Subband Downsampling for Low-Complexity Dynamic Range Control
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Solution Overview
Problem
Dynamic range control (DRC) in multi-channel audio signals is challenging due to high computational complexity and the introduction of unpleasant artifacts, particularly in noisy environments.
Innovation Solution
A dynamic range control unit that downsamples subband signals derived from audio signals, determines DRC gains based on the downsampled signals, and applies these gains to the original subband signals, reducing computational complexity while maintaining high perceptual quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DRC is applied to multi-channel audio signal using conventional methods, then dynamic range control is achieved, but computational complexity becomes high
Solution Approach 1:
The audio signal is divided into multiple subbands using a filter bank, where each subband is processed independently for DRC. This segmentation allows parallel processing of different frequency ranges, reducing overall computational complexity while maintaining effective dynamic range control across the full audio spectrum.
Solution Approach 2:
Instead of processing the entire audio signal at full resolution, the patent applies downsampling to subband signals before DRC processing. This partial action approach processes only essential frequency components at reduced resolution, achieving sufficient DRC effectiveness with significantly lower computational requirements.
2Reliability
If DRC is applied to audio signal, then average power increases and SNR improves, but audible artifacts are introduced
Solution Approach 1:
The patent applies different processing strategies to different subbands based on their characteristics. Critical frequency regions where artifacts are most noticeable are processed with higher fidelity, while less critical regions use more aggressive compression. This local quality differentiation maintains high perceptual quality while achieving effective DRC.
Solution Approach 2:
Downsampling subband signals before DRC processing reduces the amount of data requiring compression, thereby reducing the introduction of quantization and compression artifacts. The partial processing approach focuses computational resources on essential frequency components, minimizing audible artifacts while maintaining improved SNR.
Data Source
AI summary
A dynamic range control unit (210) configured to apply dynamic range control, referred to as DRC, to an audio signal (211). The DRC unit (210) is configured to downsample a subband signal (212) derived from the audio signal (211), to provide a downsampled subband signal (321), to determine a DRC gain (329) based on the downsampled subband signal (321), and to apply the DRC gain (329) to the subband signal (212), to provide a compressed subband signal (213) of a compressed audio signal (214).