media/audio/virtual_audio_output_stream.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 #ifndef MEDIA_AUDIO_VIRTUAL_AUDIO_OUTPUT_STREAM_H_
   6 #define MEDIA_AUDIO_VIRTUAL_AUDIO_OUTPUT_STREAM_H_
   7
   8 #include "base/callback.h"
   9 #include "base/threading/thread_checker.h"
  10 #include "media/audio/audio_io.h"
  11 #include "media/audio/audio_parameters.h"
  12 #include "media/base/audio_converter.h"
  13
  14 namespace media {
  15
  16 class VirtualAudioInputStream;
  17
  18 // VirtualAudioOutputStream attaches to a VirtualAudioInputStream when Start()
  19 // is called and is used as an audio source. VirtualAudioOutputStream also
  20 // implements an interface so it can be used as an input to AudioConverter so
  21 // that we can get audio frames that match the AudioParameters that
  22 // VirtualAudioInputStream expects.
  23 class MEDIA_EXPORT VirtualAudioOutputStream
  24     : public AudioOutputStream,
  25       public AudioConverter::InputCallback {
  26  public:
  27   // Callback invoked just after VirtualAudioOutputStream is closed.
  28   typedef base::Callback<void(VirtualAudioOutputStream* vaos)>
  29       AfterCloseCallback;
  30
  31   // Construct an audio loopback pathway to the given |target| (not owned).
  32   // |target| must outlive this instance.
  33   VirtualAudioOutputStream(const AudioParameters& params,
  34                            VirtualAudioInputStream* target,
  35                            const AfterCloseCallback& after_close_cb);
  36
  37   virtual ~VirtualAudioOutputStream();
  38
  39   // AudioOutputStream:
  40   virtual bool Open() OVERRIDE;
  41   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
  42   virtual void Stop() OVERRIDE;
  43   virtual void SetVolume(double volume) OVERRIDE;
  44   virtual void GetVolume(double* volume) OVERRIDE;
  45   virtual void Close() OVERRIDE;
  46
  47  private:
  48   // AudioConverter::InputCallback:
  49   virtual double ProvideInput(AudioBus* audio_bus,
  50                               base::TimeDelta buffer_delay) OVERRIDE;
  51
  52   const AudioParameters params_;
  53   // Pointer to the VirtualAudioInputStream to attach to when Start() is called.
  54   // This pointer should always be valid because VirtualAudioInputStream should
  55   // outlive this class.
  56   VirtualAudioInputStream* const target_input_stream_;
  57
  58   AfterCloseCallback after_close_cb_;
  59
  60   AudioSourceCallback* callback_;
  61   double volume_;
  62
  63   base::ThreadChecker thread_checker_;
  64
  65   DISALLOW_COPY_AND_ASSIGN(VirtualAudioOutputStream);
  66 };
  67
  68 }  // namespace media
  69
  70 #endif  // MEDIA_AUDIO_VIRTUAL_AUDIO_OUTPUT_STREAM_H_