Audio Spectral Reconstruction Using IGF for Low-Bitrate High Frequencies
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Solution Overview
Problem
Current audio codecs face limitations in encoding high-frequency content at low bitrates, leading to loss of detail and timbre due to the restriction of bandwidth extension techniques, which also require complex domain transformations and increased computational resources, especially in mobile devices.
Innovation Solution
The Intelligent Gap Filling (IGF) method allows for encoding and decoding in the same spectral domain, using frequency tiles from tonal portions to fill spectral gaps, enabling full-rate core decoding and reducing computational complexity by eliminating the need for downsampling and upsampling, while preserving tonal components and improving audio quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If bandwidth extension techniques are used to encode high-frequency content at low bitrates, then audio quality is improved, but computational complexity increases due to complex domain transformations
Solution Approach 1:
The patent segments the spectral representation into different frequency bands (low-frequency and high-frequency regions) and applies different encoding strategies to each segment. The low-frequency region is encoded with higher precision while the high-frequency region uses bandwidth extension techniques, allowing quality improvement without uniformly increasing computational complexity across the entire spectrum.
Solution Approach 2:
The patent applies local quality by maintaining higher encoding precision in specific frequency regions (low-frequency) where human perception is more sensitive, while using lower precision bandwidth extension in high-frequency regions. This selective approach improves overall audio quality perception without requiring high computational resources across all frequency bands.
2Manufacturing precision
If bandwidth extension techniques are used to encode high-frequency content, then audio quality is improved, but device resources are increased especially in mobile devices
Solution Approach 1:
The patent applies partial action by using bandwidth extension only for the high-frequency region rather than encoding the entire spectrum at high precision. This partial application of the extension technique provides sufficient audio quality improvement for mobile devices while consuming fewer device resources and energy compared to full-spectrum high-precision encoding.
3Adaptability or versatility
If spectral patching is used to reconstruct high-frequency spectral region, then bandwidth extension is enabled, but device complexity increases due to filterbank representation and domain transformations
Solution Approach 1:
The patent merges the bandwidth extension process with the existing spectral processing pipeline by integrating spectral copying and spectral envelope adjustment operations into the unified spectral domain processing. This merging eliminates the need for separate domain transformations and filterbank operations, enabling bandwidth extension while reducing device complexity.
Data Source
AI summary
An apparatus for decoding an encoded audio signal having an encoded representation of a first set of first spectral portions and an encoded representation of parametric data indicating spectral energies for a second set of second spectral portions, has: an audio decoder for decoding the encoded representation of the first set of the first spectral portions to obtain a first set of first spectral portions and for decoding the encoded representation of the parametric data to obtain a decoded parametric data for the second set of second spectral portions indicating, for individual reconstruction bands, individual energies; a frequency regenerator for reconstructing spectral values in a reconstruction band having a second spectral portion using a first spectral portion of the first set of the first spectral portions and an individual energy for the reconstruction band, the reconstruction band having a first spectral portion and the second spectral portion.