Time-Domain Stereo Downmix for Near Out-of-Phase Signals
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Solution Overview
Problem
Conventional time-domain stereo encoding technologies face issues with energy loss in primary signals, leading to decreased encoding quality, particularly when dealing with near out of phase stereo signals.
Innovation Solution
A time-domain stereo encoding method that dynamically adjusts coding modes and channel combination schemes based on the correlation between left and right channel signals, using anticorrelated and correlated signal channel combination schemes to optimize downmix and upmix processing, enhancing encoding and decoding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional time-domain downmix processing is used for near out of phase signals, then encoding complexity is reduced, but energy loss occurs in primary signals leading to decreased encoding quality
Solution Approach 1:
The patent implements dynamic selection between different downmix processing modes (conventional time-domain downmix and anticorrelated signal coding mode) based on the correlation characteristics of the input signal. The encoder determines whether the signal is near out of phase and switches processing modes accordingly, making the system adaptive rather than static. This resolves the contradiction by allowing the simpler conventional method to be used for correlated signals while applying the specialized anticorrelated mode only when needed for near out of phase signals.
Solution Approach 2:
The patent changes the processing parameters (downmix coefficients and processing methodology) based on the signal characteristics. For anticorrelated signals, it uses a different downmix approach that prevents energy loss in primary signals, while for correlated signals it uses the conventional approach. This parameter adaptation resolves the contradiction by optimizing the balance between complexity and quality for different signal types.
2Device complexity
If a single downmix processing method is used for all signal types, then device complexity is reduced, but encoding quality deteriorates for specific signal types like near out of phase signals
Solution Approach 1:
The system dynamically adapts its processing method based on signal correlation characteristics. It includes a determination step that analyzes whether the signal is near out of phase and switches between conventional downmix and anticorrelated signal coding mode accordingly. This dynamic adaptation ensures high encoding quality for all signal types while maintaining reasonable complexity by only applying the specialized method when necessary.
Solution Approach 2:
The patent creates a universal encoding system that can handle multiple signal types (correlated signals, anticorrelated signals, near out of phase signals) through a single unified framework. The system includes both conventional and specialized processing modes within one encoder, allowing it to universally process different signal types appropriately without requiring separate dedicated systems for each signal type.
3Manufacturing precision
If time-frequency conversion is performed for spatial perception parameter extraction, then stereo encoding quality is improved, but encoding delay increases
Solution Approach 1:
The patent segments the encoding process into different modes based on signal characteristics. For near out of phase signals, it uses time-domain anticorrelated signal coding mode that avoids time-consuming frequency domain conversion while maintaining quality. For other signals, it can use conventional methods. This segmentation allows the system to avoid the delay penalty of frequency domain conversion when not strictly necessary, while still providing high quality encoding where needed.
Data Source
AI summary
An audio encoding and decoding method and a related apparatus are provided. The audio encoding method may include: determining a coding mode of a current frame; when determining that the coding mode of the current frame is an anticorrelated signal coding mode, performing time-domain downmix processing on left and right channel signals in the current frame by using a time-domain downmix processing manner corresponding to the anticorrelated signal coding mode, to obtain a primary channel signal and a secondary channel signal, where the time-domain downmix processing manner corresponding to the anticorrelated signal coding mode is a time-domain downmix processing manner corresponding to an anticorrelated signal channel combination scheme, and the anticorrelated signal channel combination scheme is a channel combination scheme corresponding to a near out of phase signal; and encoding the obtained primary channel signal and secondary channel signal in the current frame.