Audio Coding Method Using Dynamic Bandwidth Extension
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Solution Overview
Problem
Existing audio coding systems face challenges in efficiently encoding audio signals when certain parts of the spectrum are not encoded, leading to poor performance for signals where the high band is perceptually more important than the low band.
Innovation Solution
The proposed technology introduces decision logic to include parts of the a-priori assumed non-important band in the fine structure encoding, allowing for more flexible audio coding schemes. This is achieved by determining the energy relations between bands and using a second coding method when sufficient bits are available, or subjecting the band to bandwidth extension or noise fill otherwise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If bandwidth extension is used to encode only the low band, then the bitrate consumption is reduced and power consumption is lowered, but the encoding accuracy deteriorates for signals where the high band is perceptually more important
Solution Approach 1:
The patent applies dynamics by making the coding mode selectable between conventional BWE mode and flexible mode based on signal characteristics. The encoder dynamically adjusts its behavior by analyzing the audio signal and determining whether to use the conventional low-band only encoding or switch to flexible mode that encodes both low and high bands, thereby adapting to different signal requirements and resolving the contradiction between energy saving and encoding accuracy.
Solution Approach 2:
The patent changes the encoding parameters by introducing a flexible mode that modifies the traditional BWE parameter allocation. Instead of fixed allocation where only low band is encoded, the system can allocate bits to both low and high bands based on perceptual importance, effectively changing the encoding parameters to balance between bitrate consumption and encoding accuracy for different signal types.
2Device complexity
If the frequency spectrum is divided into low and high bands with fixed encoding assumptions, then the coding scheme is simplified, but the adaptability deteriorates for signals that do not fit the a-priori assumptions
Solution Approach 1:
The patent introduces dynamic adaptability by enabling the encoder to switch between different coding modes (conventional BWE and flexible mode) based on the analyzed signal characteristics. This dynamic behavior allows the system to maintain simplicity for typical signals while adapting to atypical signals where the high band is perceptually more important, thus resolving the contradiction between simplicity and adaptability.
Solution Approach 2:
The patent achieves universality by designing a flexible coding mode that can handle multiple signal types within a single framework. The encoder can universally apply the same basic BWE structure while also accommodating signals that require high band encoding by allocating additional bits, making the system versatile enough to handle both conventional and atypical audio signals without requiring separate coding schemes.
3Reliability
If bits are allocated primarily to the low band envelope representation, then the perceptual importance is maintained, but the fine structure encoding quality deteriorates for signals requiring high band fidelity
Solution Approach 1:
The patent applies parameter changes by modifying the bit allocation strategy between envelope and fine structure components. In the flexible mode, the system can allocate additional bits to the high band fine structure encoding based on the specific signal characteristics, thereby changing the parameter distribution to improve fine structure quality without completely sacrificing envelope representation, thus resolving the contradiction between perceptual importance and encoding precision.
Solution Approach 2:
The patent implements local quality by applying different encoding strategies to different frequency bands and signal components based on their specific requirements. Instead of uniform encoding, the system can concentrate bits on the high band fine structure when needed, while maintaining appropriate envelope representation in the low band, thereby achieving locally optimized quality for different parts of the audio spectrum.
Data Source
AI summary
An audio signal, having first and second regions of frequency spectrum, is coded. Spectral peaks in the first region are encoded by a first coding method. For a segment of the audio signal, a relation between energy of bands in the first and second regions is determined. A relation between the energy of the band in the second region and energy of neighboring bands in the second region is determined. A determination is made whether available bits are sufficient for encoding at least one non-peak segment of the first region and the band in the second region. Responsive to first and second relations fulfilling a respective predetermined criterion and a sufficient number of bits, encoding the band in the second region using a second coding method different from the first coding method, and otherwise, subjecting the band in the second region to BandWidth Extension BWE or noise fill.