JPH02165780A - Contour enhancing circuit - Google Patents

Abstract

PURPOSE:To enhance a contour according to a noise level by deciding that a noise is inputted and stopping enhancing the contour when many noise components exist and deciding that a normal contour correcting signal is inputted and enhancing the contour when few noise components exist. CONSTITUTION:When a detected signal under a state in which many noises exist is inputted to an enhance quantity adjusting circuit 36, the circuit 36 never substantially enhances the contour until the level of the first contour correcting signal exceeds a level l3. On the other hand, when another detected signal under a state in which few noise exists is inputted to the circuit 36, the circuit 36 enhances the contour from a point where the level of the first contour correcting signal is a small level to exceed a level l0. Further, a noise quantity detecting period 16 operates only in a vertical blanking period and detects noise quantity in the vertical blanking period. Thus, the contour can be enhanced according to the noise level.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an edge enhancement circuit. In particular, the present invention relates to an edge enhancement circuit that automatically adjusts the effect of edge enhancement depending on the noise level.

(b) Conventional Techniques It is well known that edge enhancement circuits are used to sharpen image quality.

Furthermore, if a video signal containing many noise components is processed by an edge enhancement circuit, the noise components will be emphasized and the image quality will deteriorate.

For this reason, Japanese Patent Application Laid-Open No. 61-220567 (IO4N
No. 5/208) proposes an edge enhancement circuit that detects noise components in a video signal and automatically adjusts the degree of edge enhancement effect in accordance with this detection signal.

(c) Problems to be Solved by the Invention However, with the above configuration, contour enhancement is not performed in a video signal with many noise components. Therefore, the present invention provides an edge enhancement circuit that determines that even when a video signal containing many noise components is input, it performs edge enhancement to the same degree as the conventional technique.

(d) Means for Solving the Problems The present invention provides a noise detection circuit (161 (2g+) that detects the noise level of a video signal and outputs a detection signal, and creates a first contour correction symbol from the video signal. a contour correction signal generation circuit (32), an amplifier circuit (36) that inputs the first contour correction body symbol, amplifies it according to the detection signal and outputs a second contour correction body symbol, and this amplifier circuit ( an addition circuit (36) for adding the second contour correction body symbol and the video signal;
38), wherein the amplifier circuit (36) has a figure-8 characteristic in which the amplification factor is smaller when the level of the first contour correction figure is small than when the level is large. , and when the noise level is large according to the detection signal, the rise level (f,) of the character 8 characteristic is 1
．． ) (12) It is characterized by increasing (73).

(E) Effect According to the present invention, if the first contour correction signal is thick, it is determined that it is a regular contour correction signal, and contour enhancement is performed regardless of the value of the noise detection signal. If the contour correction body symbol is small, it is unclear whether it is noise or a regular contour correction signal, so the determination is made based on the noise detection signal. That is, if there is a large amount of noise components, it is determined that the signal is noise and the edge is not emphasized, and if there is a small amount of noise components, it is determined that the signal is a normal contour correction signal and the edge is emphasized.

(f) Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 and 4.

In Figure 1, (10) is a video signal input terminal, (12
1 is an AD converter that converts an analog video signal into a digital video signal. (14) is a video signal processing circuit.

(!6) is a noise amount detection circuit that outputs a noise amount signal (K). (18) is a low-pass filter, (20)
is a delay circuit for timing adjustment having the same delay time as the delay time in the low-pass filter (18).

(22) is an adder that extracts only the high frequency components of the video signal. This adder (22) subtracts the low frequency component of the video signal from the low-pass filter (!8) from the video signal from the delay circuit (20). (24) is an absolute value @path. (26) is an integrating circuit.

Depending on the
” and “3” detection signal is output.

(30) is an enhancer circuit. Reference numeral (32) is a contour correction signal generation circuit, an example of which is shown in the above-mentioned publication, which outputs a first contour correction signal (FIG. 3b) obtained by second-order differentiation of the video signal (FIG. 3a). (36) amplifies this first contour correction body symbol (Figure 3b) to create a second contour correction body symbol (Figure 3C)
This is an enhancement amount adjustment circuit that outputs . (34) is
This is a delay circuit that requires timing adjustment to compensate for the time delay in circuits (32) +36), and outputs the video signal shown in FIG. 3d. (38) is an adder that adds the second contour correction symbol (FIG. 3C) and the video signal (FIG. 3d) and outputs the contour-enhanced video signal shown in FIG. 3E.

(40) is a digital-to-analog converter. (42)
is a picture tube.

The feature of this embodiment is that the characteristics of the enhancement amount adjustment circuit (36) are switched depending on the magnitude of the detection signal.

That is, the characteristics of this enhancement amount rA adjustment circuit (36) are shown in FIG. As can be seen from this figure, when the detection signal "3" when there is a lot of noise is input to the enhancement amount adjustment circuit (36), the level of the first contour correction figure is adjusted to the level shown in FIG.
1, ), substantial contour enhancement is performed. or,
When the detection signal "0" when there is little noise is input, the first
Contour correction When the level of the body symbol is small and exceeds level 10, contour enhancement is performed.

Note that the noise amount detection circuit (16) operates only during the vertical retrace period to detect the amount of noise during the vertical retrace period.

FIG. 5 shows a second embodiment of the invention, which is a MUSE decoder.

In addition, the MUSE signal is a color signal that is time-domain pressure m and is converted to TCI (Time CoIApres) together with a luminance signal.
sed1otBratioa, hereinafter abbreviated as TCI)
This is a high-definition signal encoded into a signal and band-compressed by multiple subsampling processing. This M.U.
Regarding the SE signal, please refer to "Nikkei Elec! Ronix 1984"
It is introduced on pages 112 to 116 of the March 12, 2016 issue.

In FIG. 5, (10') is an input terminal for the MUSE signal, (11) is a low-pass filter, and (12) is an A/D converter. (44) is a de-emphasis circuit, (46)
1 is an inter-frame processing circuit, (48) is an intra-field processing circuit, (50) is a motion detection circuit, and (52) is a mixing circuit that switches the mixing ratio according to the amount of motion. (54) is a synchronous control signal detection circuit. (56) is TC
It is an I decoder. (58) is a matrix circuit. (30) is an enhancer circuit, and (16) is a noise amount detection circuit. This circuit (16) operates only during the clamp level signal period based on the timing signal from the synchronous control signal detection circuit (54). (28) is an enhancement amount control circuit.

The noise amount detection circuit (!6) described above detects the noise amount using a clamp level signal added to a fixed level period of the MUSE signal, for example, a vertical retrace period. M.U.
The clamp level signals at the 563rd line and 112th line of the SE signal are 37 out of 480 samples in one horizontal scanning period.
4 samples (sampling frequency 16.2MHx)
The clamp level signal is at a constant level (128/256>) during this period. Therefore, the variation from the constant level in this clamp level signal period can be detected as noise superimposed on the transmission path or the like.

Similarly to Figure 1, the amount of noise for each sample is calculated by subtracting the clamp level signal that has passed through the LPF (18) for removing noise components from the clamp level signal, and determining the absolute value using the absolute value circuit (24). can be detected. Furthermore, the amount of noise can be detected by integrating the output of the absolute value circuit (24) over 374 samples using the integrating circuit (26). It is possible that the crank level signal has an offset instead of 128/256, but since the output of the LPF (18) also has the same offset, only the noise component can always be extracted by calculating the difference with the adder circuit (22).

Note that this enhancement may be performed at the R, G, and B signal stages.

(G) Effects of the Invention According to the present invention, contour enhancement can be performed according to the noise level.

[Brief explanation of the drawing]

1 to 4 show a first embodiment of the present invention, in which FIG. 1 is a block diagram, and FIGS. 2, 3, and 4 are diagrams for explaining the characteristics of each part. FIG. 5 is a diagram showing a second embodiment of the present invention. (6)...Noise amount detection circuit (noise detection circuit), (
28)...Enhancement amount control circuit (noise detection circuit)
, (32... Contour correction signal creation circuit, (36... Enhancement amount adjustment circuit (amplification circuit), (3
8)...Adder (addition circuit).

Claims (1)

[Claims] (1) A noise detection circuit (16) (28) that detects the noise level of a video signal and outputs a detection signal; and a contour correction signal creation circuit (28) that creates a first contour correction signal from the video signal.
32), and an amplifier circuit (36) which inputs this first contour correction signal, amplifies it according to the detection signal, and outputs a second contour correction signal.
and an addition circuit (38) for adding the second contour correction signal from the amplifier circuit (36) and the video signal, wherein the amplifier circuit (36) When the level of the contour correction signal is low, it has an S-shaped characteristic with a smaller amplification factor than when the level is high, and according to the detection signal, when the noise level is large, the rising level of the S-shaped characteristic (l_0) (l_1 )(l_2)(l_3).