Audio Sub-Band Bit Allocation Using Modified Low-Frequency Envelopes
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Solution Overview
Problem
Existing frequency domain encoding algorithms face poor signal encoding and decoding performance due to inadequate bit allocation in low frequency sub-bands, which fails to meet their bit requirements effectively.
Innovation Solution
A signal processing method and device that selects low frequency sub-bands, modifies their envelope values based on energy and spectral attributes, and performs bit allocation according to these modified values and original envelope values of other sub-bands to better meet bit requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bit allocation is performed on each sub-band according to frequency envelope size, then encoding process is simple, but encoding and decoding performance is poor
Solution Approach 1:
The patent applies local quality by differentiating bit allocation strategies for low frequency sub-bands versus high frequency sub-bands. Low frequency sub-bands receive modified envelope values and adjusted bit allocation to meet their specific bit requirements, while high frequency sub-bands use original envelope values. This localized differentiation resolves the contradiction by improving performance in critical low frequency regions without overcomplicating the entire encoding process.
Solution Approach 2:
The patent changes the envelope value parameter for low frequency sub-bands by introducing a modification factor derived from spectral flatness and energy distribution. This parameter change allows the bit allocation to better reflect the actual bit requirements of low frequency sub-bands, thereby improving encoding and decoding performance while maintaining a relatively simple encoding framework.
2Manufacturing precision
If more bits are allocated to low frequency sub-bands, then bit requirements are better met, but overall bit allocation efficiency decreases
Solution Approach 1:
The patent introduces dynamic bit allocation by calculating modification factors based on spectral flatness and energy distribution of each low frequency sub-band. This dynamic approach allows bits to be allocated according to actual needs rather than static rules, satisfying bit requirements more precisely while maintaining overall allocation efficiency through adaptive adjustment rather than uniform increase.
Solution Approach 2:
The patent applies partial action by modifying envelope values only for low frequency sub-bands that require additional bits, while leaving high frequency sub-bands unchanged. This selective modification ensures that bit requirements are met for critical sub-bands without unnecessarily allocating extra bits to sub-bands that already have sufficient allocation, thereby maintaining overall efficiency.
Data Source
AI summary
A signal processing method and device includes obtaining spectral coefficients of a current frame of an audio signal, in which N sub-bands of the current frame comprises at least one of the spectral coefficients. A total energy of M successive sub-bands of the N sub-bands, a total energy of K successive sub-bands of the N sub-bands, and an energy of a first sub-band are obtained to determine whether to modify original envelope values of the M sub-bands. When the original envelope values of the M sub-bands are modified, encoding bits are allocated to each of the N sub-bands according to the modified envelope values of the M sub-bands.