Fade audio in or out

Ramp an audio file's (or a video's audio track's) volume up from silence at the start, down to silence at the end, or both, linear or logarithmic, decoded and re-encoded as WAV through the same PCM path as audio-reverse. WAV decodes everywhere; AAC, MP3, Opus, FLAC and Vorbis need a browser.

Fade audio in or out slides a clip's volume from silence up to full at the start, back down at the end, or both, following a linear or logarithmic curve. Samples decode to PCM, get scaled frame by frame, and encode fresh as WAV. WAV opens everywhere; AAC, MP3, Opus and FLAC need a browser tab to decode.

Questions

What is the difference between the linear and log curve?

Linear ramps the gain in a straight line from silent to full volume. Log rises quickly at first and then levels off, which tends to sound smoother, since human loudness perception is itself roughly logarithmic.

Can I fade in and out at the same time?

Yes. fadeInSec and fadeOutSec are independent, both defaulting to half a second, and either can be set to 0 to skip that end. At least one of the two must be greater than 0.

Does this work on a video file?

Yes, on its audio track. The video itself is not touched by this tool; only the decoded audio samples are faded and written back out as a standalone WAV file.

Why is the output always WAV?

Because the samples are decoded to raw PCM, scaled frame by frame, and re-encoded, and WAV is the format that path writes. Convert audio afterward if you need MP3 or another format.

Why does it need a browser for some files?

WAV decodes in Node as well as the browser, since it carries raw PCM samples. AAC, MP3, Opus and FLAC input need a browser, because those codecs only decode through WebCodecs.

Related Video tools

n→nConvert audioChange an audio file between MP3, WAV, FLAC, Ogg and M4A (AAC). In the browser only, like video-convert, because mediabunny decodes and encodes through WebCodecs, which Node has no equivalent of.n→nNormalize audio volumeScale an audio (or video's audio track) so its loudest sample hits a target peak level: a two-pass peak scan followed by a gain-scaled re-encode, both through WebCodecs, so this runs in the browser only, like video-convert. Always outputs MP4 with an unchanged video track (if any).n→1Trim or merge audioCut an audio file down to a start-end range, or concatenate two or more audio files one after another. A packet-level copy with no decoding, so this runs in Node, the CLI and MCP as well as the browser. Output is always an MP4 audio file (.m4a).n→nExtract audio from videoPull the audio track out of a video into its own MP4 audio file. A packet-level copy with no decoding or re-encoding, so this runs in Node, the CLI and MCP as well as the browser.n→nMute videoDrop the audio track from a video, keeping the picture untouched. A packet-level copy of the video track only, no decoding, so this runs in Node, the CLI and MCP as well as the browser.n→nReverse audioPlay an audio file (or a video's audio track) end to start, decoded to raw samples and re-encoded as WAV. WAV input decodes in Node, the CLI and MCP as well as the browser, the same PCM path audio-trim-merge's packet copy sits next to; AAC, MP3, Opus, FLAC and Vorbis need a browser.n→nConvert mono to stereo or backChange an audio file's (or a video's audio track's) channel count: average every channel down to mono, duplicate a mono track into identical left and right channels, or swap left and right, decoded and re-encoded as WAV through the same PCM path as audio-reverse. WAV decodes everywhere; other codecs need a browser.n→nDraw a waveform imageDraw an audio file's (or a video's audio track's) peaks as a PNG, one column per pixel of width, decoded through the same PCM path as audio-reverse and drawn straight into a pixel buffer, the way font-preview rasterizes glyphs, with no canvas. WAV decodes everywhere; other codecs need a browser.