this_file: README.md

AudioStretchy

Change audio duration without changing pitch, using David Bryant's audio-stretch TDHS engine. Pedalboard reads and writes WAV, MP3, FLAC, OGG and AIFF; NumPy handles samples and linear-interpolation resampling.

uv tool install audiostretchy
# 10% shorter, at the same pitch:
audiostretchy input.mp3 output.mp3 --ratio 0.9

For a Python project, use uv add audiostretchy:

from audiostretchy import AudioStretch, stretch_audio

stretch_audio("input.wav", "output.wav", ratio=0.9)

processor = AudioStretch()
processor.open("input.wav")
processor.stretch(ratio=1.2)  # 20% longer
processor.resample(24000)
processor.save("output.wav")

Run audiostretchy --help for all parameters. Ratios from 0.25 to 4.0 are supported; the extended range automatically cascades two TDHS instances. Input must be mono or stereo. Stretching uses 16-bit PCM internally. gap_ratio, buffer_ms, threshold_gap_db, and normal_detection remain compatibility arguments: separate silence stretching is not implemented.

Installation and platforms

Python 3.10 or newer. Published wheels contain one freshly compiled native library and the corresponding C sources and license:

• Linux x86_64 and aarch64 (manylinux/glibc).
• macOS Intel and Apple Silicon (macOS 11 or newer).
• Windows x86_64.

The native library uses ctypes and is independent of the CPython ABI, so wheels carry py3-none-<platform> tags. Dependencies install separately; NumPy and Pedalboard are not copied into the wheel. Other platforms can build from the source distribution when a C compiler and dependency wheels are available. Linux musl and Windows ARM are not part of the tested wheel matrix.

All required TDHS source is bundled under src/audiostretchy/_vendor/audio-stretch. There is no submodule initialization, build-time download, or compiler needed when installing a compatible wheel. UPSTREAM.md records the pinned upstream commit. Builds are reproducible from that snapshot; upstream is not fetched implicitly during releases.

Development

uv sync --frozen
./test.sh                # lint, format check and all tests
uvx hatch test          # alternative Hatch test environment
uv build                # sdist, then a native wheel built from that sdist

Building from source needs a C compiler (cc on Unix or MSVC cl on Windows). On Windows run from a Visual Studio developer shell. The Hatch wheel hook and scripts/compile_c.py share the same compiler implementation. Editable installs compile the library too. CC, CFLAGS, and LDFLAGS are honoured on Unix; MACOSX_DEPLOYMENT_TARGET defaults to 11.0 on macOS.

Releases

hatch-vcs derives package versions from stable vMAJOR.MINOR.PATCH tags. Untagged commits get a development version; source archives preserve their version without needing a Git checkout.

After committing your changes on main:

./publish.sh --check     # tests + local builds + metadata checks; no release
./publish.sh             # auto patch version, push, CI builds, uv publish
./publish.sh minor       # choose a minor or major bump when appropriate
./publish.sh --resume v1.3.14  # resume the same release after fixing an external failure

The release command uses uvx gitnextver to create and atomically push the tag and branch, waits for the Release workflow, downloads its exact artifacts, and checks their metadata. GitHub Actions builds and tests all five platform wheels, checks metadata, publishes with uv publish, and attaches the same files to the GitHub release. Re-running upload is safe for identical files. It never silently creates a new version when resuming a failed release.

Local prerequisites: uv, authenticated gh, and Git push access. GitHub runs uv publish and uses the repository secret PYPI_TOKEN; without it, configure a PyPI trusted publisher for release.yml. Token values must stay out of files and command arguments.

The CI workflow also tests Python 3.10 and 3.14 on Linux, macOS and Windows and builds the same five wheels on pull requests and manual runs.

License

AudioStretchy wrapper: BSD-3-Clause. Bundled TDHS source: David Bryant's BSD-style license in _vendor/audio-stretch/license.txt. Pedalboard is a separate dependency licensed under GPLv3; consult its license when distributing applications that use it.