Post Filter Band-Specific Spectrum Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing post filters fail to effectively improve speech quality when speech quality varies between bands in scalable coding, as they apply uniform filtering criteria across all bands, leading to inadequate noise reduction in certain frequency regions.
Innovation Solution
A post filter configuration that includes a band determining section, a spectrum correcting section, and a filter section using coefficients derived from corrected spectra, allowing for adaptive filtering based on the specific speech quality of each band to reduce quantization noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a uniform post filter is applied across all bands, then the device complexity is reduced and ease of operation is improved, but speech quality in bands where it varies is degraded and noise reduction is insufficient
Solution Approach 1:
The post filter is divided into multiple independent filter units, each corresponding to a specific frequency band. Each filter unit processes its designated band independently with band-specific coefficients, allowing tailored noise reduction for each band while maintaining overall system manageability through modular architecture.
Solution Approach 2:
Different filter coefficients are applied to different frequency bands based on the local speech quality characteristics of each band. The band determining section identifies which bands require post filtering, and the spectrum correcting section applies appropriate coefficients only to those specific bands, optimizing speech quality locally rather than uniformly across all bands.
2Manufacturing precision
If band-specific post filtering is applied to improve speech quality in varying bands, then speech quality and noise reduction are improved, but device complexity increases
Solution Approach 1:
The post filter is divided into multiple independent filter units, each corresponding to a specific frequency band. Each filter unit processes its designated band independently with band-specific coefficients, allowing tailored noise reduction for each band while maintaining overall system manageability through modular architecture.
Solution Approach 2:
The post filter structure is designed to be universally applicable across different bands and coding schemes. The same basic filter architecture is reused for each band, with only the coefficients varying, reducing overall complexity through component reuse and standardization.
3Object-generated harmful factors
If post filtering is applied to high bit rate coded signals, then noise reduction may be achieved, but the spectrum shape that should not be modified is altered and subjective quality decreases
Solution Approach 1:
The band determining section performs preliminary analysis to identify bands that actually require noise reduction. By pre-identifying problematic bands before filtering, the system avoids applying post filtering to bands where it would harm the spectrum shape and subjective quality, thus preventing rather than correcting quality degradation.
Solution Approach 2:
The system dynamically adjusts filter coefficients based on the input signal characteristics and band-specific quality requirements. By changing the filtering parameters adaptively rather than applying fixed filtering, the system achieves noise reduction in appropriate bands while preserving the natural spectrum shape in bands where quality is already good.
Data Source
AI summary
A post filter and a decoder enabling improvement of the sound quality of a decoded signal even when the sound quality of the decoded signal is different from the bands are disclosed. A frequency converting section determines a decoded spectrum. A power spectrum computing section computes the power spectrum from the decoded spectrum. A correction band determining section determines the band in which the power spectrum is corrected according to layer information. A power spectrum correcting section corrects the power spectrum in the corrected band in such a way that the variation along the frequency axis is suppressed. An inverse converting section subjects the corrected power spectrum to inverse conversion to determine an autocorrelation function. An LPC analyzing section determines an LPC coefficient of the determined autocorrelation function.