JPS5913483A - Method and device for processing channel limited in band width of color television signal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Description: FIELD OF THE INVENTION The present invention relates to a method and apparatus for processing, e.g. recording, reproducing or transmitting color television signals in a limited bandwidth channel. When transmitting a color television signal through a signal channel with limited transmission capacity, the color difference signal component 1t-Y.

B-Y is often transmitted in sequence.

At this time, the period is T=1/21H. In this case, the luminance signal and the color signal are time-multiplexed.

When using a known method, color difference signal components R-Y, B-Y
The selection is made by a switch whose switching frequency corresponds to 1/2fH. The color information flow is then reduced. At this time, the necessary pre-filtering is not performed. In addition, in all known devices, in order to reproduce complete color information on the reproduction side, the storage capacity (6
A memory device with a storage time of 25 scan lines (scan line base 1''-6·l/13) is provided for scan line repetition, and a switch for twice the demultiplexer is provided. This changeover switch operates at a switching frequency of 1/2"H, and reconstructed color difference signals It-Y and 13-Y are taken out from its output terminal.

However, the color difference signal component It-Y, +3-"l' is l/2
When reproduced at a line frequency, not only the vertical resolution in the color signal region decreases but also alias noise occurs. This alias noise prevents normal reconstruction of color information.

In a color television system with 625 scan lines, there are 575 visible scan lines, which is 7.37 Mll2 in the vertical direction.
corresponds to the frequency of Therefore, after frequency division, the local frequency becomes 3.68 Mll or less.

As long as the 111g-order scan is performed, alias noise will occur above this frequency. In the case of interlaced scanning, this frequency is halved. Therefore, when it exceeds 1.8 M117, alias noise and flicker noise occur. Scanning by shifting the frame frequency (2V sequence)
This can also prevent this noise from becoming an eyesore.

However, this method cannot be applied to continuously changing image content that does not satisfy the offset condition.

For example, the data book for the image pickup tube XQ1500 from VALVO Company
1982'', the following is known: In modern image pickup tubes, when the frequency is about 1.8'M117., the modulation-transmission frequency is above 80, so it is pre-existing with 6M waves. is not suitable, and the amplitude increases depending on the number of original images. In this case, for example, a pre-wave by a transpersal filter has little effect and may therefore be omitted to save circuit cost. There are many.

Effects of the Invention In contrast, the method according to the invention with the features set forth in claim 1 has the advantage that two color difference signals can be transmitted simultaneously without loss of signal information. Another advantage is that no pre-filtering is required.

The embodiment section describes improved embodiments of the invention. In this case, it is very advantageous that during reproduction the signal components can be reproduced by means of known transversal filters. .

DESCRIPTION OF EMBODIMENTS The method and apparatus of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an apparatus implementing the known method. In this case, the input signals rt, o, and B are processed by the matrix circuit 1, and a luminance signal Y and color difference signal components I+, -Y, and 11-Y are generated on the output side thereof. In this example, the luminance signal YI'i is recorded directly on the trunk of the magnetic tape of the video tape recorder 2. On the other hand, the color difference signal component I1. -Y.

B-Y is sent to two contacts of a changeover switch 3, which is switched at the frequency of the 1/2 axis.

Therefore, the color difference signal component 1t-Y of a certain scanning line and the signal component B-Y of the next scanning line appear alternately at the switching contact of the switch 3. These color difference f8 components are recorded on the second track of the video tape recorder 2 or on the second recording device.

When reproducing color image signal components recorded on a magnetic tape, color difference signal component elements t-
y, ny is the delay time τ corresponding to the scanning line length on the one hand;
and on the other hand a two-pole changeover switch 5 operating at a switching frequency of 1/2 fH.
0 to the two outer contacts. Therefore, the changeover switch 5
Color difference signal components 11. -Y appears, and the color difference signal component +3-Y is always applied to the second contact. However, in this case, the information content changes every two scan lines. The two color difference signal components are supplied to the matrix circuit 6. The luminance signal Y obtained from another recording device of the video recorder 2 is fed to a delay device 7, which also has a delay time τ corresponding to the scanning line period, in order to compensate for the travel time difference caused by the delay device 4; From there it is sent to the third input of the matrix circuit 6. Matrix circuit 6
At the output □1NIl, primary color signals + (, , G, B appear.The disadvantage of the above-described method of recording color television signals in at least two narrowband recording channels is that during playback, the primary color signals The problem is that the resolution deteriorates in the vertical direction compared to

FIG. 2 is a block circuit diagram of an embodiment of the device according to the invention. In this device as well, the color image signal components It, G
, B are supplied to an IJ circuit 21, where a luminance signal Y and color difference signals RY and BY are formed. The luminance signal Y is recorded directly in a recording channel of the video recorder 22 in a known manner. The color difference signals R, -Y, BY are simultaneously recorded on the second recording channel. for that,
One of the two color difference signals, in this example the signal component 几-Y
is supplied to the modulation stage 23. This modulation stage performs modulation using a polarity conversion function g(t).

In this case, the following equation holds true for the time order.

g(t) = ], g(t+TH)-!
, g(tJ2.= 1 and gft)=], but the interval is 0 (t('1"H when g
(t + TH) -1+ Interval TH(t(2TH
After this time, the two color difference signal components are spectrally shifted by 1/2 scan line in baseband.

After linear combination in summing stage 24, the shape of the amplitudes corresponds to the next scan line sequence.

tJ + g (tlV Also, U + V, U-V is U + g (t + T
H) V is compatible.

Next, the above relationship will be explained in detail using the frequency spectrum shown in FIG. FIG. 3a shows the frequency spectrum of the color difference signal component [3-Y] as it is. FIG. 3 shows the frequency spectrum of the signal component R-Y with an opposite phase to the signal component B-Y, modified by the function g(tl()(,-Y)).

After adding the two signal components, the output of the addition stage 24 has the following value, corresponding to the function (B Y)+g(t)(几-Y):
Two color difference signal components appear with intersecting frequencies (third
(See Figure C). This signal component is recorded on the second recording channel of the video recorder 22.

A device for recording color image signals on a magnetic tape with mixed frequencies is disclosed, for example, in Swiss Federal Patent No. 5899.
No. 89.

The simultaneously recorded color image signals are reconstructed by a known transversal filter during playback. This type of filter is commonly known as a comb filter.

In this case, the signal sequence U0g (tlV , U + g (
t + TH) V is the delay time τ corresponding to the scanning line period
is supplied to a delay device with a The output terminals of the delay device are connected to the addition and subtraction points, to which the undelayed signal is also supplied. In FIG. 2, the delay device is indicated by 25, the addition point is 26, and the subtraction point is 27. In order to normalize the signal appearing at the output of the addition and subtraction points, this signal is halved in level in a level reduction stage 28,29. 1/2 remaining on the output side of the subtraction point
The output signal of the subtraction point is fed to a modulator 30 after level reduction in stage 28 in order to eliminate the entire scan line shift. This modulator has the same < 172fH as modulator 23
operates at a frequency of In order to fully compensate for the transit time difference between the luminance signal Y and the chrominance signals R, -Y, B-Y stored in separate channels, the luminance signal Y is transferred in a delay device 3 during the scanning line period. Delayed by the corresponding amount of time. The primary color signals R, G, B are reproduced in the matrix circuit 32.

FIG. 4 shows a delay device 25, addition point 26, and subtraction point 2.
7 is shown enlarged. As is known, the signals appear separately at the output terminals of the addition point 26 and the subtraction point 27.

This is because the amplitude frequency characteristic of the addition point is expressed by the following equation, 1n(r, old-21-tate 1 This is because the subtraction point is expressed by the following formula.

This means: That is, in the first case, a spectral component that is shifted by 1/2 scanning line with respect to the line frequency (odd multiple of 1/2 scanning line frequency, that is, (2n 1
) fH/2) is blocked, and the component without deviation (n-f
H) is allowed to pass. In the second case, this relationship is reversed.

The signal appearing at the subtraction point 27 is multiplied by the coefficients g(1) to g(t+', rH) in order to perform a complete reconstruction. Thereby, the original signal becomes g(t)2=1
Therefore, the coefficient is restored to 2. This factor 2 is eliminated in stage 28.29, as already mentioned. Theoretically, there is an additional 3 dB signal-to-noise ratio gain due to the reduced noise bandwidth of the transpersal filter.

For correct reconstruction, the switching phases of stages 23 to 30 must be synchronized, which requires special signals. To this end, it is advantageous to mix an additional identification pulse into one of the color difference signals before processing. This, u
The pulse has a period of fH/2 for the duration of two fields and is then reset. Therefore, a 2V cycle occurs. It's the first one with a 2V cycle! .

Alternatively, it is also conceivable to evaluate the vertical synchronization signal in the Y signal after the second field.

Additionally, additional information of 1/2 scanning line period can be inserted into the horizontal blanking period to indicate the switching state of one color difference signal. This additional information is a DC or AC voltage pulse (burst) of suitable magnitude and can be derived from the vertical synchronization pulse.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus for implementing the known method, FIG. 2 is a block diagram of an embodiment of a color television signal processing apparatus according to the present invention, and FIG. 3 shows the original color difference signal components and their nine modifications. A diagram showing the spectrum of the received signal components. FIG. 4 is an enlarged diagram of a part of FIG. 2. 1.6, 21.32... Matrix circuit, 2.22.
. . . Video tape recorder, 3, 5 . . . Changeover switch, 4, 7, 25. 31 . . . Delay device, 23. : U0・
- Modulator, 24... Addition stage, 26... Addition point, 27.
Subtraction, do, 28, 29... level reduction stage.

Claims (1)

[Claims] 1. A method for processing a color television signal in a bandwidth-limited channel, in which two color difference signals are transmitted over a common channel at baseband, wherein one color difference signal is After shifting the color difference signal by 1/2 scanning line, transmitting the two color difference signals, and separating the spectra, this one is processed by a transpersal filter.
1. A method for processing a color television signal in a limited bandwidth channel, characterized in that a shift of /2 scan lines is removed and the luminance signal is further transmitted via a second channel. 2. In an apparatus for processing color television signals in channels with limited bandwidth, a videotape recorder (22)
is provided, one of the color difference signals B-Y and R-Y is shifted by 1./2 scanning line with respect to the remaining one, and the luminance signal Y is transmitted to one channel of the video tape recorder (22). and are recorded therein, two color difference signals are also fed into a second channel of the videotape recorder and recorded therein, and the simultaneously recorded color difference signals are passed through a transversal filter (25, 26, 27). is separated at the time of reproduction, its amplitude is normalized by the level reduction stage (28, 29), and the difference output appearing on the output side of the subtraction point is newly shifted by 1/2 scanning line. Apparatus for processing a color television signal according to scope 5 in a bandwidth limited channel. 3 A matrix circuit (21) is provided, to which the color image signal components It, , G, B are supplied, and a videotape recorder (22) for two-channel recording is provided, the first channel of which A luminance signal Y is recorded in the second channel, two color difference signal components are simultaneously recorded in the second channel, a modulation circuit (23) is provided for modulating the color difference signal component 1'L-Y, and the color difference signal B- Addition element (2) that adds Y and the modulated color difference signal fl-Y
4), a delay device (31) is provided on the Y channel output side of the video tape recorder (22), and a second delay device (31) is provided on the output side of the second recording channel for simultaneously recording two color difference signal components. A device (25) is provided and a summing element (
26), a non-delayed signal is supplied from the input side of the delay line (25) to the addition element, and a delayed signal is supplied from the output side of the delay line (25), and a subtraction element (27) is provided; The subtracting element is also supplied with a delayed signal and a non-delayed signal from the output side or input side of the delay device (25), and a normalization stage (29) is provided at the output side of the adding element (26).
A normalization stage (28) is provided on the output side of the subtracting element (27), a modulation stage (30) is provided on the output side of the normalization stage (28), and another 7-trix circuit (32) is provided. The color image is input to the matrix circuit as signal components Y and R.
-Y, l3-Y are supplied, and primary color signals of 1%, G, and B are generated on the output side thereof.
Apparatus for processing a color television signal as described in paragraph 2 in a limited bandwidth channel.