Separate Codec Bring-Up from Acoustic Tuning
Prove clocks, framing, routing and gain before judging microphones, speakers or enclosure acoustics.
codec
SDP Is Where Signalling Hands the Call to Media
A SIP call can connect perfectly and still carry no useful audio if the negotiated media description is wrong.
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.
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.
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.
Volume Stuck Near 80 Percent Was a Gain-Path Problem, Not a UI Problem
A slider value is meaningless until every digital and analog gain stage is mapped.
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.