Two-Stage Audio Gain Control for Stable Speech Levels
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Solution Overview
Problem
Existing video conferencing systems face challenges in maintaining a stable and consistent audio signal level, leading to an unpleasant auditory experience for recipients.
Innovation Solution
A two-stage automatic gain control (AGC) module is implemented, which applies a first stage gain based on a long-term signal level estimate and a second stage gain based on a short-term signal level estimate, to amplify the input signal to a target level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage gain control is used, then the device complexity is reduced, but the audio signal level stability deteriorates
Solution Approach 1:
The gain control is divided into two distinct stages: a long-term gain control that adjusts gain based on historical signal levels to maintain overall stability, and a short-term gain control that responds to immediate signal level changes. This segmentation allows each stage to specialize in different time scales of signal stabilization, achieving better overall audio level stability without requiring an overly complex single-stage system.
2Stability of the object's composition
If long-term signal level estimation is used, then the audio signal level stability is improved, but the response speed to sudden level changes deteriorates
Solution Approach 1:
The system maintains continuous gain adjustment through two parallel estimation processes: long-term signal level estimation that provides stable baseline adjustment, and short-term signal level estimation that captures immediate changes. Both estimations operate continuously and their gains are combined, ensuring that the useful action of gain control remains continuous and responsive across all time scales, preventing gaps in response to sudden level changes.
Solution Approach 2:
The gain control system dynamically adapts by switching between long-term and short-term gain adjustments based on the current signal conditions. When signal levels change gradually, the long-term gain dominates; when sudden changes occur, the short-term gain becomes more influential. This dynamic behavior allows the system to maintain stability during normal operation while responding quickly to abrupt changes.
3Speed
If short-term signal level estimation is used, then the response speed is improved, but the audio signal level stability deteriorates
Solution Approach 1:
The system implements feedback mechanisms where the short-term gain adjustment is continuously monitored and balanced against the long-term gain. The short-term estimation provides rapid response to level changes, while the long-term estimation acts as a stabilizing feedback that prevents excessive or erratic gain adjustments. This feedback loop ensures that fast response does not compromise overall signal level stability.
Data Source
AI summary
Disclosed are systems and methods for generating a long-term signal level estimate during automatic gain control. In an example method, a computing device selects a first subset of an input signal, the input signal being a portion of a captured audio signal including at least a variable speech component. The computing device divides the first subset of the input signal into a first set of intervals. The computing device computes a first statistical measure of each interval of the first set of intervals. The computing devices generates a first statistical distribution based on the first statistical measure of at least a portion of the first set of intervals. The computing device determines the long-term signal level estimate based on one or more characteristics of the first statistical distribution. The computing device generates a first stage gain based on the long-term signal level estimate. The computing device applies the first stage gain to the input signal to cause the variable speech component to approach a target level.