JPH06245229A - Transmitter and receiver for video signal - Google Patents

Abstract

PURPOSE:To prevent any flicker from being caused to a color edge of a reproduced picture comprising a video signal in which a chrominance signal is sent while being subjected to subsampling processing. CONSTITUTION:Processing circuits 22R, 22B generate color difference signals (R-Y)',(B-Y)' subjected to subsampling processing. Gamma characteristic circuits 25R, 25G, 25B provide a signal to luminance conversion characteristic of a picture tube to color signals R,G,B obtained from a signal Y and the signals (R-Y)',(B-Y)' via an LPF simulating a transmission system at a matrix circuit 23, the result is fed to a matrix circuit 26 to obtain a luminance signal Yo corresponding to a tube screen luminance by the signals Y, (R-Y)', (B-Y)'. The signals Y, (R-Y), (B-Y) are fed to an object luminance signal generating circuit 28, an object luminance signal Yref corresponding to the tube screen luminance by the signals Y, (R-Y),(B-Y) is obtained. An output Yc(=Yref-Yo) of a subtractor circuit 27 is added to the signal Y by an adder circuit 21 to obtain a signal Y'. The signals Y', (R-Y)',(B-Y)' are sent (recorded).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal transmitting apparatus for sub-sampling a color signal and transmitting it, and a video signal receiving apparatus for re-sampling a received color signal.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the structure of a video tape recorder.

First, the recording system will be described. The video signal SV is supplied to the Y / C separation circuit 2 via the AGC circuit 1 and separated into a luminance signal Y and a color signal (carrier color signal) C. Luminance signal Y output from Y / C separation circuit 2
Is supplied to the luminance signal processing circuit 3 and is FM-modulated, and the modulated luminance signal YFM is supplied to the adder 4.

The color signal C output from the Y / C separation circuit 2 is supplied to the color demodulation circuit 5. This color demodulation circuit 5
Output red color difference signal R-Y and blue color difference signal B-
Y is the sub-sampling circuit 7 via the pre-filter 6.
Are subjected to sub-sampling processing such as field offset or line offset, and band-compressed.

The color difference signals R-Y and B-Y subjected to the sub-sampling processing by the sub-sampling circuit 7 are supplied to the color signal processing circuit 8. In this processing circuit 8, the color difference signal R-
After Y, B-Y are color-modulated to form the color signal C, they are converted to the low frequency range to form the low frequency conversion color signal CL. The low frequency conversion color signal CL output from the processing circuit 8 is
The band is limited by the low-pass filter 9 and then supplied to the adder circuit 4.

The adder circuit 4 adds the low frequency conversion color signal CL to the modulated luminance signal YFM to form a recorded video signal,
This recording video signal is supplied to the magnetic head 12 via the recording amplifier 10 and recorded on the magnetic tape 12.

Next, the reproducing system will be described. The signal reproduced by the magnetic head 11 from the magnetic tape 12 is supplied to the luminance signal processing circuit 14 via the reproduction amplifier 13. In the processing circuit 14, the modulated luminance signal YFM is extracted, and the modulated luminance signal YFM is demodulated to obtain the luminance signal Y. The luminance signal Y output from the processing circuit 14 is supplied to the adding circuit 15.

The output signal of the reproduction amplifier 13 is supplied to a low-pass filter 16 to extract a low-pass conversion color signal CL, and this low-pass conversion color signal CL is supplied to a color signal processing circuit 17. In the processing circuit 17, the color difference signal R-Y,
BY is obtained.

The color difference signal R- output from the processing circuit 17
Y and B-Y are resampled by a resampling circuit 18, interpolated by an interpolation circuit (post filter) 19, and then supplied to a color modulation circuit 20. The color signal C output from the color modulation circuit 20 is It is supplied to the adder circuit 15. In the adding circuit 15, the color signal C is added to the luminance signal Y to obtain the reproduced video signal SV.

In the example of FIG. 5, the color difference signals RY and BY are subjected to sub-sampling processing and band compression in the recording system, and the color difference signals RY and BY are subjected to resampling processing in the reproducing system. Since this is performed and the band is expanded, the recording frequency band of the color signal can be expanded and the image quality can be improved.

[0011]

There is no problem when the resampling process is performed in the reproducing system as in the example of FIG. 5, but when the reproducing system in which the resampling process is not performed is used. , Color difference signals RY, B in the recording system
Since -Y is sub-sampled, there is a problem that flicker occurs on the color edge of the reproduced image. The main component of this flicker is 30 Hz when the video signal SV is of the NTSC system and the field offset subsampling process is performed.

Here, FIG. 6 shows the time-frequency characteristic of vision, but the relative contrast sensitivity to a color change (r-g, y-b) of 30 Hz is sufficiently higher than that of a light-dark change (Br). The above-mentioned flicker whose main component is 30 Hz due to the sub-sampling of the color difference signals R-Y and B-Y should not be a significant problem visually.

However, in order to supplement the luminance characteristics of the picture tube,
Generally, the video signal SV is gamma-corrected in the video camera. Therefore, the color difference signals R-Y and B-Y include a luminance component, and the above-mentioned flicker having a main component of 30 Hz is visually conspicuous.

Therefore, in the present invention, the flicker is prevented from occurring in the color edge of the reproduced image by the video signal transmitted by sub-sampling the color signal.

[0015]

According to a first aspect of the present invention, there is provided a video signal transmitting apparatus for sub-sampling a color signal together with a luminance signal and transmitting the color signal. It is characterized in that the luminance signal is corrected so that

A video signal receiving apparatus according to a second aspect of the present invention receives the luminance signal and the sub-sampled color signal transmitted from the video signal transmitting apparatus of the first aspect, and restores the color signal. It is characterized by performing the sample processing and correcting the luminance signal so that the tube surface luminance before and after the re-sampling processing becomes equal.

[0017]

According to the first aspect of the invention, since the color signal subjected to the sub-sampling and the luminance signal corrected so that the tube luminance before and after the sub-sampling are equal are transmitted as a video signal, It is possible to prevent flicker from occurring on the color edge of the reproduced image when a receiving system that does not perform sample processing is used.

According to the second aspect of the present invention, the color signal is resampled and the luminance signal is corrected so that the tube surface luminance before and after the resample processing becomes equal.
Even if a video signal composed of a color signal subjected to sub-sampling processing and a corrected luminance signal transmitted by the invention according to claim 1 is received, flicker is prevented from occurring on a color edge of a reproduced image. obtain.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a video signal transmitting apparatus according to the present invention will be described below with reference to FIG. 1 corresponds to the Y / C separation circuit 2 and the luminance signal processing circuit 3 in the example of FIG. 5 for the luminance signal Y, and corresponds to the pre-filter 6 and the sub-sampling circuit 7 in the example of FIG. 5 for the color signal C. To do.

In FIG. 1, the luminance signal Y output from the Y / C separation circuit 2 is supplied to the addition circuit 21. Also,
The color difference signals RY and BY output from the color demodulation circuit 5 are supplied to sub-sample processing circuits 22R and 22B, respectively, and the sub-sample processed color difference signals (R- Y) ', (B-
Y) ′ is supplied to the color signal processing circuit 8. The sub-sample processing circuits 22R and 22B perform the processes corresponding to the pre-filter 6 and the sub-sampling circuit 7 in the example of FIG. 5, respectively.

The luminance signal Y output from the Y / C separation circuit 2 is supplied to the matrix circuit 23. The matrix circuit 23 further includes color difference signals (RY) ′, output from the sub-sample processing circuits 22R and 22B.
(BY) 'are low-pass filters 24R and 2R, respectively.
4B. These low pass filters 24
R and 24B simulate the low-pass characteristics of the transmission system.

The red, green, and blue color signals R, G, and B obtained by the matrix processing in the matrix circuit 23 respectively simulate a signal-luminance conversion characteristic (gamma characteristic) of a picture tube, and a gamma characteristic circuit 25R. , 25G, 25B. These gamma characteristic circuits 25R, 25G, 25B
The color signals R, G, and B to which the gamma characteristic is added are supplied to the matrix circuit 26, and the luminance signal Yo output from the matrix circuit 26 is supplied to the subtraction circuit 27.

The luminance signal Yo obtained by the matrix circuit 26 includes a luminance signal Y, color difference signals (RY) ', (B
-Y) 'corresponds to the brightness of the surface of the picture tube. The luminance signal Y, the color difference signals (RY) ', (B-
The image reproduced by Y) 'has color difference signals (RY)', (B
Since -Y) 'has been sub-sampled, flicker will occur at the color edge.

The luminance signal Y output from the Y / C separation circuit 2 and the color difference signal R output from the color demodulation circuit 5
-Y and BY are supplied to the target luminance signal forming circuit 28. The forming circuit 28 is the matrix circuit 2 described above.
3, the gamma characteristic circuits 25R, 25G, 25B and the matrix circuit 26 have the same configuration. Forming circuit 2
The target luminance signal Yref output from 8 is supplied to the subtraction circuit 27. The target luminance signal Yref corresponds to the luminance of the surface of the picture tube by the luminance signal Y and the color difference signals RY and BY. The luminance signal Y and the color difference signals RY, B
In the reproduced image by -Y, since the color difference signals RY and BY are not subjected to the sub-sampling process, flicker does not occur on the color edge.

The subtraction circuit 27 subtracts the brightness signal Yo from the target brightness signal Yref, and the output signal of the subtraction circuit 27 is supplied to the addition circuit 21 as the brightness correction signal Yc. The adder circuit 21 adds the brightness correction signal Yc to the brightness signal Y, and the corrected brightness signal Y ′ output from the adder circuit 21 is supplied to the brightness signal processing circuit 3.

In the present example, the brightness correction signal Yc is a target brightness signal Yref formed from a brightness signal Y which does not cause flicker on the color edge of the reproduced image and color difference signals RY and BY.
From the luminance signal Y which causes flicker on the color edge of the reproduced image and the luminance signal Yo formed from the color difference signals (RY) 'and (BY)'. Therefore, the brightness correction signal Yc suppresses flicker, and the brightness signal Y ′ output from the adder circuit 21 and the color difference signals (RY) ′ and (BY) output from the sub-sample processing circuits 22R and 22B. The reproduced image by) 'has no flicker on the color edge. Therefore, it is possible to favorably prevent the occurrence of flicker on the color edge of the reproduced image when a reproducing system in which the resample processing is not performed is used.

Next, another embodiment of the video signal transmitting apparatus according to the present invention will be described with reference to FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 2, the luminance signal Y output from the Y / C separation circuit 2 is supplied to the matrix circuit 23 via the adder circuit 21. Further, the output signal of the subtraction circuit 27 is supplied to the addition circuit 21 via the feedback amplifier 29.
Then, the luminance signal Y ′ output from the adding circuit 21 is supplied to the luminance signal processing circuit 3.

Here, the operating frequency of the closed loop composed of the adder circuit 21, the matrix circuit 23, the gamma characteristic circuits 25R, 25G and 25B, the matrix circuit 26, the subtraction circuit 27, and the amplifier 29 is the sampling frequency of the luminance signal Y or the like. Set much higher than.

The present example is constructed as described above, and the others are constructed in the same manner as the example of FIG. In the present example, the brightness signal Yo supplied to the subtraction circuit 27 is controlled to be equal to the target brightness signal Yref by the closed loop negative feedback operation described above. Therefore, the luminance signal Y ′ output from the adding circuit 21 is the luminance signal Y ′ and the color difference signal (R−
Y) 'and (BY)' are corrected so that flicker does not occur on the color edge of the reproduced image. Therefore, the same effect as that of the example of FIG. 1 can be obtained. In this example, feedback control is performed at high speed, and there is an advantage that the correction accuracy of the luminance signal Y'can be made higher than that in the example of FIG.

Next, an embodiment of the video signal receiving apparatus according to the present invention will be described with reference to FIG.
3, the luminance signal Y is between the luminance signal processing circuit 14 and the adding circuit 15 in the example of FIG. 5, and the chrominance signal C is the resampling circuit 18 and the interpolation circuit 19 in the example of FIG.
It corresponds to.

In this case, the recording system is constructed as shown in FIG. 1 or 2, and the magnetic tape 12 records the sub-sampled color difference signals (RY) 'and (BY)'. At the same time, it is assumed that the luminance signal Y'corrected so that flicker does not occur on the color edge of the reproduced image is recorded.

In FIG. 1, the luminance signal Y ′ output from the luminance signal processing circuit 14 is supplied to the adding circuit 30.
In addition, the color difference signal (R
-Y) 'and (BY)' are supplied to the resample processing circuits 31R and 31B, respectively, and these processing circuits 31R and 3B are supplied.
1B is the resampled color difference signal R-
Y and BY are supplied to the color modulation circuit 20. The resample processing circuits 31R and 31B perform processes corresponding to the resampling circuit 18 and the interpolation circuit 19 in the example of FIG. 5, respectively.

The luminance signal Y'output from the luminance signal processing circuit 14 and the resampling processing circuits 31R and 31R.
The color difference signals R-Y and B-Y output from B are supplied to the matrix circuit 32.

The red, green, and blue color signals R, G, and B obtained by the matrix processing by the matrix circuit 32 respectively simulate a signal-luminance conversion characteristic (gamma characteristic) of the picture tube, and a gamma characteristic circuit 33R. , 33G, 33B. These gamma characteristic circuits 33R, 33G, 33B
The color signals R, G, and B to which the gamma characteristic has been added are supplied to the matrix circuit 34, and the luminance signal Yo output from the matrix circuit 34 is supplied to the subtraction circuit 35.

The luminance signal Yo obtained by the matrix circuit 34 corresponds to the luminance of the surface of the picture tube by the luminance signal Y'and the color difference signals RY and BY. The reproduced image based on the luminance signal Y ′ and the color difference signals R−Y and B−Y is the color difference signals R−Y and B− after the color difference signals (R−Y) ′ and (B−Y) ′ are resampled. Since Y is formed, flicker occurs on the color edge.

The luminance signal Y ′ output from the luminance signal processing circuit 14 and the color difference signals (RY) ′ and (BY) ′ output from the color signal processing circuit 17 are the target luminance signal forming circuit 36. Is supplied to. This forming circuit 36 includes the matrix circuit 32 and the gamma characteristic circuits 33R, 3R described above.
The configuration is similar to that of the 3G, 33B and matrix circuit 34. The target luminance signal Yref output from the forming circuit 36 is supplied to the subtracting circuit 35. The target luminance signal Yref is the luminance signal Y ', the color difference signals (RY)', (B-
Y) 'corresponds to the brightness of the surface of the picture tube.
The luminance signal Y ', the color difference signals (RY)', (B-
In the reproduced image by Y) ', flicker does not occur on the color edge as described in the example of FIG.

The subtraction circuit 35 subtracts the brightness signal Yo from the target brightness signal Yref, and the output signal of the subtraction circuit 35 is supplied to the addition circuit 30 as the brightness correction signal Yc. The adder circuit 30 adds the brightness correction signal Yc to the brightness signal Y, and supplies the corrected brightness signal Y adder circuit 15 output from the adder circuit 30.

In this example, the brightness correction signal Yc is a target brightness signal formed by a brightness signal Y ', which does not cause flicker on the color edge of the reproduced image, and color difference signals (RY)' and (BY) '. It is formed by subtracting the luminance signal Y'formed from Yref from the luminance signal Y'which causes flicker at the color edge of the reproduced image and the color difference signals RY and BY.
Therefore, the luminance correction signal Yc suppresses flicker, and the reproduced image by the luminance signal Y output from the addition circuit 30 and the color difference signals RY and BY output from the resample processing circuits 31R and 31B is Flicker does not occur on the color edge.

Therefore, the recording system is constructed as shown in FIG. 1 or 2, and the sub-sampled color difference signals (RY) 'and (BY)' are recorded on the magnetic tape 12. It is possible to favorably prevent the occurrence of flicker on the color edge of the reproduced image when the luminance signal Y'corrected so as not to cause flicker on the reproduced image is recorded.

Next, another embodiment of the video signal receiving apparatus according to the present invention will be described with reference to FIG. 4, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 4, the luminance signal Y'output from the luminance signal processing circuit 14 is supplied to the matrix circuit 32 via the adding circuit 30. Further, the output signal of the subtraction circuit 35 is supplied to the addition circuit 30 via the feedback amplifier 37. Then, the luminance signal Y ′ output from the adding circuit 30 is supplied to the adding circuit 15.

Here, the operating frequency of the closed loop composed of the adder circuit 30, the matrix circuit 32, the gamma characteristic circuits 33R, 33G and 33B, the matrix circuit 34, the subtraction circuit 35, and the amplifier 37 is the sampling frequency of the luminance signal Y or the like. Set much higher than.

The present example is constructed as described above, and the others are constructed in the same manner as the example of FIG. In this example, the brightness signal Yo supplied to the subtraction circuit 35 is controlled to be equal to the target brightness signal Yref by the above-described closed loop negative feedback operation. Therefore, the luminance signal Y output from the adder circuit 30 is corrected so that flicker does not occur in the color edge of the reproduced image due to the luminance signal Y and the color difference signals RY and BY. Therefore, the same effect as that of the example of FIG. 3 can be obtained. In this example, the feedback control is performed at a high speed, and there is an advantage that the correction accuracy of the luminance signal Y can be increased as compared with the example of FIG.

Although the field offset sub-sampling is performed as the sub-sampling process in the above embodiment, the problem of flicker of the color edge of the reproduced image occurs even when the line offset sub-sampling is performed. The problem can be solved by adopting the same configuration as the above-mentioned embodiment.

Further, although the above-mentioned embodiment is applied to the recording system and the reproducing system of the VTR, it is needless to say that it is similarly applicable to the transmitting system and the receiving system in the other video signal transmitting apparatus.

[0047]

According to the first aspect of the present invention, the color signal subjected to the sub-sampling and the luminance signal corrected so that the tube luminances before and after the sub-sampling are equal are transmitted as video signals. Therefore, it is possible to favorably prevent the occurrence of flicker on the color edge of the reproduced image when a receiving system in which the resample processing is not performed is used.

According to the second aspect of the present invention, the color signal is resampled, and the luminance signal is corrected so that the tube surface luminance before and after the resample processing becomes equal. Even when the video signal composed of the color signal subjected to the sub-sampling process and the corrected luminance signal transmitted in step S3 is received, it is possible to favorably prevent the occurrence of flicker on the color edge of the reproduced image.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video signal transmitting apparatus according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the video signal transmitting apparatus according to the present invention.

FIG. 3 is a block diagram showing an embodiment of a video signal receiving apparatus according to the present invention.

FIG. 4 is a block diagram showing another embodiment of the video signal receiving apparatus according to the present invention.

FIG. 5 is a block diagram showing an example of a video tape recorder.

FIG. 6 is a diagram showing a visual time-frequency characteristic.

[Explanation of symbols]

21, 30 Adder circuit 22R, 22B Sub-sample processing circuit 23, 26, 32, 34 Matrix circuit 24R, 24B Low pass filter 25R, 25G, 25B, 33R, 33G, 33B Gamma characteristic circuit 27, 35 Subtractor circuit 28, 36 Target brightness Signal forming circuit 29, 37 Feedback amplifier 31R, 31B Resample processing circuit

Claims (2)

[Claims] 1. A transmitter for a video signal for sub-sampling and transmitting a color signal together with a luminance signal, wherein the luminance signal is corrected so that the tube luminance before and after the sub-sampling processing becomes equal. And a video signal transmitter. 2. The luminance signal and the sub-sampled color signal transmitted from the video signal transmitting apparatus according to claim 1 are received, the color signal is re-sampled, and the re-sample processing is performed. A device for receiving a video signal, characterized in that the brightness signal is corrected so that the tube brightness before and after is equalized.