Audio Bandwidth Extension Joint Envelope and Excitation Control
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Solution Overview
Problem
Conventional bandwidth extension techniques for audio signals often result in undesired artifacts due to uncontrolled interaction between the high band envelope and excitation, leading to a less accurate representation of the high band envelope and increased noise perception.
Innovation Solution
A method for jointly controlling the envelope shape and excitation noisiness of a bandwidth extended audio signal using a common control parameter, which adapts the spectral envelope and excitation mixing to improve the accuracy and quality of the high band extension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the high band envelope is represented accurately, then the perceptual quality improves, but the interaction with excitation produces undesired artifacts
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the envelope shaping parameter based on the excitation type. For periodic excitations, the envelope is shaped to preserve harmonicity, while for aperiodic excitations, the envelope is flattened to avoid artifacts. This conditional parameter adjustment resolves the contradiction by adapting the envelope representation to the characteristics of the excitation signal.
Solution Approach 2:
The patent implements dynamics by making the envelope shaping adaptive rather than static. The system dynamically switches between different envelope shaping strategies depending on whether the excitation is periodic or aperiodic. This dynamic adaptation allows the system to maintain high envelope accuracy when appropriate while avoiding artifact generation in other cases.
2Object-generated harmful factors
If the high band envelope is flattened to limit interaction, then artifacts are reduced, but the envelope becomes less accurate and more noisy
Solution Approach 1:
The patent uses parameter changes to adjust the envelope shaping degree based on excitation characteristics. Instead of always flattening the envelope, the system modifies the shaping parameter conditionally: reducing flattening for periodic signals to maintain accuracy, and increasing flattening for aperiodic signals to reduce artifacts. This resolves the contradiction by making envelope accuracy and artifact reduction context-dependent.
3Measurement precision
If bandwidth is increased to improve intelligibility and presence, then audio quality improves, but the required transmission bandwidth increases
Solution Approach 1:
The patent applies parameter changes by using a control parameter that adapts the high band envelope representation based on signal characteristics and available resources. This allows the system to achieve improved intelligibility and presence when conditions permit, while efficiently using available bandwidth by adjusting the degree of envelope shaping and high band reconstruction accordingly.
Data Source
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AI summary
There is provided a method for encoding an audio signal. The method comprises determining, for transmission to an audio decoder, a temporal shaping procedure that is used by the audio decoder to reconstruct a temporal structure of the audio signal, wherein the audio decoder is configured to generate a high band extension of the audio signal from an envelope and an excitation, wherein the generation includes the step of jointly controlling envelope shape and excitation noisiness with a common control parameter (f). There is provided an audio encoder configured to determine, for transmission to an audio decoder, a temporal shaping procedure that is used by the audio decoder to reconstruct a temporal structure of the audio signal, wherein the audio decoder is configured to generate a high band extension of the audio signal from an envelope and an excitation, and to jointly control envelope shape and excitation noisiness with a common control parameter (f).