WAV to NumPy NPY Converter

What this tool does

Paste an uncompressed RIFF/WAVE file as base64 or hex and this tool writes the decoded PCM samples as a real NumPy .npy v1.0 array. The output starts with the \x93NUMPY magic header and can be loaded directly with np.load() after you decode the returned base64 or hex string.

Use it when you need a small browser-safe bridge from WAV audio into Python, DSP notebooks, ML preprocessing, fixture generation, or regression tests. The decoder supports PCM integer WAVs (8, 16, 24, and 32 bit) plus IEEE-float WAVs (32 and 64 bit). Compressed containers such as MP3, AAC/M4A, FLAC, and Ogg are rejected with named errors instead of guessed.

Key controls:

• Output dtype — write normalized float32/float64, scaled int16/int32/uint8, or auto to keep the source dtype in the style of scipy.io.wavfile.read.
• Array shape — keep the usual (frames,) or (frames, channels) layout, force always-2D (frames, channels), transpose to (channels, frames), or flatten interleaved samples.
• Frame windowing — export a start_frame and max_frames slice when you only need a short fixture.
• Info report — inspect sample rate, shape, dtype, order, and byte counts before emitting the actual .npy text.

Worked example

The placeholder WAV is a 16 kHz mono, 16-bit PCM clip with three samples. Leave the defaults and run it as Base64 .npy to get this exact output:

k05VTVBZAQB2AHsnZGVzY3InOiAnPGY0JywgJ2ZvcnRyYW5fb3JkZXInOiBGYWxzZSwgJ3NoYXBlJzogKDMsKSwgfSAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAoAAAA/AACAvgAAAAA=

Decode it with:

printf '%s' 'k05VTVBZAQB2AHsnZGVzY3InOiAnPGY0JywgJ2ZvcnRyYW5fb3JkZXInOiBGYWxzZSwgJ3NoYXBlJzogKDMsKSwgfSAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAoAAAA/AACAvgAAAAA=' | base64 -d > audio.npy
python3 - <<'PY'
import numpy as np
x = np.load('audio.npy')
print(x.dtype, x.shape, x.tolist())
PY

The array loads as float32, shape (3,), with normalized values [0.5, -0.25, 0.0].

Limits and edge cases

• .npy stores the array only; it does not store WAV metadata such as sample rate. Use Output as: Info report and save the displayed sample rate beside your array.
• The decoded WAV input is capped at 32 MiB. Emitted .npy data is capped separately for base64 and hex output so the page stays responsive.
• max_frames=0 means “to the end of the clip”; any positive value is capped at 1,000,000 frames.
• A mono downmix averages channels and is lossy. It is off by default so multichannel data is preserved.
• This is a pure WASM parser. Convert compressed audio to uncompressed WAV first with an audio conversion tool, then paste the resulting bytes here.

FAQ