Audio Encoding Transform Parameters for Playback Adaptation
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Solution Overview
Problem
Current audio signal processing methods, such as HRIR/BRIR convolution, require substantial computational resources and can degrade sound quality when used for both headphone and loudspeaker playback, as they apply localization cues twice, leading to artifacts and incorrect spatial imaging.
Innovation Solution
A method for encoding and decoding audio signals that determines transform parameters to minimize differences between playback stream presentations for different audio reproduction systems, allowing for efficient transformation of audio content from one system to another, including the use of time-varying and frequency-dependent gain matrices to adapt binaural and acoustic environment simulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HRIR/BRIR convolution is applied to simulate multi-channel speaker setup over headphones, then spatial localization cues (ILDs, ITDs, spectral cues) are reinstated for accurate spatial imaging, but computational complexity increases substantially and sound quality degrades when used for both headphone and loudspeaker playback
Solution Approach 1:
The patent transforms the audio signal using time-varying and frequency-dependent gain matrices that adapt the binaural and acoustic environment simulation parameters. This allows the same encoded content to be efficiently rendered for both headphone and loudspeaker playback by changing the transformation parameters rather than applying full HRIR convolution in all cases, thereby reducing computational complexity while maintaining spatial localization accuracy.
2Reliability
If HRIR/BRIR convolution is applied for both headphone and loudspeaker playback, then spatial cues are reinstated, but localization cues are applied twice causing artifacts and incorrect spatial imaging
Solution Approach 1:
The patent employs dynamic rendering that adapts the processing applied to the audio signal based on the output modality. The system determines whether to apply binaural rendering, acoustic environment simulation, or both, based on whether the output is for headphones or loudspeakers. This dynamic approach prevents double-application of localization cues while maintaining spatial imaging accuracy for each specific playback system.
Solution Approach 2:
The patent applies different processing qualities to different output modalities. For headphone output, full binaural rendering with HRIR/BRIR convolution is applied. For loudspeaker output, the processing is adapted or reduced to avoid double-application of spatial cues. This local differentiation of processing quality eliminates spatial artifacts while preserving accurate spatial imaging for each specific playback system.
3Reliability
If dedicated rendering process is applied to transform content for specific playback system, then artistic intent is conveyed correctly, but device complexity and processing requirements increase
Solution Approach 1:
The patent performs preliminary encoding of the audio content with embedded transformation parameters that enable efficient rendering for different playback systems. The encoder prepares multiple playback stream presentations and determines transform parameters in advance, allowing the decoder to efficiently transform the content for the specific playback system without requiring complex real-time rendering processes, thus maintaining artistic intent fidelity while reducing processing complexity.
Data Source
AI summary
A method for encoding an input audio stream including the steps of obtaining a first playback stream presentation of the input audio stream intended for reproduction on a first audio reproduction system, obtaining a second playback stream presentation of the input audio stream intended for reproduction on a second audio reproduction system, determining a set of transform parameters suitable for transforming an intermediate playback stream presentation to an approximation of the second playback stream presentation, wherein the transform parameters are determined by minimization of a measure of a difference between the approximation of the second playback stream presentation and the second playback stream presentation, and encoding the first playback stream presentation and the set of transform parameters for transmission to a decoder.