WasapiOutputPlugin.cxx

/*
 * Copyright 2020-2021 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.
 */

#undef NOUSER // COM needs the "MSG" typedef

#include "WasapiOutputPlugin.hxx"
#include "ForMixer.hxx"
#include "AudioClient.hxx"
#include "Device.hxx"
#include "PropertyStore.hxx"
#include "output/OutputAPI.hxx"
#include "lib/icu/Win32.hxx"
#include "lib/fmt/AudioFormatFormatter.hxx"
#include "mixer/MixerList.hxx"
#include "output/Error.hxx"
#include "pcm/Export.hxx"
#include "thread/Cond.hxx"
#include "thread/Mutex.hxx"
#include "thread/Name.hxx"
#include "thread/Thread.hxx"
#include "util/AllocatedString.hxx"
#include "util/ConstBuffer.hxx"
#include "util/Domain.hxx"
#include "util/RuntimeError.hxx"
#include "util/ScopeExit.hxx"
#include "util/StringBuffer.hxx"
#include "win32/Com.hxx"
#include "win32/ComPtr.hxx"
#include "win32/ComWorker.hxx"
#include "win32/HResult.hxx"
#include "win32/WinEvent.hxx"
#include "Log.hxx"
#include "config.h"

#include <boost/lockfree/spsc_queue.hpp>

#include <algorithm>
#include <cinttypes>
#include <cmath>
#include <optional>
#include <variant>

#include <audioclient.h>
#include <initguid.h>
#include <functiondiscoverykeys_devpkey.h>
#include <mmdeviceapi.h>

namespace {
static constexpr Domain wasapi_output_domain("wasapi_output");

constexpr uint32_t
GetChannelMask(const uint8_t channels) noexcept
{
	switch (channels) {
	case 1:
		return KSAUDIO_SPEAKER_MONO;
	case 2:
		return KSAUDIO_SPEAKER_STEREO;
	case 3:
		return SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT | SPEAKER_FRONT_CENTER;
	case 4:
		return KSAUDIO_SPEAKER_QUAD;
	case 5:
		return SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT | SPEAKER_FRONT_CENTER |
		       SPEAKER_BACK_LEFT | SPEAKER_BACK_RIGHT;
	case 6:
		return KSAUDIO_SPEAKER_5POINT1;
	case 7:
		return KSAUDIO_SPEAKER_5POINT1 | SPEAKER_BACK_CENTER;
	case 8:
		return KSAUDIO_SPEAKER_7POINT1_SURROUND;
	default:
		gcc_unreachable();
	}
}

template <typename Functor>
inline bool
SafeSilenceTry(Functor &&functor) noexcept
{
	try {
		functor();
		return true;
	} catch (...) {
		return false;
	}
}

std::vector<WAVEFORMATEXTENSIBLE>
GetFormats(const AudioFormat &audio_format) noexcept
{
#ifdef ENABLE_DSD
	if (audio_format.format == SampleFormat::DSD) {
		AudioFormat dop_format = audio_format;
		PcmExport::Params params;
		params.dsd_mode = PcmExport::DsdMode::DOP;
		dop_format.sample_rate =
			params.CalcOutputSampleRate(audio_format.sample_rate);
		dop_format.format = SampleFormat::S24_P32;
		return GetFormats(dop_format);
	}
#endif
	std::vector<WAVEFORMATEXTENSIBLE> Result;
	if (audio_format.format == SampleFormat::S24_P32) {
		Result.resize(2);
		Result[0].Format.wBitsPerSample = 24;
		Result[0].Samples.wValidBitsPerSample = 24;
		Result[1].Format.wBitsPerSample = 32;
		Result[1].Samples.wValidBitsPerSample = 24;
	} else {
		Result.resize(1);
		Result[0].Format.wBitsPerSample = audio_format.GetSampleSize() * 8;
		Result[0].Samples.wValidBitsPerSample = audio_format.GetSampleSize() * 8;
	}
	const DWORD mask = GetChannelMask(audio_format.channels);
	const GUID guid = audio_format.format == SampleFormat::FLOAT
				  ? KSDATAFORMAT_SUBTYPE_IEEE_FLOAT
				  : KSDATAFORMAT_SUBTYPE_PCM;
	for (auto &device_format : Result) {
		device_format.dwChannelMask = mask;
		device_format.Format.wFormatTag = WAVE_FORMAT_EXTENSIBLE;
		device_format.Format.nChannels = audio_format.channels;
		device_format.Format.nSamplesPerSec = audio_format.sample_rate;
		device_format.Format.cbSize =
			sizeof(WAVEFORMATEXTENSIBLE) - sizeof(WAVEFORMATEX);
		device_format.SubFormat = guid;
		device_format.Format.nBlockAlign = device_format.Format.nChannels *
						   device_format.Format.wBitsPerSample /
						   8;
		device_format.Format.nAvgBytesPerSec =
			audio_format.sample_rate * device_format.Format.nBlockAlign;
	}
	return Result;
}

#ifdef ENABLE_DSD
void
SetDSDFallback(AudioFormat &audio_format) noexcept
{
	audio_format.format = SampleFormat::FLOAT;
	audio_format.sample_rate = 384000;
}
#endif

} // namespace

class WasapiOutputThread {
	Thread thread{BIND_THIS_METHOD(Work)};
	WinEvent event;
	WinEvent data_poped;
	IAudioClient &client;
	ComPtr<IAudioRenderClient> render_client;
	const UINT32 frame_size;
	const UINT32 buffer_size_in_frames;
	const bool is_exclusive;

	/**
	 * This flag is only used by the calling thread
	 * (i.e. #OutputThread), and specifies whether the
	 * WasapiOutputThread has been told to play via Play().  This
	 * variable is somewhat redundant because we already have
	 * "state", but using this variable saves some overhead for
	 * atomic operations.
	 */
	bool playing = false;

	bool started = false;

	std::atomic_bool cancel = false;

	std::atomic_bool empty = true;

	enum class Status : uint32_t { FINISH, PLAY, PAUSE };

	alignas(BOOST_LOCKFREE_CACHELINE_BYTES) std::atomic<Status> status =
		Status::PAUSE;
	alignas(BOOST_LOCKFREE_CACHELINE_BYTES) struct {
		std::atomic_bool occur = false;
		std::exception_ptr ptr = nullptr;
	} error;
	boost::lockfree::spsc_queue<BYTE> spsc_buffer;

public:
	WasapiOutputThread(IAudioClient &_client,
			   ComPtr<IAudioRenderClient> &&_render_client,
			   const UINT32 _frame_size, const UINT32 _buffer_size_in_frames,
			   bool _is_exclusive)
		:client(_client),
		 render_client(std::move(_render_client)), frame_size(_frame_size),
		 buffer_size_in_frames(_buffer_size_in_frames), is_exclusive(_is_exclusive),
		 spsc_buffer(_buffer_size_in_frames * 4 * _frame_size)
	{
		SetEventHandle(client, event.handle());
		thread.Start();
	}

	void Finish() noexcept {
		SetStatus(Status::FINISH);
		thread.Join();
	}

	void Play() noexcept {
		playing = true;
		SetStatus(Status::PLAY);
	}

	void Pause() noexcept {
		if (!playing)
			return;

		playing = false;
		SetStatus(Status::PAUSE);
	}

	std::size_t Push(ConstBuffer<void> input) noexcept {
		empty.store(false);

		std::size_t consumed =
			spsc_buffer.push(static_cast<const BYTE *>(input.data),
					 input.size);

		if (!playing) {
			playing = true;
			Play();
		}

		return consumed;
	}

	/**
	 * Check if the buffer is empty, and if not, wait a bit.
	 *
	 * Throws on error.
	 *
	 * @return true if the buffer is now empty
	 */
	bool Drain() {
		if (empty)
			return true;

		CheckException();
		Wait();
		CheckException();

		return empty;
	}

	/**
	 * Instruct the thread to discard the buffer (and wait for
	 * completion).  This needs to be done inside this thread,
	 * because only the consumer thread is allowed to do that.
	 */
	void Cancel() noexcept {
		cancel.store(true);
		event.Set();

		while (cancel.load() && !error.occur.load())
			Wait();

		/* not rethrowing the exception here via
		   CheckException() because this method must be
		   "noexcept"; the next WasapiOutput::Play() call will
		   throw */
	}

	/**
	 * Wait for the thread to finish some work (e.g. until some
	 * buffer space becomes available).
	 */
	void Wait() noexcept {
		data_poped.Wait();
	}

	void InterruptWaiter() noexcept {
		data_poped.Set();
	}

	void CheckException() {
		if (error.occur.load()) {
			std::rethrow_exception(error.ptr);
		}
	}

private:
	void SetStatus(Status s) noexcept {
		status.store(s);
		event.Set();
	}
	void Work() noexcept;
};

class WasapiOutput final : public AudioOutput {
	const bool is_exclusive;
	const bool enumerate_devices;
#ifdef ENABLE_DSD
	const bool dop_setting;
#endif

	/**
	 * Only valid if the output is open.
	 */
	bool paused;

	std::atomic_flag not_interrupted = true;

	const std::string device_config;

	std::shared_ptr<COMWorker> com_worker;
	ComPtr<IMMDevice> device;
	ComPtr<IAudioClient> client;
	WAVEFORMATEXTENSIBLE device_format;
	std::optional<WasapiOutputThread> thread;
	std::size_t watermark;
	std::optional<PcmExport> pcm_export;

public:
	static AudioOutput *Create(EventLoop &, const ConfigBlock &block);
	WasapiOutput(const ConfigBlock &block);

	auto GetComWorker() noexcept {
		// TODO: protect access to the shard_ptr
		return com_worker;
	}

	void Enable() override {
		com_worker = std::make_shared<COMWorker>();

		try {
			com_worker->Async([&]() { ChooseDevice(); }).get();
		} catch (...) {
			com_worker.reset();
			throw;
		}
	}
	void Disable() noexcept override {
		com_worker->Async([&]() { DoDisable(); }).get();
		com_worker.reset();
	}
	void Open(AudioFormat &audio_format) override {
		com_worker->Async([&]() { DoOpen(audio_format); }).get();
		paused = false;
	}
	void Close() noexcept override;
	std::chrono::steady_clock::duration Delay() const noexcept override;
	size_t Play(const void *chunk, size_t size) override;
	void Drain() override;
	void Cancel() noexcept override;
	bool Pause() override;
	void Interrupt() noexcept override;

	constexpr bool Exclusive() const { return is_exclusive; }
	constexpr size_t FrameSize() const { return device_format.Format.nBlockAlign; }
	constexpr size_t SampleRate() const {
		return device_format.Format.nSamplesPerSec;
	}

private:
	friend bool wasapi_is_exclusive(WasapiOutput &output) noexcept;
	friend IMMDevice *wasapi_output_get_device(WasapiOutput &output) noexcept;
	friend IAudioClient *wasapi_output_get_client(WasapiOutput &output) noexcept;

	void DoDisable() noexcept;
	void DoOpen(AudioFormat &audio_format);

	void ChooseDevice();
	bool TryFormatExclusive(const AudioFormat &audio_format);
	void FindExclusiveFormatSupported(AudioFormat &audio_format);
	void FindSharedFormatSupported(AudioFormat &audio_format);
	static void EnumerateDevices(IMMDeviceEnumerator &enumerator);
	static ComPtr<IMMDevice> GetDevice(IMMDeviceEnumerator &enumerator,
					   unsigned index);
	static ComPtr<IMMDevice> SearchDevice(IMMDeviceEnumerator &enumerator,
					      std::string_view name);
};

WasapiOutput &
wasapi_output_downcast(AudioOutput &output) noexcept
{
	return static_cast<WasapiOutput &>(output);
}

bool
wasapi_is_exclusive(WasapiOutput &output) noexcept
{
	return output.is_exclusive;
}

std::shared_ptr<COMWorker>
wasapi_output_get_com_worker(WasapiOutput &output) noexcept
{
	return output.GetComWorker();
}

IMMDevice *
wasapi_output_get_device(WasapiOutput &output) noexcept
{
	return output.device.get();
}

IAudioClient *
wasapi_output_get_client(WasapiOutput &output) noexcept
{
	return output.client.get();
}

inline void
WasapiOutputThread::Work() noexcept
try {
	SetThreadName("Wasapi Output Worker");
	LogDebug(wasapi_output_domain, "Working thread started");
	COM com;

	AtScopeExit(this) {
		if (started) {
			try {
				Stop(client);
			} catch (...) {
				LogError(std::current_exception());
			}
		}
	};

	while (true) {
		event.Wait();

		if (cancel.load()) {
			spsc_buffer.consume_all([](auto &&) {});
			cancel.store(false);
			empty.store(true);
			InterruptWaiter();
		}

		Status current_state = status.load();
		switch (current_state) {
		case Status::FINISH:
			LogDebug(wasapi_output_domain,
				 "Working thread stopped");
			return;

		case Status::PAUSE:
			if (!started)
				/* don't bother starting the
				   IAudioClient if we're paused */
				continue;

			/* stop the IAudioClient while paused; it will
			   be restarted as soon as we're asked to
			   resume playback */
			Stop(client);
			started = false;
			continue;

		case Status::PLAY:
			break;
		}

		UINT32 write_in_frames = buffer_size_in_frames;
		if (!is_exclusive) {
			UINT32 data_in_frames =
				GetCurrentPaddingFrames(client);
			if (data_in_frames >= buffer_size_in_frames) {
				continue;
			}
			write_in_frames -= data_in_frames;
		}

		BYTE *data;
		DWORD mode = 0;

		if (HRESULT result =
		    render_client->GetBuffer(write_in_frames, &data);
		    FAILED(result)) {
			throw MakeHResultError(result, "Failed to get buffer");
		}

		AtScopeExit(&) {
			render_client->ReleaseBuffer(write_in_frames, mode);

			if (!started) {
				Start(client);
				started = true;
			}
		};

		const UINT32 write_size = write_in_frames * frame_size;
		UINT32 new_data_size = 0;
		new_data_size = spsc_buffer.pop(data, write_size);
		if (new_data_size == 0)
			empty.store(true);

		std::fill_n(data + new_data_size,
			    write_size - new_data_size, 0);
		InterruptWaiter();
	}
} catch (...) {
	error.ptr = std::current_exception();
	error.occur.store(true);

	/* wake up the client thread which may be inside Wait() */
	InterruptWaiter();
}

AudioOutput *
WasapiOutput::Create(EventLoop &, const ConfigBlock &block)
{
	return new WasapiOutput(block);
}

WasapiOutput::WasapiOutput(const ConfigBlock &block)
	:AudioOutput(FLAG_ENABLE_DISABLE | FLAG_PAUSE),
	 is_exclusive(block.GetBlockValue("exclusive", false)),
	 enumerate_devices(block.GetBlockValue("enumerate", false)),
#ifdef ENABLE_DSD
	 dop_setting(block.GetBlockValue("dop", false)),
#endif
	 device_config(block.GetBlockValue("device", ""))
{
}

/// run inside COMWorkerThread
void
WasapiOutput::DoDisable() noexcept
{
	assert(!thread);

	device.reset();
}

/// run inside COMWorkerThread
void
WasapiOutput::DoOpen(AudioFormat &audio_format)
{
	client.reset();

	if (GetState(*device) != DEVICE_STATE_ACTIVE) {
		device.reset();
		ChooseDevice();
	}

	client = Activate<IAudioClient>(*device);

	if (audio_format.channels > 8) {
		audio_format.channels = 8;
	}

#ifdef ENABLE_DSD
	if (!dop_setting && audio_format.format == SampleFormat::DSD) {
		SetDSDFallback(audio_format);
	}
#endif
	if (Exclusive()) {
		FindExclusiveFormatSupported(audio_format);
	} else {
		FindSharedFormatSupported(audio_format);
	}
	bool require_export = audio_format.format == SampleFormat::S24_P32;
#ifdef ENABLE_DSD
	require_export |= audio_format.format == SampleFormat::DSD;
#endif
	if (require_export) {
		PcmExport::Params params;
#ifdef ENABLE_DSD
		params.dsd_mode = PcmExport::DsdMode::NONE;
		if (audio_format.format == SampleFormat::DSD) {
			params.dsd_mode = PcmExport::DsdMode::DOP;
		}
#endif
		params.shift8 = false;
		params.pack24 = false;
		if (device_format.Format.wBitsPerSample == 32 &&
		    device_format.Samples.wValidBitsPerSample == 24) {
			params.shift8 = true;
		}
		if (device_format.Format.wBitsPerSample == 24) {
			params.pack24 = true;
		}
		FmtDebug(wasapi_output_domain, "Packing data: shift8={} pack24={}",
			 params.shift8, params.pack24);
		pcm_export.emplace();
		pcm_export->Open(audio_format.format, audio_format.channels, params);
	}

	using s = std::chrono::seconds;
	using ms = std::chrono::milliseconds;
	using ns = std::chrono::nanoseconds;
	using hundred_ns = std::chrono::duration<uint64_t, std::ratio<1, 10000000>>;

	// The unit in REFERENCE_TIME is hundred nanoseconds
	REFERENCE_TIME default_device_period, min_device_period;

	if (HRESULT result =
		    client->GetDevicePeriod(&default_device_period, &min_device_period);
	    FAILED(result)) {
		throw MakeHResultError(result, "Unable to get device period");
	}
	FmtDebug(wasapi_output_domain,
		 "Default device period: {} ns, Minimum device period: "
		 "{} ns",
		 ns(hundred_ns(default_device_period)).count(),
		 ns(hundred_ns(min_device_period)).count());

	REFERENCE_TIME buffer_duration;
	if (Exclusive()) {
		buffer_duration = default_device_period;
	} else {
		const REFERENCE_TIME align = hundred_ns(ms(50)).count();
		buffer_duration = (align / default_device_period) * default_device_period;
	}
	FmtDebug(wasapi_output_domain, "Buffer duration: {} ns",
		 ns(hundred_ns(buffer_duration)).count());

	if (Exclusive()) {
		if (HRESULT result = client->Initialize(
			    AUDCLNT_SHAREMODE_EXCLUSIVE,
			    AUDCLNT_STREAMFLAGS_EVENTCALLBACK, buffer_duration,
			    buffer_duration,
			    reinterpret_cast<WAVEFORMATEX *>(&device_format), nullptr);
		    FAILED(result)) {
			if (result == AUDCLNT_E_BUFFER_SIZE_NOT_ALIGNED) {
				// https://docs.microsoft.com/en-us/windows/win32/api/audioclient/nf-audioclient-iaudioclient-initialize
				UINT32 buffer_size_in_frames =
					GetBufferSizeInFrames(*client);
				buffer_duration =
					std::ceil(double(buffer_size_in_frames *
							 hundred_ns(s(1)).count()) /
						  SampleRate());
				FmtDebug(wasapi_output_domain,
					 "Aligned buffer duration: {} ns",
					 ns(hundred_ns(buffer_duration)).count());
				client.reset();
				client = Activate<IAudioClient>(*device);
				result = client->Initialize(
					AUDCLNT_SHAREMODE_EXCLUSIVE,
					AUDCLNT_STREAMFLAGS_EVENTCALLBACK,
					buffer_duration, buffer_duration,
					reinterpret_cast<WAVEFORMATEX *>(&device_format),
					nullptr);
			}

			if (FAILED(result)) {
				throw MakeHResultError(result, "Unable to initialize audio client");
			}
		}
	} else {
		if (HRESULT result = client->Initialize(
			    AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_EVENTCALLBACK,
			    buffer_duration, 0,
			    reinterpret_cast<WAVEFORMATEX *>(&device_format), nullptr);
		    FAILED(result)) {
			throw MakeHResultError(result,
					       "Unable to initialize audio client");
		}
	}

	auto render_client = GetService<IAudioRenderClient>(*client);

	const UINT32 buffer_size_in_frames = GetBufferSizeInFrames(*client);

	watermark = buffer_size_in_frames * 3 * FrameSize();
	thread.emplace(*client, std::move(render_client), FrameSize(),
		       buffer_size_in_frames, is_exclusive);

	paused = false;
}

void
WasapiOutput::Close() noexcept
{
	assert(thread);

	try {
		thread->CheckException();
	} catch (...) {
		LogError(wasapi_output_domain, "exception while stopping");
	}
	thread->Finish();
	com_worker->Async([&]() {
		thread.reset();
		client.reset();
	}).get();
	pcm_export.reset();
}

std::chrono::steady_clock::duration
WasapiOutput::Delay() const noexcept
{
	if (paused) {
		// idle while paused
		return std::chrono::seconds(1);
	}

	return std::chrono::steady_clock::duration::zero();
}

size_t
WasapiOutput::Play(const void *chunk, size_t size)
{
	assert(thread);

	paused = false;

	not_interrupted.test_and_set();

	ConstBuffer<void> input(chunk, size);
	if (pcm_export) {
		input = pcm_export->Export(input);
	}
	if (input.empty())
		return size;

	do {
		const size_t consumed_size = thread->Push({input.data, input.size});

		if (consumed_size == 0) {
			thread->Wait();
			thread->CheckException();
			if (!not_interrupted.test_and_set()) {
				throw AudioOutputInterrupted{};
			}
			continue;
		}

		thread->CheckException();

		if (pcm_export) {
			return pcm_export->CalcInputSize(consumed_size);
		}
		return consumed_size;
	} while (true);
}

bool
WasapiOutput::Pause()
{
	paused = true;
	thread->Pause();
	thread->CheckException();
	return true;
}

void
WasapiOutput::Interrupt() noexcept
{
	if (thread) {
		not_interrupted.clear();
		thread->InterruptWaiter();
	}
}

void
WasapiOutput::Drain()
{
	assert(thread);

	not_interrupted.test_and_set();

	while (!thread->Drain()) {
		if (!not_interrupted.test_and_set())
			throw AudioOutputInterrupted{};
	}

	/* TODO: this needs to wait until the hardware has really
	   finished playing */
}

void
WasapiOutput::Cancel() noexcept
{
	assert(thread);

	thread->Cancel();
}

/// run inside COMWorkerThread
void
WasapiOutput::ChooseDevice()
{
	ComPtr<IMMDeviceEnumerator> enumerator;
	enumerator.CoCreateInstance(__uuidof(MMDeviceEnumerator), nullptr,
				    CLSCTX_INPROC_SERVER);

	if (enumerate_devices) {
		try {
			EnumerateDevices(*enumerator);
		} catch (...) {
			LogError(std::current_exception());
		}
	}

	if (!device_config.empty()) {
		unsigned int id;
		if (!SafeSilenceTry([this, &id]() { id = std::stoul(device_config); })) {
			device = SearchDevice(*enumerator, device_config);
			if (!device)
				throw FormatRuntimeError("Device '%s' not found",
							 device_config.c_str());
		} else
			device = GetDevice(*enumerator, id);
	} else {
		device = GetDefaultAudioEndpoint(*enumerator);
	}
}

/// run inside COMWorkerThread
bool
WasapiOutput::TryFormatExclusive(const AudioFormat &audio_format)
{
	for (auto test_format : GetFormats(audio_format)) {
		HRESULT result = client->IsFormatSupported(
			AUDCLNT_SHAREMODE_EXCLUSIVE,
			reinterpret_cast<WAVEFORMATEX *>(&test_format), nullptr);
		const auto result_string = std::string(HRESULTToString(result));
		FmtDebug(wasapi_output_domain, "Trying {} {} {}-{} (exclusive) -> {}",
			 audio_format, test_format.Format.nSamplesPerSec,
			 test_format.Format.wBitsPerSample,
			 test_format.Samples.wValidBitsPerSample,
			 result_string);
		if (SUCCEEDED(result)) {
			device_format = test_format;
			return true;
		}

		if (result == AUDCLNT_E_EXCLUSIVE_MODE_NOT_ALLOWED)
			throw std::runtime_error("Exclusive mode not allowed");
	}
	return false;
}

/// run inside COMWorkerThread
void
WasapiOutput::FindExclusiveFormatSupported(AudioFormat &audio_format)
{
	for (uint8_t channels : {0, 2, 6, 8, 7, 1, 4, 5, 3}) {
		if (audio_format.channels == channels) {
			continue;
		}
		if (channels == 0) {
			channels = audio_format.channels;
		}
		auto old_channels = std::exchange(audio_format.channels, channels);
#ifdef ENABLE_DSD
		bool was_dsd = false;
		if (audio_format.format == SampleFormat::DSD) {
			if (dop_setting && TryFormatExclusive(audio_format)) {
				return;
			}
			was_dsd = true;
			SetDSDFallback(audio_format);
		}
#endif
		for (uint32_t rate : {0, 384000, 352800, 192000, 176400, 96000, 88200,
				      48000, 44100, 32000, 22050, 16000, 11025, 8000}) {
			if (audio_format.sample_rate <= rate) {
				continue;
			}
			if (rate == 0) {
				rate = audio_format.sample_rate;
			}
			auto old_rate = std::exchange(audio_format.sample_rate, rate);
			for (SampleFormat format : {
				     SampleFormat::UNDEFINED,
				     SampleFormat::S32,
				     SampleFormat::S24_P32,
				     SampleFormat::S16,
				     SampleFormat::S8,
			     }) {
				if (audio_format.format == format) {
					continue;
				}
				if (format == SampleFormat::UNDEFINED) {
					format = audio_format.format;
				}
				auto old_format =
					std::exchange(audio_format.format, format);
				if (TryFormatExclusive(audio_format)) {
					return;
				}
				audio_format.format = old_format;
			}
			audio_format.sample_rate = old_rate;
		}
#ifdef ENABLE_DSD
		if (was_dsd) {
			audio_format.format = SampleFormat::DSD;
		}
#endif
		audio_format.channels = old_channels;
	}
}

/// run inside COMWorkerThread
void
WasapiOutput::FindSharedFormatSupported(AudioFormat &audio_format)
{
	HRESULT result;

	// In shared mode, different sample rate is always unsupported.
	auto mixer_format = GetMixFormat(*client);

	audio_format.sample_rate = mixer_format->nSamplesPerSec;
	device_format = GetFormats(audio_format).front();

	ComHeapPtr<WAVEFORMATEXTENSIBLE> closest_format;
	result = client->IsFormatSupported(
		AUDCLNT_SHAREMODE_SHARED,
		reinterpret_cast<WAVEFORMATEX *>(&device_format),
		closest_format.AddressCast<WAVEFORMATEX>());
	{
		const auto result_string = std::string(HRESULTToString(result));
		FmtDebug(wasapi_output_domain, "Trying {} {} {}-{} (shared) -> {}",
			 audio_format, device_format.Format.nSamplesPerSec,
			 device_format.Format.wBitsPerSample,
			 device_format.Samples.wValidBitsPerSample,
			 result_string);
	}

	if (FAILED(result) && result != AUDCLNT_E_UNSUPPORTED_FORMAT) {
		throw MakeHResultError(result, "IsFormatSupported failed");
	}

	switch (result) {
	case S_OK:
		break;
	case AUDCLNT_E_UNSUPPORTED_FORMAT:
	default:
		// Trying channels fallback.
		audio_format.channels = mixer_format->nChannels;

		device_format = GetFormats(audio_format).front();

		result = client->IsFormatSupported(
			AUDCLNT_SHAREMODE_SHARED,
			reinterpret_cast<WAVEFORMATEX *>(&device_format),
			closest_format.AddressCast<WAVEFORMATEX>());
		{
			const auto result_string = std::string(HRESULTToString(result));
			FmtDebug(wasapi_output_domain,
				 "Trying {} {} {}-{} (shared) -> {}",
				 audio_format,
				 device_format.Format.nSamplesPerSec,
				 device_format.Format.wBitsPerSample,
				 device_format.Samples.wValidBitsPerSample,
				 result_string);
		}
		if (FAILED(result)) {
			throw MakeHResultError(result, "Format is not supported");
		}
		break;
	case S_FALSE:
		if (closest_format->Format.wFormatTag == WAVE_FORMAT_EXTENSIBLE) {
			device_format = *closest_format;
		} else {
			device_format.Samples.wValidBitsPerSample =
				device_format.Format.wBitsPerSample;
			device_format.Format = closest_format->Format;
			switch (std::exchange(device_format.Format.wFormatTag,
					      WAVE_FORMAT_EXTENSIBLE)) {
			case WAVE_FORMAT_PCM:
				device_format.SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
				break;
			case WAVE_FORMAT_IEEE_FLOAT:
				device_format.SubFormat = KSDATAFORMAT_SUBTYPE_IEEE_FLOAT;
				break;
			default:
				gcc_unreachable();
			}
		}
		break;
	}

	// Copy closest match back to audio_format.
	audio_format.channels = device_format.Format.nChannels;
	audio_format.sample_rate = device_format.Format.nSamplesPerSec;
	if (device_format.SubFormat == KSDATAFORMAT_SUBTYPE_PCM) {
		switch (device_format.Format.wBitsPerSample) {
		case 8:
			audio_format.format = SampleFormat::S8;
			break;
		case 16:
			audio_format.format = SampleFormat::S16;
			break;
		case 32:
			audio_format.format =
				device_format.Samples.wValidBitsPerSample == 32
					? SampleFormat::S32
					: SampleFormat::S24_P32;
			break;
		}
	} else if (device_format.SubFormat == KSDATAFORMAT_SUBTYPE_IEEE_FLOAT) {
		audio_format.format = SampleFormat::FLOAT;
	}
}

/// run inside COMWorkerThread
void
WasapiOutput::EnumerateDevices(IMMDeviceEnumerator &enumerator)
{
	const auto device_collection = EnumAudioEndpoints(enumerator);

	const UINT count = GetCount(*device_collection);
	for (UINT i = 0; i < count; ++i) {
		const auto enumerated_device = Item(*device_collection, i);

		const auto property_store =
			OpenPropertyStore(*enumerated_device);

		auto name = GetString(*property_store,
				      PKEY_Device_FriendlyName);
		if (name == nullptr)
			continue;

		FmtNotice(wasapi_output_domain,
			  "Device \"{}\" \"{}\"", i, name);
	}
}

/// run inside COMWorkerThread
ComPtr<IMMDevice>
WasapiOutput::GetDevice(IMMDeviceEnumerator &enumerator, unsigned index)
{
	const auto device_collection = EnumAudioEndpoints(enumerator);
	return Item(*device_collection, index);
}

/// run inside COMWorkerThread
ComPtr<IMMDevice>
WasapiOutput::SearchDevice(IMMDeviceEnumerator &enumerator,
			   std::string_view name)
{
	const auto device_collection = EnumAudioEndpoints(enumerator);

	const UINT count = GetCount(*device_collection);
	for (UINT i = 0; i < count; ++i) {
		auto d = Item(*device_collection, i);

		const auto property_store = OpenPropertyStore(*d);
		auto n = GetString(*property_store, PKEY_Device_FriendlyName);
		if (n != nullptr && name.compare(n) == 0)
			return d;
	}

	return nullptr;
}

static bool
wasapi_output_test_default_device()
{
	return true;
}

const struct AudioOutputPlugin wasapi_output_plugin = {
	"wasapi",
	wasapi_output_test_default_device,
	WasapiOutput::Create,
	&wasapi_mixer_plugin,
};