Multi-Channel Audio Shaping with Intermediate-Resolution Envelopes
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Solution Overview
Problem
Current multi-channel audio coding methods struggle to accurately reproduce the spatial distribution of signals with high temporal granularity, particularly for transient events like applause, leading to poor transient reproduction and unnatural sound perception due to limitations in temporal and spectral envelope control.
Innovation Solution
The proposed solution involves a decoder and encoder system that uses a waveform parameter representation with intermediate time resolution to shape upmixed channels, allowing for finer temporal control of the signal envelope without increasing data complexity, and applies guided envelope shaping to match the original channel's envelope, enhancing spatial sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If frame-based parametric coding is used to reduce data rate, then coding efficiency is improved, but temporal resolution is reduced leading to poor transient reproduction
Solution Approach 1:
The patent segments the temporal representation into multiple resolution levels: frame-level parameters for overall structure and slot-level parameters for fine temporal details. This hierarchical segmentation allows the system to maintain low bit rate while preserving transient accuracy by applying different coding densities to different temporal scales.
Solution Approach 2:
The patent introduces an intermediate temporal dimension (slots) between frames and samples. By organizing parameters at this intermediate level with duration shorter than frames but longer than individual samples, the system achieves a dimensional compromise that captures transient events without requiring full sample-rate parameter transmission.
2Manufacturing precision
If high temporal resolution parameter transmission is used to improve transient reproduction, then transient accuracy is improved, but bit rate increases
Solution Approach 1:
The patent applies local quality by transmitting high-resolution parameters only for slots containing transient events, while using coarser frame-level parameters for steady-state portions. This localized high-fidelity representation ensures transient accuracy where needed while maintaining overall bit rate efficiency.
Solution Approach 2:
The patent dynamically changes the resolution of transmitted parameters based on signal characteristics. During transient events, it transmits higher-resolution slot-level parameters; during steady-state, it uses lower-resolution frame-level parameters, thereby adapting the parameter rate to the actual information content.
3Reliability
If frame-level envelope shaping is applied, then spatial sound quality is improved, but temporal granularity is reduced causing unnatural transient perception
Solution Approach 1:
The patent makes the temporal granularity dynamic by allowing different time resolutions at different hierarchical levels. The system dynamically selects between frame-level and slot-level parameter updates based on the temporal characteristics of the signal, enabling flexible adaptation to transient or steady-state conditions.
Solution Approach 2:
The patent performs preliminary envelope shaping at the frame level to establish the overall spatial characteristics, then applies corrective slot-level adjustments to refine transient details. This two-stage preliminary action ensures both spatial quality and temporal accuracy are achieved systematically.
Data Source
AI summary
A selected channel of a multi-channel signal represented by frames composed from sampling values having a high time resolution is provided that can be encoded with higher quality when a wave form parameter representation representing a wave form of an intermediate resolution representation of the selected channel is derived. The wave form parameter representation with the intermediate resolution can be used to shape a reconstructed channel to retrieve a channel having a signal envelope close to a selected original channel. The time scale on which the shaping is performed is shorter than the time scale of a framewise processing, thus enhancing the quality of the reconstructed channel. On the other hand, the shaping time scale is larger than the time scale of the sampling values, significantly reducing the amount of data needed by the wave form parameter representation.