METHOD AND APPARATUS FOR REMOVING IMAGE NOISE
First Claim
1. A method for removing an image noise which is generated when image data which have been compression-encoded in a given format are decoded to reproduce an image, comprising:
- a) a deduction step for examining a digital frequency response of image data which compose an image of a complete image or a frame of image and have been compression-encoded/decoded, to deduce analog frequency characteristics of the image before compression encoding;
b) a parameter setting step for changing a parameter of a below-mentioned digital filter in accordance with a deduction result by the deduction step; and
c) a processing step for performing a filtering process to the image data after they are decoded and before they are digital/analog converted by using a sampled-data H∞
filter having a parameter calculated by solving a computational equation with H∞
control under a predetermined condition or with a rigorous calculation which corresponds to the H∞
control, the computational equation being obtained by approximately converting a conditional equation to a finite-dimensional discrete-time system, and the conditional equation being set to design the digital filter so as to reduce an error between an original analog image signal and an analog image signal obtained through an analog/digital conversion, coding/decoding, and digital/analog conversion.
3 Assignments
0 Petitions
Accused Products
Abstract
An FFT analysis is performed to the image data of one frame which has been decoded, and a cutoff frequency on the assumption that the original signal has first-order attenuation characteristics is obtained each in the horizontal direction and in the vertical direction. A sampled-data H∞ filter (digital filter) which has been previously designed in such a manner as to have different parameters corresponding to different cutoff frequencies is selected. By using this filter, a filtering process is performed to the image data which has been decoded both in the horizontal direction and in the vertical direction. Since the variety of the analog frequency characteristics of the original image is taken into account for every frame of image, the information that seems to be a noise yet actually exists in the original image is less likely to be removed, and a mosquito noise and block noise associated with a coding/decoding process can be efficiently removed.
-
Citations
20 Claims
-
1. A method for removing an image noise which is generated when image data which have been compression-encoded in a given format are decoded to reproduce an image, comprising:
-
a) a deduction step for examining a digital frequency response of image data which compose an image of a complete image or a frame of image and have been compression-encoded/decoded, to deduce analog frequency characteristics of the image before compression encoding; b) a parameter setting step for changing a parameter of a below-mentioned digital filter in accordance with a deduction result by the deduction step; and c) a processing step for performing a filtering process to the image data after they are decoded and before they are digital/analog converted by using a sampled-data H∞
filter having a parameter calculated by solving a computational equation with H∞
control under a predetermined condition or with a rigorous calculation which corresponds to the H∞
control, the computational equation being obtained by approximately converting a conditional equation to a finite-dimensional discrete-time system, and the conditional equation being set to design the digital filter so as to reduce an error between an original analog image signal and an analog image signal obtained through an analog/digital conversion, coding/decoding, and digital/analog conversion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 19)
-
-
10. An apparatus for removing an image noise which is generated when image data which have been compression-encoded in a given format are decoded to reproduce an image, comprising:
-
a) a deduction means for examining a digital frequency response of image data which compose an image of a complete image or a frame of image and have been compression-encoded/decoded, to deduce analog frequency characteristics of the image before compression encoding; b) a parameter setting means for changing a parameter of a below-mentioned digital filter in accordance with a deduction result by the deduction means; and c) a processing means for performing a filtering process to the image data after they are decoded and before they are digital/analog converted by using a sampled-data H∞
filter having a parameter calculated by solving a computational equation with H∞
control under a predetermined condition or with a rigorous calculation which corresponds to the H∞
control, the computational equation being obtained by approximately converting a conditional equation to a finite-dimensional discrete-time system, and the conditional equation being set to design the digital filter so as to reduce an error between an original analog image signal and an analog image signal obtained through an analog/digital conversion, coding/decoding, and digital/analog conversion. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 20)
-
Specification