Parametric Audio Mixing Stage for Bandwidth and Complexity Trade-offs
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Solution Overview
Problem
Existing multichannel audio coding methods face challenges in bandwidth efficiency, computational efficiency, and robustness, particularly in low-bitrate applications where error propagation in downmix signals can occur, and there is a need for efficient resource allocation in devices with limited processing power.
Innovation Solution
The proposed audio decoding and encoding systems utilize a parametric mixing stage with independently assignable mixing parameters to form two-channel output signals, allowing for superior adaptation to coding and downmix operations, reducing sensitivity to transmission errors, and enabling more efficient use of computational and bandwidth resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If parametric coding methods are used to achieve excellent coding efficiency, then bandwidth efficiency is improved, but computational complexity increases
Solution Approach 1:
The audio signal is divided into multiple frequency subbands, with different coding strategies applied to each. High-frequency subbands use parametric coding while low-frequency subbands use different methods, allowing the system to achieve good bandwidth efficiency without requiring full parametric processing across all frequencies.
Solution Approach 2:
Different coding approaches are applied to different frequency regions based on their specific characteristics. The system applies parametric coding selectively to frequency ranges where it provides the best efficiency, while using alternative methods in ranges where computational complexity would be excessive.
2Manufacturing precision
If parametric coding methods are used to achieve excellent coding efficiency, then listening quality is improved, but structural complexity increases
Solution Approach 1:
The audio processing is segmented into different stages: downmix processing, parametric coding for high frequencies, and alternative processing for low frequencies. This segmentation allows the system to achieve high listening quality through parametric methods where they are most effective, while avoiding their structural complexity in other regions.
Solution Approach 2:
The system dynamically selects between different coding methods based on the characteristics of the audio signal and the capabilities of the playback system. This dynamic adaptation allows optimal listening quality to be achieved without permanently committing to a complex parametric structure throughout the entire system.
3Productivity
If downmix signals are used in parametric coding, then coding efficiency is improved, but robustness against errors deteriorates
Solution Approach 1:
The system changes the parameter representation of the audio signal by transforming it into the frequency domain through subband decomposition. This parameter transformation allows the coding to be more efficient while the error propagation is limited to specific frequency bands rather than affecting the entire signal.
Solution Approach 2:
By segmenting the frequency spectrum into subbands, the system isolates error propagation to individual frequency regions. Errors in the downmix signal affect only specific subbands rather than the entire audio signal, thereby improving robustness while maintaining coding efficiency through parametric methods.
Data Source
AI summary
An audio decoding system (100) for processing a two-channel input signal (X) comprises a parametric mixing stage (110). The parametric mixing stage receives the two-channel input signal and a set of mixing parameters (P1), and outputs a two-channel output signal (Y1). The parametric mixing stage comprises a decorrelation stage (111) outputting a decorrelated signal (D1) based on the input signal. The parametric mixing stage further comprises a mixing matrix (112) receiving the input signal and the de-correlated signal, and forming a two-channel linear combination of channels from the input signal and the decorrelated signal. The mixing matrix outputs the linear combination as the two-channel output signal. Coefficients of the linear combination are controllable by the set of mixing parameters, and at least four mixing parameters of the set are independently assignable. In example embodiments, multiple parametric mixing stages are used to independently reconstruct additional channels encoded in the input signal.