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bc4d4f0f95
This adds an abstract `Audio::PlaybackStream` class to allow cross- platform audio playback to be done in an opaque manner by applications in both Serenity and Lagom. Currently, the only supported audio API is PulseAudio, but a Serenity implementation should be added shortly as well.
73 lines
3.2 KiB
C++
73 lines
3.2 KiB
C++
/*
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* Copyright (c) 2023, Gregory Bertilson <zaggy1024@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/AtomicRefCounted.h>
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#include <AK/Function.h>
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#include <AK/Queue.h>
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#include <AK/Time.h>
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#include <LibAudio/SampleFormats.h>
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#include <LibCore/Forward.h>
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#include <LibThreading/ConditionVariable.h>
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#include <LibThreading/MutexProtected.h>
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#include <LibThreading/Thread.h>
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namespace Audio {
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enum class OutputState {
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Playing,
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Suspended,
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};
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// This class implements high-level audio playback behavior. It is primarily intended as an abstract cross-platform
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// interface to be used by Ladybird (and its dependent libraries) for playback.
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//
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// The interface is designed to be simple and robust. All control functions can be called safely from any thread.
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// Timing information provided by the class should allow audio timestamps to be tracked with the best accuracy possible.
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class PlaybackStream : public AtomicRefCounted<PlaybackStream> {
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public:
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using AudioDataRequestCallback = Function<ReadonlyBytes(Bytes buffer, PcmSampleFormat format, size_t sample_count)>;
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// Creates a new audio Output class.
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//
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// The initial_output_state parameter determines whether it will begin playback immediately.
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//
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// The AudioDataRequestCallback will be called when the Output needs more audio data to fill
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// its buffers and continue playback.
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static ErrorOr<NonnullRefPtr<PlaybackStream>> create(OutputState initial_output_state, u32 sample_rate, u8 channels, u32 target_latency_ms, AudioDataRequestCallback&&);
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virtual ~PlaybackStream() = default;
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// Sets the callback function that will be fired whenever the server consumes more data than is made available
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// by the data request callback. It will fire when either the data request runs too long, or the data request
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// returns no data. If all the input data has been exhausted and this event fires, that means that playback
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// has ended.
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virtual void set_underrun_callback(Function<void()>) = 0;
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// Resume playback from the suspended state, requesting new data for audio buffers as soon as possible.
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//
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// The value provided to the promise resolution will match the `total_time_played()` at the exact moment that
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// the stream was resumed.
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virtual NonnullRefPtr<Core::ThreadedPromise<Duration>> resume() = 0;
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// Completes playback of any buffered audio data and then suspends playback and buffering.
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virtual NonnullRefPtr<Core::ThreadedPromise<void>> drain_buffer_and_suspend() = 0;
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// Drops any buffered audio data and then suspends playback and buffering. This can used be to stop playback
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// as soon as possible instead of waiting for remaining audio to play.
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virtual NonnullRefPtr<Core::ThreadedPromise<void>> discard_buffer_and_suspend() = 0;
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// Returns a accurate monotonically-increasing time duration that is based on the number of samples that have
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// been played by the output device. The value is interpolated and takes into account latency to the speakers
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// whenever possible.
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//
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// This function should be able to run from any thread safely.
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virtual ErrorOr<Duration> total_time_played() = 0;
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virtual NonnullRefPtr<Core::ThreadedPromise<void>> set_volume(double volume) = 0;
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};
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}
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