Get the recordings off your voice recorder, then find, mark and share your EVPs.
Free and open source. One installer, Windows 10 and 11.
A lot of us hunt with older digital voice recorders, because they're the ones known for catching EVPs. You probably know the problem. Great recorder, dead software: the program it came with won't run on a modern Windows PC, if it still exists at all. So I wrote this for my team. You plug the recorder in, OpenEVP pulls the recordings off, and you can go through them properly. 👻
Right now it talks to the Sony ICD-ST25 and ICD-ST10, with more recorders on the way. And whatever you record on, it opens WAV and MP3 files too.
No Sony software, and no old 32-bit computer kept around just to read the recorder. Install OpenEVP, plug in the recorder, tick the recordings and click Export. It only ever reads from the recorder, so nothing on it gets changed or deleted.
Every recording opens with its waveform and a spectrogram underneath. The spectrogram is a picture of the sound: time runs across, pitch goes up, and louder is brighter. A voice shows up as a stack of bright stripes, so you can often spot it even when it's buried in noise.
Found something faint? Loop it. Slow it down to a quarter of normal speed (or speed it up to 2×), with the voice kept at its normal pitch or dropped like a slowed-down tape.
The Enhance tab makes it louder, evens out the volume, keeps only the range voices sit in, and takes out rumble, hiss and electrical hum. It all happens live while you listen. There's also noise reduction that learns your room's background noise (fans, air conditioning, traffic) and turns it down.
None of this touches the recording. It only changes what you hear.
Drag across the waveform, press M, and pick a class: A if anyone would hear the words, B if most people would agree, C if it's faint. Write down what you hear. Marks save themselves.
Everything you've saved lands in the EVP Library, with a folder per investigation. You can see at a glance how many A, B and C EVPs each recording has, and filter down to "has EVPs" or "not reviewed yet" when you're working through a night's audio.
Each EVP can be saved as its own short clip, an MP3 for sharing or a full-quality WAV. Then drag it from the library straight into Discord, WhatsApp, an email or a folder. Or right-click it, pick Copy file, and paste it with Ctrl+V.
Dragging out a Sony .dvf file (which other programs can't play)? OpenEVP
sends a playable copy instead. Your original never moves.
Click Record live to record straight from a microphone or any other input on your PC. The waveform and spectrogram scroll by as it records, and pressing M marks the moment you heard something, so it's easy to find again. When you stop, the recording is in the EVP Library. If the PC crashes halfway through, what was recorded is still saved.
Got a recorder with no USB at all? Run a cable from its headphone jack to the PC's line-in, pick Import from a recorder, and play it. OpenEVP saves each recording on it as its own file.
- It opens WAV and MP3 files from anywhere on your PC, including voice notes and clips saved from WhatsApp Web.
- Right-click any recording to show it in File Explorer, rename it, or delete it. Deleted recordings go to the Recycle Bin, and if you restore one, its EVP marks come back with it.
- It updates itself. When there's a new version it tells you and installs it for you.
| Recorder | Works? |
|---|---|
| Sony ICD-ST25 | Yes |
| Sony ICD-ST10 | Yes, in all three of its recording modes (ST, SP and LP) |
| Panasonic RR-DR60 | Works, through Import. It has no PC connection, so plug its headphone output into the PC with a USB audio adapter, press Record in OpenEVP, and play it in. |
| Panasonic RR-QR80 | Works the same way. It also has no PC connection, so plug its headphone output into the PC with a USB audio adapter, press Record in OpenEVP, and play it in. |
Got a different recorder? Open an issue (that's GitHub's name for a request or bug report) and tell me which one.
- Download
OpenEVP-Setup-<version>.exeand run it. When Windows asks for permission, click Yes. The installer sets up everything, including the driver that lets the PC talk to the recorder. - Plug in your recorder and open OpenEVP from the Start menu. Click the
recorder on the left, tick the recordings you want and click Export.
They're saved to
Documents\OpenEVP. - Click a recording to play it. When you hear something, drag across that part of the waveform and press M to mark it.
That's enough to get through your first hunt. The user guide covers the rest.
Yes, with no trial and no account. It's open source under the GPL licence (see Licence), so anyone can read the code and check what it does.
Click More info, then Run anyway. Windows shows that warning the first time because the installer isn't code-signed, meaning it doesn't carry a paid certificate from a commercial company that tells Windows who made it. It isn't a sign that anything is wrong. The code is public, and every update is checked against the project's own signing key before it's installed.
No. OpenEVP only reads from your recorder, so nothing on it is changed or deleted. Saved files are never overwritten. Speed, Enhance and noise reduction only change what you hear, never the file. Your EVP marks are kept separately from the audio, so they're safe too.
The only time a file goes anywhere is when you delete it yourself. OpenEVP asks first, and it goes to the Recycle Bin.
Not yet, sorry Mac people. It needs 64-bit (x64) Windows 10, version 2004 or later, or Windows 11. It won't run on Windows in "S mode" (a locked-down mode that only allows apps from the Microsoft Store), and PCs with an ARM chip aren't supported yet. Not sure what you've got? Settings → System → About shows it under "System type".
To Documents\OpenEVP, with one subfolder per folder on the recorder. Click
the Save to path in the app to open it, or Change… to pick another
folder. Your EVP marks and settings are kept separately, in
%APPDATA%\OpenEVP (paste that into File Explorer's address bar to get
there).
When OpenEVP starts, it checks GitHub for a newer version. If there is one, it shows what's new and offers Update now or Not now. Update now downloads the installer, checks that it really comes from this project, asks Windows for permission and reopens OpenEVP on the new version. You can also click Check for updates at the top of the window any time.
See Troubleshooting in the user guide. It's usually fixed by one button or by unplugging the cable.
- User guide: every feature, step by step.
- Technical documentation: how OpenEVP talks to the recorders, why the ICD-ST25 needed it, the driver setup, the command-line tool and how to build it.
- Adding a recorder, for developers.
Try it after your next hunt, and if something breaks, tell me.
Copyright (C) 2026 Michael Barcelo. OpenEVP is free software under the
GNU General Public License v3.0 or later; see LICENSE.
OpenEVP is an independent project and is not affiliated with, endorsed by, or supported by Sony or Panasonic. "Sony", "ICD-ST25", "ICD-ST10" and "Digital Voice Editor" are trademarks of Sony Corporation. "Panasonic" and "RR-DR60" are trademarks of Panasonic Corporation.
To play and convert recordings made on Sony IC recorders, OpenEVP includes
numeric tables needed to read Sony's LPEC audio formats (LPEC LP, used by the
ICD-ST25 and ICD-ST10, and LPEC SP and LPEC ST, used by the ICD-ST10). They are
included only so owners can access their own recordings (interoperability).
Rights holders who object can open an issue at
https://github.com/MBarc/OpenEVP/issues and the tables will be removed
promptly. The tables ship inside the installer only, as three data files
(openevp/decoders/sony_lpec/data/lpec_tables.json for LPEC LP,
openevp/decoders/sony_lpec/data/lpec_sp_tables.json for LPEC SP and
openevp/decoders/sony_lpec_st/data/lpec_st_tables.json for LPEC ST); they are
not part of this repository.
OpenEVP is provided "as is", without warranty of any kind.
OpenEVP includes work by other people. Here is what it uses and under which licence:
- libusb:
vendor/libusb-1.0.30/libusb-1.0.dllis libusb 1.0.30 (MinGW64 build) from the official PGP-signed release (signed by Tormod Volden), licensed LGPL-2.1; seevendor/libusb-1.0.30/COPYING. The build script checks its SHA-256. - lameenc and LAME: MP3 clips are encoded with
lameenc (installed from PyPI,
requirements-app.txt), licensed LGPL-3.0-or-later, which includes the LAME MP3 encoder, licensed LGPL-2.0-or-later. The app bundles it as a separate extension module (_internal\lameenc.*.pyd), with its license in_internal\lameenc-*.dist-info. - minimp3: MP3 files are decoded with
minimp3, dedicated to the public domain
under CC0 1.0 Universal; see
vendor/minimp3/LICENSE.vendor/minimp3/minimp3.his commitea99364f61c14656440e8d77e9c233ccf3124633(2026-07-27), pinned by SHA-256 intools/build_lpec_core.py; it is compiled intoopenevp/decoders/mp3/mp3_core.dllwith OpenEVP's own wrapper (_mp3.c). On x86-64 minimp3 always takes its SSE2 code path, so the same file decodes to the same samples on every PC. - Chromium DynamicsCompressor: the Leveler (
openevp/leveler.py) is a port of Chromium's Web Audio DynamicsCompressor (third_party/blink/renderer/platform/audio/dynamics_compressor.cc, Copyright (C) 2011 Google Inc.), licensed BSD-3-Clause; the full notice is inLICENSES/chromium-dynamics-compressor.txt, which the app bundles (_internal\LICENSES\) and the release check verifies. - WebView2:
vendor/webview2/MicrosoftEdgeWebview2Setup.exeis Microsoft's Evergreen WebView2 bootstrapper (Authenticode-signed by Microsoft; the build checks its SHA-256). It is redistributable, and the installer runs it only when WebView2 is missing. - wavesurfer.js:
app/ui/vendor/wavesurfer.min.jsis wavesurfer.js (BSD-3-Clause).