Asymmetric Windowing for Audio Temporal Envelope Energy Continuity
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Solution Overview
Problem
The existing process of calculating and quantizing a temporal envelope in audio signal processing leads to discontinuous intra-frame energy due to excessive time-domain resolution, resulting in a poor auditory experience.
Innovation Solution
The method involves using different window lengths and/or shapes under various conditions to reduce the impact of energy discontinuity caused by large differences between temporal envelopes, specifically employing asymmetric window functions for the first and last subframes and symmetric window functions for the remaining subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple temporal envelopes are calculated according to lookahead buffer length to ensure inter-subframe and inter-frame aliasing, then aliasing performance is improved, but energy discontinuity in intra-frame increases
Solution Approach 1:
The patent applies different window functions (symmetric vs asymmetric) to different subframes based on their position. Specifically, symmetric window functions are used for subframes where aliasing is critical, while asymmetric window functions are used for subframes where energy continuity is more important, thereby optimizing both aliasing performance and energy discontinuity reduction locally across the signal frame
Solution Approach 2:
The patent introduces asymmetric window functions that are not symmetric around their center point. These asymmetric windows are applied to specific subframes to reduce energy discontinuity at the boundaries of temporal envelopes, while maintaining the overall aliasing performance through the combination of different window types across the full frame
2Device complexity
If symmetric window function is used for all subframes to simplify processing, then computational complexity is reduced, but energy discontinuity cannot be effectively reduced
Solution Approach 1:
Instead of using a uniform window function across all subframes, the patent selectively applies symmetric or asymmetric window functions based on the specific requirements of each subframe position, optimizing energy continuity where needed while maintaining simplicity where possible
Solution Approach 2:
The patent dynamically selects between symmetric and asymmetric window functions based on the subframe index and position within the temporal envelope calculation, allowing the processing characteristics to adapt to local signal requirements rather than using a fixed approach throughout
Data Source
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AI summary
A method and an apparatus for processing a temporal envelope of an audio signal, and an encoder are disclosed. When multiple temporal envelopes are solved, continuity of signal energy can be well maintained, and in addition, complexity of calculating a temporal envelope is reduced. The method includes: obtaining a high-band signal of the current frame audio signal according to the received current frame audio signal (S21); dividing the high-band signal of the current frame audio signal into M subframes according to a predetermined temporal envelope quantity M, where M is an integer, M is greater than or equal to 2 (S22); calculating a temporal envelope of each of the subframes (S23); performing windowing on the first subframe of the M subframes and the last subframe of the M subframes by using an asymmetric window function; and performing windowing on a subframe except the first subframe and the last subframe of the M subframes.