Multi-channel Encoder Reduces Inter-channel Interference
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Solution Overview
Problem
Contemporary multi-channel encoders experience significant inter-channel interference when decoding output signals, particularly in generating a good stereo image during two-channel down-mix, which affects the quality of the decoded audio.
Innovation Solution
A multi-channel encoder that processes input signals to generate down-mix output signals and complementary parametric data, using a down-mixer and analyzer to predict discarded channel information, thereby reducing inter-channel interference and enhancing signal regeneration. This encoder operates on time/frequency tiles and employs optimization techniques like minimizing the Euclidean norm to generate parametric data, allowing for backward compatibility with two-channel stereophonic systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If contemporary multi-channel encoders are used to generate down-mix output signals, then the encoding process is simple, but significant inter-channel interference occurs during decoding
Solution Approach 1:
The encoder performs preliminary analysis of the input signals to generate parametric data that describes the relationship between channels before down-mixing occurs. This advance preparation allows the decoder to reconstruct signals without inter-channel interference by using the pre-computed parametric information to guide the signal regeneration process.
Solution Approach 2:
Parametric data acts as an intermediary between the multi-channel input signals and the down-mix output signals. This intermediate representation captures the essential spatial and temporal relationships of the original channels, enabling accurate reconstruction at the decoder while avoiding direct interference between channels during the down-mixing process.
2Quantity of substance
If parametric descriptions are used to represent spatial audio information, then transmission capacity is reduced, but decoding quality may be compromised
Solution Approach 1:
The invention transforms the audio signal representation from time-domain waveforms to frequency-domain parametric descriptions. By changing the domain and representation format, the system achieves compact data transmission while preserving the essential characteristics needed for high-quality signal regeneration through optimization techniques.
Solution Approach 2:
The encoder incorporates optimization processes that use feedback mechanisms to adjust parametric data generation, ensuring that the compressed representation maintains sufficient information for accurate signal reconstruction. The feedback loops refine the parametric descriptions to maximize decoding quality within the reduced data capacity constraints.
Data Source
AI summary
There is described a method of encoding input signals (CHI to CH3; 400 to 450) in a multi-channel encoder (5; 15) to generate corresponding output data comprising down-mix output signals (610, 620) together with complementary parametric data (600). The method includes a first step of down-mixing input signals (CHI to CH3; 400 to 450) to generate the corresponding down-mix output signals (610, 620), and a second step of processing the input signals (CHI to CH3; 400 to 450) during down-mixing to generate said parametric data (600) complementary to the down-mix output signals (610, 620). Processing of the input signals (CHI to CH3; 400 to 450) involves including information in the down-mix signals (610, 620) which is useable during subsequent decoding of the down-mix output signals (610, 620) and the parametric data (600) to determine at least some parameter data and thereby enabling representations of the input signals (CHI to CH3; 400 to 450) to be subsequently regenerated. Coders for use in the encoder (5; 15) for performing essential signal processing operations therein are also elucidated.