The extra bytes do not add detail
Video sound is often stored as lossy AAC, Opus or Vorbis. Converting it to WAV decodes what remains after that earlier compression; it cannot reconstruct missing detail or clean up the microphone. PrivateMP3 writes uncompressed 16-bit PCM. That gives an editor direct samples to work with, but the larger file is not a better recording.
The 16-bit detail matters with unusual source material. If a video contains PCM with more than 16 bits of precision, this WAV output reduces it to 16 bits. Most ordinary video soundtracks are already lossy, so their earlier codec is usually the larger quality constraint.
The size calculation used here
The page preserves the source sample rate and channel count and writes two bytes per sample. Its estimate is based on:
sample rate × channels × 2 bytes × kept duration
Stereo therefore needs twice the audio data of mono at the same sample rate. A higher sample rate also increases size in direct proportion. Cuts reduce the estimate because removed time is not written. PrivateMP3 does not offer resampling, bit-depth or mono controls, so choosing WAV does not silently change those source settings apart from writing 16-bit samples.
Use WAV as a working file
WAV is useful before editing in a digital audio workstation, signal analysis, speech cleanup or mixing. Those jobs commonly work with PCM internally, so WAV avoids adding an MP3 or AAC encode before the work starts. Make the smaller delivery file after the edits. For ordinary listening, choose MP3 when compatibility matters. If the source is AAC, AC-3 or E-AC-3 and you need the complete, unchanged track, M4A may copy it without re-encoding.
Measured: mono and stereo sources
Tested on 6 October 2026 in Chrome 154.0.8037.98 and Edge 154.0.4258.53 on Windows 11 (Intel Core i5-13600KF, 32 GB), with files generated by FFmpeg from a 220 Hz tone and quiet pink noise. Times are from Chrome; Edge differed by at most 0.7 s on any row. Each saved file was read back with ffprobe. The method is described in the screen recording test results.
| Source, 5:00 | WAV | Formula |
|---|---|---|
| MP4 with mono AAC, 44.1 kHz, 96 kbps | 0.8 s, 26,460,044 bytes, 1 channel | 44,100 × 1 × 2 × 300 = 26,460,000, plus a 44-byte header |
| MP4 with stereo AAC, 48 kHz, 128 kbps | 2.4 s, 57,600,044 bytes, 2 channels | 48,000 × 2 × 2 × 300 = 57,600,000, plus 44 |
The mono source stayed mono and kept 44.1 kHz, as the formula above says it will. For the same five minutes the mono file's other outputs were an MP3 of 7,201,174 bytes (mono at 192 kbps, in 3.4 s) and an unchanged M4A copy of 3,665,528 bytes (in 0.3 s). The WAV is about seven times the size of that copy and holds the same decoded sound.
Before a long WAV export
- Check the output duration after cuts; duration is part of the size formula.
- If the file has several audio tracks, choose the intended language or mix before converting.
- Leave enough local storage for an uncompressed result.
- If no waveform appears, the browser may understand the video container but lack a decoder for its audio codec.