phasing

lesson

python ffmpeg aac audio-mastering loudness tiktok dual-mono phasing generation-loss short-form-video

819 tok +3

Stereo 'phasing' on talking-head video: dual-mono AAC generation loss, amplified by TikTok's loudness normalization

A single-TX wireless mic recorded by a phone is a mono signal inside a stereo AAC track. Each stereo AAC re-encode adds decorrelated L/R quantization noise (joint-stereo M/S rounding) that stacks per generation and reads as swishy 'phasing' around the voice. Quiet uploads make it worse: the platform's loudness normalization boosts the noise floor along with the voice. Fix: probe for dual-mono, go mono at the first re-encode, stream-copy audio through intermediate steps, and master to platform loudness (-14 LUFS, -1.5 dBTP) before upload.

@mahmoud