JPH0685588B2 - Emphasis circuit for color television signals - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for use when transmitting a color television signal in a time series, for example, recording / reproducing by increasing the compression ratio of a color difference signal rather than a luminance signal. The present invention relates to emphasis circuits for color television signals.

Background Art and Its Problems Conventionally, for example, in a VTR (video tape recorder),
Although the color signal is recorded as amplitude and phase information, this causes a problem that the color reproducibility is deteriorated due to, for example, jitter during reproduction. Therefore, in recent years, a method of recording / reproducing a color signal with only the same amplitude information as the luminance signal has been proposed. That is, the luminance signal and the color difference signal are respectively time-axis compressed into a time series signal, and the time series signal is recorded and reproduced.

1 and 2 show a recording system and a reproducing system of such a VTR.

In FIG. 1, a terminal (1) is supplied with a composite color television signal S _V (shown in FIG. 3A), and this television signal S _V is supplied to a luminance / color separation circuit (2). The luminance signal Y (shown in FIG. 3B) obtained from the separation circuit (2) is supplied to the time axis compression circuit (3). The color signal C obtained from the separation circuit (2) is the color demodulation circuit (4).
Is supplied to. Then, from the color demodulation circuit (4), the red color difference signal RY (illustrated in FIG. 3C) and the blue color difference signal BY are obtained.
(Shown in FIG. 3D) are obtained, which are compression circuits (3)
Is supplied to.

In the compression circuit (3), the supplied luminance signal Y and color difference signals RY, BY are more color difference signals RY, B- than the luminance signal Y.
The Y compression ratio is increased and compressed along the time axis and arranged in time series, so that, for example, a TCI (Time Compressed Integration) television signal S _TCI as shown in FIG. 3E is obtained.

The television signal S _TCI is supplied to the FM modulator (6) via the pre-emphasis circuit (5). Instead of the FM modulator (6), an AM modulator, a PM modulator or the like may be used. The FM-modulated television signal S _TCI is supplied to the magnetic head (7) and recorded on the magnetic tape (8).

Next, in FIG. 2, the FM-modulated television signal S _TCI reproduced from the magnetic tape (8) by the magnetic head (9) is supplied to the FM demodulator (10) and demodulated. The television signal S _TCI obtained from the FM demodulator (10) is supplied to the post-time axis expansion circuit (12) via the de-emphasis circuit (11).

The decompression circuit (12) performs a process reverse to that of the compression circuit (3), and outputs on its output side a luminance signal Y (illustrated in FIG. 3B) and a chrominance signal which are respectively decompressed on the normal time axis. R-
Y (shown in FIG. 3C) and BY (shown in FIG. 3D) are obtained.

The luminance signal Y obtained from the expansion circuit (12) is supplied to the synthesizer (13). The color difference signals RY and BY obtained from the expansion circuit (12) are supplied to the color modulation circuit (14),
For example, quadrature two-phase modulation is performed with a color subcarrier of 3.58MHz. Then, the color signal C obtained from the modulation circuit (14) is supplied to the synthesizer (13). The composite color television signal S _V is obtained at the output terminal (15) derived from the synthesizer (13).

As shown in FIGS. 1 and 2, by recording / reproducing the color difference signal only with the amplitude information like the luminance signal, the color reproducibility is improved without deterioration of the color reproducibility due to, for example, a jitter during reproduction. .

By the way, with respect to the luminance signal Y, it is possible to obtain a better image by visually adding a precision and an overshoot, that is, enhancing the high range to perform contour correction. In this case, the first
In the example shown in FIG. 2 and the example shown in FIG. 2, the pre-emphasis circuit (5) and the de-emphasis circuit (11) add overshoot and preshute to the television signal S _TCI (shown in FIG. 4D), resulting in the fourth As shown in FIG. A, the brightness signal Y is added with a precision and an overshoot. However, in this case, the television signal S
_{At the TCI} stage, the color difference signals RY and BY have the same characteristics as the luminance signal Y. Then, since the color difference signals R-Y and B-Y have a large compression ratio, as shown in FIGS. 4B and 4C, the width of the precision and the overshoot becomes wide at the time of decompression, which noticeably deteriorates the image quality. Will result.

In this sense, as shown in FIGS. 1 and 2, it is not preferable to apply the same pre-emphasis and de-emphasis to the luminance signal Y and the color difference signals RY and BY.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is capable of obtaining a good image by applying emphasis to the luminance signal and the color difference signal with suitable characteristics.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention transmits a color television signal in a time-series manner with a compression ratio of a color difference signal larger than that of a luminance signal, and if the emphasis characteristics for the luminance signal and the color difference signal are different from each other. It is characterized by having been done.

Therefore, the luminance signal and the color difference signal are subjected to the emphasis with the preferable characteristics, respectively, and a good image can be obtained.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 5 and 6. In FIGS. 5 and 6, parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 5 (recording system), the luminance signal Y obtained from the separation circuit (2) is supplied to the compression circuit (3) via the preence phase circuit (16). Also, a color demodulation circuit (4)
The red color difference signal R-Y and the blue color difference signal B-Y obtained by
It is supplied to the compression circuit (3) via the pre-emphasis circuits (17) and (18), respectively. The broken lines in FIGS. 7A, 7B and 7C represent the luminance signal Y and the color difference signals RY and BY, respectively.

Also, from the compression circuit (3), a television signal S _TCI as shown in FIG. _3E is obtained as in the example of FIG.
It is supplied to the magnetic head (7) through the FM modulator (6),
It is recorded on the magnetic tape (8).

Next, in FIG. 6 (reproduction system), the television signal S _TCI obtained from the FM demodulator (10) is supplied to the expansion circuit (12).

From the expansion circuit (12), similarly to the example of FIG. 2, the luminance signal Y and the color difference signals RY and BY which are expanded on the normal time axis, respectively.
Is obtained. Then, the luminance signal Y is supplied to the synthesizer (13) via the de-emphasis circuit (19). The color difference signals RY and BY are respectively supplied to the de-emphasis circuit (20).
And (21) to the color modulation circuit (14). Then, the color signal C obtained from the modulation circuit (14) is supplied to the synthesizer (13). The composite color television signal S _V is obtained at the output terminal (15) derived from the synthesizer (13).

Further, in the examples of FIGS. 5 and 6, the total characteristics of the pre-emphasis circuit (16) and the de-emphasis circuit (19) provided in the system of the luminance signal Y are high as shown by the solid line in FIG. 7A. It is made to have a region emphasis characteristic. In addition, the pre-emphasis circuit (1
7), the overall characteristics of the de-emphasis circuit (20) and the pre-emphasis circuit (1) provided in the blue difference signal BY system.
8), the overall characteristics of the de-emphasis circuit (21) are made to be flat characteristics as shown by the solid lines in FIGS. 7B and 7C, respectively.

Others are the same as those in the examples of FIGS. 1 and 2.

In the examples of FIGS. 5 and 6, the luminance signal Y is the pre-emphasis circuit (16) and the de-emphasis circuit (19).
The red difference signal R-Y is transmitted through the pre-emphasis circuit (1
7), through the de-enmphasis circuit (20), the blue difference signal BY is passed through the pre-emphasis circuit (18) and the de-emphasis circuit (21), and the luminance signal Y and the color difference signals RY, B-
Different emphasis is applied to Y. That is, finally, the luminance signal Y has a high-frequency emphasis characteristic, and the color difference signals RY and BY have a flat characteristic.

Therefore, according to the examples of FIGS. 5 and 6, it is possible to apply a suitable emphasis to the luminance signal Y and the color difference signals R-Y and B-Y, and a good image can be obtained.

Next, FIG. 8 and FIG. 9, FIG. 10 and FIG. 11, and FIG. 12 and FIG.
14 and 15 show another embodiment of the present invention, respectively. In these figures, parts corresponding to those in FIGS. 5 and 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, FIGS. 8 and 9 will be described.

In FIG. 8 (recording system), the luminance signal Y obtained from the separation circuit (2) and the color difference signals RY and BY obtained from the color demodulation circuit (4) are supplied to the compression circuit (3). From the compression circuit (3), the television signal S as shown in FIG.
_TCI is obtained. And this television signal S
_{The TCI} is supplied to one and the other fixed terminals (24a) and (24b) of the switch circuit (24) via the pre-emphasis circuits (22) and (23), respectively.

A switching control signal is supplied from the compression circuit (3) to the switch circuit (24), and the luminance signal Y of the television signal S _TCI is supplied.
Corresponding to the terminal (24a) side, while the terminal (24a) corresponding to the color difference signals RY and BY of the television signal S _TCI.
Switched to b) side. That is, this switch circuit (24)
From the luminance signal Y through the pre-emphasis circuit (22) and the color difference signal R through the pre-emphasis circuit (23).
A television signal S _TCI consisting of -Y, BY is obtained.

The television signal S _TCI is supplied to the magnetic head (7) via the FM modulator (6) and recorded on the magnetic tape (8).

Next, in FIG. 9 (reproduction system), the television signal S _TCI obtained from the FM demodulator (10) is supplied to the de-emphasis circuits (26) and (27) via the switch circuit (25). Then, these de-emphasis circuits (26) and (2
The output of 7) is supplied to the expansion circuit (12).

In this case, the switch circuit (25) is supplied with a switching control signal from the expansion circuit (12) and switched to the terminal (25a) side in correspondence with the luminance signal Y of the television signal S _TCI , while the television signal S The color difference signals RY and BY of _TCI are switched to the terminal (25b) side. Therefore, the luminance signal Y of the television signal S _TCI is supplied to the decompression circuit (12) through the de-emphasis circuit (26), while the color difference signals R-Y, BY
Is supplied to the decompression circuit (12) via the de-enmphasis circuit (27).

From the expansion circuit (12), the luminance signal Y and the color difference signals R-Y and BY are expanded on the normal time axis, respectively. The luminance signal Y is supplied to the synthesizer (13), and the color difference signals RY and BY are supplied to the color modulation circuit (14). The color signal C obtained from this color modulation circuit (14) is the synthesizer (13).
Is supplied to. Then, the composite color television signal S _V is obtained at the output terminal (15).

Further, in the example of FIG. 8 and the example of FIG. 9, the total characteristics of the pre-emphasis circuit (22) and the de-emphasis circuit (26) are the high-frequency emphasis characteristics as shown by the solid line in FIG. 7A. . The pre-emphasis circuit (23) and the de-emphasis circuit (27) are made to have a flat characteristic as shown by the solid line in FIG. 7B or C.

Others are the same as those in the examples of FIGS. 5 and 6.

In the example of FIG. 8 and the example of FIG. 9, the luminance signal Y is the pre-emphasis circuit (22) and the de-emphasis circuit (26).
The color difference signals R-Y and B-Y are passed through a pre-emphasis circuit (23) and a de-emphasis circuit (27) to be subjected to different emphasis. That is, finally, the luminance signal Y is set to have the high-frequency emphasis characteristic, and the color difference signals RY and BY
Is a flat characteristic.

Next, the example of FIG. 10 and the example of FIG. 11 will be described.

In FIG. 10 (recording system), the luminance signal Y obtained from the separation circuit (2) is supplied to the compression circuit (3) via the pre-emphasis circuit (28) and the color difference obtained from the color demodulation circuit (4). The signals R-Y and B-Y are supplied to a compression circuit (3), and a television signal S _TCI as shown in FIG. _3E is obtained from this compression circuit (3). Then, the television signal S _TCI is supplied to the magnetic head (7) through the pre-emphasis circuit (29) and the FM modulator (6) and recorded on the magnetic tape (8).

Next, in FIG. 11 (reproduction system), the television signal S _TCI obtained from the FM demodulator (10) is supplied to the decompression circuit (12) via the de-emphasis circuit (30).

From the expansion circuit (12), the luminance signal Y and the color difference signals R-Y and BY are expanded on the normal time axis, respectively. Then, the luminance signal Y is supplied to the synthesizer (13) via the de-emphasis circuit (31). Also, the color difference signals R-Y and B-
Y is supplied to the color modulation circuit (14), and the color signal C obtained thereby is supplied to the synthesizer (13). Then, the composite color television signal S _V is obtained at the output terminal (11).

Further, in the example of FIG. 10 and the example of FIG. 11, the pre-emphasis circuits (28), (29), the de-emphasis circuit (30),
The overall characteristic of (31) is set to a high-frequency emphasis characteristic as shown by the solid line in FIG. 7A. The total characteristics of the pre-emphasis circuit (29) and the de-emphasis circuit (30) are made flat as shown by the solid line in FIG. 7B or C.

Other than that, the configuration is the same as in the example of FIGS. 5 and 6.

In the example of FIG. 10 and the example of FIG. 11, the luminance signal Y is passed through the pre-emphasis circuits (28), (29) and the de-emphasis circuits (30), (31), and the color difference signals R-Y, B-Y are The pre-emphasis circuit (29) and the de-emphasis circuit (30) are used to apply different emphasis to each. That is,
Finally, the luminance signal Y has a high-frequency emphasis characteristic, and the color difference signals RY and BY have a flat characteristic.

Next, the examples of FIGS. 12 and 13 will be described.

In FIG. 12 (recording system), the luminance signal Y obtained from the separation circuit (2) is supplied to the compression circuit (3), and the color difference signals R-Y and B-Y obtained from the color demodulation circuit (4). Are supplied to the compression circuit (3) via the pre-emphasis circuits (32) and (33) respectively, and the television circuit S _TCI as shown in FIG. _3E is obtained from this compression circuit (3). Then, the television signal S _TCI is supplied to the magnetic head (7) through the pre-emphasis circuit (34) and the FM modulator (6) and recorded on the magnetic tape (8).

Next, in FIG. 13 (reproduction system), the television signal S _TCI obtained from the FM demodulator (10) is supplied to the decompression circuit (12) via the de-emphasis circuit (35).

From the expansion circuit (12), the luminance signal Y and the color difference signals R-Y and BY are expanded on the normal time axis, respectively. Then, the luminance signal Y is supplied to the synthesizer (13). The color difference signals R-Y and B-Y are supplied to the de-emphasis circuit (3
Is supplied to the color modulation circuit (14) via 6) and (37),
The color signal C obtained from this is supplied to the synthesizer (13). Then, the composite color television signal S _V is obtained at the output terminal (15).

In addition, in the examples of FIGS. 12 and 13, the total characteristics of the pre-emphasis circuit (34) and the de-emphasis circuit (35) are high-frequency emphasis characteristics as shown by the solid line in FIG. 7A. . In addition, the pre-emphasis circuit (32), (3
4), the total characteristics of the de-emphasis circuits (35), (36) and the pre-emphasis circuits (33), (34) and the de-emphasis circuits (35), (37) are shown in FIGS. 7B and 7C, respectively.
As shown by the solid line in FIG.

Others are the same as those in the examples of FIGS. 5 and 6.

In the example of FIG. 12 and the example of FIG. 13, the luminance signal Y is the pre-emphasis circuit (34) and the de-emphasis circuit (35).
The color difference signal R-Y is transmitted through the pre-emphasis circuit (3
2), (34), the de-emphasis circuit (35), (36), and the color difference signal BY passes through the pre-emphasis circuit (33),
(34), through the deenmphasis circuit (35), (37),
Different emphasis is applied to the luminance signal Y and the color difference signals RY and BY. That is, finally, the luminance signal Y has a high-frequency emphasis characteristic, and the color difference signals RY and BY have a flat characteristic.

Next, the example of FIG. 14 and the example of FIG. 15 will be described. This first
14 and 15 are examples applied to broadcasting, for example satellite broadcasting.

In FIG. 14 (transmission system), the television signal S _TCI from the compression circuit (3) is supplied to the transmission antenna (39) via the transmitter (38). Further, in FIG. 15 (reception system), the signal obtained from the reception antenna (40) is the receiver (4
1), a television signal S _TCI is obtained from the receiver (41), and this is supplied to the decompression circuit (12).

Others are the same as those in the example of FIG. 5 and FIG.

Also in these FIG. 14 example and FIG. 15 example, as in the case of FIG. 5 example and FIG. 6 example, the luminance signal Y is finally set to the high-frequency emphasis characteristic, and the color difference signals RY, BY Is a flat characteristic.

As described above, also in the other embodiments (shown in FIGS. 8 to 15), different emphasis is applied to the luminance signal Y and the color difference signals RY and BY, and finally the luminance signal Y Is a high-frequency emphasis characteristic, and is a flat characteristic with respect to the color difference signals R-Y and B-Y.
It is possible to obtain the same effect as that of the illustrated example.

It should be noted that the CATV can also be configured in the same manner as the example of FIG. 14 and the example of FIG.

EFFECTS OF THE INVENTION According to the present invention described above, the emphasis characteristics for the luminance signal and the color difference signal are made different from each other, so that a favorable emphasis can be applied to each and a good image can be obtained. You can

[Brief description of drawings]

1 and 2 are configuration diagrams showing a conventional example, FIGS. 3 and 4 are waveform diagrams for explaining the respective examples, and FIGS. 5 and 6 are examples of the present invention. FIG. 7 is a configuration diagram, FIG. 7 is a diagram for explaining it, and FIGS. 8 to 15 are configuration diagrams showing other embodiments of the present invention. (2) is a luminance / color separation circuit, (3) is a time axis compression circuit,
(4) is a color demodulation circuit, (6) is an FM modulator, (10) is an FM demodulator, (12) is a time axis expansion circuit, (13) is a combiner, and (1
4) is a color modulation circuit, (16) to (18) are pre-emphasis circuits, and (19) to (21) are de-emphasis circuits.

Claims (1)

[Claims] 1. A color television signal transmitted in a time series with a compression ratio of a color difference signal higher than that of a luminance signal, wherein the luminance signal and the luminance signal are controlled so that the compression ratio of the color difference signal is greater than that of the luminance signal. Each of the color difference signals is time-axis-compressed, and the time-axis-compressed luminance signal and the color-difference signal are arranged in time series after the synchronization signal. And an emphasis circuit for a color television signal, which has different emphasis characteristics for the color difference signals transmitted in time series.