Direct Ambience Extraction from Downmix Audio Signals
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Solution Overview
Problem
Current audio processing technologies lack effective methods for extracting direct and ambience signals from downmix signals using spatial parametric information, which is essential for enhancing binaural reproduction of multi-channel audio, particularly in applications like movie soundtracks and music recordings.
Innovation Solution
An apparatus and method that utilize a direct/ambience estimator and extractor, leveraging spatial parametric information to estimate level information and separate direct and ambience signals from downmix signals, incorporating binaural rendering devices and combiners to process these signals for improved binaural reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional inter-channel signal comparison methods are used for direct/ambience separation, then the separation can be performed on stereo signals, but the method cannot effectively extract direct/ambience components from downmix signals with reduced channels
Solution Approach 1:
The patent introduces spatial side information as an intermediary element that bridges the gap between multi-channel audio and downmix signals. This side information contains spatial parameters (inter-channel coherence, level differences) that enable estimation of direct/ambience ratios even when the full multi-channel signal is not available, thus resolving the contradiction between working with downmix signals and preserving spatial information
Solution Approach 2:
The patent adds a new dimension to the signal processing approach by incorporating spatial side information alongside the audio signal. This dimensional expansion allows the system to infer direct/ambience separation in the downmix domain by combining temporal/spectral information from the audio signal with spatial information from the side data, enabling effective separation despite channel reduction
2Adaptability or versatility
If spatial side information is used to estimate direct/ambience levels, then extraction from downmix signals becomes possible, but the complexity of the processing system increases
Solution Approach 1:
The patent segments the processing system into distinct functional modules: a first converter that transforms the audio signal into a spectral representation, a second converter that processes spatial side information, and a separator that performs the actual direct/ambience separation. This segmentation allows each module to handle specific tasks independently, making the overall complex system more manageable and easier to implement
Solution Approach 2:
The patent performs preliminary transformations by converting the audio signal to the spectral domain before separation operations. This preliminary action simplifies subsequent processing steps by operating in a domain where linear algebra operations are more efficient and computationally less intensive, thus managing system complexity while maintaining extraction capability
3Ease of operation
If multi-channel audio is downmixed to reduce channels, then compatibility with existing playback systems improves, but the ability to perform accurate direct/ambience separation deteriorates
Solution Approach 1:
The patent uses spatial side information as an intermediary that preserves the spatial relationships encoded during the downmixing process. By leveraging this intermediary data, the system can accurately estimate direct/ambience ratios in the downmix domain without needing to reconstruct the original multi-channel signal, thus maintaining both compatibility and accuracy
Solution Approach 2:
The patent replaces traditional mechanical signal processing approaches (direct inter-channel comparison) with a computational approach using spectral analysis and linear algebra operations on spatial parameters. This substitution enables accurate separation in the downmix domain by transforming the problem into a mathematical estimation task that can be solved with available side information
Data Source
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AI summary
An apparatus for extracting a direct and/or ambience signal from a downmix signal and spatial parametric information, the downmix signal and the spatial parametric information representing a multi-channel audio signal having more channels than the downmix signal, wherein the spatial parametric information comprises inter-channel relations of the multi-channel audio signal, is described. The apparatus comprises a direct/ambience estimator and a direct/ambience extractor. The direct/ambience estimator is configured for estimating a level information of a direct portion and/or an ambient portion of the multi-channel audio signal based on the spatial parametric information. The direct/ambience extractor is configured for extracting a direct signal portion and/or an ambient signal portion from the downmix signal based on the estimated level information of the direct portion or the ambient portion.