Stereo Coding Phase Offset Adaptation
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Solution Overview
Problem
Conventional mid/side (M/S) stereo coding methods are ineffective when applied to groups of signals with considerable relative mutual phase or time offsets, as they fail to efficiently compress data and maintain audio quality.
Innovation Solution
A method of encoding input signals by determining parameters for relative phase and temporal differences, applying complex rotation to generate dominant and residual signals, and multiplexing quantized data to achieve efficient encoding, while optionally discarding perceptually non-relevant time-frequency information to enhance compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional M/S stereo coding is applied to signals with considerable phase or time offsets, then the coding process is simple, but data compression efficiency deteriorates and audio quality is lost
Solution Approach 1:
The patent applies dynamic rotation angle adjustment based on signal characteristics. Instead of using a fixed 45° rotation angle as in conventional M/S coding, the system calculates optimal rotation angles adaptively for different signal conditions, particularly for signals with phase or time offsets. This dynamic approach maintains coding effectiveness while preserving audio quality for diverse signal types.
Solution Approach 2:
The patent changes the rotation angle parameter from a fixed value to a variable parameter that adapts to signal characteristics. By modifying this key parameter based on phase and time offset measurements, the system resolves the contradiction between simple coding and quality preservation, achieving both efficiency and fidelity.
2Loss of information
If variable rotation angle is applied to enhance compression, then data compression improves, but device complexity increases
Solution Approach 1:
The patent performs preliminary analysis of signal characteristics (phase and time offsets) before applying rotation coding. By pre-calculating optimal rotation angles based on measured signal parameters, the system avoids complex real-time adjustments during encoding, thus reducing overall device complexity while maintaining compression efficiency.
3Reliability
If complex rotation is applied to signals with phase offsets, then audio quality is maintained, but computational requirements increase
Solution Approach 1:
The patent changes the rotation angle parameter from a fixed value to a variable parameter that adapts to signal characteristics. By modifying this key parameter based on phase and time offset measurements, the system resolves the contradiction between simple coding and quality preservation, achieving both efficiency and fidelity.
Data Source
AI summary
A method of encoding input signals (l, r) to generate encoded data (100) is provided. The method involves processing the input signals (l, r) to determine first parameters (φ1, φ2) describing relative phase difference and temporal difference between the signals (l, r), and applying these first parameters (φ1, φ2) to process the input signals to generate intermediate signals. The method involves processing the intermediate signals to determine second parameters (α; IID, ρ) describing angular rotation of the first intermediate signals to generate a dominant signal (m) and a residual signal (s), the dominant signal (m) having a magnitude or energy greater than that of the residual signal (s). These second parameters are applicable to process the intermediate signals to generate the dominant (m) and residual (s) signals. The method also involves quantizing the first parameters, the second parameters, and dominant and residual signals (m, s) to generate corresponding quantized data for subsequent multiplexing to generate the encoded data (100).