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 "media/audio/audio_io.h"
  10 #include "media/audio/audio_parameters.h"
  11 #include "media/base/audio_converter.h"
  12
  13 namespace base {
  14 class MessageLoopProxy;
  15 }
  16
  17 namespace media {
  18
  19 class VirtualAudioInputStream;
  20
  21 // VirtualAudioOutputStream attaches to a VirtualAudioInputStream when Start()
  22 // is called and is used as an audio source. VirtualAudioOutputStream also
  23 // implements an interface so it can be used as an input to AudioConverter so
  24 // that we can get audio frames that match the AudioParameters that
  25 // VirtualAudioInputStream expects.
  26 class MEDIA_EXPORT VirtualAudioOutputStream
  27     : public AudioOutputStream,
  28       public AudioConverter::InputCallback {
  29  public:
  30   // Callback invoked just after VirtualAudioOutputStream is closed.
  31   typedef base::Callback<void(VirtualAudioOutputStream* vaos)>
  32       AfterCloseCallback;
  33
  34   // Construct an audio loopback pathway to the given |target| (not owned).
  35   // |target| must outlive this instance.
  36   VirtualAudioOutputStream(const AudioParameters& params,
  37                            base::MessageLoopProxy* message_loop,
  38                            VirtualAudioInputStream* target,
  39                            const AfterCloseCallback& after_close_cb);
  40
  41   virtual ~VirtualAudioOutputStream();
  42
  43   // AudioOutputStream:
  44   virtual bool Open() OVERRIDE;
  45   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
  46   virtual void Stop() OVERRIDE;
  47   virtual void SetVolume(double volume) OVERRIDE;
  48   virtual void GetVolume(double* volume) OVERRIDE;
  49   virtual void Close() OVERRIDE;
  50
  51  private:
  52   // AudioConverter::InputCallback:
  53   virtual double ProvideInput(AudioBus* audio_bus,
  54                               base::TimeDelta buffer_delay) OVERRIDE;
  55
  56   const AudioParameters params_;
  57   base::MessageLoopProxy* const message_loop_;
  58   // Pointer to the VirtualAudioInputStream to attach to when Start() is called.
  59   // This pointer should always be valid because VirtualAudioInputStream should
  60   // outlive this class.
  61   VirtualAudioInputStream* const target_input_stream_;
  62
  63   AfterCloseCallback after_close_cb_;
  64
  65   AudioSourceCallback* callback_;
  66   double volume_;
  67
  68   DISALLOW_COPY_AND_ASSIGN(VirtualAudioOutputStream);
  69 };
  70
  71 }  // namespace media
  72
  73 #endif  // MEDIA_AUDIO_VIRTUAL_AUDIO_OUTPUT_STREAM_H_