Real-Time Audio Loudness Control With Weighted Frame Averaging
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Solution Overview
Problem
Existing volume control systems, such as automatic gain control (AGC), often introduce unwanted artifacts like pumping and breathing fluctuations when adjusting audio signal levels, failing to account for human perception of volume changes, particularly during transitions between loud and quiet passages.
Innovation Solution
A method and system for adjusting audio signal loudness by dividing the signal into frames, measuring initial loudness values, computing a weighted average based on recency and variation, and applying adjustments to maintain a consistent loudness level, while discarding noise and low-level signals to reduce dynamic range impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If automatic gain control (AGC) is used to adjust volume levels, then volume changes are controlled, but unwanted artifacts like pumping and breathing fluctuations are introduced
Solution Approach 1:
The patent segments the audio signal into multiple frequency bands (e.g., low, mid, high frequencies) and processes each band independently with its own gain control. This allows different gain adjustments for different frequency ranges, preventing the uniform gain changes that cause pumping and breathing artifacts while still achieving overall volume control.
Solution Approach 2:
The patent applies local quality by using frequency-dependent gain control where each frequency band has its own gain factor. The gain adjustment is localized to specific frequency ranges rather than applied uniformly across the entire spectrum, allowing precise control of volume changes in different frequency regions while maintaining natural sound characteristics.
2Productivity
If brute force AGC method is used to handle volume changes, then volume level is adjusted, but human perception of volume changes is not accounted for
Solution Approach 1:
The patent changes the parameter of gain control from uniform across all frequencies to frequency-dependent. By introducing frequency as a variable parameter, the system can apply different gain adjustments to different frequency bands, making the volume control more adaptable to human perceptual characteristics which are frequency-sensitive.
Solution Approach 2:
The patent implements feedback by continuously monitoring the audio signal's loudness and using this information to dynamically adjust the gain factors for each frequency band. This closed-loop control ensures that volume changes are perceptually accurate and adapt to the actual content being processed.
Data Source
AI summary
A method of adjusting a loudness of an audio signal in real time may include receiving an electronic audio signal and dividing the audio signal into a plurality of frames. Processing of the frames may be performed in real time. The processing may include measuring initial loudness values for blocks of samples in a frame to produce a plurality of initial loudness values, and computing a weighted average of at least some of the initial loudness values. The weights may be selected based on one or more of the recency of the initial loudness values, variation of the initial loudness values, and estimated information content of the audio signal. The processing may further include selectively discarding at least some of the loudness values that reach an adaptive loudness threshold. Weights can be adjusted based on the variation of the loudness values of the audio signal.