JPH03139089A - MUSE down converter - 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] [Industrial Application Field] This number relates to a MUSE type C high-definition down converter signal processing circuit.

[Prior art]

As shown in FIG. 2, an analog-to-digital converter 2 down-conversion circuit 4. It is composed of an inverse matrix circuit 5 and a digital-to-analog converter 9, and uses the pseudo-constant luminance transmission method that is a feature of the MUSE method, that is, the pseudo-linear processing of signals such as transmission inverse gamma correction and gamma correction of CRT displays etc. is not performed. , Therefore, the luminance signal and color difference signal cannot be faithfully reproduced.

[Problem to be solved by the invention]

The present invention has been made in view of the conventional example, and an object of the present invention is to faithfully reproduce a luminance signal and a color difference signal adapted to a pseudo-constant luminance transmission method in a MUSE method down converter.

[Means to solve the problem]

In order to adapt to the pseudo-constant luminance transmission method of the MUSE method, the present invention performs transmission inverse gamma correction on the luminance signal and the color difference signal, and furthermore, the R, G, B
The feature is that the signal is subjected to display gamma correction such as CRT and linear processing to increase the fidelity of the reproduced signal and improve the image quality.

[Effect]

In Fig. 1, a MUSE high-visibility signal 1 input from a transmission line is converted into a digital signal by an analog-to-digital converter 2 including a clamp circuit, and at the same time, the input signal level is held constant by an auto level control (not shown). . An inverse gamma correction circuit 3 performs inverse gamma correction on only the luminance signal for the transmission line to return it to its original linear characteristic, and a down-conversion circuit 4 connects the separated luminance signal after decoding processing directly to an inverse matrix circuit 5. Further, the color difference signal is subjected to inverse gamma correction for the transmission line in an inverse gamma correction circuit 6, and after being outputted from an interpolation filter, it is input to the inverse matrix circuit 5 together with the luminance signal for R, G.

Obtain B signal. The R, G, and B signals are passed through a gamma correction circuit 8 for gamma correction of a display such as a CRT, and then converted into an analog signal 10 by a digital-to-analog converter 9 and output.

〔Example〕

To faithfully reproduce the MUSE system high-definition signal, the luminance signal and color difference signal are each subjected to inverse gamma correction using a non-linear transmission path, and then the R, G, and B signals are converted to R, G, and B signals by an inverse matrix circuit, and then the gamma correction of CRT, etc. It is necessary to apply a corrected pseudo-constant luminance transmission. As shown in Figure 1,
The tuner output base punt MUSE signal 1 is connected to the analog-to-digital converter 2, and the digital signal output from the converter 2 is converted into a brightness signal component that corrects the non-linear transmission line gamma characteristic to reduce noise in dark areas and improve S/N. It is connected to the first transmission line inverse gamma correction circuit 3 which is compatible only with
The signal linearly processed by the inverse gamma correction circuit 3 of
) is connected to a second transmission line inverse gamma correction circuit 6 corresponding to color difference signal components for correcting non-linear transmission line gamma characteristics for S/N improvement, and the output of the second inverse gamma correction circuit 6 is connected internally. Connected to the interpolation filter 7, the color difference signal of the MUSE method, which is compressed to 1/4 the information amount of the luminance signal by the interpolation filter 7, is made to have the same signal rate as the luminance signal, and is output from the interpolation filter 7. color difference signal and the down conversion circuit 4
connecting the output luminance signal to the inverse matrix circuit 5;
The inverse matrix circuit 5 inversely matrixes the luminance signal m and the color difference signals (R-Y) and (B-Y) output from the interpolation filter 7 to output faithful R2O and B reproduction signals. Furthermore, C
In order to reproduce images faithful to RT, etc., a gamma correction circuit 8 (T -2,2~2.6),
The output signals of the gamma correction circuit 8 are converted into analog R, G, and B signals IO by a digital-to-analog converter 9, and are output to a display device such as a CRT (not shown).

〔Effect of the invention〕

As described above, the present invention achieves the intended purpose by applying inverse gamma correction on the transmission path to each of the luminance signal and color difference signal, and further applying gamma correction on the inverse matrix output R, G, and B signals respectively using a CRT or the like. It is possible to improve the overall image quality by increasing the fidelity of the reproduced signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a MUSE down converter showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional MUSE down converter. 1 is a baseband MUSE signal, 2 is an analog-to-digital converter, 3 is a luminance signal transmission line inverse gamma correction circuit, 4
5 is a down conversion circuit, 5 is an inverse matrix circuit, 6 is a color difference signal transmission line inverse gamma correction circuit, 7 is an interpolation filter, 8 is a gamma correction circuit such as a CRT, and 9 is a digital-to-analog converter.

Claims (1)

[Claims] The baseband signal of the MUSE method is connected to an analog-to-digital converter, and the output of the analog-to-digital converter is connected to an inverse gamma correction circuit for a first transmission line that performs inverse gamma correction of the luminance signal component. The output of the inverse gamma correction circuit for the transmission line is connected to a down-conversion circuit, and the color difference signal output from the down-conversion circuit is connected to the inverse gamma correction circuit for the second transmission line that supports the color difference signal component. Connect the output of the inverse gamma correction circuit to an interpolation filter, connect the color difference signal output from the interpolation filter and the luminance signal output from the down-conversion circuit to an inverse matrix circuit, and connect the output of the inverse matrix circuit to the gamma correction circuit. The output of the gamma correction circuit is connected to a digital-to-analog converter, and the digital-to-analog converter outputs a video signal suitable for high-definition pseudo-constant brightness transmission.