Node / Video Ffmpeg · guide

Audio tracks

Current Apexify.js 6.0.0 documentation for Audio tracks.

apexify.jsRuntime: nodeCURRENTSince 6.0.0

See also: Video audio operations (full) — normalizeAudio, mixAudio.

Multi-step edits: Video pipeline. Generated SFX: Advanced → createAudio → mux with mixAudio or pipeline .audio().

extractAudio

Demux first audio stream (requires audio track).

Option	Default	Notes
`outputPath`	✓	Target file.
`format`	`mp3`	`mp3` (libmp3lame), `wav` (pcm_s16le), `aac`, `ogg` (libvorbis).
`bitrate`	128	`kbps` (`-ab`).

1await painter.createVideo({2  source: './talk.mp4',3  extractAudio: {4    outputPath: './talk.wav',5    format: 'wav',6  },7});

removeAudio

Video-only output (-an -c:v copy).

1await painter.createVideo({2  source: './with-sound.mp4',3  removeAudio: { outputPath: './silent.mp4' },4});

mute

Mode	Behaviour
No `ranges`	Same strip as `removeAudio` (`-an`).
`ranges: [{ start, end }]`	`volume=enable='between(t,...)':volume=0` segments on audio (`-c:v copy`).

1await painter.createVideo({2  source: './podcast.mp4',3  mute: {4    outputPath: './podcast-beeped.mp4',5    ranges: [6      { start: 30, end: 35 },7      { start: 120, end: 125 },8    ],9  },10});

mixAudio — MixAudioOperation

Mixes N overlay clips onto the output timeline while optionally keeping the original mix.

Top-level

Field	Default	Notes
`outputPath`	✓	Mixed MP4 (`-c:v copy`, AAC 192k).
`overlays`	✓	`MixAudioOverlayClip[]` — see below.
`keepOriginalAudio`	`true`	`false` → overlays only (no silent bed mixed under SFX — avoids quiet/muddy mixes).
`originalVolume`	1	Linear gain on [0:a] before `amix`.
`originalSpeed`	1	`atempo` chain (~0.25–4 clamp).
`originalPitchSemitones`	0	`asetrate` trick without rubberband.

MixAudioOverlayClip

Field	Notes
`source`	Path / URL / Buffer (resolved like video).
`startTime`	Seconds on output timeline when clip begins.
`duration`	Seconds from overlay after trim — default `min(fileRemainder, videoEnd-start)` logic inside helper.
`sourceStart`	Skip seconds into overlay file (default 0).
`volume`	Linear gain (default 1).
`speed`	`atempo` chain (~0.25–4) — changes playback speed of trimmed overlay audio.
`pitchSemitones`	`asetrate` + compensating `atempo` (duration-preserving, no rubberband).

Skips overlays whose playable window < ~0.04s or start past video end.

Example — bed music under narrator

1await painter.createVideo({2  source: './voice.mp4',3  mixAudio: {4    outputPath: './voice-plus-bed.mp4',5    keepOriginalAudio: true,6    originalVolume: 1,7    overlays: [8      {9        source: './music-loop.mp3',10        startTime: 0,11        duration: 120,12        sourceStart: 5,13        volume: 0.35,14      },15      {16        source: './whoosh.wav',17        startTime: 8.5,18        duration: 1.2,19        volume: 0.9,20      },21    ],22  },23});

Example — replace soundtrack entirely

1await painter.createVideo({2  source: './reference.mp4',3  mixAudio: {4    outputPath: './rescored.mp4',5    keepOriginalAudio: false,6    overlays: [{ source: './score.mp3', startTime: 0 }],7  },8});

adjustVolume

Global mode (no ranges)

volume is percentage of unity (100 = unchanged) → volume={volume/100}.

1await painter.createVideo({2  source: './quiet.mp4',3  adjustVolume: {4    outputPath: './boosted.mp4',5    volume: 180,6  },7});

Interval mode (ranges)

Each range:

Field	Notes
`start`, `end`	Seconds inclusive window (FFmpeg `between(t,...)`).
`volume`	Percent /100 multiplier inside window.
`speed`, `pitchSemitones`	Optional — triggers `rubberband` filter substring (needs FFmpeg + librubberband).

1await painter.createVideo({2  source: './mix.mp4',3  adjustVolume: {4    outputPath: './ducked.mp4',5    ranges: [6      { start: 0, end: 10, volume: 100 },7      { start: 10, end: 20, volume: 35 },8      { start: 20, end: 9999, volume: 100 },9    ],10  },11});

normalizeAudio

-c:v copy audio pipeline — video pixels unchanged.

For what each option does, LUFS vs peak, and honest limits of peak/rms, see Video audio operations (full).

1await painter.createVideo({2  source: './podcast.mp4',3  normalizeAudio: {4    outputPath: './podcast-loudnorm.mp4',5    method: 'lufs',6    targetLevel: -16,7  },8  onProgress: (p) => console.log(p.percent),9});

#extractAudio

#removeAudio

#mute

#mixAudio — MixAudioOperation

##Top-level

##MixAudioOverlayClip

##Example — bed music under narrator

##Example — replace soundtrack entirely

#adjustVolume

##Global mode (no ranges)

##Interval mode (ranges)

#normalizeAudio

Related guides and reference

Next steps