WebRTC AEC Module: Acoustic Echo Cancellation Implementation

The AEC (Acoustic Echo Cancellation) module in WebRTC serves as the core component for handling echo issues in real-time communication. This module significantly improves speech quality by employing frequency-domain NLMS (Normalized Least Mean Squares) filtering technology combined with nonlinear processing techniques.

Frequency-Domain NLMS Filtering Traditional time-domain NLMS algorithms face computational complexity limitations. The AEC module addresses this by converting the processing to the frequency domain. Through FFT-based signal segmentation, each sub-band undergoes independent adaptive filtering, effectively reducing computational load while maintaining rapid tracking capability for echo path variations. In code implementation, this typically involves partitioning the signal into frequency bins using FFT and applying separate NLMS filters to each bin with optimized step size parameters.

Nonlinear Processing Pure linear filtering cannot completely eliminate residual echoes. Therefore, the module incorporates subsequent nonlinear processing stages. These include energy-based signal suppression, residual echo estimation, and dynamic threshold detection for voice activity segments. The implementation uses statistical models to distinguish between echo and desired speech, employing gain control algorithms that further suppress echoes while preventing double-talk clipping. Key functions often involve real-time energy calculations and adaptive threshold adjustments based on signal characteristics.

This MATLAB implementation replicates the core logic of the WebRTC AEC module. Developers can adapt the algorithm to different environments by adjusting parameters such as step size factors and filter lengths. The code provides a verification foundation for embedded system porting or algorithm optimization, featuring configurable parameters and modular structure for easy experimentation and performance testing.