JPS62172879A - Decoder control method - Google Patents

Abstract

PURPOSE:To prevent malfunction in the detection of a moving area by detecting a transmission line noise, and switching the degree of noise reduction corresponding to a noise level. CONSTITUTION:The difference of one clock of a CK1 in a flip-flop 4 is obtained by a difference calculator 8, and it is fixed with an appropriate timing clock CK2 at a flip-flop 5. Afterwards an inter-frame difference is obtained by the flip-flop 5 and a difference calculator 9 using the clock CK2, and an absolute value in found by an absolute circuit 1, and a signal having a level corresponding to the noise level is obtained by applying a temporary filter 3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for controlling a decoder for multiple sub-sampled transmission signals, in which reception characteristics are adaptively changed according to the magnitude of transmission line noise. The aim is always to obtain the best possible image quality.

[Summary of the Disclosure] The present invention is a control method for a decoder of multiple sub-sampled transmission signals in the presence of transmission line noise,
1) Detect the noise level, (2) change the strength of noise reduction according to the noise level, and (3) change the motion detection characteristics in the same way.

The present invention can essentially be applied to both a multiplex sub-sample transmission system and a transmission system that does not include inter-frame aliasing components in the low frequency range of the transmission signal, as will be described later. In addition,
From now on, unless otherwise specified, the multiple subsample transmission method (
or signal) includes both expressions.

[Prior Art] There is no prior art particularly related to the present invention, but the present invention is specifically related directly to broadcasting systems, and is a device that utilizes the fact that random noise has inter-frame correlation or no correlation. is common as seen in noise reducers and the like.

Note that one of the methods for band compression of television signals is
Multiple subsample transmission schemes using interframe and interfield offset subsampling, e.g. MLIS
E(Multiple Sub-NyquistSam
There is a current high-definition television signal multiplex subsample transmission method called pling encoding.
Bandwidth compression is effectively achieved. For details, see, for example, "Technical Research Report of the Institute of Electronics and Communication Engineers, Image Engineering IE84-72.
It is stated in J.

Furthermore, by performing motion detection using a complete frame-to-frame difference signal, the inter-frame aliasing component is removed in the low frequency range of the transmitted signal, which simplifies the configuration of the receiver and significantly improves the image quality. A multiplex subsample transmission system that does not include this has also been proposed (see Japanese Patent Application No. 60-106132).

[Problems to be Solved by the Invention] The problems to be solved by the present invention are, for example, when high-definition broadcasting is performed using a transmission method that does not include aliasing components between frames in the low frequency range of the transmission signal. Since it may not be possible to obtain C/N, the ideal C/N
The purpose is to enable reception with good image quality even when the image quality is lower.

Noise reduction is effective as a method for obtaining good image quality with a low C/N. However, when noise reduction is performed, although the S/N ratio is improved, the image quality deteriorates to some extent. In other words, a noise reduction system optimized for a certain human-powered S/N
However, for a signal with a better human S/N ratio, there is no more noise to be improved, and the image quality may deteriorate. Therefore, it is desirable that this problem be resolved.

The same thing can be said about dynamic area detection. In other words, when the human S/N is good, the higher the sensitivity of the moving area detection, the better.
This is preferable in terms of image quality since a moving object cannot be mistaken for a stationary object, but when the S/N ratio is poor, a stationary object can be mistaken for a moving object due to noise. In the case of flat noise, this is not much of a problem, and at the S/N ratio that causes this error, the image quality is also low to begin with, so it can be balanced. However, when using nonlinear emphasis as in satellite broadcasting, noise remains only around the edges, so -
Even if the image quality is good and the S/N ratio is good, the moving area detection may malfunction, causing problems.

The present invention aims to solve the above problems.

[Means for Solving the Problems] The present invention is characterized in that a decoder for multiple sub-sampled transmission signals detects transmission line noise and switches the degree of noise reduction according to the noise level.

[Example] FIG. 1 shows a specific example of noise detection and noise reduction control according to the present invention.

In Figure 1, 1 is an absolute value circuit, 2 is a threshold logic, 3 is a temporal filter, 4, 5.6 and 7 are D-type flip-flops, 8.9 and 10 are subtracters, and 11 is an adder. , 12 is a multiplier with a multiplier α, and 13 is a frame memory.

The human signal uses the multiple sub-sampled transmission signal itself. First, a difference of 1 clock (161 Hz) is obtained from the clock C of the flip-flop 4 by the subtracter 8, and then this is fixed in the flip-flop 5 with an appropriate timing clock (2 for C). This clock is one clock per frame that rises, for example, in the middle of the crumb line or in the flat part of the first half of the frame line.

All that is left to do is to use this clock (2 for C) to convert the flip-flop 5. A difference between frames is obtained by a subtractor 9, an absolute value is obtained by a circuit 1, and the signal is multiplied by a temporal filter 3 to obtain a signal having a level corresponding to the noise level.

The actual control is to prepare, for example, four levels of noise reduction using the threshold logic (actually I'IOM) Th.
/N is very good (i.e. when the detected level is low)
does not apply any noise reduction at all, but applies stronger noise reduction in order according to the level.

In the example shown in Fig. 1, if the crumb line is used as is, only one data per frame can be used, which is a loss, so the data of each field is used as shown in Fig. 2. This will double the detection speed. In FIG. 2, 19 is an added D-type flip-flop, and the rest is the same as in FIG. 1.

At this time, Clock 2 is a clock that rises on the crumb lines of both fields.

Although the hard-wired Rosic is shown in Figures 1 and 2, this part operates in at most 60112 cycles (3QIIZ in Figure 1), so for example, a 4- to 8-bit microprocessor One piece is enough to achieve the functions.

Next, regarding the control of dynamic area detection, dynamic area detection does not simply take the difference between frames, but also divides the absolute value of the difference between frames by the edge (actually, nonlinear processing is performed in ROM).
etc. ) The system shown in Figure 3 is used.

In FIG. 3, 13 is a frame memory, 14 is a low-pass filter, 15 is a frame (inter) frame difference absolute value circuit, 16 is an edge detection circuit, 17 is a divider, 18 is a multiplier, and 2 is a threshold logic. .

In such a control system for detecting a moving area, the multiplier 18 and the threshold logic 2 adjust the magnification of the edge detection signal from the detection circuit 16 according to the noise level so that the edge becomes more effective when the noise is large. When the control is applied, even in the case of non-linear emphasis, the C/N decreases and noise remains at the edges.
Batch processing is performed using table looking logic such as M, and therefore control is performed by replacing tables. Therefore, as shown in Figure 3, m61
Although it is a little difficult to think about it separately, the principle is as follows.

Although FIG. 3 takes 1-frame detection as an example, the same applies to 2-frame detection.

[Effects of the Invention] The present invention provides a decoder/decoder for multiple sub-sampled transmission signals.
The image quality received by the receiver can be maintained at its best even if the transmission path S/N decreases. Further, the circuit scale itself can be extremely small since the operating speed is low.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a first embodiment of the present invention, Fig. 2 is a system diagram showing a part of the second embodiment, and Fig. 3 is a system diagram showing a part of the second embodiment. It is a system diagram showing an example. 1... Absolute value circuit, 2... Threshold logic, 4.5, 6.7... D-type flip-flop, 8.9.
10... Subtractor, 11... Adder, 12... Multiplier.

Claims (1)

[Claims] 1) In a decoder for multiple sub-sampled transmission signals,
A decoder control method that detects transmission line noise and switches the degree of noise reduction according to the noise level. 2) In the decoder control method according to claim 1, the transmission line noise is detected by detecting the noise level of the clamp line period or the first half of the frame pulse line. . 3) A decoder control method according to claim 1, characterized in that the absolute value of the difference between samples is taken as the noise level. 4) A decoder control method according to claim 3, characterized in that the absolute value of the inter-frame difference of the inter-sample differences is taken as the noise level. 5) A decoder control method according to claim 3 or 4, characterized in that the obtained noise level is used for control by removing time-varying components using a temporal filter. 6) The decoder control method according to claim 1, 2, 3, 4, or 5, characterized in that the sensitivity of moving area detection is switched according to the noise level. Decoder control method. 7) Claims 1, 2, 3, 4,
In the decoder control method described in item 5 or 6,
A decoder control method characterized by switching the edge dependence of the sensitivity of moving area detection.