Bandwidth Extended Signal Generation Using Multi-Density Patches
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Solution Overview
Problem
Existing audio signal bandwidth extension methods often result in reduced subjective audio quality due to band limitation and inefficient energy distribution across frequency bands, leading to unnatural timbre and insufficient noise content in the high-frequency range.
Innovation Solution
An apparatus and method that generate a bandwidth extended signal by combining patches with different spectral densities, where a low spectral density patch is filled by a high spectral density patch, ensuring the spectral envelope of the original signal is maintained through scaling, thereby improving audio quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single patching algorithm is used for bandwidth extension, then the device complexity is reduced, but the subjective audio quality deteriorates due to insufficient energy distribution and unnatural timbre
Solution Approach 1:
The patent divides the bandwidth extension process into multiple independent patching algorithms (first patching algorithm and second patching algorithm). Each algorithm generates patches with different spectral densities, which are then combined to form the final extended bandwidth signal. This segmentation allows each algorithm to specialize in different aspects of spectral reconstruction, improving overall audio quality while maintaining manageable system complexity through modular design.
Solution Approach 2:
The patent combines patches generated by different patching algorithms to create a composite spectral representation. The first patch (from first algorithm) and second patch (from second algorithm) are merged to form a combined patch that leverages the strengths of both algorithms. This composite approach ensures more natural energy distribution and timbre characteristics compared to using a single algorithm, while the modular composite structure keeps device complexity controlled.
2Measurement precision
If the spectral envelope is strictly maintained through scaling, then the approximation accuracy of the original signal is improved, but the natural energy distribution across frequency bands is reduced
Solution Approach 1:
The patent applies different scaling treatments to different parts of the spectral patches. Rather than uniformly scaling all patches to match the spectral envelope, the system allows local variations in energy distribution within patches while maintaining the overall spectral envelope shape. This local quality approach preserves natural timbre characteristics and energy distribution patterns in critical frequency regions while still achieving accurate approximation of the original signal's spectral envelope through controlled scaling of individual patches.
Data Source
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Figure 3A
AI summary
An apparatus for generating a bandwidth extended signal from an input signal comprises a patch generator and a combiner. The input signal is represented for a first band by a first resolution data, and for a second band by a second resolution data, the second resolution being lower than the first resolution. The patch generator generates a first patch from the first band of the input signal according to a first patching algorithm and generates a second patch from the first band of the input signal according to a second patching algorithm. A spectral density of the second patch generated according to the second patching algorithm is higher than a spectral density of a first patch generated according to the first patching algorithm. The combiner combines the first patch, the second patch and the first band of the input signal to obtain the bandwidth extended signal. The apparatus for generating a bandwidth extended signal scales the input signal according to the first patching algorithm and according to the second patching algorithm or scales the first patch and the second patch, so that the bandwidth extended signal fulfills a spectral envelope criterion.