Extract WAV audio for editing an MP4 soundtrack
MP4 to WAV creates an audio-only file for an editor, transcription workflow, or delivery specification that requests uncompressed sound. The video track stays in the original MP4. WAV is useful for subsequent audio work, while MP3 is usually more convenient for compact listening copies.
MP4 and WAV: video delivery versus audio editing
MP4, short for MPEG-4 Part 14, is a container standardized by the MPEG group. It packages video, audio and other tracks in one file. Phones and recording apps often use it with compressed picture and sound, making it convenient for sharing a complete recording. The .mp4 extension alone does not tell you its quality or codecs.
WAV, or Waveform Audio File Format, was introduced by Microsoft and IBM in 1991. It is an audio container commonly used for uncompressed PCM: sound stored as a sequence of samples. That makes it useful for recording and editing, but usually much larger than compressed audio. WAV can hold other encodings. FastConvert produces PCM WAV.
Converting here extracts the soundtrack and leaves out the picture. You get a file an audio editor can use without another lossy encoding step, at the cost of a potentially larger download. It cannot recover detail already lost in the MP4 soundtrack. Keep the MP4 for watching. Choose WAV when the next tool or editor needs it.
What determines the size of a WAV?
| Setting | Effect on PCM audio |
|---|---|
| Duration | Twice the running time needs roughly twice the space at the same settings. |
| Channels | Stereo stores two channels. Mono stores one. Keep stereo when the recording needs it. |
| Sample rate and bit depth | Higher values store more data. Match the receiving project rather than increasing them to improve an already compressed source. |
Keep the WAV suitable for its next use
Uncompressed does not mean restored
MP4 soundtracks often already use lossy compression. Decoding that audio to PCM WAV avoids another lossy delivery format, but cannot restore frequencies or detail that the source encoder discarded.
Allow room for larger files
PCM WAV size depends on duration, sample rate, bit depth, and channel count. A soundtrack can occupy more space as WAV than the entire compressed MP4, even though the pictures are removed.
Match the receiving audio project
Keep the source sample rate and channels unless your editor requires a particular setting. Increasing the sample rate or bit depth does not create new information in the recording.
How to convert MP4 to WAV online
Begin with Recommended and PCM audio. Keep the source sample rate and channels unless the receiving editor specifies otherwise, and apply the same settings to a batch of interviews or video takes.
The free allowance is 2 files per batch, up to 100 MB each, and 20 conversions per 24 hours. No account or watermark. Files are uploaded for server-side processing, then scheduled for deletion after 24 hours on the Free plan.
Prepare interview audio for an editor
Set the sample rate, bit depth and channels requested by the editor, then save them as a WAV recipe. Apply it to each new batch of MP4 interviews instead of rebuilding the export settings.
A free account includes 1 saved conversion recipe. Paid plans add larger batches, more recipes and delivery to Google Drive or Dropbox after you start each batch.