AEC Starts with the Correct Far-End Reference
An echo canceller cannot remove playback it never receives as a reference signal.
AEC
AEC Reference Is the Far-End Signal, Not Another Microphone
Echo cancellation only has a useful reference when the reference represents what the loudspeaker actually played.
128-Sample AEC Blocks vs 160-Sample G.711 Frames
The AEC library consumed a block size that did not divide evenly into the telephony frame size.
ES7210 Channel Mapping Was an Audio-Architecture Problem
Codec detection alone did not prove the capture channels meant what the DSP assumed they meant.
Bypassing AEC Was a Diagnostic Tool, Not a Product Direction
Turning processing off can reveal whether the artifact is created before, inside or after the algorithm.
Raw Multichannel Capture Is the Ground Truth for AEC Debugging
Processed audio alone hides whether the wrong signal entered the algorithm.
Latency Can Break AEC Even When the Signals Are Correct
A valid reference that arrives at the wrong time can be almost as useless as the wrong reference.
Downsampling 16 kHz Microphone Audio to 8 kHz PCMA
The physical capture clock and the network codec did not run at the same sample rate.
AEC Only Worked Once the Reference Signal Was Actually the Far-End Audio
An echo canceller cannot remove what its reference channel does not represent.
AEC Acceptance Should Include Double-Talk
A speakerphone must handle the user talking while the far end is also active.
AEC Startup Needs a Defined State
The first seconds of a call should not depend on whatever history remains in DSP buffers.
V117 Was Useful Because It Failed Clearly
A bad experimental build can be valuable when it changes a small set of variables and is easy to revert.
AEC Debugging Started with Channel Mapping, Not DSP Tuning
Before tuning echo cancellation I verified that the algorithm was receiving the microphone and far-end reference channels I thought it was.
Why 8 kHz Telephony Can Sound Robotic After 16 kHz Playback Conversion
The downlink could be packet-complete and still sound gritty or artificial after conversion to the physical playback rate.
AEC Starts with a Truthful Reference Signal
Echo tuning was meaningless if the AEC reference did not represent what the loudspeaker actually played.
An AEC-Off Run Is a Control Experiment, Not a Product Setting
AEC was implicated in several symptoms, but disabling it permanently would remove a required speakerphone function.