PulseAudio Sound Playback on Linux

media/audio/linux/pulse_output.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Creates an audio output stream based on the PulseAudio asynchronous API.
+//
+// If the stream is successfully opened, Close() must be called before the
+// stream is deleted as Close() is responsible for ensuring resource cleanup
+// occurs.
+//
+// This object is designed so that all AudioOutputStream methods will be called
+// on the same thread that created the object.
+//
+// WARNING: This object blocks on internal PulseAudio calls after Start() is

[vrk (LEFT CHROMIUM), 2011/08/18 18:22:22]

Also blocks on Open(), waiting for PulseAudio to be ready or to fail.

[slock, 2011/08/18 18:54:16]

Done.

+// invoked and repeatedly throughout playback as it waits for PulseAudio write
+// callbacks to occur.
+
+#ifndef MEDIA_AUDIO_LINUX_PULSE_OUTPUT_H_
+#define MEDIA_AUDIO_LINUX_PULSE_OUTPUT_H_
+
+#include <pulse/pulseaudio.h>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/task.h"
+#include "media/audio/audio_io.h"
+#include "media/base/channel_layout.h"
+
+namespace media {
+class SeekableBuffer;
+}
+
+class AudioManagerLinux;
+struct AudioParameters;
+class MessageLoop;
+
+class PulseAudioOutputStream : public AudioOutputStream {
+ public:
+  PulseAudioOutputStream(const AudioParameters& params,
+                         AudioManagerLinux* manager,
+                         MessageLoop* message_loop);
+
+  virtual ~PulseAudioOutputStream();
+
+  // Implementation of AudioOutputStream.
+  virtual bool Open();
+  virtual void Close();
+  virtual void Start(AudioSourceCallback* callback);
+  virtual void Stop();
+  virtual void SetVolume(double volume);
+  virtual void GetVolume(double* volume);
+
+ private:
+  // PulseAudio Callbacks.
+  static void ContextStateCallback(pa_context* context, void* state_addr);
+  static void WriteRequestCallback(pa_stream* playback_handle, size_t length,
+                                   void* stream_addr);
+
+  // Iterate the PulseAudio mainloop to get write requests.
+  void WaitForWriteRequest();
+
+  // Get another packet from the data source and write it to the client buffer.
+  bool BufferPacketFromSource();
+
+  // Fulfill a write request from the write request callback.  If the write
+  // can't be finished a first, post a new attempt to the message loop.
+  void FulfillWriteRequest(size_t requested_bytes);
+
+  // Write data from the client buffer to the PulseAudio stream.
+  void WriteToStream(size_t bytes_to_write, size_t* bytes_written);
+
+  // API for Proxying calls to the AudioSourceCallback provided during Start().
+  uint32 RunDataCallback(uint8* dest, uint32 max_size,
+                         AudioBuffersState buffers_state);
+
+  // Close() helper function to free internal structs.
+  void Reset();
+
+  // Configuration constants from the constructor.  Referencable by all threads
+  // since they are constants.
+  const ChannelLayout channel_layout_;
+  const uint32 channel_count_;
+  const pa_sample_format_t sample_format_;
+  const uint32 sample_rate_;
+  const uint32 bytes_per_frame_;
+
+  // Audio manager that created us.  Used to report that we've closed.
+  AudioManagerLinux* manager_;
+
+  // PulseAudio API structs.
+  pa_context* pa_context_;
+  pa_mainloop* pa_mainloop_;
+
+  // Handle to the actual PulseAudio playback stream.
+  pa_stream* playback_handle_;
+
+  // Device configuration data.  Populated after Open() completes.
+  uint32 packet_size_;
+  uint32 frames_per_packet_;
+
+  // Client side audio buffer feeding pulse audio's server side buffer.
+  scoped_ptr<media::SeekableBuffer> client_buffer_;
+
+  // Float representation of volume from 0.0 to 1.0.
+  float volume_;
+
+  // Flag indicating the code should stop reading from the data source or
+  // writing to the PulseAudio server.  This is set because the device has
+  // entered an unrecoverable error state, or the Close() has executed.
+  bool stream_stopped_;
+
+  // Whether or not PulseAudio has called the WriteCallback for the most recent
+  // set of pa_mainloop iterations.
+  bool write_callback_handled_;
+
+  // Message loop used to post WaitForWriteTasks.  Used to prevent blocking on
+  // the audio thread while waiting for PulseAudio write callbacks.
+  MessageLoop* message_loop_;
+
+  // Allows us to run tasks on the PulseAudioOutputStream instance which are
+  // bound by its lifetime.
+  ScopedRunnableMethodFactory<PulseAudioOutputStream> method_factory_;
+
+  // Callback to audio data source.
+  AudioSourceCallback* source_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(PulseAudioOutputStream);
+};
+
+#endif  // MEDIA_AUDIO_LINUX_PULSE_OUTPUT_H_