audio-extract-mix

audio-extract-mix

Extract / mix / replace / duck / loudness-normalize audio on a clip, the way the Reframe media_studio sidecar actually does it. Every command below is copied from real source — no invented flags.

Source modules (read these for ground truth)

• sidecar/media_studio/features/audiomix.py — audiomix.merge (duck→mix→loudnorm)
  • audiomix.normalize (loudnorm only). Owns build_mix_filter, build_mix_argv, build_loudnorm_argv, PLATFORM_LOUDNESS, resolve_loudness_target.
• sidecar/media_studio/features/tracks_audio.py — tracks.audio.{list,mux,replace,strip}. Owns build_mux_argv, build_replace_argv, build_strip_audio_argv, probe_streams, original_tracks_from_probe.
• sidecar/media_studio/features/audio_saliency.py — PANNs CNN14 audio tagging + pure RMS loudness_curve. Owns compute_audio_signals, peak_windows, sample_windows, the decode argv in _default_audio_loader.
• sidecar/media_studio/ffmpeg.py — the shared seam: ffmpeg_path / ffprobe_path (resolve binary by absolute path), run (argv-list Popen, both pipes drained, -progress parsing, cooperative cancel), ffprobe_duration (drives the progress %).

The whole module follows one law (audiomix.py docstring, CONTRACTS §4/§6/§7): argv LISTS only, never shell=True; the filter graph and every path is a single argv element; the ffmpeg binary is resolved by absolute path; both stdout and stderr are drained by the shared run. Keep that when you hand-run these.

Recipe 1 — Mix a music bed / VO UNDER speech with sidechain ducking + loudnorm

Recipe 2 — Loudness-normalize an export (no bed)

Per-platform LUFS targets (PLATFORM_LOUDNESS, audiomix.py:67-80)

Recipe 3 — Extract / decode audio to raw samples

Recipe 4 — Mux / replace / strip an audio track (preserve everything else)

Pitfalls that actually bite

GPU / HF-model notes (audio_saliency only)

Worked example: lay a -10 dB music bed under a TikTok clip at -14 LUFS