KR100400013B1 - Apparatus and method for controlling a filter according to variation of frequency characteristic of input signal - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus and method, and more particularly, to control a filter according to a frequency characteristic change of an input signal for automatically varying a frequency characteristic of a filter in association with the frequency characteristic of a signal in a signal processing process. An apparatus and method are provided.

According to the present invention, by detecting a frequency characteristic that varies according to the format conversion of the signal, and controlling the frequency characteristic of the filter in conjunction with the frequency characteristic of the variable signal, by matching the frequency characteristic of the signal input to the filter to the optimum The effect of processing the signal in a state is generated. In particular, when the present invention is applied to a noise reduction circuit and a detail enhancer, only a signal of a high frequency component from which the noise component is removed can be accurately extracted, thereby producing an effect of obtaining a good image.

Description

Apparatus and method for controlling a filter according to variation of frequency characteristic of input signal}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus and method, and more particularly, to control a filter according to a frequency characteristic change of an input signal for automatically varying a frequency characteristic of a filter in association with the frequency characteristic of a signal in a signal processing process. An apparatus and method are disclosed.

In general, a signal processing apparatus performs signal processing to enlarge an image by interpolation signal processing to improve the resolution of a video signal, or to reduce an image by subtractive signal processing to reduce the amount of data in the signal. That is, for example, in order to increase the resolution, the standard is converted into a 720 x 480 video signal into a 1920 x 1080 video signal. However, when the standard of the video signal is converted in this way, a phenomenon occurs in which the frequency band of the signal is changed.

As shown in FIG. 1, a general signal processing apparatus according to the related art includes a format converter 101, a filter 102, and a synthesizer 103.

The format converter 101 executes signal processing for varying the number of pixels per frame by interpolation or deduction. As an example, when the video signal is extended to 1: 2, the frequency bandwidth of the format-converted signal is reduced to 1/2 compared to the signal input to the format converter 101.

That is, when the input signal of the format converter 101 has a frequency bandwidth as shown in FIG. 2 (a), when the format of the signal is converted to 1: 2 by interpolation in the format converter 101. As shown in FIG. 2 (b), the output signal is reduced in frequency bandwidth by half compared to the input signal.

However, according to the related art, the filter 102 is designed to have a frequency characteristic as shown in FIG. 2 (c) in accordance with the frequency characteristic of the input signal in a fixed manner irrespective of the change in the frequency characteristic of the signal. It is not matched with the frequency characteristics of the format-converted signal, so that high frequency noise components are included and output. FIG. 2 (d) shows the frequency characteristics of the output signal of the filter 102.

The high frequency component of the signal is extracted by generating an output signal corresponding to the difference between the signal A not passing through the filter output from the synthesis unit 103 and the signal B passing through the filter 102. High frequency noise was included in the signal output at 102, and only high frequency components could not be extracted accurately.

For this reason, when a high frequency component is extracted by the same method as in the related art and supplied to a noise reduction, detail enhancer, or the like for improving the signal, a noise component is included or part of the signal. There was a problem that the loss of image quality was deteriorated.

That is, according to the related art, there is a problem that noise is generated or a signal is lost during signal processing because the frequency characteristic of the filter is not adaptively changed according to the frequency characteristic change of the signal input to the filter.

The technical problem to be solved by the present invention is to solve the above problems, when the frequency characteristics of the signal input to the filter is variable in conjunction with the input signal for automatically varying the frequency characteristics of the filter used in the signal processing apparatus An object of the present invention is to provide an apparatus and method for controlling a filter according to a change in frequency characteristics.

1 is a block diagram of a general signal processing apparatus including a filter according to the prior art.

2 (a)-(d) are diagrams showing frequency characteristics of main signals shown in FIG.

3 is a block diagram of a filter control apparatus according to a change in frequency characteristics of an input signal according to the present invention.

4 (a)-(c) are diagrams showing the frequency characteristics of the main signal shown in FIG.

5 is a flowchart illustrating a filter control method according to a change in frequency characteristics of an input signal according to the present invention.

In order to achieve the above technical problem, a filter control apparatus according to a change in frequency characteristics of an input signal according to the present invention includes a format conversion unit for converting the number of pixels per screen of an input signal into a ratio of N: M in a signal processing apparatus; A conversion rate determination unit for inputting an input signal and an output signal of the format conversion unit to obtain an image enlargement / reduction conversion ratio (N / M) of the input signal and the output signal, and the conversion ratio (N) obtained by the conversion rate determination unit. / M) to filter the filter coefficient setting unit for determining the filter coefficient to vary the cutoff frequency of the filter and the signal output from the format converter, and apply the filter coefficient determined by the filter coefficient setting unit to filter It characterized in that it comprises a filter for.

In order to achieve the above object, the filter control method according to the change in the frequency characteristic of the input signal according to the present invention is a filter control method in a signal processing apparatus, (a) whether the format of a signal processed in the signal processing apparatus is converted; Determining (b) obtaining the image enlargement / reduction ratio (N / M) of the input signal and the output signal when the format of the signal is converted in step (a), and (c) the step and varying the filter coefficient corresponding to the image enlargement / reduction conversion ratio (N / M) obtained in (b).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, the filter control apparatus according to the frequency characteristic change of the input signal according to the present invention includes a format conversion unit 301, a synthesis unit 302, a filter 303, a conversion rate determination unit 304, and A filter coefficient setting unit 305 is provided.

The format converter 301 is a means for varying the number of pixels output per frame of the input signal. The format converter 301 enlarges the image by an interpolation process or reduces the image by an iteration process. In other words, signal processing for enlarging or reducing the number of screen configuration pixels of the input signal by N: M ratio is executed.

Accordingly, the frequency band width of the signal output from the format converter 301 is changed at an N / M ratio compared to the frequency band width of the input signal before format conversion.

As an example, when the format converter 301 enlarges the image of the input signal to 1: 2 by interpolation, the signal output from the format converter 301 is a signal input to the format converter 301. In comparison, the frequency bandwidth is reduced to 1/2. That is, when the input signal before the format conversion has a frequency characteristic as shown in Fig. 2A, the output signal of the format conversion unit 301 in which the image is enlarged at a ratio of 1: 2 is shown in Fig. 4B. It has the same frequency characteristic.

The conversion rate determining unit 304 inputs a signal before the format conversion input to the format conversion unit 301 and a signal after the format conversion output from the format conversion unit 301, and counts the number of horizontal / vertical lines of both input signals. The image enlargement / reduction conversion ratio (N / M) value is calculated.

Then, the filter coefficient setting unit 305 determines the filter coefficient for varying the cutoff frequency of the filter 303 by using the image enlargement / reduction conversion ratio (N / M) information obtained by the conversion rate determination unit 304. .

For example, in the case where the filter 303 is a low pass filter, it is assumed that the frequency characteristic of the input signal is as follows.

Passband; omega _C = omega <= omega _C,

Stopband; omega _c = omega <= pi,-pi = omega <=-omega _c

Then, as the input signal passes through the format converter 301, the frequency characteristic is changed, and the filter coefficient is determined to change the frequency characteristic of the filter to be suitable for the changed frequency characteristic. The filter coefficients are determined to have characteristics.

Passband;

Stopband; ,

After the filter coefficient set by the filter coefficient setting unit 305 is determined by the filter coefficient setting unit 305 to apply the filter coefficient set by the filter coefficient setting unit 305 to the filter 303, the filter is linked in accordance with the change of the frequency bandwidth of the input signal. The frequency bandwidth of 303 is also changed.

The synthesizer 302 synthesizes the signal 1 output from the format converter 301 and the signal 2 inverted 180 degrees from the filter 303. Accordingly, the signal output from the combining unit 302 corresponds to a high frequency signal component, and noise reduction signal processing and detail enhancer signal processing to improve image quality using these high frequency signal components are performed. Will run.

Accordingly, the frequency characteristic of the signal 1 output from the format converter 301 is as shown in FIG. 4 (a), and the frequency characteristic of the filter 303 is linked to the frequency characteristic change of the input signal as shown in FIG. 4 (b). The frequency characteristic of the signal 2 output from the filter 303 becomes variable as shown in FIG. 4C. Therefore, the filter 303 operates to accurately match the frequency characteristic of the signal input to the filter 303.

Next, a filter control method according to a change in frequency characteristic of an input signal according to the present invention will be described with reference to the flowchart of FIG. 5.

First, the signal processing apparatus determines whether the format of the signal input to the filter is converted (step 501). Here, format conversion of a signal means that the number of vertical / horizontal lines of an image constituting a frame is changed by signal processing such as interpolation or extraction.

If the format of the signal is converted as a result of the determination in step 501, a format conversion rate value is detected (step 502). That is, the format conversion rate value is detected by comparing the number of vertical / horizontal lines of the signal before format conversion with the number of vertical / horizontal lines after format conversion.

After detecting the format conversion rate value, filter coefficients for varying the frequency characteristics of the filter are generated using the detected format conversion rate value (step 503). The filter coefficient is determined so that when the format conversion rate value is N / M, the cutoff frequency of the filter is multiplied by the N / M value by the cutoff frequency of the input signal before the format conversion.

The filter coefficient thus generated is applied to the filter to process the format-converted signal input to the filter (step 504). As a result, the frequency characteristic of the filter may be linked to vary according to the changed frequency characteristic of the format-converted signal.

The invention can be practiced as a method, apparatus, system, or the like. When implemented in software, the constituent means of the present invention are code segments that necessarily perform the necessary work. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memories, E ² PROMs, floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, and the like. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described.

As described above, according to the present invention, the frequency characteristic of the signal input to the filter is detected by detecting a frequency characteristic that varies according to the format conversion of the signal, and controlling the frequency characteristic of the filter to vary with the frequency characteristic of the variable signal. The effect of matching the signal to the optimal state is generated. In particular, when the present invention is applied to a noise reduction circuit and a detail enhancer, only a signal of a high frequency component from which the noise component is removed can be accurately extracted, thereby producing an effect of obtaining a good image.

Claims (8)

In the signal processing apparatus, A format converter for converting the number of pixels per screen of the input signal into a ratio of N: M; Inputting an input signal and an output signal of the format conversion unit to obtain an image enlargement / reduction conversion ratio N / M of the input signal and the output signal, where N and M are the number of 1-frame screen pixels before and after format conversion A conversion rate determination unit; A filter coefficient setting unit for determining a filter coefficient so as to vary a cutoff frequency of the filter according to the conversion ratio N / M obtained by the conversion rate determining unit; And And a filter for inputting the signal output from the format converter and filtering the filter by applying the filter coefficient determined by the filter coefficient setting unit. The filter coefficient of claim 1, wherein the filter coefficient is a cutoff frequency of the filter (omega _ MC). (Here, the cutoff frequency of the input signal before the omega _C format conversion, N is the number of 1-frame pixels before format conversion, and M is the number of 1-frame pixels after format conversion.) Filter control apparatus according to the frequency characteristic change of the input signal, characterized in that it is determined to vary. The frequency characteristic change of the input signal according to claim 1, wherein the image enlargement / reduction conversion ratio N / M is calculated by calculating a ratio of the number of vertical and horizontal lines of the input signal and the output signal of the format converter. Filter control device according to. The filter control apparatus according to claim 1, further comprising a synthesizer configured to subtract a signal output from the filter from a signal output from the format converter. In the filter control method in the signal processing apparatus, (a) determining whether a format of a signal processed by the signal processing apparatus is converted; (b) obtaining an image enlargement / reduction ratio (N / M) of the input signal and the output signal when the format of the signal is converted in step (a); And and (c) varying the filter coefficient corresponding to the image enlargement / reduction conversion ratio (N / M) obtained in the step (b). The method according to claim 5, wherein the step (a) detects a change in the number of vertical / horizontal lines constituting the screen and determines whether to convert the format. 6. The method of claim 5, wherein the step (b) calculates a screen enlargement / reduction ratio by calculating a ratio between the number of vertical and horizontal lines of the input signal before format conversion and the output signal after format conversion. Filter control method according to frequency characteristic change. 6. The method of claim 5, wherein the step (c) determines the filter coefficients such that the value obtained by multiplying the image enlargement / reduction ratio (N / M) by the cutoff frequency of the input signal before format conversion is the cutoff frequency of the filter. Filter control method according to the frequency characteristic change of the input signal characterized in that.