Transient-Based Audio Decorrelator Circuit for Artifact Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing decorrelation circuits in audio signal processing suffer from degraded transient response, susceptibility to downmix artifacts, and a limited number of mutually decorrelated outputs, particularly when handling transient signals, leading to unnatural sound reproduction and temporal smearing.

Innovation Solution

A method that separates input audio signals into transient and continuous components based on time-varying characteristics, processes the continuous component through a decorrelation circuit while leaving the transient component untouched, and combines them to form an output signal, using all-pass delay sections and envelope prediction to minimize distortion and artifacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If decorrelation filtering is applied to the complete input signal, then spatial diffuseness is improved, but transient response is degraded

Engineering Contradiction:

Improvespatial diffusenessVSAvoidtransient response

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The input signal is segmented into transient and continuous components based on envelope analysis. The transient component is identified when the envelope exceeds a threshold, and the continuous component is processed through the decorrelator while the transient component bypasses it. This segmentation allows different processing paths for different signal types, resolving the contradiction between spatial diffuseness and transient response.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of applying decorrelation to the complete signal, only the continuous component is decorrelated while the transient component is left untouched. This partial action approach applies the beneficial effect (spatial diffuseness) only where needed without causing the harmful effect (transient degradation), thus resolving the technical contradiction.

Inventive Principle:

Principle #16Partial or excessive action

2Adaptability or versatility

If decorrelation is applied to transient signals, then spatial width is increased, but temporal smearing occurs

Engineering Contradiction:

Improvespatial widthVSAvoidtemporal smearing

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The system performs preliminary analysis of the input signal envelope before applying decorrelation. By detecting transient components in advance through envelope thresholding, the system can route them through a different path that avoids decorrelation filtering, thereby preventing temporal smearing before it occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The decorrelation effect is applied partially - only to the continuous component of the signal - rather than to the complete signal. This selective application increases spatial width for continuous sounds while avoiding temporal smearing of transient signals.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If post-decorrelation attenuation is used to correct temporal artifacts, then transient response is improved, but the number of decorrelated outputs is limited

Engineering Contradiction:

Improvetransient responseVSAvoidnumber of decorrelated outputs

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

Instead of correcting transient artifacts after decorrelation, the system performs preliminary separation of transient and continuous components before the decorrelation stage. This prevents transient degradation from occurring in the first place, allowing multiple decorrelated continuous outputs without being limited by the need to correct artifacts afterward.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively reduces temporal distortion and artifacts, enhances transient response, and allows for multiple mutually decorrelated outputs without introducing comb-filter artifacts, improving the naturalness and spatial diffuseness of audio reproduction.

Implementation Method 1

A transient-based decorrelator separates a transient component from a continuous component of an input signal, processes the continuous signal through a decorrelator, and combines it with the transient component to form an output signal

Methodology Applied

Scientific EffectAll-pass filter:

Data Source

PatentEP3028274B1Apparatus and method for reducing temporal artifacts for transient signals in a decorrelator circuit

Publication Date: 2019.03.20 DOLBY LABORATORIES LICENSING CORP

Figure 1
Figure 2
Figure 3~4

AI summary

Embodiments are directed to a method for processing an input audio signal, comprising: splitting the input audio signal into at least two components, in which the first component is characterized by fast fluctuations in the input signal envelope, and a second component that is relatively stationary over time; processing the second, stationary component by a decorrelation circuit; and constructing an output signal by combining the output of the decorrelator circuit with the input signal and/or the first component signal.