Audio Compressor Transfer Function for Target Loudness Range
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Solution Overview
Problem
Existing methods for controlling the loudness range of audio signals, such as Dynamic Range Control (DRC), face challenges in predicting the range of resulting gains and often lead to computational complexity and suboptimal results due to limitations in the selection of initial transfer functions and iterative processes.
Innovation Solution
An apparatus and method that evaluates the loudness of an input audio signal to determine a compressor transfer function based on a target loudness range, actual loudness value, and statistical moments, using a calculator to compute loudness range control gains and adjust the signal accordingly, ensuring minimal audio quality degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a predefined compressor transfer function is applied to control the loudness range, then the loudness range can be adjusted according to predefined criteria, but the target loudness range cannot be guaranteed at the output
Solution Approach 1:
The patent changes the parameters of the transfer function dynamically based on the actual loudness range of the input audio signal. Instead of using a fixed predefined transfer function, the system calculates and adjusts the transfer function parameters (such as threshold and ratio) to match the specific characteristics of the input signal, thereby ensuring the target loudness range is achieved
Solution Approach 2:
The system measures the actual loudness range of the input audio signal and uses this feedback information to adjust the transfer function parameters. This closed-loop approach allows the system to adapt to different input signals and guarantee the target loudness range at the output
2Manufacturing precision
If an iterative process is used to determine the transfer function, then the loudness range control can be optimized, but the computational complexity increases
Solution Approach 1:
The patent performs preliminary analysis of the input audio signal to determine its loudness range characteristics before applying the transfer function. By pre-calculating the necessary parameters based on the input signal's actual loudness range, the system avoids complex iterative processes during real-time processing while still achieving precise loudness range control
3Device complexity
If a fixed transfer function is used, then the device complexity is reduced, but the audio quality degradation increases
Solution Approach 1:
The patent makes the transfer function dynamic by adjusting its parameters according to the actual loudness range of the input audio signal. This dynamic adaptation allows the system to optimize audio quality for different types of input signals without requiring complex device architecture, as the transfer function automatically adapts to the signal characteristics
Data Source
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AI summary
An apparatus (1) for processing an input audio signal (100) comprises an evaluator (10) for evaluating a loudness of the input audio signal (100) to determine a loudness range (LRAin) and an actual loudness value. A calculator (11) determines a compressor transfer function based on the determined loudness range (LRAin), based on a target loudness range (LRAdes) and based on the determined actual loudness value. The calculator (11) further determines at least one loudness range control gain based on the determined compressor transfer function. An adjuster (12) provides an output audio signal (101) based on the input audio signal (100) and based on the at least one determined loudness range control gain. The calculator (11) is configured to determine the compressor transfer function such that a difference between a mean loudness (μout) of the output audio signal (101) and a mean loudness (μin) of the input audio signal (100) is minimized. A corresponding method is also provided.