrix circuit 12, and three gamma correction circuits 13a to 13c. Encoder 1
Rr'G corresponding to the R'G'B 'signal is obtained by decoding the luminance signal Y output from the color signals C1 and C2.
The r'Br 'signal is reproduced and supplied to a display (not shown) for display.

Each of the low-pass filter circuits 10a and 10b takes in the color signals C1 and C2 output from the encoder 1 and cuts high frequency components of these color signals C1 and C2 to eliminate unnecessary noise signals mixed in the transmission line. After removing the interfering signal, the processed color signals C1 and C2 are supplied to the transmission color signal restoration circuit 11.

The transmission color signal restoration circuit 11 takes in the luminance signal Y output from the encoder 1 and converts it into a signal F (Y) having a preset characteristic, and this nonlinear level conversion circuit. Signal F (Y) output from each of the low-pass filter circuits 10
It is provided with two multiplication circuits 15a and 15b for respectively multiplying the two color signals C1 and C2 outputted from a and 10b, respectively, and taking in the luminance signal Y to obtain a signal having a preset characteristic. The signal F (Y) is converted into F (Y) and the color signals C1 and C2 are respectively multiplied to obtain color difference signals (RY) r and (BY) r, which are inverse matrixes. Each is supplied to the circuit 12.

The inverse matrix circuit 12 outputs the luminance signal Y output from the encoder 1 and the color difference signals (RY) r and (B-Y) output from the transmission color signal restoration circuit 11.
Y) r is taken in, and these are subjected to inverse matrix processing to generate an RrGrBr signal indicating the three primary colors of the image,
This is supplied to each of the gamma correction circuits 13a to 13c.

The gamma correction circuits 13a to 13c respectively have
RrGrB output from the inverse matrix circuit 12
Each r signal is gamma-corrected to generate an Rr'Gr'Br 'signal, which is output as a decoder output to a display or the like for display.

Next, the above-mentioned nonlinear level conversion circuit 7,
14 will be described in detail.

First, as shown in FIG. 4, the non-linear level conversion circuits 7 and 14 set the nominal dynamic range of the luminance signal Y to 1
The range from 00% black to 100% white falls within the range of "0" to "1", and the allowable range is "-B1" to "(1 + B
2) ”(however,“ B1 ”and“ B2 ”are positive values).

In this case, the value of the luminance signal Y does not become negative in a normal state, but when the television camera performs excessive contour compensation, or when the television camera performs linear color correction for primary color point correction. It can be negative when having a matrix.

Therefore, a variable d is introduced as a parameter of the signal F (Y), and the value of this variable d is set as shown in the following equation.

[0030]

[Equation 1]

By doing so, the value of the color signal C1 can be expressed by the following equation at low frequencies.

C1 = (R−Y) / (Y + d) (2) As a result, even if the value of the luminance signal Y takes any value within the allowable range, the value of the color signal C1 is always a finite positive value. be able to.

The value B1 is usually a small value, and for example, in CCIR Recommendation 601, the value is given by the following equation.

[0034]

[Equation 2]

In this case, the signal (RY) / Y is "NHK."
Volume "Color Television", P. 199, Japan Broadcast Publishing Association, 1961 ", it is a signal (chromaticity signal) corresponding to the chromaticity of light on a one-to-one basis. Even if the band is limited to "1/5" or less of the band, the image quality is hardly deteriorated.

That is, when the color saturation of the subject is high and the luminance is low, the color signal band has a great influence on the image quality of the received image. However, when the luminance is high, the color signal band has a small influence on the image quality of the received image. The effect of using it as a chromaticity signal is small.

On the other hand, the low-pass filter circuit 6 shown in FIG.
Since ringing occurs in the waveform response in a and 6b in general, the luminance signal Y and the color difference signal (BY) output from the matrix circuit 4 have waveforms as shown in FIGS. When the output signal output from the two low-pass filter circuits 6b has ringing of amplitude "e" as shown in FIG. 5C, "F" as shown by the dotted line in FIG.
Assuming that (Y) = Y + d ″, the following equation holds on the upper side of the output signal output from the low-pass filter circuit 6b,

[0038]

[Equation 3]

The multiplication circuit 15b of the transmission color signal restoration circuit 11
To the color difference signal (BY) of the waveform shown by the dotted line in FIG.
r is output.

At this time, since the step amount of the waveform shown by the dotted line in FIG. 5 (d) is "P1 (Y1 + d)", the relative ringing amount "gr '" with respect to the step amount is the value shown by the following equation. become.

[0041]

[Equation 4]

The low pass filter circuit 10b
In the color signal C2 output from the above, the value represented by the equation (5) is "g = e / P1". Therefore, the amplification degree "gr '/ g" of the transmission color signal restoration circuit 11 with respect to the ringing is obtained.
Is the value shown in the following equation.

[0043]

[Equation 5]

Therefore, at this time, assuming that the relationship shown in the following equation holds, Y1 >> d, Y2 >> d (7) The ringing generated in the color signals C1 and C2 is "Y2" on the image receiving side.
/ Y1 "times. Then, assuming that the relationship shown in the following equation holds, Y2> Y1 (8) The image quality of the received image is greatly deteriorated due to ringing.

For example, "Y2 = 1", "Y1 = 0.
When 1 ”and“ d = 0.08 ”, the ringing is“ about 6 ”.
It will be amplified twice.

As described above, in the portion where the brightness of the image is high, not only the transmission by the chromaticity signal is less effective, but also the image quality is deteriorated.

Therefore, in this embodiment, the signal F
(Y) has a characteristic as shown by the solid line in FIG. 4,
When “Y <0.3”, the color signals C1 and C2 are approximately equal to the chromaticity signal, and when “Y> 0.3”, the signal F (Y) is set to a substantially constant value to obtain the color signal C1. , C2 to the color difference signal (R-
Y) and (B-Y) are almost equal to each other, and the advantages of both are provided together.

At this time, the signal output from the multiplication circuit 15b provided in the transmission color signal restoration circuit 11 is shown in FIG.
As shown by the solid line.

Here, when the ringing amplification degree is obtained in the same manner as described above, "Y2>0.3" and "Y1 <
If 0.3 ", the following equation holds, and er = e (0.3 + d) gr = e (0.3 + d) / P1 (Y1 + d) g = e / P1 (9) From this equation (9), The formula holds.

Gr / g = (0.3 + d) / (Y1 + d) (10) Then, assuming that “Y1 = 0.1” and “d = 0.08”, the following equation holds,

[0051]

[Equation 6]

As is apparent from the equation (11), the defect of the chromaticity signal transmission can be considerably reduced as compared with the case where the signal F (Y) is "F (Y) = Y + d".

At this time, the Y1 side (chromatic color side) of the waveform is almost equal to the chromaticity signal transmission, so that FIG.
As shown in (c) and (d), on the chromatic side (Y1 side), the pulse rise time “Δtr” can be shortened from the rise time “Δt” determined by the constants of the low-pass filter circuits 10a and 10b. This can improve the color freshness of the received image.

Thus, in this embodiment, when "Y <0.3" as shown by the solid line in FIG. 4, the color signals C1 and C are
2 is almost equal to the chromaticity signal, and "Y> 0.
3 '', the signal F (Y) is set to a substantially constant value, and the luminance signal Y is set to the signal F (Y) so that the color signals C1 and C2 are substantially equal to the color difference signals (RY) and (BY). ), The color signal band is changed to “1” of the luminance signal band.
It is possible to prevent the image quality from deteriorating even if it is / 5 "or less.

FIG. 6 is a block diagram showing an example of a television system to which another embodiment of the color television signal transmission system according to the present invention is applied.

The television system shown in this figure is provided with an encoder 20 provided on the image transmitting side and a decoder 21 provided on the image receiving side, and transmits the R'G'B 'signal obtained by a television camera or the like. The luminance signal YD and the color signals C1D and C2D in a digital format are taken in and transmitted to the decoder 21 provided on the image receiving side for decoding, and Rr'Gr 'corresponding to the R'G'B' signal is produced. B
Regenerate the r'signal.

As shown in FIG. 7, the encoder 20 includes a preprocessing circuit 22, a transmission color signal generating circuit 23, and a postprocessing circuit 24.
And R'obtained by a TV camera or the like.
G'B 'signal is captured and digital format luminance signal YD
And color signals C1D and C2D are generated and transmitted to the decoder 21 provided on the image receiving side.

The preprocessing circuit 22 has three A circuits as shown in FIG.
The R / G conversion circuit 25a to 25c, the three inverse gamma correction circuits 26a to 26c, and the one matrix circuit 27 are provided, and R'G 'obtained by a television camera or the like.
The B ′ signal is taken in, converted into a digital signal, subjected to inverse gamma correction, and then processed into a matrix to generate a luminance signal Y, which is supplied to the transmission color signal generation circuit 23 and the post-processing circuit 24. At the same time, two color difference signals (RY), (B-
Y) is supplied to the transmission color signal generation circuit 23.

The A / D conversion circuits 25a to 25c respectively
Each of the R'G'B 'signals obtained by a television camera or the like is taken in, and the sufficient sampling frequency fs is obtained.
Sufficient quantization bit number (eg 10
Bit) digital signals and supplies them to the respective inverse gamma correction circuits 26a to 26c.

The inverse gamma correction circuits 26a to 26c take in digital R'G'B 'signals output from the A / D conversion circuits 25a to 25c, respectively, and perform inverse gamma correction on them to make linear signals. An RGB signal is generated and supplied to the matrix circuit 27.

The matrix circuit 27 takes in the RGB signals output from each of the inverse gamma correction circuits 26a to 26c, and performs matrix processing on the RGB signals to perform a luminance signal Y and two color difference signals RY and BY. And the luminance signal Y is supplied to the post-processing circuit 24, and the luminance signal Y and the two color difference signals RY and BY are supplied to the transmission color signal generation circuit 23.

The transmission color signal generation circuit 23 uses the luminance signal Y
Is output from the matrix circuit 27 by the non-linear level conversion circuit 28 that takes in and converts it into a signal F (Y) having a preset characteristic, and the signal F (Y) output from the non-linear level conversion circuit 28. Two division circuits 2 for respectively dividing the two color difference signals R-Y and B-Y
9a and 29b, the luminance signal Y is captured and converted into a signal F (Y) having a preset characteristic, and the color difference signal R- is generated by the signal F (Y).
Y and BY are each divided to obtain a signal (RY) / F
(Y), (BY) / F (Y) are obtained and are supplied to the post-processing circuit 24.

As shown in FIG. 9, the post-processing circuit 24 includes two low-pass filter circuits 30a and 30b, two sub-samplers 31a and 31b, and two transmission gamma correction circuits 32.
a, 32b, and three quantizing circuits 33a to 33c. The luminance signal Y output from the preprocessing circuit 22 is taken in to generate a luminance signal YD, which is transmitted to the decoder 21 on the image receiving side. And a signal (RY) / F (Y) output from the transmission color signal generation circuit 23.
(B-Y) / F (Y) is taken in and color signals C1D and C2D
And the low-pass filter circuits 30a and 30b for transmitting the signals to the decoder 21 on the image receiving side output the respective signals (RY) / F output from the transmission color signal generation circuit 23.
(Y), (B−Y) / F (Y) are taken in, and the high frequency components are cut off, and the signals (R−Y) / F (Y), ( BY) /
The color signal C is limited by limiting the F (Y) band to about "1/5".
1 and C2 are generated, and each of these sub-samplers 31a, 31
b respectively.

The sub-samplers 31a and 31b are the above-mentioned A
The sampling frequency fs of the D / D conversion circuits 25a to 25c is "1".
The color signals C1 and C2 output from the low-pass filter circuits 30a and 30b are sampled on the basis of the sampling frequency fs / 5 thinned to / 5 ", and are sampled to the transmission gamma correction circuits 32a and 32b, respectively. , Supply.

The transmission gamma correction circuits 32a and 32b take in the respective color signals C1 and C2 output from the respective sub-samplers 31a and 31b and perform transmission gamma correction on the color signals C1 and C2 to make the nonlinear color signals C1 and C2. Each quantization circuit 33
b and 33c, respectively. The transmission gamma correction circuits 32a and 32b will be described in detail later.

The quantizing circuits 33b and 33c take in the color signals C1 and C2 output from the transmission gamma correcting circuits 32a and 32b, respectively, and quantize the color signals C1 and C2 individually to obtain a "5" -bit color signal C1D, C2D is generated, and this is transmitted to the decoder 21 on the image receiving side.

The remaining quantizing circuit 33a takes in the luminance signal Y output from the preprocessing circuit 22 and quantizes the luminance signal Y to generate an "8" -bit luminance signal YD.
This is transmitted to the decoder 21 on the image receiving side.

In this case, the transmission bit rate of the luminance signal YD output from the post-processing circuit 24 is set to "8fs (bit / bit /
s) ”and the transmission bit rate of each color signal C1D, C2D is“ (fs / 5) × 5 = 1fs (bit /
s) ", the transmission bit rate of each color signal C1D, C2D can be compressed to" 1/8 "with respect to the transmission bit rate of the luminance signal YD.

This is a normal digital transmission "4:
Transmission bit rate "4f" in color signal of 2: 2 "system
Compared with s (bit / s) ", it is further" 1/4 ".

However, according to the present invention, since the color signal whose color information has a great influence on the image quality of the image directly corresponds to the chromaticity, the quantization error of the transmission path causes the color signal in the image to be received. As long as it is set to be visually equal regardless of the level, high image quality can be maintained even if quantization is performed to a low bit number as described above.

The decoder 21 is obtained by modifying the decoder 2 shown in FIG. 3 so as to correspond to the encoder 20 shown in FIGS. 7 to 9, and the digital format luminance signal YD and color output from the encoder 20. Signal C1D, C2D
To decode Rr 'corresponding to the R'G'B' signal
Reproduce the Gr'Br 'signal. In addition, this decoder 21
2 corresponds to the decoder 2 shown in FIG. 3 corresponding to the encoder 20 shown in FIGS. 7 to 9, and since it is easy to analogize, detailed circuit configuration will be omitted.

Next, the transmission gamma correction circuits 32a and 32b described above will be described in detail with reference to FIG.

First, since the dynamic range of the chromaticity signal is generally not symmetrical with respect to positive and negative, the dynamic range of the chromaticity signal is not symmetrical with positive and negative in the embodiment shown in FIG.

For example, assuming that the characteristic shown in FIG. 4 (d = 0.08) is used as the signal F (Y) and the relationship shown in the following equation is established, Y = 0.30.R + 0. 59 · G + 0.11 · B (12) The dynamic range of the color signal C2 is “B = 1, G = 0,
When R = 0 ", the maximum value is given by the following equation, and C2 = (1-0.11) / (0.11 + 0.08) = 4.68 (13) Also," R = G = 1, B When = 0 ”, the minimum value is given by the following equation.

C2 = − (0.30 + 0.59) / (0.3 + 0.08) = − 2.34 (14) Therefore, in the embodiment shown in FIG. 6, the transmission inverse gamma correction circuits 32a and 32b are provided. , "4.68" to "-
The output is defined only for the input signal in the range where a slight margin is provided in the range of 2.34 ″.

At this time, the visual characteristic is B on the chromaticity diagram.
It has been revealed that the color discrimination ability of the human eye is superior as it approaches the primary color direction. Therefore, in order to make the quantization error in the received image look uniform, the larger the value of the color signal C2 is, Finer quantization is required. Therefore, in this embodiment, the characteristics of the transmission inverse gamma correction circuits 32a and 32b are as shown in FIG.
The characteristic shown by the characteristic curve A of 0 is used.

However, this characteristic is such that when the value of the input signal is "0", the value of the output signal does not become "0", which may cause inconvenience in signal processing in the transmission path. Sometimes, the characteristic shown by the characteristic curve B in FIG. 10 is used. In this case, by using the characteristic curve B,
Although the effect is slightly lower than that of the characteristic curve A, it is possible to secure an effect that does not impair practical use.

Thus, in this embodiment, the signal F
The characteristics of (Y) are changed to those shown by the solid line in FIG.
When “Y <0.3”, the color signals C1 and C2 are approximately equal to the chromaticity signal, and when “Y> 0.3”, the signal F (Y) is set to a substantially constant value to obtain the color signal C1. , C2 to the color difference signal (R-
Y) and (B-Y) are made substantially equal to each other so that the merits of both can be provided together, so that the band of the chrominance signal can be set to "1/5" or less of the brightness signal band, and It is possible to prevent the image quality from deteriorating.

Further, in digital transmission, transmission gamma correction is applied to the above-mentioned color signals C1 and C2, so that it is possible to prevent an increase in the quantization error peculiar to the chromaticity signal and to increase the high error. It is possible to perform low bit rate transmission of image quality color signals.

In each of the above-described embodiments, the case where the R'G'B 'signal output from the television camera or the like is non-linear is explained, but the linear RGB signal output from the television camera is described. Is output from the encoders 1 and 20, the inverse gamma correction circuit 3a ...
3c, 26a to 26c, etc. are deleted, and the decoders 2 and 2 are also deleted.
When the RrGrBr signal from 1 may be directly output, the gamma correction circuit 13a is output from the decoders 2 and 21.
It is needless to say that ~ 13c is deleted.

When the television system shown in FIG. 1 is composed of digital circuits, a large capacity RO is used.
The transmission color signal generation circuit 11 may be configured by M.

[0082]

As described above, according to the present invention, it is possible to prevent the image quality from deteriorating even when the band of the color signal is "1/5" or less of the band of the luminance signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a television system to which an embodiment of a color television signal transmission system is applied.

FIG. 2 is a block diagram showing a detailed circuit example of the encoder shown in FIG.

FIG. 3 is a block diagram showing a detailed circuit example of the decoder shown in FIG.

FIG. 4 is a schematic diagram showing a characteristic example of the non-linear level conversion circuit shown in FIGS. 2 and 3.

5 is a waveform chart showing an example of effects of the embodiment shown in FIG.

FIG. 6 is a block diagram showing an example of a television system to which another embodiment of a color television signal transmission system is applied.

7 is a block diagram showing a detailed circuit example of the encoder shown in FIG.

8 is a block diagram showing a detailed circuit example of the preprocessing circuit and the non-linear level conversion circuit shown in FIG.

9 is a block diagram showing a detailed circuit example of the post-processing circuit shown in FIG.

10 is a schematic diagram showing a characteristic example of the transmission gamma correction circuit shown in FIG.

[Explanation of symbols]

1 encoder 2 decoder 5 Transmission color signal generation circuit 6a, 6b low-pass filter circuit, 7,14 Non-linear level conversion circuit 8a, 8b Division circuit 11 Transmission color signal restoration circuit 31a, 31b Subsampler 33a-33c Quantization circuit

Claims (4)

[Claims] 1. In a television system for converting a three-primary-color signal into a luminance signal and two color signals and transmitting the same, a color-difference signal is taken in and a color-difference signal is output to a pixel with high luminance, and the luminance is low. The pixel includes a transmission color signal generation circuit that divides a color difference signal by a luminance signal and outputs the pixel, and a low-pass filter circuit that limits the band of the signal output from the transmission color signal generation circuit. A color television signal transmission system characterized in that the output of the circuit is transmitted as a color signal. 2. The color according to claim 1, further comprising a transmission color signal restoration circuit which restores a color difference signal by performing a process opposite to that of the transmission color signal generation circuit output from the low pass filter circuit on the image receiving side. Television signal transmission system. 3. The transmission color signal generation circuit and the transmission color signal restoration circuit take in a luminance signal, and when the value of the luminance signal is small, generate an output signal having a value proportional to the luminance signal, And a division circuit that divides the color difference signal and the transmission color signal by the output signal output from the non-linear level conversion circuit when the value of is large. Item 1. The color television signal transmission system according to Item 1 or 2. 4. When the signal level of the output signal of the low-pass filter circuit is high, non-linear quantization is performed so as to obtain fine quantization, and before or after this quantization operation,
The color television signal transmission system according to claim 1, wherein sampling is performed at a sampling frequency which is a fraction of the luminance signal at the same time as the quantization.