Adaptive Image Post-Processing Circuit for Noise and Sharpness Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional post-processing circuits for image signals face challenges in effectively eliminating noise and sharpening images due to conflicting characteristics between noise elimination and sharpening processes, particularly when image signals are compressed using block-DCT, leading to artifacts like ringing and blocking.
Innovation Solution
A post-processing circuit that includes low-frequency, high-frequency, and intermediate-frequency extracting units, with gain settings adjusted based on pixel location in the spatial domain to optimize noise elimination and sharpening, using a low-pass filter for noise reduction and high-pass filtering for sharpening, and adaptive gain settings to minimize artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise elimination process is performed first, then noise is reduced, but high-frequency components are deleted and cannot be recovered
Solution Approach 1:
The patent segments the frequency spectrum into low-frequency, intermediate-frequency, and high-frequency components, processing each segment separately with appropriate gain factors. This allows noise elimination in low-frequency bands while preserving and enhancing high-frequency components through selective processing of each frequency segment.
Solution Approach 2:
The patent applies different gain factors (first gain for high-frequency, second gain for intermediate-frequency) to different frequency bands based on their local characteristics. This local quality approach enables optimal noise elimination where needed while preserving important high-frequency information in other regions.
2Manufacturing precision
If sharpening process is performed before noise elimination, then image sharpness is improved, but noise is amplified and cannot be eliminated effectively
Solution Approach 1:
The patent segments the processing into distinct frequency band handling: low-frequency processing for noise elimination, high-frequency processing for sharpness enhancement. By segmenting the frequency domains, the system can apply noise elimination where appropriate without amplifying noise in high-frequency bands, then separately enhance sharpness in high-frequency components.
Solution Approach 2:
The patent changes the gain parameters adaptively based on frequency band and spatial location. Different gain factors are applied to different frequency bands, and the gains are adjusted according to whether the pixel is in a flat or fine region, enabling optimal balance between noise elimination and sharpness enhancement.
3Loss of energy
If block-DCT compression is applied, then image compression is achieved, but blocking artifacts and ringing are generated
Solution Approach 1:
The patent detects whether a pixel is located in a flat region or a fine region, and applies different processing strategies accordingly. In flat regions, stronger noise elimination is applied, while in fine regions, sharpness enhancement is prioritized. This local quality approach effectively reduces blocking artifacts at block boundaries while preserving important image details.
Solution Approach 2:
The patent dynamically adjusts gain factors based on spatial location and frequency content. By changing the gain parameters according to the local image characteristics and compression artifacts, the system effectively reduces blocking and ringing artifacts while maintaining compression efficiency.
Data Source
AI summary
A post-processing circuit for processing an image signal according to frequency components of an image signal includes: a low-frequency extracting unit outputting a low-frequency image component of the image signal as a low-frequency signal; a high-frequency extracting unit multiplying a high-frequency image component of the image signal by a first gain and outputting the multiplication product as a high-frequency signal; an intermediate-frequency extracting unit multiplying an intermediate-frequency image component of the image signal by a second gain and outputting the multiplication product as an intermediate-frequency signal; and an adder adding the low-frequency signal, the high-frequency signal, and the intermediate-frequency signal and outputting the addition sum as a post-processed signal, wherein the first gain and the second gain are differently set according to a pixel location in a spatial domain.