Spatial Noise Filling for Low-Bitrate Multi-Channel Codecs
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Solution Overview
Problem
Multi-channel codecs experience noise ambience collapse at low bitrates due to coding artifacts, reduced background noise energy, and failure of decorrelators to generate uncorrelated channels with desired spectral shape.
Innovation Solution
Generate multi-channel noise with desired spatial and spectral shape using spatial information from the encoder or decoder, and add it to the decoder output to regenerate background noise ambience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If low bitrate encoding is used in multi-channel codec, then data transmission efficiency is improved, but background noise ambience collapses
Solution Approach 1:
The patent introduces an intermediary noise generation mechanism that synthesizes background noise ambience from spectral parameters transmitted in the bitstream. This mediator reconstructs the missing noise characteristics at the decoder without requiring additional bandwidth, thus resolving the contradiction between compression efficiency and ambience preservation
Solution Approach 2:
The patent changes the representation parameters of background noise from full-spectrum signals to compact spectral parameters (e.g., spectral shape descriptors, noise floor levels). This parameter transformation enables efficient transmission while preserving the essential characteristics needed for ambience reconstruction at the decoder
2Measurement precision
If audio essence is preserved at low bitrates, then perceptual quality is improved, but background noise ambience is lost
Solution Approach 1:
The patent extracts the essential characteristics of background noise (spectral shape, energy distribution, spatial properties) and transmits them as separate parameters. This extraction allows the decoder to reconstruct ambience independently from the main audio signal, preventing information loss while maintaining perceptual quality
Solution Approach 2:
The encoder performs preliminary analysis of the background noise characteristics and pre-computes spectral parameters before encoding. This preliminary action prepares the necessary information in advance, enabling accurate ambience reconstruction at the decoder without consuming excessive bitrate during real-time transmission
Data Source
AI summary
Embodiments are disclosed for spatial noise filling in multi-channel codecs. In an embodiment, a method of regenerating background noise ambience in a multi-channel codec by generating spatial hole filling noise comprises: computing noise estimates based on a primary downmix channel generated from an input audio signal representing a spatial audio scene with background noise ambience; computing spectral shaping filter coefficients based on the noise estimates; spectrally shaping the multi-channel noise signal using the spectral shaping filter coefficients and a noise distribution, the spectral shaping resulting in a diffused, multi-channel noise signal with uncorrelated channels; spatially shaping the diffused, uncorrelated multi-channel noise signal with uncorrelated channels based on a noise ambience of the spatial audio scene; and adding the spatially and spectrally shaped multi-channel noise to a multi-channel codec output to synthesize the background noise ambience of the spatial audio scene.