Color television signal transmission system and improved-definition receiver for use in the system

• US 4,870,481 A
• Filed: 12/01/1987
• Issued: 09/26/1989
• Est. Priority Date: 12/01/1987
• Status: Expired due to Term

• Current Assignee: Ikegami Tsushinki Co Limited (Ikegami Tsushinki)
• Original Assignee: Ikegami Tsushinki Co Limited (Ikegami Tsushinki)
• Inventors: Kawamata, Seiji
• Primary Examiner(s): Chin, Tommy P.
• Application Number:
  US07/127,260
• Time in Patent Office: 665 Days
• Field of Search: 358/12, 358/13, 358/16, 358/21 R, 358/31, 358/39, 358/23, 358/7
• US Class Current: 348/451
• CPC Class Codes: H04N 11/24 High-definition television systems
• CPC Class Codes: H04N 7/015 High-definition television systems

Abstract

A color television signal transmission system in which, at the transmitter end the frequency bandwidths of the brightness and chrominance signals are extended by two to three times as compared with the NTSC system to improve horizontal resolution and color reproducibility. At the receiver end, the received composite signal is subjected to both interframe separation and picture adaptive separation to provide two brightness signals and two chrominance signals. A combined brightness signal is formed by adding the two brightness signals after they have been multiplied by weights which are determined on the basis of picture movement, and a combined chrominance signal is formed in the same way. The combined brightness and chrominance signals are converted into red, green and blue color signals, and then the vertical resolution is improved by movement adaptive line interpolation. The transmission system has vertical resolution and horizontal resolution superior to the NTSC, IDTV, and EDTV systems, and furthermore can be realized by simpler and cheaper equipment than the HDTV system.

Claims

1. A system for transmitting a movable picture via a color television signal, said system comprising:

at a transmitter end

first means, responsive to red, green and blue input color signals, for generating a composite color television signal including a brightness signal modulated on a main carrier and having a frequency bandwidth of 8 to 15 MHz, and a chrominance signal modulated on a color subcarrier and having a frequency bandwidth of 1.8 to 3.5 MHz, said chrominance signal being interleaved with the brightness signal; and

second means for transmitting the composite color television signal; and

at a receiver end

third means, responsive to the signal transmitted by the second means, for generating a received composite color television signal having a brightness component and a chrominance component;

fourth means for deriving from the received composite color television signal mutually separated first brightness and chrominance signals, the fourth means including an interframe brightness/chrominance separator;

fifth means for deriving from the received composite color television signal mutually separated second brightness and chrominance signals, the fifth means including a picture adaptive brightness/chrominance separator;

sixth means for deriving mutually separated further brightness and chrominance signals by adding said mutually separated first and second brightness and chrominance signals, respectively, in accordance with a weight determined by the movement of the picture;

seventh means for effecting contour enhancement of the further brightness signal to derive an enhanced brightness signal;

eight means for decoding the enhanced brightness signal and the further chrominance signal to derive red, green and blue color signals; and

ninth means for generating interpolated signals to provide additional scanning lines by effecting movement adaptive line interpolation for the red, green and blue color signals, the movement adaptive line interpolation reducing spurious after images when there is movement of the picture.

2. A system according to claim 1, wherein said chrominance signal is composed of a color difference signal (R-Y) and a color difference signal (B-Y), and wherein the first means comprises means for modulating the color difference signals (R-Y) and (B-Y) in quadrative on the color subcarrier.

3. A system according to claim 2, wherein the brightness signal included in the composite color television signal to be transmitted has a frequency bandwidth of about 12 MHz, wherein the color difference signals (R-Y) and (B-Y) are provided in the form of double-sidebands having a frequency bandwidth of about 2.4 MHz, wherein the color subcarrier has a frequency of about 7.151223 MHz, and wherein the number of scanning lines per frame is set to 525, the number of frames per second is set to 30, and an interlace ratio of 2:

1 is effected.

4. A system according to claim 1, wherein said sixth means comprises means for generating an interframe movement coefficient which increases when the movement of the picture decreases.

5. A system according to claim 4, wherein said means for generating an interframe movement coefficient comprises means for deriving a first difference in the brightness component of the received composite color television signal between successive frames, means for deriving a second difference in the brightness and chrominance components of the received composite color television signal between every other frame, means for generating first and second interframe movement coefficients corresponding to said first and second differences, and means for selecting the larger of the first and second interframe movement coefficients.

6. A system according to claim 1, wherein said picture adaptive brightness/chrominance separator comprises first means for filtering the received composite color television signal to provide a first filtered chrominance signal, the first filter means including a comb filter, second filter means for filtering the received composite color television signal to provide a second filtered chrominance signal, the second filter means including a band pass filter, means for generating image change coefficients derived from the picture contents, and means for subjecting the first and second filtered chrominance signals to weighted addition in accordance with the image change coefficients.

7. A system according to claim 6, wherein said means for generating an image change coefficient comprises means for deriving a vertical change signal and a lateral change signal for changes in the picture, means for deriving a vertical change coefficient which varies in accordance with said vertical change signal in a substantially inversely proportional manner, means for deriving a lateral change coefficient which varies in accordance with said lateral change signal in a substantially proportional manner, and means for comparing said vertical and lateral change coefficients with each other and selecting the larger as the image change coefficient.

8. A system according to claim 1, wherein said ninth means comprises means for deriving bilinear data in an I field, means for deriving data of an I-1 previous field, means for generating an interfield movement coefficient, and means for subjecting the bilinear data and the data of the I-1 previous field to a weighted addition in accordance with the interfield movement coefficient.

9. A system according to claim 8, wherein said means for generating an interfield movement coefficient comprises means for deriving a first difference in the brightness component of the received composite color television signal between successive frames;

means for deriving a second difference in the brightness and chrominance components of the received composite color television signal between every other frame;

means for generating first and second interframe movement coefficients corresponding to said first and second differences;

means for selecting the larger of the first and second interframe movement coefficients as a final interframe movement coefficient;

means including a pair of one field delay elements for delaying the final interframe movement coefficient to generate a non-delayed interframe movement and two interframe movement coefficients delayed by one and two fields, respectively; and

means for selecting among these three interframe movement coefficients the largest interframe movement coefficient as an interfield movement coefficient.

10. A receiving apparatus for use in a color television system for transmitting a movable picture by converting red, green, and blue input signals into a composite color television signal which includes a brightness signal modulated on a main carrier and having a frequency bandwidth of 8 to 15 MHz and a chrominance signal modulated on a color subcarrier and having a frequency bandwidth of 1.8 to 3.5 MHz, the chrominance signal being interleaved with the brightness signal;

and by transmitting the composite color television signal, said receiving apparatus comprising;

receiving means, responsive to the transmitted composite color television signal, for generating a received composite color television signal having a brightness component and a chrominance component;

first separating means, responsive to the received composite color television signal, for deriving brightness and chrominance signals Y_F and C_F, the first separating means employing an interframe brightness and chrominance separation mode;

a second separating means, responsive to the received composite color television signal, for deriving brightness and chrominance signals Y_P and C_P, the second separating means employing a picture adaptive brightness and chrominance separation mode;

generating means for generating an interframe movement coefficient representing the movement in a picture;

combining means for weighting the brightness signals Y_F and Y_P and the chrominance signals C_F and C_P, in accordance with weighting factors which are derived from the interframe movement coefficient, to provide weighted brightness signals Y_F and Y_P and weighted chrominance signals C_F and C_P, the combining means additionally including means for adding the weighted brightness signals Y_F and Y_P to provide a combined brightness signal and means for adding the weighted chrominance signals C_F and C_P to provide a combined chrominance signal;

enhancement means for effecting contour enhancement of the combined brightness signal to provide an enhanced brightness signal;

decoding means for decoding the enhanced brightness signal and the combined chrominance signal to provide red, green, and blue color signals; and

interpolation means for generating interpolated signals to provide additional scanning lines by effecting movement adaptive line interpolation for the red, green, and blue color signals, the movement adaptive line interpolation reducing spurious after images when there is movement in the picture.

11. A receiving apparatus according to claim 10, wherein said second separating means comprises a comb filter, a band pass filter, a detector means for detecting a further movement coefficient, and a weighting circuit means adding output signals from said comb filter and band pass filter in accordance with weights related to the further movement coefficient.

12. A receiving apparatus according to claim 11, wherein said detector means comprises a means for deriving a vertical change in the picture contents, a vertical change coefficient generator means for generating a vertical change coefficient in accordance with said vertical change, a means for deriving a lateral change in the picture contents, a lateral change coefficient generator means for generating a lateral change coefficient in accordance with said lateral change, a comparator means for comparing the vertical and lateral change coefficients with each other, a selector means responsive to said comparator for selecting the larger change coefficient, and a movement coefficient generator means for generating the further movement coefficient in accordance with the larger change coefficient.

13. A receiving apparatus for use in a color television system for trnasmitting a movable picture by converting red, green, and blue input signals into a composite color television signal which includes a brightness signal modulated on a main carrier and having a frequency bandwidth of 8 to 15 MHz and a chrominance signal modulated on a color subcarrier and having a frequency bandwidth of 1.8 to 3.5 MHz, the chrominance signal being interleaved with the brightness signal, and by transmitting the composite color television signal, said receiving apparatus comprising:

receiving means, responsive to the transmitted composite color television signal, for generating a received composite color television signal having a brightness component and a chrominance component;

deriving means for deriving from the received composite color television signal mutually separated first brightness and chrominance signals, the deriving means including an interframe brightness/chrominance separator;

additional deriving means for deriving from the received composite color television signal mutually separated second brightness and chrominance signals, the additional deriving means including a picture adaptive brightness/chrominance separator;

further deriving means for deriving mutually separated further brightness and chrominance signals by adding the mutually separated first and second brightness and chrominance signals, respectively, in accordance with a weight determined by movement of the picture;

enhancement means for effecting contour enhancement of the further brightness signal to derive an enhanced brightness signal;

decoding means for decoding the enhanced brightness signal and the further chrominance signal to derive red, green, and blue color signals; and

interpolation means for generating interpolated signals to provide additional scanning lines by effecting movement adaptive line interpolation for the red, green, and blue color signals, the movement adaptive line interpolation reducing spurious after images when there is movement in the picture, the interpolation means including

a means for deriving a bilinear data in a field,

means for deriving an interfield movement coefficient, and

a means for effecting the movement adaptive line interpolation by adding said bilinear data and data in a previous field in accordance with a weight determined by said interfield movement coefficient.

14. A receiving apparatus according to claim 13, wherein said means for deriving an interfield movement coefficient comprises

a means for deriving a first difference between a first frame and a second frame immediately prior to the first frame;

a means for deriving a second difference between the first frame and a third frame immediately prior to the second frame;

a first generator means for producing a first interframe movement coefficient in accordance with said first difference;

a second generator means for producing a second interframe movement coefficient in accordance with said second difference;

a comparator for comparing said first and second interframe movement coefficients with each other;

a first selector means for selecting the larger interframe movement coefficient among the first and second interframe movement coefficients as a final interframe movement coefficient;

a first delay means for delaying the final interframe movement coefficient for one field period to generate a one-field delayed interframe movement coefficient;

a second delay means for delaying said one-field delayed interframe movement coefficient for one field period to generate a two-field delayed interframe movement coefficient; and

a second selector means for comparing the nondelayed, one-field delayed, and two-field delayed interframe movement coefficients and selecting the smallest interframe movement coefficient as an interfield movement coefficient.