MP4 → WAV
MP4 to WAV converter
The audio in the MP4 is decoded once and written as uncompressed PCM in a WAV file, with no further loss. The video stream is discarded.
…or drag files and folders here. Add as many as you like — everything is processed on this device.
.3g2 .3gp .asf .avi .f4v .flv .m4v .mk3d .mka .mkv .mov .mp4 .qt .weba .webm .wmv
In one paragraph
WAV is what editors, DAWs and transcription tools want: every sample is stored plainly, so there is no decoding delay when you scrub, and nothing is lost if you edit and export again. Pulling a WAV out of an MP4 is the usual first step before cleaning up interview audio, syncing a separate recorder, sampling a clip, or feeding a speech-to-text tool that rejects video.
Sonic Batch reads the MP4 locally with a WebAssembly build of FFmpeg, decodes its audio track (typically AAC, sometimes PCM from cameras and recorders) and writes RIFF PCM at the bit depth and sample rate you choose. The video stream is never decoded, so even a large 4K file finishes quickly, and the file stays on your device the whole time.
Does this change the audio quality?
Decoding to WAV adds no loss of its own. If the MP4 holds AAC, the WAV sounds exactly like the AAC, including whatever the AAC encoder already discarded; it cannot restore the original microphone signal.
- WAV is large: about 10 MB per stereo minute at 44.1 kHz/16-bit, and about 11 MB per minute at the 48 kHz most video uses. A one-hour recording is over 600 MB.
- Surround tracks keep all their channels unless you set Channels to stereo or mono.
- Only the first audio track is extracted.
A worked example
Getting interview audio out of a phone video for editing
- Add the MP4 files from the shoot. The queue reads each duration straight away.
- Leave 16-bit and the source sample rate (usually 48 kHz for video) so the WAV lines up with the video timeline.
- Set Channels to mono if the clip was recorded on a single phone microphone.
- Convert, then drop the WAVs into your editor or DAW alongside the video.
Keep the 48 kHz sample rate for anything going back to video
Video is almost always recorded at 48 kHz. Keep the source rate if the WAV will be edited and laid back against the picture, because resampling to 44.1 kHz can introduce drift in some editors. Choose 24-bit only if you plan heavy processing; for an AAC source, 16-bit already holds everything the file contains.
Supported formats, limits and browser notes
Sonic Batch decodes with the browser when it can (faster, no engine download) and falls back to the self-hosted WebAssembly engine when it cannot. Every combination below works in every listed browser; the column only tells you which decoder does the work.
| Input | What it is | Chrome | Firefox | Safari | iOS |
|---|---|---|---|---|---|
| MP4 | The standard video container. Its audio track is almost always AAC. | Native | Partial | Native | Native |
| MOV | QuickTime video from iPhone and DSLR cameras. Audio is normally AAC or PCM. | Partial | Engine | Native | Native |
| MKV | Open video container used for films, TV recordings and OBS captures. Audio is often AAC, AC-3, DTS, Opus or FLAC. | Partial | Partial | Engine | Engine |
| WebM | Open container used by browser recorders and YouTube downloads. Audio is Opus or Vorbis. | Native | Native | Partial | Partial |
| AVI | Legacy Windows video container from camcorders, older cameras and DivX/Xvid files. Audio is usually MP3, PCM or AC-3. | Engine | Engine | Engine | Engine |
| WMV | Windows Media video in an ASF container. Audio is almost always WMA (Windows Media Audio). | Engine | Engine | Engine | Engine |
| FLV | Flash-era web video, still produced by some stream recorders. Audio is AAC or MP3. | Engine | Engine | Engine | Engine |
| 3GP | Legacy phone recording container, normally AMR-NB or low-bitrate AAC audio. | Engine | Engine | Partial | Partial |
| Output | Encoder | Bitrates / depth | Sample rates | Tags |
|---|---|---|---|---|
| WAV | pcm_s16le | 16, 24, 32-bit | 8–96 kHz | Yes |
- Max per file
- 400.0 MB
- Max per queue
- 4.00 GB
- Max duration
- 4:00:00
- Max archive
- 1.50 GB
These are enforced ceilings, checked before any decoding starts, not measured maximums — a file over the limit is rejected rather than allowed to exhaust the tab’s memory. Real-world capacity is lower on older phones, which is why the scheduler runs one file at a time on iOS and Safari.
Where your audio goes
Nowhere. Your file is read from disk into this browser tab with the File API, decoded and encoded by code running in that same tab, and handed back to you as a download. It is never transmitted.
That is a structural property of the application, not a policy promise: there are no API routes, no server actions and no third-party processing services in this project, so there is nothing capable of receiving a file. The page’s Content-Security-Policy also restricts connections to this origin, and the automated test suite includes a browser test that fails if any network request during import, preview, conversion or download carries media bytes.
The trade-off, stated plainly: results live in your tab’s memory until you download them. Closing or reloading the page discards them. There is nothing on a server to recover, because nothing was ever put there.
Troubleshooting
The WAV is huge compared to the MP4.
That is expected. The MP4 audio was compressed roughly 10 to 1; WAV stores every sample. If you only need to listen, MP4 to MP3 gives a far smaller file.
My editor says the sample rate does not match my project.
Set Sample rate to your project rate (44.1 or 48 kHz) before converting, or change the project to 48 kHz, which is the video standard.
The first conversion takes longer than the rest.
The first job downloads the conversion engine (about 31 MB) from this site. Your browser caches it, so later files and later visits start straight away.
Frequently asked questions
How do I extract WAV audio from an MP4?
Add your MP4s above, pick a bit depth (16-bit is right for most uses), and press Convert all. Each WAV can be downloaded on its own or as part of a ZIP.
Is MP4 to WAV lossless?
The conversion step is: nothing further is discarded. But most MP4 audio is AAC, which is lossy, so the WAV is a perfect copy of compressed audio rather than of the original recording.
Are my files uploaded?
No. Decoding happens in your browser, either through its own decoder or the self-hosted WebAssembly engine. There is no server that receives files.
Can I get a smaller lossless file instead?
Yes. MP4 to FLAC stores exactly the same samples as the WAV in roughly half the space, and most editors and players open FLAC.