JPH03224327A - Multiplex signal transmission equipment - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Object of the Invention (Industrial Application Field) This invention is directed to HDTV (Extended Definition)
The present invention relates to a multiplex signal transmission device suitable for use in a television signal transmission/reception system of the init-1on (Te1evis1on) system.

(Prior Art) As is well known, EDT is a new type of television system that aims to improve image quality on both the transmitting and receiving sides while maintaining compatibility with current terrestrial television broadcasting.
The V method has been developed and put into practical use. This EDTV
The system uses the brightness signal band (4.2M) of the conventional NTSC system.
This is an attempt to achieve high image quality by multiplexing and transmitting additional signals with an expanded band within a frequency range (Hz).

By the way, in this EDTV system, the additional signal is multiplexed with the main signal and transmitted, so if it is reproduced by a receiver that only has the function of reproducing the main signal, the additional signal will be considered as a type of noise. , a problem arises in that image quality is disturbed.

Conventionally, therefore, a circuit as shown in FIG. 3 has been used to reduce such image quality disturbance. In addition, the third
The circuit shown in the figure adaptively performs multiplexing only in the still image area, and (a) shows the transmitting side, and (b) shows the receiving side. First, in FIG. 3(a), 11 is an input terminal to which a television signal in the 0 to 6 MHz band is supplied. The television signal supplied to this input terminal 11 is filtered through a two-dimensional band pass filter (hereinafter referred to as 2DB).
2DBPF 12.13 via the field memory 14.
is supplied to.

Here, the 2D-BPF 12 acts as a low-pass filter for the vertical component of the television signal, and acts as a 4.2-6 MHz band-pass filter for the horizontal component. The luminance (YH) signal region shown by the shaded area A in the two-dimensional frequency domain spectrum of FIG. 4 is extracted as an additional signal component. Further, the 2D-BPF 13 acts as a high-pass filter for the vertical component of the television signal, and as a band-pass filter for the horizontal component from 0 to 4.2 MHz, and as a result, as shown in FIG. It acts to extract the signal area surrounded by solid lines excluding the shaded area A, that is, the main signal component.

The additional signal component output from the 2D-BPF 12 is supplied to the vertical emphasis circuit 15. This vertical emphasis circuit 15 is composed of a cyclic filter as shown in FIG. That is, the input terminal 15
The output signal of the 2D-BPF 12 supplied to a is subtracted by a subtracting circuit 15b, which delays the output of the subtracting circuit 15b by a line delay circuit 15c, and then subtracts a signal multiplied by a coefficient multiplier circuit 15d. By multiplying the output of the circuit 15b by (1-K) in the coefficient multiplication circuit 15e, an emphasis output having the characteristics shown in FIG. 6 is obtained from the output terminal 15f.

The output of the vertical emphasis circuit 15 obtained in this way is supplied to the amplitude compression circuit 16 to suppress the entire signal level at a uniform rate, and then the 520 fH output is supplied to the input terminal 18 by the multiplication circuit 17. (-8,2MHz
) is multiplied by a single-frequency sine wave signal whose phase is inverted for each field and shifted in frequency, thereby folding back into the area shown by the shaded area B in FIG. The additional signal component output from this multiplication circuit 17 and the above-mentioned 2
The main signal component output from the D-BPF 13 is added by the adder circuit 19 to be multiplexed, and then taken out from the output terminal 20.

On the other hand, on the receiving side shown in FIG. 3(b), 21 is an input terminal to which the multiplexed signal generated on the transmitting side is supplied as described above. The multiplexed signal supplied to this input terminal 2] is directly supplied to the 2D-BPF 22, and
The signal is supplied to the 2D-BPF 22 via the field memory 23.

Here, the 2D-BPF 22 acts as a high-pass filter for the vertical component of the television signal, and as a band-pass filter of 2.2 to 4 MHz for the horizontal component. It acts to extract only the additional signal component indicated by the shaded area B in the figure.

Then, from the multiplexed signal outputted from the field memory 23, a subtraction circuit 24 subtracts the additional signal component extracted by the 2D-BPF 22, thereby obtaining a main signal component. Further, the additional signal component extracted by the 2D-BPF 22 is converted to 520 fH (-8, 2 MHz) supplied to the input terminal 26 by the multiplier circuit 25.
) is multiplied by a single-frequency sine wave signal whose phase is inverted for each field and shifted in frequency.
The image is returned to the area indicated by the shaded area A in the figure. The additional signal component output from the multiplier circuit 25 is then supplied to an amplitude expansion circuit 27, where the suppression previously applied by the amplitude compression circuit 16 is undone, and then supplied to a vertical de-emphasis circuit 28. Ru.

This vertical de-emphasis circuit 28 is composed of an acyclic filter as shown in FIG.

That is, the amplitude expansion circuit 2 supplied to the input terminal 28a
The output signal of No. 7 is added by an adder circuit 28b to a signal obtained by delaying the output of the amplitude expansion circuit 27 by a line delay circuit 28c and multiplying the output by a coefficient multiplier circuit 28d. + in the multiplication circuit 28e
1/(1-K) is multiplied by 1 and taken out from the output terminal 28f. As shown in FIG. 8, the frequency characteristics of the vertical de-emphasis circuit 28 are opposite to the emphasis characteristics on the transmitting side, and are set so that the entire transmitting and receiving system is flat. Then, the additional signal component outputted from the vertical de-emphasis circuit 28 and the main signal component outputted from the subtraction circuit 24 are added by the addition circuit 29, thereby restoring and outputting the original television signal. It is taken out from the terminal 30.

The television signal transmission and reception system based on the EDTV method described above focuses on the fact that due to the statistical nature of images, the energy of additional signals with high vertical correlation is concentrated near direct current. By reducing the level near DC and transmitting it, it is possible to reduce image quality interference caused by the additional signal even when the signal is reproduced by a receiver that only has the function of reproducing the main signal.

However, in such conventional multiplexed signal transmission systems, because the gain near DC is reduced on the transmitting side, small amplitude signals with low vertical frequencies are lost, resulting in a loss of image definition. occurs. In addition to the characteristic deterioration caused by the emphasis processing performed by the vertical emphasis circuit 15, the amplitude compression causes the loss of minute amplitude signals, resulting in the inconvenience that the definition of the image is impaired.

(Problems to be Solved by the Invention) As described above, the conventional multiplex signal transmission device has the problem that small amplitude signals are easily lost on the transmitting side, resulting in loss of image definition on the receiving side. There is.

Therefore, the present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide an extremely good multiplex signal transmission device that can reduce image quality deterioration on the receiving side due to minute amplitude signals lost on the transmitting side. .

[Structure of the Invention] (Means for Solving the Problems) A multiplex signal transmission device according to the present invention expands a minute amplitude component of an additional signal component, performs emphasis processing and compression processing on the expanded output, and converts the main signal into a main signal. The components are frequency multiplexed.

(Function) According to the above configuration, the small amplitude signal of the additional signal is expanded before being subjected to emphasis processing or amplitude compression processing, so that the gain near DC can be reduced,
By performing emphasis processing and amplitude compression, it is possible to prevent minute amplitude signals from being lost, and it is possible to reduce image quality deterioration without impairing the fineness of the reproduced image on the receiving side.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In FIG. 1, the same parts as in FIG. 3 are indicated by the same symbols, and only the different parts will be described here. That is, as shown in FIG. 1(a), 2D-
A small amplitude expansion circuit 31 is interposed between the BPF 12 and the vertical emphasis circuit 15, and the signal level of the luminance (YH) signal component, that is, the additional signal component shown in the shaded area A in FIG. The difference from the conventional method is that only small components of the image are selectively level-stretched.

FIG. 2 shows a specific example of the configuration of the small amplitude expansion circuit 31. That is, for example, an 8-bit additional signal output from the 2DBPF 12 is supplied to the input terminal 31a. The additional signal supplied to this input terminal 31a is directly supplied to the first input terminal 11 of the selector 31b, and is also supplied to the 1-bit shift register 31c, the 2-bit shift register 31d, and the 3-bit shift register 31e.
the second, third and fourth input terminals 12. of the selector 31b, respectively. I3. I4 is correspondingly supplied. These 1-bit shift register 31c, 2-bit shift register 31d, and 3-bit shift register 31e shift the input additional signal by 1 bit, 2 bits, and 3 bits, respectively, thereby doubling, quadrupling, and 8
It doubles.

Further, the additional signal supplied to the input terminal 31a is supplied to the control circuit 31f. This control circuit 31f compares the input additional signal level with a preset reference level and outputs a selection signal to the control terminal C of the selector 31b. In this case, the selector 31b selects and outputs the signal supplied to the first input terminal If when the additional signal level is high, and as the additional signal level becomes lower, the second. Third and fourth input terminals 12゜13, I4
It is controlled to sequentially select and output the expanded signals supplied to the circuit. The signal selected by the selector 31b is supplied to the vertical emphasis circuit 15 via the output terminal 31g.

Therefore, according to the configuration of the above embodiment, the small amplitude signal of the additional signal output from the 2D-BPFI 2 is expanded on the transmitting side before being subjected to emphasis processing or amplitude compression processing. By reducing the gain in the vicinity of DC and performing emphasis processing and amplitude compression, it is possible to prevent the loss of minute amplitude signals, thereby reducing image quality deterioration without sacrificing the definition of the reproduced image on the receiving side. can be reduced. Furthermore, since the minute amplitude signal is expanded, it is effective against transmission deterioration due to external noise.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an extremely good multiplex signal transmission device that can reduce image quality deterioration on the receiving side due to minute amplitude signals lost on the transmitting side.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a multiplex signal transmission device according to the present invention, FIG. 2 is a block diagram showing a specific example of the main parts of the same embodiment, and FIG. 3 is a block diagram showing a conventional multiplex signal transmission system. FIG. 4 is a block diagram showing the system; FIG. 4 is a diagram for explaining frequency multiplexing; FIGS. 5 and 6 are block diagrams and characteristic diagrams for explaining the vertical emphasis circuit of the conventional system; 7 and 8 are a block diagram and a characteristic diagram, respectively, for explaining the vertical de-emphasis circuit of the conventional system. 11...Input terminal, 12.13...2D-BPF. 14... Field memory, 15... Vertical emphasis processing, 16... Amplitude compression circuit, 17... Multiplication circuit, 18... Input terminal, 19... Addition circuit, 20.
...Output terminal, 21...Input terminal, 22...2D-
BPF, 23...Field memory, 24...Subtraction circuit, 25...Multiplication circuit, 26...Input terminal, 27...
... Amplitude expansion circuit, 28... Vertical de-emphasis circuit, 29... Addition circuit, 30... Output terminal, 31.
...Small amplitude expansion circuit.

Claims (1)

[Claims] A multiplex signal transmission device that frequency-multiplexes and transmits a main signal component and an additional signal component constituting a television signal, including an expansion means for expanding a minute amplitude component of the additional signal component, and an emphasis process on the output of the expansion means. A multiplex signal transmission apparatus comprising: signal processing means for performing compression processing; and multiplexing means for frequency multiplexing the output signal of the signal processing means and the main signal component.