Audio mixing is the act of summing several participants' audio into a single stream, with level management and limiting to stop the combined signal from clipping. It is the core job of an MCU and of server-side recording, where many talkers must become one coherent track, and it also happens on the client when a layout blends multiple remote streams. Good mixing is more than addition: it manages gain so a loud talker doesn't bury a quiet one, applies a limiter to catch peaks, and often mixes only the few active speakers (chosen via audio-level) to save work and keep the result clean. Done poorly it produces clipping, pumping, or a muddy, fatiguing blend.
The book · Volume 5 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From Jitter Buffers and Lip Sync to Atmos, Quality Metrics, and Neural Codecs
Audio mixing on the server is what keeps large calls affordable for clients, but it costs CPU, adds delay and removes per-speaker control. Volume 5 covers audio mixing in detail within group call audio: mixing versus forwarding, bitrate and topology decisions, jitter buffers, recording and diagnosing call audio problems by symptom. Written by Nikolay Sapunov, CEO at Fora Soft.
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