Parametric Audio Representation for Low-Bitrate Multi-Channel Signals
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Solution Overview
Problem
Existing multi-channel audio coding techniques require high bitrates for accurate reconstruction, especially under low-bitrate conditions, and are prone to errors when inter-channel level differences are lost during transmission, leading to suboptimal sound reconstruction.
Innovation Solution
A method that determines the direction of the local sound energy maximum in a multi-channel signal and encodes this information, allowing for the selection of relevant speaker channels to reconstruct the sound field without transmitting redundant energy distribution data, using direction parameter information to position sound sources across a speaker array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inter-channel level differences are transmitted for accurate multi-channel reconstruction, then sound field accuracy is improved, but bitrate increases and error propagation occurs when data is lost
Solution Approach 1:
The patent extracts only the essential directional information (direction of sound energy maximum) from the full inter-channel level difference data. Instead of transmitting complete energy distribution across all channels, it isolates and transmits only the direction parameter that defines the sound energy maximum, eliminating redundant data while preserving reconstruction accuracy.
Solution Approach 2:
The patent creates a simplified representation of the sound field by copying only the critical directional characteristic (direction of energy maximum) rather than the complete energy distribution. This copied directional information is sufficient for accurate reconstruction when combined with the downmix signal, avoiding the need to transmit all original channel data.
2Measurement precision
If complete multi-channel data is transmitted, then reconstruction accuracy is improved, but complexity of encoding and decoding increases
Solution Approach 1:
The patent extracts only the direction of sound energy maximum from the multi-channel signal, eliminating the need to process and transmit complete inter-channel level differences. This extraction simplifies both encoding (calculating only direction) and decoding (reconstructing from direction + downmix) while maintaining reconstruction accuracy.
Solution Approach 2:
The patent copies only the essential directional parameter rather than the complete multi-channel energy distribution. This reduced representation significantly lowers computational complexity for both encoding and decoding operations while preserving the critical information needed for accurate sound field reconstruction.
3Quantity of substance
If direction parameter information is used instead of full energy distribution data, then bitrate is reduced, but information completeness decreases
Solution Approach 1:
The patent extracts the direction of sound energy maximum as the sole spatial parameter, discarding redundant energy distribution details. This extraction achieves significant bitrate reduction because the direction information, when combined with the downmix signal, is sufficient for accurate reconstruction without needing complete energy distribution data.
Solution Approach 2:
The patent copies only the critical direction parameter rather than the complete energy distribution. This selective copying reduces bitrate substantially while avoiding information loss that would degrade reconstruction quality, because the direction information contains the essential spatial characteristics needed for accurate sound field recovery.
Data Source
AI summary
For generating a parametric representation of a multi-channel signal especially suitable for low-bit rate applications, only the location of the maximum of the sound energy within a replay setup is encoded and transmitted using direction parameter information. For multi-channel reconstruction, the energy distribution of the output channels identified by the direction parameter information is controlled by the direction parameter information, while the energy distribution in the remaining ambience channels is not controlled by the direction parameter information.