media/audio/pulse/pulse_output.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5 // Creates an audio output stream based on the PulseAudio asynchronous API;
   6 // specifically using the pa_threaded_mainloop model.
   7 //
   8 // If the stream is successfully opened, Close() must be called before the
   9 // stream is deleted as Close() is responsible for ensuring resource cleanup
  10 // occurs.
  11 //
  12 // This object is designed so that all AudioOutputStream methods will be called
  13 // on the same thread that created the object.
  14 //
  15 // WARNING: This object blocks on internal PulseAudio calls in Open() while
  16 // waiting for PulseAudio's context structure to be ready.  It also blocks in
  17 // inside PulseAudio in Start() and repeated during playback, waiting for
  18 // PulseAudio write callbacks to occur.
  19
  20 #ifndef MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_
  21 #define MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_
  22
  23 #include <string>
  24
  25 #include "base/memory/scoped_ptr.h"
  26 #include "media/audio/audio_io.h"
  27 #include "media/audio/audio_parameters.h"
  28
  29 struct pa_context;
  30 struct pa_operation;
  31 struct pa_stream;
  32 struct pa_threaded_mainloop;
  33
  34 namespace media {
  35 class AudioManagerBase;
  36
  37 class PulseAudioOutputStream : public AudioOutputStream {
  38  public:
  39   PulseAudioOutputStream(const AudioParameters& params,
  40                          const std::string& device_id,
  41                          AudioManagerBase* manager);
  42
  43   virtual ~PulseAudioOutputStream();
  44
  45   // Implementation of AudioOutputStream.
  46   virtual bool Open() OVERRIDE;
  47   virtual void Close() OVERRIDE;
  48   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
  49   virtual void Stop() OVERRIDE;
  50   virtual void SetVolume(double volume) OVERRIDE;
  51   virtual void GetVolume(double* volume) OVERRIDE;
  52
  53  private:
  54   // Called by PulseAudio when |pa_stream_| change state.  If an unexpected
  55   // failure state change happens and |source_callback_| is set
  56   // this method will forward the error via OnError().
  57   static void StreamNotifyCallback(pa_stream* s, void* p_this);
  58
  59   // Called by PulseAudio when it needs more audio data.
  60   static void StreamRequestCallback(pa_stream* s, size_t len, void* p_this);
  61
  62   // Fulfill a write request from the write request callback.  Outputs silence
  63   // if the request could not be fulfilled.
  64   void FulfillWriteRequest(size_t requested_bytes);
  65
  66   // Close() helper function to free internal structs.
  67   void Reset();
  68
  69   // AudioParameters from the constructor.
  70   const AudioParameters params_;
  71
  72   // The device ID for the device to open.
  73   const std::string device_id_;
  74
  75   // Audio manager that created us.  Used to report that we've closed.
  76   AudioManagerBase* manager_;
  77
  78   // PulseAudio API structs.
  79   pa_context* pa_context_;
  80   pa_threaded_mainloop* pa_mainloop_;
  81   pa_stream* pa_stream_;
  82
  83   // Float representation of volume from 0.0 to 1.0.
  84   float volume_;
  85
  86   // Callback to audio data source.  Must only be modified while holding a lock
  87   // on |pa_mainloop_| via pa_threaded_mainloop_lock().
  88   AudioSourceCallback* source_callback_;
  89
  90   // Container for retrieving data from AudioSourceCallback::OnMoreData().
  91   scoped_ptr<AudioBus> audio_bus_;
  92
  93   DISALLOW_COPY_AND_ASSIGN(PulseAudioOutputStream);
  94 };
  95
  96 }  // namespace media
  97
  98 #endif  // MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_