Subband Dynamic Range Control With Downsampled Gain Estimation

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Solution Overview

Problem

Existing dynamic range control (DRC) methods for multi-channel audio signals face high computational complexity and can introduce unpleasant artifacts, particularly in noisy environments.

Innovation Solution

A method involving downsampling subband signals after conversion to the subband domain, determining DRC gains on the downsampled signals, and applying these gains to the original subband signals, while maintaining the original resolution, to reduce computational complexity and improve perceptual quality.

Engineering Contradictions & Design Principles

VSEngineering 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

Engineering Contradiction:

Improvedynamic range control effectivenessVSAvoidcomputational complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The audio signal is divided into multiple channels, and DRC is applied independently to each channel rather than processing all channels simultaneously. This segmentation reduces the computational burden while maintaining effective dynamic range control for each individual channel

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the processing parameters by working in the frequency domain (using FFT-transformed spectral coefficients) rather than time domain, and applies channel-specific gain adjustments. This parameter transformation enables more efficient computation compared to conventional time-domain processing of multi-channel signals

Inventive Principle:

Principle #35Parameter changes

2Reliability

If DRC is applied to audio signal, then average power increases and SNR improves, but audible artifacts are introduced

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidaudible artifacts

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies different gain adjustments to different frequency bins and channels based on their local characteristics. By analyzing the spectral content and applying targeted compression only where needed rather than uniform compression across all frequencies and channels, the system improves SNR while minimizing the introduction of artifacts

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The DRC system dynamically adjusts gain parameters based on the instantaneous spectral content and energy distribution across channels. This dynamic adaptation allows the system to respond to actual signal conditions, improving SNR when needed while avoiding excessive compression that would create artifacts

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4154251B1Method and unit for performing dynamic range control

Publication Date: 2026.03.25 DOLBY INTERNATIONAL AB

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AI summary

The present document describes 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).