Asymmetric Windowing for Multichannel Audio Decoding
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Solution Overview
Problem
Multichannel audio coding systems face challenges in reducing decoding delay and improving sound quality, particularly due to mismatches in encoder and decoder windowing schemes, which can lead to audio artifacts.
Innovation Solution
The implementation of asymmetric windowing schemes in both the encoder and decoder, with unevenly weighted smoothing to offset the effects of unequal window overlaps, allows for reduced decoding delay and improved sound quality by interpolating stereo parameters between frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If look ahead portions are used in windowing schemes, then audio artifacts are reduced, but decoding delay increases
Solution Approach 1:
The patent applies asymmetric windowing schemes where the encoder and decoder use different window configurations. The encoder uses a first windowing scheme with specific look-ahead portions, while the decoder uses a second windowing scheme that compensates for the delay introduced by the encoder's look-ahead, thereby reducing overall decoding delay while maintaining audio quality.
Solution Approach 2:
The patent modifies windowing parameters (window length, overlap portions, look-ahead portions) to optimize the balance between artifact reduction and delay. By adjusting these parameters in the asymmetric windowing schemes, the system achieves reduced audio artifacts without proportionally increasing decoding delay.
2Loss of time
If encoder and decoder use different windowing schemes, then decoding delay is reduced, but audio artifacts increase
Solution Approach 1:
The patent incorporates feedback mechanisms where the decoder's second windowing scheme is designed to compensate for the encoder's first windowing scheme. This feedback loop ensures that the asymmetric windowing does not introduce significant audio artifacts, as the decoder adjusts its processing to match the encoder's output characteristics.
Solution Approach 2:
The patent performs preliminary planning of the asymmetric windowing schemes during system design. The encoder and decoder windowing parameters are pre-coordinated to ensure compatibility, allowing the system to achieve reduced delay without artifacts through carefully designed complementary windowing strategies.
3Object-affected harmful factors
If stereo parameters are interpolated between frames, then sound quality is improved, but processing complexity increases
Solution Approach 1:
The patent applies partial interpolation of stereo parameters between frames rather than full interpolation. By selectively interpolating only the necessary parameters and using uneven weighting, the system improves sound quality while avoiding the full processing complexity of complete parameter interpolation.
Data Source
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AI summary
A method includes generating a windowed time-domain mid channel by applying two first asymmetric windows to a first frame of a time-domain mid channel and applying two second asymmetric windows to a second frame of the time-domain mid channel. The method includes transforming the windowed time-domain mid channel to a transform domain to generate sets of transform-domain mid channel data including first transform-domain mid channel data corresponding to a first mid channel window of the first frame and second transform-domain mid channel data corresponding to a second mid channel window of the first frame. The method includes performing an up-mix operation using the sets of transform-domain mid channel data, stereo parameters from the bit stream, and an interpolated parameter determined using an unevenly weighted interpolation between a first stereo parameter value associated with the first frame and a second stereo parameter value associated with the second frame.