Audio Transform Coding with Direct Long-to-Short Window Switching
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Solution Overview
Problem
Current audio coding techniques face challenges in adapting to non-stationary audio signals, particularly in detecting transient events like strong attacks in speech or musical signals, which requires changing window sizes, leading to additional delays and inefficiencies in coding and decoding processes.
Innovation Solution
A method for decoding digital audio signals that allows direct transition from a long window to a short window without using transition windows, enabling real-time detection and coding of transient events within the current frame, thus eliminating the need for additional delay and maintaining perfect reconstruction quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transition windows are used to switch between long and short window sizes, then the adaptability to non-stationary signals is improved, but the coding delay increases
Solution Approach 1:
The patent extracts and removes the transition window from the window switching process. By directly switching between long and short windows without using transition windows, the invention eliminates the additional delay that transition windows introduce, while still maintaining the ability to adapt to non-stationary signals through window size changes.
Solution Approach 2:
The patent performs preliminary detection of transient events within the current frame before making the window size decision. This allows the encoder to detect transient events and switch to short windows within the same frame, rather than waiting for the next frame as in conventional approaches, thereby reducing coding delay.
2Productivity
If transient event detection is performed in the current frame, then the coding speed is improved, but the detection precision may be compromised
Solution Approach 1:
The patent performs transient event detection as a preliminary action within the current frame before final encoding decisions are made. This allows the system to maintain high coding speed by making decisions based on current frame data, while the detection algorithm is designed to maintain sufficient precision for effective window size selection.
3Device complexity
If direct window size switching is implemented, then the device complexity is reduced, but the reconstruction quality may be affected
Solution Approach 1:
By removing the transition window component from the window switching mechanism, the patent simplifies the device structure and reduces computational complexity. The direct switching approach eliminates the need for complex transition window management while maintaining reconstruction quality through proper overlap-add processing.
Solution Approach 2:
The patent changes the window size parameter directly from long to short or vice versa without using transition windows. This parameter change approach simplifies the system while maintaining reconstruction quality through appropriate handling of the window boundaries and overlap regions.
Data Source
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AI summary
The invention relates to method for the transform coding/decoding of a digital audio signal represented by a succession of frames, using windows of different lengths. According to the invention, the coding method comprises the following steps, namely: trying to detect (51) a particular event, such as an attack, in a current frame (Ti); and, if said particular event is at least detected at the start of the current frame (53), directly applying a short window (54) in order to code (56) the current frame (Ti) without applying a transition window. Consequently, the coding method has a reduced delay in relation to the prior art. In addition, an ad hoc processing step is applied during decoding in order to compensate for the direct passage from a long window to a short window during coding.