media/audio/audio_output_proxy.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_AUDIO_OUTPUT_PROXY_H_
   6 #define MEDIA_AUDIO_AUDIO_OUTPUT_PROXY_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/compiler_specific.h"
  10 #include "base/memory/ref_counted.h"
  11 #include "base/threading/non_thread_safe.h"
  12 #include "media/audio/audio_io.h"
  13 #include "media/audio/audio_parameters.h"
  14
  15 namespace media {
  16
  17 class AudioOutputDispatcher;
  18
  19 // AudioOutputProxy is an audio otput stream that uses resources more
  20 // efficiently than a regular audio output stream: it opens audio
  21 // device only when sound is playing, i.e. between Start() and Stop()
  22 // (there is still one physical stream per each audio output proxy in
  23 // playing state).
  24 //
  25 // AudioOutputProxy uses AudioOutputDispatcher to open and close
  26 // physical output streams.
  27 class MEDIA_EXPORT AudioOutputProxy
  28   : public AudioOutputStream,
  29     public NON_EXPORTED_BASE(base::NonThreadSafe) {
  30  public:
  31   // Caller keeps ownership of |dispatcher|.
  32   explicit AudioOutputProxy(AudioOutputDispatcher* dispatcher);
  33
  34   // AudioOutputStream interface.
  35   bool Open() override;
  36   void Start(AudioSourceCallback* callback) override;
  37   void Stop() override;
  38   void SetVolume(double volume) override;
  39   void GetVolume(double* volume) override;
  40   void Close() override;
  41
  42  private:
  43   enum State {
  44     kCreated,
  45     kOpened,
  46     kPlaying,
  47     kClosed,
  48     kOpenError,
  49     kStartError,
  50   };
  51
  52   ~AudioOutputProxy() override;
  53
  54   scoped_refptr<AudioOutputDispatcher> dispatcher_;
  55   State state_;
  56
  57   // Need to save volume here, so that we can restore it in case the stream
  58   // is stopped, and then started again.
  59   double volume_;
  60
  61   DISALLOW_COPY_AND_ASSIGN(AudioOutputProxy);
  62 };
  63
  64 }  // namespace media
  65
  66 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_PROXY_H_