Last updated: September 22, 2026
ZEEP is built with open-source software. This page lists the open-source third-party libraries shipped inside the App, their licenses, copyright holders, and where to obtain their source code. It also explains how ZEEP satisfies the obligations of the copyleft licenses (LGPL) used by some of these components. A few proprietary Google Play libraries are also shipped; they are not open source and are listed separately at the end of Section 3.
ZEEP uses LGPL-licensed libraries (FFmpeg via FFmpegKit, and SoundTouch) by dynamically linking to them as separate shared libraries inside the APK. You have the right to replace these shared libraries with your own modified builds. See Section 1 for details. Every other component on this page is under a permissive license (MIT, Apache 2.0, or similar).
The following libraries are licensed under the GNU Lesser General Public License (LGPL). ZEEP includes each as a
separate shared library (.so file) inside the APK and loads it at runtime via Android's
dynamic linker. You may replace these .so files with your own modified builds; the rest of the App will
continue to load and use the replacements, in keeping with the LGPL's re-linking provisions
(LGPL v3 §4(d)(1) for FFmpeg, LGPL v2.1 §6(d) for SoundTouch).
ZEEP uses the unmodified upstream releases of these libraries. If you would like the exact build flags used to produce the shared libraries shipped in the APK, please contact us at privacy@justzeep.com and we will provide them.
Used by ZEEP for audio decoding, encoding, format conversion, and filtering. All processing happens locally on your device.
Used by ZEEP for time-domain time-stretching and pitch-shifting via SoundTouch's WSOLA (Waveform Similarity OverLap-Add) implementation, surfaced in the editor as the “WSOLA” stretch algorithm.
Header-only library used by ZEEP for frequency-domain time-stretching and pitch-shifting via a phase-vocoder implementation, surfaced in the editor as the “Phase Vocoder” stretch algorithm. Distributed under the following terms:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: the above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND.
STFT/FFT support library used by Signalsmith Stretch. Distributed under the following terms:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: the above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND.
Deep-learning speech enhancement (library and bundled model weights) used by ZEEP's Denoise tool, shipped as the shared library
libdeep_filter.so inside the APK and run entirely on your device. Distributed under the following terms:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: the above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND.
libdeep_filter.so also contains the following Rust crates that DeepFilterNet depends on. All are permissively licensed
(MIT, Apache 2.0, BSD-2-Clause, Zlib, 0BSD, Unlicense, or CC0); copyright is held by the authors named in each crate's repository.
| Crate | License | Project |
|---|---|---|
| tract (core, hir, onnx, pulse, linalg, nnef, data) | MIT or Apache 2.0 | sonos/tract |
| ndarray | MIT or Apache 2.0 | rust-ndarray/ndarray |
| RustFFT | MIT or Apache 2.0 | ejmahler/RustFFT |
| realfft | MIT | HEnquist/realfft |
| rubato | MIT | HEnquist/rubato |
| prost | Apache 2.0 | tokio-rs/prost |
| flate2, tar, anyhow, thiserror, log, itertools, num-complex | MIT or Apache 2.0 | crates.io |
| rust-ini, educe, nom, bytes, libm | MIT | crates.io |
| Further transitive crates | MIT, Apache 2.0, BSD-2-Clause, Zlib, 0BSD, Unlicense, or CC0 | Full list with license texts available on request (Section 5) |
Used for the optional sign-in to a personal Microsoft account when you connect OneDrive folder sync, together with its Microsoft
Identity common component (MIT). Distributed under the following terms:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: the above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND.
ZEEP includes the following libraries, all distributed under the Apache License, Version 2.0. Copyright is held by the respective authors named in each project's source repository.
Used by ZEEP for pitch-period-aware time-stretching (the PICOLA algorithm — Pointer Interval Controlled OverLap-Add).
This is the same library Android's AudioTrack uses internally for speech speed adjustment; it is ZEEP's default
stretch backend and is optimised for speech and voice content.
The following additional libraries are also Apache 2.0:
| Library | Purpose | Project |
|---|---|---|
| Oboe | Low-latency audio I/O (native C++ bridge to AAudio / OpenSL ES) | google/oboe |
| AndroidX Media3 (ExoPlayer) | Audio playback | androidx/media |
| AndroidX Room | On-device database for project metadata | developer.android.com |
| AndroidX DataStore | On-device storage for user preferences | developer.android.com |
| AndroidX WorkManager | Background scheduling of OneDrive sync runs | developer.android.com |
| AndroidX Browser (Custom Tabs) | Opens the Microsoft sign-in page in a browser tab | developer.android.com |
| Jetpack Compose & Material 3 | UI toolkit (Compose UI, Material, Adaptive layouts, Navigation, Lifecycle, Activity, Splashscreen, Core KTX) | developer.android.com |
| OkHttp & Okio | HTTP client for Microsoft Graph / OneDrive transfers (© Square, Inc.) | square/okhttp · square/okio |
| Firebase Android SDK (Analytics, Crashlytics, Crashlytics NDK, App Check) | Opt-in usage analytics and crash reporting, plus verification of Pro access-code requests (© Google LLC). Depends on proprietary Google Play services components, see below | firebase/firebase-android-sdk |
| Yubico YubiKit for Android | Dependency of the Microsoft Authentication Library (Section 2) | Yubico/yubikit-android |
| Kotlin Standard Library | Language runtime | JetBrains/kotlin |
| kotlinx.coroutines & kotlinx.serialization | Asynchronous programming and JSON serialization | github.com/Kotlin |
| Dagger Hilt | Dependency injection | google/dagger |
| Gson | JSON parsing | google/gson |
For completeness: ZEEP also ships the Google Play Billing Library, the Google Play In-App Review and In-App Update libraries, and the Google Play services components that Firebase Analytics and Crashlytics rely on. These are provided by Google LLC under the Android Software Development Kit License and the Google Play services terms, are not open source, and carry no source-code or attribution obligations. What they do and what data they handle is described in Section 5 of our Privacy Policy.
The full text of each license referenced on this page is available at the canonical sources below:
libdeep_filter.so only)If you would prefer copies hosted directly by us rather than the canonical sources, please contact us and we will provide them.
For any of the libraries listed above — including the exact source archive, version metadata, or build flags used to produce the shared libraries shipped inside the APK — please contact us at privacy@justzeep.com. We are obligated to provide source code for LGPL components and are happy to do so for any other open-source component on request.
As ZEEP evolves, this list of third-party components may change. We will update this page whenever a library is added, removed, or upgraded to a version that materially affects its license or source location.
Company: ZOR.O Software s. r. o.
Address: Popradská 743/3G, Košice - Západ 040 11, Slovakia
Email: privacy@justzeep.com
App: ZEEP — Audio Editor
Package: com.zorosoftware.zeep