output/pipewire: new output plugin

Very rough draft.  Barely works.

NEWS

@@ -3,6 +3,7 @@ ver 0.23 (not yet released)
   - new command "getvol"
   - show the audio format in "playlistinfo"
 * output
+  - pipewire: new plugin
   - snapcast: new plugin
 
 ver 0.22.7 (not yet released)

doc/plugins.rst

@@ -1054,6 +1054,21 @@ The pipe plugin starts a program and writes raw PCM data into its standard input
    * - **command CMD**
      - This command is invoked with the shell.
 
+pipewire
+--------
+
+Connect to a `PipeWire <https://pipewire.org/>``_ server.  Requires
+``libpipewire``.
+
+.. list-table::
+   :widths: 20 80
+   :header-rows: 1
+
+   * - Setting
+     - Description
+   * - **target ID**
+     - Link to the given target id.
+
 .. _pulse_plugin:
 
 pulse

meson.build

@@ -360,6 +360,7 @@ subdir('src/lib/gcrypt')
 subdir('src/lib/nfs')
 subdir('src/lib/oss')
 subdir('src/lib/pcre')
+subdir('src/lib/pipewire')
 subdir('src/lib/pulse')
 subdir('src/lib/sndio')
 subdir('src/lib/sqlite')

meson_options.txt

@@ -174,6 +174,7 @@ option('jack', type: 'feature', description: 'JACK output plugin')
 option('openal', type: 'feature', description: 'OpenAL output plugin')
 option('oss', type: 'feature', description: 'Open Sound System support')
 option('pipe', type: 'boolean', value: true, description: 'Pipe output plugin')
+option('pipewire', type: 'feature', description: 'PipeWire support')
 option('pulse', type: 'feature', description: 'PulseAudio support')
 option('recorder', type: 'boolean', value: true, description: 'Recorder output plugin')
 option('shout', type: 'feature', description: 'Shoutcast streaming support using libshout')

src/lib/pipewire/meson.build

@@ -0,0 +1,14 @@
+pipewire_dep = dependency('libpipewire-0.3', required: get_option('pipewire'))
+conf.set('ENABLE_PIPEWIRE', pipewire_dep.found())
+if not pipewire_dep.found()
+  subdir_done()
+endif
+
+pipewire_dep = declare_dependency(
+  dependencies: pipewire_dep,
+
+  # disabling -Wpedantic because libpipewire's headers are not
+  # compatible with C++; using the "#pragma" is not enough, we need to
+  # disable it at the command line
+  compile_args: ['-Wno-pedantic'],
+)

src/output/Registry.cxx

@@ -34,6 +34,7 @@
 #include "plugins/OssOutputPlugin.hxx"
 #include "plugins/OSXOutputPlugin.hxx"
 #include "plugins/PipeOutputPlugin.hxx"
+#include "plugins/PipeWireOutputPlugin.hxx"
 #include "plugins/PulseOutputPlugin.hxx"
 #include "plugins/RecorderOutputPlugin.hxx"
 #include "plugins/ShoutOutputPlugin.hxx"
@@ -85,6 +86,9 @@ constexpr const AudioOutputPlugin *audio_output_plugins[] = {
 #ifdef ENABLE_SOLARIS_OUTPUT
 	&solaris_output_plugin,
 #endif
+#ifdef ENABLE_PIPEWIRE
+	&pipewire_output_plugin,
+#endif
 #ifdef ENABLE_PULSE
 	&pulse_output_plugin,
 #endif

src/output/plugins/PipeWireOutputPlugin.cxx

@@ -0,0 +1,297 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "PipeWireOutputPlugin.hxx"
+//#include "lib/pipewire/MainLoop.hxx"
+#include "../OutputAPI.hxx"
+#include "../Error.hxx"
+#include "thread/Thread.hxx"
+
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+/* oh no, libspa likes to cast away "const"! */
+#pragma GCC diagnostic ignored "-Wcast-qual"
+/* suppress more annoying warnings */
+#pragma GCC diagnostic ignored "-Wmissing-field-initializers"
+#endif
+
+#include <pipewire/pipewire.h>
+#include <spa/param/audio/format-utils.h>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+#include <boost/lockfree/spsc_queue.hpp>
+
+#include <stdexcept>
+
+class PipeWireOutput final : AudioOutput {
+	Thread thread{BIND_THIS_METHOD(RunThread)};
+	struct pw_main_loop *loop;
+	struct pw_stream *stream;
+
+	std::byte buffer[1024];
+	struct spa_pod_builder pod_builder;
+
+	std::size_t frame_size;
+
+	boost::lockfree::spsc_queue<std::byte> *ring_buffer;
+
+	const uint32_t target_id;
+
+	volatile bool interrupted;
+
+	explicit PipeWireOutput(const ConfigBlock &block);
+
+public:
+	static AudioOutput *Create(EventLoop &,
+				   const ConfigBlock &block) {
+		pw_init(0, nullptr);
+
+		return new PipeWireOutput(block);
+	}
+
+	static constexpr struct pw_stream_events MakeStreamEvents() noexcept {
+		struct pw_stream_events events{};
+		events.version = PW_VERSION_STREAM_EVENTS;
+		events.process = Process;
+		return events;
+	}
+
+private:
+	void Process() noexcept;
+
+	static void Process(void *data) noexcept {
+		auto &o = *(PipeWireOutput *)data;
+		o.Process();
+	}
+
+	void RunThread() noexcept {
+		pw_main_loop_run(loop);
+	}
+
+	/* virtual methods from class AudioOutput */
+	void Enable() override;
+	void Disable() noexcept override;
+
+	void Open(AudioFormat &audio_format) override;
+	void Close() noexcept override;
+
+	void Interrupt() noexcept override {
+		interrupted = true;
+	}
+
+	size_t Play(const void *chunk, size_t size) override;
+
+	// TODO: void Drain() override;
+	// TODO: void Cancel() noexcept override;
+	// TODO: bool Pause() noexcept override;
+};
+
+static constexpr auto stream_events = PipeWireOutput::MakeStreamEvents();
+
+inline
+PipeWireOutput::PipeWireOutput(const ConfigBlock &block)
+	:AudioOutput(FLAG_ENABLE_DISABLE),
+	 target_id(block.GetBlockValue("target", unsigned(PW_ID_ANY)))
+{
+}
+
+void
+PipeWireOutput::Enable()
+{
+	loop = pw_main_loop_new(nullptr);
+	if (loop == nullptr)
+		throw std::runtime_error("pw_main_loop_new() failed");
+
+	try {
+		thread.Start();
+	} catch (...) {
+		pw_main_loop_destroy(loop);
+		throw;
+	}
+}
+
+void
+PipeWireOutput::Disable() noexcept
+{
+	pw_main_loop_quit(loop);
+	thread.Join();
+
+	pw_main_loop_destroy(loop);
+}
+
+static constexpr enum spa_audio_format
+ToPipeWireSampleFormat(SampleFormat format) noexcept
+{
+	switch (format) {
+	case SampleFormat::UNDEFINED:
+		break;
+
+	case SampleFormat::S8:
+		return SPA_AUDIO_FORMAT_S8;
+
+	case SampleFormat::S16:
+		return SPA_AUDIO_FORMAT_S16;
+
+	case SampleFormat::S24_P32:
+		return SPA_AUDIO_FORMAT_S24_32;
+
+	case SampleFormat::S32:
+		return SPA_AUDIO_FORMAT_S32;
+
+	case SampleFormat::FLOAT:
+		return SPA_AUDIO_FORMAT_F32;
+
+	case SampleFormat::DSD:
+		break;
+	}
+
+	return SPA_AUDIO_FORMAT_UNKNOWN;
+}
+
+static struct spa_audio_info_raw
+ToPipeWireAudioFormat(AudioFormat &audio_format) noexcept
+{
+	struct spa_audio_info_raw raw{};
+
+	raw.format = ToPipeWireSampleFormat(audio_format.format);
+	if (raw.format == SPA_AUDIO_FORMAT_UNKNOWN) {
+		raw.format = SPA_AUDIO_FORMAT_S16;
+		audio_format.format = SampleFormat::S16;
+	}
+
+	raw.flags = SPA_AUDIO_FLAG_NONE;
+	raw.rate = audio_format.sample_rate;
+	raw.channels = audio_format.channels;
+
+	raw.flags |= SPA_AUDIO_FLAG_UNPOSITIONED; // TODO
+	// TODO raw.position[]
+
+	return raw;
+}
+
+void
+PipeWireOutput::Open(AudioFormat &audio_format)
+{
+	auto props = pw_properties_new(PW_KEY_MEDIA_TYPE, "Audio",
+				       PW_KEY_MEDIA_CATEGORY, "Playback",
+				       PW_KEY_MEDIA_ROLE, "Music",
+				       PW_KEY_APP_NAME, "Music Player Daemon",
+				       PW_KEY_NODE_NAME, "mpd",
+				       nullptr);
+
+	stream = pw_stream_new_simple(pw_main_loop_get_loop(loop),
+				      "mpd",
+				      props,
+				      &stream_events,
+				      this);
+	if (stream == nullptr)
+		throw std::runtime_error("pw_stream_new_simple() failed");
+
+	auto raw = ToPipeWireAudioFormat(audio_format);
+
+	frame_size = audio_format.GetFrameSize();
+	interrupted = false;
+
+	/* allocate a ring buffer of 1 second */
+	ring_buffer = new boost::lockfree::spsc_queue<std::byte>(frame_size *
+								 audio_format.sample_rate);
+
+	const struct spa_pod *params[1];
+
+	pod_builder = {};
+	pod_builder.data = buffer;
+	pod_builder.size = sizeof(buffer);
+	params[0] = spa_format_audio_raw_build(&pod_builder,
+					       SPA_PARAM_EnumFormat, &raw);
+
+	pw_stream_connect(stream,
+			  PW_DIRECTION_OUTPUT,
+			  target_id,
+			  (enum pw_stream_flags)(PW_STREAM_FLAG_AUTOCONNECT |
+						 PW_STREAM_FLAG_MAP_BUFFERS |
+						 PW_STREAM_FLAG_RT_PROCESS),
+			  params, 1);
+}
+
+void
+PipeWireOutput::Close() noexcept
+{
+	pw_stream_destroy(stream);
+
+	// TODO synchronize with Process()?
+	delete ring_buffer;
+}
+
+inline void
+PipeWireOutput::Process() noexcept
+{
+	auto *b = pw_stream_dequeue_buffer(stream);
+	if (b == nullptr) {
+		pw_log_warn("out of buffers: %m");
+		return;
+	}
+
+	auto *buf = b->buffer;
+	std::byte *dest = (std::byte *)buf->datas[0].data;
+	if (dest == nullptr)
+		return;
+
+	const std::size_t max_frames = buf->datas[0].maxsize / frame_size;
+	const std::size_t max_size = max_frames * frame_size;
+
+	size_t nbytes = ring_buffer->pop(dest, max_size);
+	if (nbytes == 0) {
+		pw_stream_flush(stream, true);
+		return;
+	}
+
+	buf->datas[0].chunk->offset = 0;
+	buf->datas[0].chunk->stride = frame_size;
+	buf->datas[0].chunk->size = nbytes;
+
+	pw_stream_queue_buffer(stream, b);
+}
+
+size_t
+PipeWireOutput::Play(const void *chunk, size_t size)
+{
+	while (true) {
+		std::size_t bytes_written =
+			ring_buffer->push((const std::byte *)chunk, size);
+		if (bytes_written > 0)
+			return bytes_written;
+
+		if (interrupted)
+			throw AudioOutputInterrupted{};
+
+		usleep(1000); // TODO
+	}
+
+	return size;
+}
+
+const struct AudioOutputPlugin pipewire_output_plugin = {
+	"pipewire",
+	nullptr,
+	&PipeWireOutput::Create,
+	nullptr,
+};

src/output/plugins/PipeWireOutputPlugin.hxx

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2003-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_PIPEWIRE_OUTPUT_PLUGIN_HXX
+#define MPD_PIPEWIRE_OUTPUT_PLUGIN_HXX
+
+extern const struct AudioOutputPlugin pipewire_output_plugin;
+
+#endif

src/output/plugins/meson.build

@@ -85,6 +85,10 @@ if enable_pipe_output
   output_plugins_sources += 'PipeOutputPlugin.cxx'
 endif
 
+if pipewire_dep.found()
+  output_plugins_sources += 'PipeWireOutputPlugin.cxx'
+endif
+
 if pulse_dep.found()
   output_plugins_sources += 'PulseOutputPlugin.cxx'
 endif
@@ -169,6 +173,7 @@ output_plugins = static_library(
     apple_dep,
     libao_dep,
     libjack_dep,
+    pipewire_dep,
     pulse_dep,
     libshout_dep,
     libsndio_dep,