Spectral Audio Bandwidth Extension Using Intelligent Gap Filling
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Solution Overview
Problem
Current audio codecs face limitations in bandwidth extension techniques, as they restrict high-frequency content replacement and introduce artifacts due to domain transformation, leading to loss of timbre and increased computational complexity, especially in mobile devices.
Innovation Solution
The proposed solution involves performing bandwidth extension in the same spectral domain as the core decoder, allowing full-rate core decoding and using Intelligent Gap Filling (IGF) to regenerate spectral portions, which fills spectral gaps using parametric data and source spectral ranges, enabling efficient coding across the full audio range without downsampling or upsampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bandwidth extension is performed using domain transformation (e.g., filterbank representation), then high-frequency content can be reconstructed from low-frequency components, but artifacts are introduced and timbre is lost
Solution Approach 1:
The patent introduces an intermediary spectral domain processing stage that operates between the core decoder and the final output. Instead of directly transforming domains, the invention uses spectral replication and Intelligent Gap Filling (IGF) as intermediate steps to reconstruct high-frequency content while preserving the original spectral characteristics and avoiding artifacts.
Solution Approach 2:
The patent employs spectral copying techniques where low-frequency spectral components are copied and replicated to reconstruct high-frequency content. This copying approach, combined with IGF, allows faithful reproduction of the original signal's timbre without introducing transformation artifacts.
2Adaptability or versatility
If domain transformation is used for bandwidth extension, then high-frequency reconstruction is enabled, but computational complexity increases
Solution Approach 1:
The patent merges the bandwidth extension functionality with the core decoding process by operating entirely within the spectral domain. This integration eliminates the need for separate domain transformation stages, reducing computational complexity while maintaining full-bandwidth reconstruction capability.
Solution Approach 2:
The spectral domain processing leverages the existing spectral representation from the core decoder and uses self-contained IGF techniques to reconstruct high-frequency content. This self-service approach avoids additional transformation operations and reduces the overall computational burden on mobile devices.
3Measurement precision
If spectral gap filling is performed with high spectral resolution, then spectral fidelity is improved, but coding efficiency decreases
Solution Approach 1:
The patent applies local quality by using high spectral resolution only where necessary for accurate reconstruction (in the spectral domain for IGF), while maintaining coding efficiency through parametric representation. This localized high-resolution processing improves spectral fidelity without requiring high resolution throughout the entire coding process.
Solution Approach 2:
The patent changes the representation parameters by using parametric data to control the IGF process. Instead of encoding full high-resolution spectral data, the invention uses compact parametric representations that guide the spectral gap filling, thereby maintaining high spectral resolution where needed while improving overall coding efficiency.
Data Source
AI summary
An apparatus for decoding an encoded audio signal, includes a spectral domain audio decoder for generating a first decoded representation of a first set of first spectral portions, the decoded representation having a first spectral resolution; a parametric decoder for generating a second decoded representation of a second set of second spectral portions having a second spectral resolution being lower than the first spectral resolution; a frequency regenerator for regenerating every constructed second spectral portion having the first spectral resolution using a first spectral portion and spectral envelope information for the second spectral portion; and a spectrum time converter for converting the first decoded representation and the reconstructed second spectral portion into a time representation.