Skip to main content

PipeWire Standalone-Client AAudio Sink POC

This branch adds a proof-of-concept backend for standalone-client PipeWire/AAudio playback: run PipeWire on the Android side, expose its native socket to the proot guest, and bridge playback with a separate standalone PipeWire client that registers an AAudio-backed Audio/Sink.

It is intentionally not a PipeWire/SPA plugin or PipeWire module. The runtime is a host-side PipeWire daemon plus a host-side AAudio sink client.

This is now the built-in Local Desktop audio path. The supervisor is disabled on Android below API 30 and otherwise starts when the native artifacts are bundled in the APK.

Runtime Shape​

guest PipeWire client
  -> /tmp/pipewire-0
  -> host PipeWire daemon in Android app context
  -> localdesktop-aaudio-sink client
  -> AAudio

The socket path is intentionally under the proot-visible /tmp, matching the Wayland strategy:

host path:  /data/data/app.polarbear/files/arch/tmp/pipewire-0
guest path: /tmp/pipewire-0

The default guest launch now exports:

PIPEWIRE_RUNTIME_DIR=/tmp
XDG_RUNTIME_DIR=/tmp

Android-Side Artifacts​

The branch includes prebuilt arm64-v8a PipeWire assets generated from Termux's pipewire package. assets/libs/arm64-v8a/PIPEWIRE_ASSETS_MANIFEST.txt records the package source and generated files.

Place these in assets/libs/arm64-v8a before building the APK:

  • libpipewire_exec.so: renamed pipewire executable.
  • liblocaldesktop_pipewire_aaudio_sink.so: built from src/bin/localdesktop_pipewire_aaudio_sink.rs.
  • PipeWire module .so files, for example libpipewire-module-protocol-native.so.
  • SPA plugin .so files, for example libspa-support.so and libspa-audioconvert.so.

Keep the module and plugin files flat in assets/libs/arm64-v8a. The current APK packagers extract top-level .so files from that directory into Android nativeLibraryDir.

Optional:

  • libwireplumber_exec.so: renamed wireplumber executable. Without it, the generated config tries libpipewire-module-session-manager with nofail.

The supervisor also points PipeWire at Android nativeLibraryDir through both PIPEWIRE_MODULE_DIR and SPA_PLUGIN_DIR.

Building the Sink​

The sink is a normal Cargo binary, but it links libpipewire-0.3, so it sits behind the pipewire-sink feature and is excluded from the default APK build. Point PIPEWIRE_PREFIX at an Android/Termux sysroot that has libpipewire-0.3 plus the PipeWire and SPA headers, then run:

ANDROID_NDK_HOME=... PIPEWIRE_PREFIX=... ./scripts/build-pipewire-aaudio-sink.sh

The script cross-compiles for aarch64-linux-android (API 30 by default, to match the bundled Termux PipeWire) and writes:

assets/libs/arm64-v8a/liblocaldesktop_pipewire_aaudio_sink.so

The filename uses .so because Android reliably extracts native libraries from the APK. It is still an executable, following the existing libproot.so packaging pattern.

The ring buffer and argument parsing compile on any host, so they can be tested without an Android sysroot:

cargo test --features pipewire-sink --bin localdesktop_pipewire_aaudio_sink

Guest Smoke Test​

Once the APK includes the PipeWire daemon, modules, SPA plugins, and sink:

export XDG_RUNTIME_DIR=/tmp
export PIPEWIRE_RUNTIME_DIR=/tmp
pw-cli info 0
pw-play /path/to/test.wav

If policy auto-linking is not active, inspect and link manually:

pw-link -o
pw-link -i
pw-link <playback-output-port> localdesktop-aaudio-sink:input_FL
pw-link <playback-output-port> localdesktop-aaudio-sink:input_FR

Current Limits​

  • Playback only.
  • F32 interleaved output only.
  • Fixed default request of 48 kHz stereo.
  • No Android audio focus handling yet.
  • No capture/microphone path.
  • Policy is experimental; use WirePlumber if available, otherwise manual pw-link may be needed.
  • The POC starts PipeWire as Android app child processes. On Android 12+ test devices and AVDs, disable phantom-process trimming while testing: adb shell settings put global settings_enable_monitor_phantom_procs false and adb shell device_config put activity_manager max_phantom_processes 2147483647.
  • The setup path writes a guest pacman IgnorePkg hold for the PipeWire package family (libpipewire, pipewire, pipewire-audio, pipewire-alsa, pipewire-jack, pipewire-pulse, pipewire-v4l2, pipewire-zeroconf, gst-plugin-pipewire, and wireplumber). This holds an installed compatible guest PipeWire version; it does not downgrade an already newer guest install.

This is meant to prove the architecture and timing path, not to become the final audio backend as-is.