Dynamic Audio Rendering for Multichannel Signals on Fewer Speakers
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Solution Overview
Problem
Existing rendering approaches for multichannel audio on portable devices with fewer speakers than channels do not account for the time-varying behavior of input audio channels, leading to unbalanced loudness and spatial collapse.
Innovation Solution
A dynamic rendering approach using multiple rendering matrices and channel analysis to adaptively mix pre-rendered signals based on time-varying channel distributions, ensuring efficient and balanced playback on portable devices with fewer speakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed rendering matrix is used for multichannel audio rendering, then the rendering process is simple, but the loudness balance deteriorates when channel activity varies over time
Solution Approach 1:
The patent implements dynamic rendering by switching between different rendering matrices based on the actual activity of audio channels. Instead of using a fixed rendering matrix, the system analyzes channel energy levels and dynamically selects or blends rendering matrices to match the current audio content characteristics, thereby maintaining loudness balance across speakers despite varying channel contributions.
Solution Approach 2:
The patent changes the rendering parameters (rendering matrix selection) based on the detected channel activity. By monitoring the energy levels of different audio channels and adjusting the rendering matrix accordingly, the system adapts to time-varying channel distributions and maintains optimal loudness balance without requiring complex hardware modifications.
2Loss of information
If all channels are rendered to available speakers, then channel information is preserved, but spatial collapse occurs when speakers are fewer than channels
Solution Approach 1:
The patent extracts and identifies the actively contributing channels from the multichannel audio signal by analyzing channel energy levels. When certain channels are weak or inactive, the system effectively takes them out of the rendering process by selecting rendering matrices that ignore those channels, thereby preventing spatial collapse while preserving the spatial information from the active channels.
Solution Approach 2:
The system dynamically adjusts which channels are rendered to which speakers based on real-time channel activity analysis. By dynamically selecting rendering matrices that match the current active channel configuration, the system maintains proper spatial distribution of audio content and prevents spatial collapse even when the number of speakers is fewer than the number of channels.
3Manufacturing precision
If rendering ignores weak channels, then loudness balance improves, but information from those channels is lost
Solution Approach 1:
The patent implements a dynamic approach where the system continuously monitors channel activity and adapts the rendering matrix selection accordingly. When channels become active, the rendering matrix is adjusted to include them; when they are inactive, they are excluded to maintain loudness balance. This dynamic adaptation ensures that information is preserved when channels are active while maintaining balance when they are not.
Solution Approach 2:
The rendering parameters (matrix selection) are changed based on detected channel activity thresholds. The system monitors the energy levels of channels and changes the rendering configuration to either include or exclude specific channels dynamically, thereby balancing loudness preservation with information retention based on actual channel contribution.
Data Source
AI summary
An audio renderer for rendering a multi-channel audio signal having M channels to a portable device having S independent speakers, comprising a first matrix application module for applying a primary rendering matrix to the input audio signal to provide a first pre-rendered signal suitable for playback on the multiple independent speakers, a second matrix application module for applying a secondary rendering matrix to the input audio signal to provide a second pre-rendered signal suitable for playback on the multiple independent speakers, a channel analysis module configured to calculate mixing gain according to a time-varying channel distribution, and a mixing module configured to produce a rendered output signal by mixing the first and second pre-rendered signals based on the mixing gain.