Spatial Audio Comfort Noise Transition Across Coding Modes
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Solution Overview
Problem
Existing multi-mode spatial audio codecs experience perceptually annoying transitions between active and inactive coding due to changes in spatial coding modes during discontinuous transmission, particularly in stereo and multi-channel audio scenarios.
Innovation Solution
A method for generating comfort noise by adapting background noise characteristics from a first spatial coding mode to a second mode during transitions, using a transformation and combination of parameters over a transition period to smooth the switch, thereby improving audio quality and reducing bandwidth requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If discontinuous transmission (DTX) is used to reduce bandwidth during speech pauses, then transmission bandwidth is reduced, but perceptually annoying transitions occur during mode switching between active and inactive coding
Solution Approach 1:
The patent applies preliminary action by preparing transition parameters in advance during the active coding phase. The encoder collects background noise parameters and transition parameters during the last few active frames before switching to inactive coding, so that when the mode switch occurs, the parameters are already ready to ensure a smooth transition. This prevents perceptible artifacts by having the transition preparation done beforehand rather than during the actual mode switch.
Solution Approach 2:
The patent introduces an intermediary mechanism by using transition parameters as a bridge between active and inactive coding modes. These transition parameters include background noise parameters and spatial parameters that mediate the switch, allowing the decoder to generate comfort noise that smoothly connects the two modes. The intermediary parameters enable a gradual transition rather than an abrupt switch, eliminating perceptible artifacts.
2Productivity
If spatial coding modes are changed during transitions between active and inactive segments, then bandwidth efficiency is improved, but audio quality deteriorates due to perceptible transitions
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting spatial parameters (such as inter-channel correlation and inter-channel level difference) during the transition from active to inactive coding and vice versa. Instead of using fixed parameters for comfort noise generation, the encoder transmits updated spatial parameters that reflect the current audio environment. This allows the decoder to adapt the comfort noise characteristics to match the original spatial audio properties, maintaining audio quality while enabling bandwidth-efficient DTX operation.
3Quantity of substance
If comfort noise is generated using traditional methods during inactive segments, then bandwidth is reduced, but the background noise characteristics do not match the original spatial audio properties
Solution Approach 1:
The patent implements feedback by using the actual background noise characteristics observed during active coding segments to inform the comfort noise generation during inactive segments. The encoder continuously monitors and transmits background noise parameters and spatial parameters during active coding, providing feedback about the true acoustic environment. The decoder uses this feedback to generate comfort noise that accurately matches the original spatial audio properties, rather than relying on static or estimated parameters.
Data Source
AI summary
A method for generating comfort noise is provided. The method includes providing a first set of background noise parameters N1 for at least one audio signal in a first spatial audio coding mode and a second set of background noise parameters N2 for the first audio signal in a second spatial audio coding mode. The first spatial audio coding mode is used for active segments; the second spatial audio coding mode is used for inactive segments. The method further includes adapting the first set of background noise parameters N1 to the second spatial audio coding mode, thereby providing a first set of adapted background noise parameters {circumflex over (N)}1. The method further includes generating comfort noise parameters by combining {circumflex over (N)}1 and N2 over a transition period. The method further includes generating comfort noise based on the comfort noise parameters.