Audio Spatial Engine Up-mixing via Adaptive Filter Smoothing
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Solution Overview
Problem
Existing audio processing systems struggle to convert audio data optimally from one format to another, such as from stereo to surround sound, resulting in unsatisfactory and unstable sound quality due to the lack of adaptive handling of spatial cues.
Innovation Solution
An audio spatial environment engine that up-mixes M-channel data to N-channel data by using psycho-acoustic spatial cues like inter-channel level difference and inter-channel coherence across frequency bands, generating adaptive filters for accurate and consistent sound field representation, with a scalable architecture for various channel configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional up-mix methods are used to convert stereo to surround sound, then the conversion can be performed with simple fixed-channel processing, but the resulting sound quality is unstable and spatially indistinct
Solution Approach 1:
The patent implements dynamic processing by using time-varying filter coefficients that adapt to the input signal characteristics. The system continuously analyzes inter-channel level differences and coherence to generate updated spatial cues, allowing the up-mixing process to respond dynamically to changing audio content rather than relying on fixed static mappings.
Solution Approach 2:
The system changes processing parameters by extracting time-varying spatial cues (inter-channel level differences and coherence) from the input signal and using these parameters to dynamically adjust the filter coefficients. This allows the processing to adapt to different spatial configurations and signal characteristics, improving reliability while managing complexity through parameter-driven adaptation.
2Measurement precision
If adaptive processing based on spatial cues is implemented, then spatial distinction and sound quality are improved, but the processing complexity increases
Solution Approach 1:
The patent segments the audio processing into distinct functional stages: spatial cue extraction from the input signal, filter coefficient generation based on extracted cues, and application of filters to generate output channels. This segmentation allows each stage to be optimized independently, achieving high spatial cue accuracy while managing overall processing complexity through modular architecture.
Solution Approach 2:
The system introduces intermediate spatial cue parameters (inter-channel level differences and coherence measurements) that serve as mediators between the input signal and the final up-mixed output. These intermediate representations capture essential spatial information in a compact form, enabling accurate spatial processing without requiring direct complex manipulation of all signal parameters.
3Adaptability or versatility
If fixed-channel sound field processing is used, then the processing architecture is simple, but the surround sound experience is unstable and spatially indistinct
Solution Approach 1:
The patent creates a universal up-mixing architecture that can handle multiple channel configurations and spatial environments through a single unified processing framework. The system extracts general spatial cues from the input signal and uses these to generate appropriate filter coefficients for the target configuration, making the processor adaptable to different surround sound environments without requiring separate dedicated processing paths for each configuration.
Data Source
AI summary
An audio spatial environment engine for flexible and scalable up-mixing from an M channel audio system to an N channel audio system, where M and N are integers and N is greater than M, is provided. The input M channel audio is provided to an analysis filter bank which converts the time domain signals into frequency domain signals. Relevant inter-channel spatial cues are extracted from the frequency domain signals on a sub-band basis and are used as parameters to generate adaptive N channel filters which control the spatial placement of a frequency band element in the up-mixed sound field. The N channel filters are smoothed across both time and frequency to limit filter variability which could cause annoying fluctuation effects. The smoothed N channel filters are then applied to adaptive combinations of the frequency domain input signals and are provided to a synthesis filter bank which generates the N channel time domain output signals.