Dynamic Window Mix for Audio Frame Loss Concealment
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Solution Overview
Problem
Existing audio coding methods face challenges in maintaining a smooth transition between frames, especially when frames are lost, due to the use of a single overlap window that does not account for varying cross-correlation properties between signals, leading to audible distortions.
Innovation Solution
A dynamic mix of windows is used to overlap signals based on their cross-correlation properties, decomposing signals into correlated and uncorrelated components for separate processing or applying a weighted mix of windows to achieve a smooth transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single overlap window is used for all signals, then the device complexity is reduced, but the manufacturing precision of the transition smoothness deteriorates due to audible distortions
Solution Approach 1:
The patent applies dynamics by making the overlap window adaptive rather than fixed. The system dynamically selects or mixes windows based on the cross-correlation properties of the signals being processed. This allows the window characteristics to change in real-time according to signal conditions, resolving the contradiction between using a simple fixed window and achieving precise smooth transitions.
Solution Approach 2:
The patent changes the parameters of the overlap window based on signal characteristics. Specifically, it measures cross-correlation between adjacent frames and adjusts the window type or mixing ratio accordingly. This parameter adaptation enables the system to maintain high transition precision without requiring a single complex window design.
2Manufacturing precision
If a dynamic mix of windows is used to adapt to cross-correlation properties, then the transition smoothness is improved, but the device complexity increases
Solution Approach 1:
The patent segments the window selection process into distinct components: a correlated signal component and an uncorrelated signal component. By decomposing the overlap-add operation into these segments and applying appropriate windows to each, the system achieves high transition precision while managing complexity through structured processing.
Solution Approach 2:
The system changes window parameters adaptively based on measured cross-correlation. Rather than using a single complex window, it dynamically adjusts the mixing ratio between different window types based on signal properties. This parameter-based adaptation achieves precision while keeping the underlying structure relatively simple.
3Manufacturing precision
If the optimal window for uncorrelated signals is used for correlated signals, then the energy transition is smooth, but the signal amplitude is modulated causing audible distortion
Solution Approach 1:
The patent applies local quality by using different window characteristics for different signal components. Instead of applying a uniform window to all signals, it identifies correlated and uncorrelated components and applies locally optimized windows to each. This ensures that energy transitions are smooth for uncorrelated signals while preserving amplitude fidelity for correlated signals.
Solution Approach 2:
The system dynamically selects or mixes windows based on the correlation properties of the specific signal components being processed. This dynamic adaptation allows the system to switch between window types or mixing ratios according to whether signals are correlated or uncorrelated, preventing amplitude modulation artifacts while maintaining smooth energy transitions.
4Reliability
If the optimal window for correlated signals is used for uncorrelated signals, then the signal amplitude is preserved, but the energy is modulated causing audible distortion
Solution Approach 1:
The patent applies local quality by tailoring window characteristics to the specific correlation properties of each signal component. For uncorrelated signals, it uses windows optimized for smooth energy transitions, while for correlated signals, it uses windows that preserve amplitude relationships. This local optimization eliminates the energy modulation problem that would occur with mismatched windows.
Solution Approach 2:
The system dynamically adapts window selection or mixing ratios based on real-time measurement of signal cross-correlation. This dynamic behavior allows the system to automatically select the appropriate window characteristics for each signal component, ensuring both amplitude preservation and smooth energy transitions without manual configuration.
Data Source
AI summary
A method for overlap-adding signals useful for performing frame loss concealment (FLC) in an audio decoder as well as in other applications. The method uses a dynamic mix of windows to overlap two signals whose normalized cross-correlation may vary from zero to one. If the overlapping signals are decomposed into a correlated component and an uncorrelated component, they are overlap-added separately using the appropriate window, and then added together. If the overlapping signals are not decomposed, a weighted mix of windows is used. The mix is determined by a measure estimating the amount of cross-correlation between overlapping signals, or the relative amount of correlated to uncorrelated signals.