ALL VIDEO TOOLS23
MP4 to WAV
Convert MP4 to WAV Online — Free & Instant
Turn an MP4's audio track into an uncompressed WAV file for editing or transcription.
About MP4 to WAV
The audio inside an MP4 is almost always AAC — compressed, lossy, and fine for listening but awkward for working with. Editing suites, mastering chains, transcription services and speech-to-text tools generally want uncompressed PCM in a WAV container, and some of them refuse anything else outright. This tool bridges the two: it demuxes the audio stream out of the MP4, decodes it, and writes a standard 16-bit WAV at the track's own sample rate, which is the shape those tools expect to receive. It is worth being clear about what the conversion does and does not do. It does not restore quality — whatever AAC discarded when the video was made is gone, and decoding to WAV cannot bring it back. What it does give you is a lossless working copy, so that every edit, filter and export after this point adds nothing further. The other thing to expect is size: uncompressed stereo audio runs about 10 MB per minute, so a one-hour recording becomes a file over half a gigabyte. When you just want something to listen to, MP3 is the better output and the audio extractor offers it. FFmpeg compiled to WebAssembly does the demux and the decode inside this tab; the video never leaves your device.
Questions
What is inside an MP4's audio track?
Almost always AAC — compressed and lossy, fine for listening and awkward for working with. This tool demuxes that stream out of the container, decodes it, and writes the samples into a standard 16-bit WAV at the track's own sample rate, which is the shape editing and transcription software expects.
How large is the resulting WAV?
Around 10 MB for every minute of stereo audio, so an hour-long recording becomes a file over half a gigabyte. It is assembled in the browser tab in one piece before the download appears, which is the practical ceiling here — the MP4 itself is mounted rather than loaded, so its size costs nothing.
Does this restore quality the MP4 lost?
No. Whatever AAC discarded when the video was made is gone, and no conversion brings it back. The WAV is lossless from this point forward, not lossless all the way back — which is still exactly what you want before editing, because nothing further is lost downstream.
Can I use a MOV or M4V file too?
Yes — this page accepts .mp4, .m4v and .mov, which are all ISO base media containers holding the same kinds of audio track. For WebM, AVI or MKV sources, use the more general video to WAV page, which takes the wider list.
Why is the first conversion slower than the next one?
Because the engine has to arrive first. FFmpeg is compiled to WebAssembly and is roughly a 31 MB download, served from this site rather than a CDN, fetched once and then cached by your browser. Every conversion after that starts immediately, and all of them run on your own machine.
Is my file uploaded to a server?
No. Transmute processes everything locally in your browser using JavaScript and WebAssembly. Your files never leave your device — there is no server, no upload, no cloud processing.