OpenA2DP

A minimal Windows-only Bluetooth A2DP control tool. Reconnect, reset, and (optionally) tune the codec settings of your Bluetooth audio devices.

Windows only. Built directly on Win32 Bluetooth APIs, MMDevice/WASAPI, and D3D11. Will not run under WINE and is not a candidate for cross-platform porting. On Linux, use BlueZ + PipeWire.

Download

Grab the latest release zip — contains OpenA2DP.exe (GUI) and OpenA2DP-cli.exe (headless CLI). No installer, fully portable, no VC++ Redistributable required.

Bleeding-edge builds: Actions tab → latest run → Artifacts → OpenA2DP-windows-x64.

Features

• Reconnect / Reset — the 99% workflow: fix a Bluetooth audio device that connected but isn't playing.
• Test Audio — one-click playback of a short Windows system sound (%WINDIR%\Media\tada.wav) through the default audio endpoint to confirm your Bluetooth device is actually receiving audio.
• Set as Default — one-click "make this BT device the system default audio endpoint for all roles (Console, Multimedia, Communications)". Uses the undocumented IPolicyConfig COM interface, same as SoundSwitch / EarTrumpet.
• Audio visualizer — live WASAPI-loopback driven, four modes (cycle by clicking anywhere on it): bars with peak-hold lines, scrolling spectrogram waterfall, oscilloscope, and CRT-style L/R vectorscope. Auto-recovers when the default audio endpoint changes (e.g. after a Reconnect).
• Opt-in tray notifications for auto-heal recovery, low battery (≤20%), HFP fallback (when Windows demotes a device to mono 8/16 kHz voice mode), and new GitHub releases. All gated by a master "Tray Notifications" checkbox in the top-right header. Default off.
• Auto-Heal — optional per-device watchdog for the Windows 11 connect-but-silent bug, with toast notifications.
• HFP Watchdog — optional periodic Handsfree-disable so Windows can't fall back to narrowband mono SCO.
• System tray — right-click menu for Reconnect / Disable HFP / Switch Stack / Show / Quit. Minimizes to tray.
• CLI mode — OpenA2DP-cli.exe for Task Scheduler / scripts.
• Approachable by default — first launch only shows the basics. The Advanced Mode checkbox in the top-right unlocks everything below.

Advanced Mode unlocks

• Live codec settings via Alternative A2DP Driver — read+write SBC/AAC parameters in the driver's per-device registry config (codec, sample rates, channel mode, block size, allocation, subbands, AAC bitrate, ABR). Bitpool slider clamped to the device's reported max with an admin-only override.
• A2DP stack control — start/stop A2DP services from the Windows SCM, or one-click switch the entire active stack (Microsoft ↔ AltA2DP). Needs admin. The "Use AltA2DP" button auto-disables (with a hint pointing at bluetoothgoodies.com) if the Alternative A2DP Driver isn't installed. When both stacks happen to be loaded simultaneously — common because Windows refuses to unload the BthA2dp kernel driver at runtime — the active-stack indicator correctly reports "Alternative A2DP Driver (Microsoft also loaded)" since AltA2DP's user-mode service intercepts WASAPI before BthA2dp can route audio.
• Status panel — sample rate, bit depth, channels, codec bitrate, audio latency, matched WASAPI endpoint, battery, and a Device Capabilities subsection from the driver's Capability\<addr> registry subtree.
• Bluetooth remote-event tracking — logs play/pause/next/prev/volume from your headphones via three observation surfaces (low-level keyboard hook, WASAPI default-endpoint volume polling, WinRT SMTC poller).
• Per-device manual service toggles for AudioSink and Handsfree.
• Connection history, activity counters, diagnostic log with severity filters and Copy-to-Clipboard.

See CHANGELOG.md for the full per-version inventory.

Usage

1. Pair your Bluetooth audio device in Windows Settings.
2. Run OpenA2DP.exe, select the device on the left.
3. Click Reconnect if audio is broken, or Reset to cycle all audio services.
4. Click Test Audio to play a short Windows sound and confirm playback is working.
5. Optionally enable Auto-Heal (Advanced Mode → Watchdogs).
6. Right-click the tray icon for quick actions without opening the window.
7. To switch A2DP stacks, run as Administrator and use the Use Microsoft / Use AltA2DP buttons in Advanced Mode.

CLI

OpenA2DP-cli.exe --reconnect AA:BB:CC:DD:EE:FF
OpenA2DP-cli.exe --list-devices
OpenA2DP-cli.exe --switch-stack ms      # needs admin
OpenA2DP-cli.exe --help

Full command list: --reconnect, --disable-hfp, --enable-a2dp, --list-devices, --list-stacks, --switch-stack, --start-service, --stop-service, --show-codec-config, --set-codec, --set-bitpool, --set-aac-bitrate, --probe-registry. Service-control commands need admin.

Building

Requires Visual Studio 2022+ with Desktop development with C++ + Windows SDK + Git.

git clone --recurse-submodules https://github.com/birdybro/OpenA2DP.git
cd OpenA2DP
scripts\build.bat

Outputs build\OpenA2DP.exe (GUI, /SUBSYSTEM:WINDOWS) and build\OpenA2DP-cli.exe (CLI, /SUBSYSTEM:CONSOLE).

To cut a release: bump OA2DP_VER_* in both scripts/version_*.rc, add a CHANGELOG entry, then git tag v0.X.Y && git push --tags. CI builds, zips, and attaches to a new GitHub Release automatically.

Tests: tests\build_and_test.bat.

See CLAUDE.md for architecture notes.

Known Limitations

• Codec detection on the Microsoft stack: Windows doesn't expose A2DP codec negotiation parameters in user mode, so without the Alternative A2DP Driver the status panel can only show what WASAPI measures.
• Battery: only shown if the device exposes DEVPKEY_Bluetooth_Battery to Windows. Many headphones don't.
• Service control needs admin. Start/Stop and Switch Stack are greyed out otherwise.
• Tested stacks: Microsoft stock and Alternative A2DP Driver. Other third-party stacks should work but aren't tested.

License

GPL-3.0. See LICENSE.

Credits

Application icon by Ramy W. on Flaticon.