Spectral Mapping for Multi-Mic Audio Encoding
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Solution Overview
Problem
Existing audio encoding technologies face challenges in efficiently encoding multiple audio signals captured by multiple microphones, particularly due to temporal shifts and phase mismatches between channels, which affect coding efficiency and spatial balance.
Innovation Solution
The implementation of an encoder that selects a non-reference target channel based on a high-band reference channel indicator, generates a synthesized non-reference high-band channel, estimates spectral mapping parameters, and applies these parameters to shape the channel, resulting in an encoded bitstream for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If audio signals from multiple microphones are encoded using traditional stereo-encoding methods, then the encoding process is simple, but temporal shifts and phase mismatches between channels degrade coding efficiency and spatial balance
Solution Approach 1:
The patent applies preliminary action by performing temporal alignment and spectral mapping on audio signals before encoding. The system identifies temporal shifts between microphone channels and applies compensatory delays or advances to align the signals in time, preventing phase mismatches that would otherwise degrade coding efficiency and spatial balance during encoding
Solution Approach 2:
The patent changes parameters by adjusting temporal parameters (time alignment) and spectral parameters (frequency-domain characteristics) of audio signals from different microphones. By modifying these parameters to compensate for temporal shifts and phase differences, the system improves both coding efficiency and spatial balance without requiring complex encoding schemes
2Manufacturing precision
If spectral mapping parameters are estimated and applied to synthesized channels, then spatial balance and signal quality improve, but encoding complexity increases
Solution Approach 1:
The patent introduces an intermediary synthesized channel that acts as a bridge between the original microphone signals and the final encoded output. This synthesized channel undergoes spectral mapping with estimated parameters to improve spatial balance and quality, while the intermediary nature allows for efficient processing that limits the increase in encoding complexity
Solution Approach 2:
The patent creates a copy or synthesis of audio channels from the original microphone inputs, then applies spectral mapping to this copied signal. This approach allows the original signals to remain unchanged while the synthesized copy receives the quality-enhancing spectral adjustments, separating the complexity of spectral processing from the core encoding process
Data Source
AI summary
A method includes generating a synthesized non-reference high-band channel based on a non-reference high-band excitation corresponding to a non-reference target channel. The method further includes estimating one or more spectral mapping parameters based on the synthesized non-reference high-band channel and a high-band portion of the non-reference target channel. The method also includes applying the one or more spectral mapping parameters to the synthesized non-reference high-band channel to generate a spectrally shaped synthesized non-reference high-band channel. The method further includes generating an encoded bitstream based on the one or more spectral mapping parameters and the spectrally shaped synthesized non-reference high-band channel.