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Subband coding of images using asymmetrical filter banks
Summary
This study introduces new two-band filter banks for image coding, significantly reducing ringing artifacts. These filters offer improved energy compaction and reduced quantization errors for better visual quality.
Area of Science:
- Digital Signal Processing
- Image Compression Technologies
Background:
- Subband coding is crucial for image compression.
- Ringing artifacts are a major distortion in current subband image coding schemes.
- Classical Quadrature Mirror Filters (QMF) have limitations in mitigating these distortions.
Purpose of the Study:
- To present a novel set of two-band filter banks specifically designed for image coding applications.
- To address and reduce the unpleasant ringing effects observed in subband-based image compression.
- To improve the overall performance and visual quality of reconstructed images.
Main Methods:
- Design of two-band filter banks with properties of linear phase, perfect reconstruction, asymmetric length, and maximum regularity.
- Analysis of filter performance in image coding contexts, comparing with classical QMF filters.
- Incorporation of natural image statistics and quantization error effects into the filter design process.
Main Results:
- The proposed asymmetric length filters demonstrate superior energy compaction, particularly in highpass subbands.
- A reduction in quantization error is achieved through a shorter lowpass synthesis filter.
- Significant reduction in ringing artifacts due to the improved step response of the lowpass synthesis filter.
Conclusions:
- The novel filter banks provide better overall performance for image coding compared to traditional QMF filters.
- Asymmetric filter lengths and optimized synthesis filters effectively minimize distortions like ringing.
- The design's consideration of image statistics and quantization effects leads to enhanced coding performance and visual fidelity.
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