Share one thread between all AudioOutputControllers instead of creating one per stream.

media/audio/audio_io.h

 // Copyright (c) 2010 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.
 
 #ifndef MEDIA_AUDIO_AUDIO_IO_H_
 #define MEDIA_AUDIO_AUDIO_IO_H_
 
 #include "base/basictypes.h"
 
 // Low-level audio output support. To make sound there are 3 objects involved:
@@ skipping 135 matching lines @@
   virtual void Stop() = 0;
 
   // Close the stream. This also generates AudioInputCallback::OnClose(). This
   // should be the last call made on this object.
   virtual void Close() = 0;
 
  protected:
   virtual ~AudioInputStream() {}
 };
 
-// Manages all audio resources. In particular it owns the AudioOutputStream
-// objects. Provides some convenience functions that avoid the need to provide
-// iterators over the existing streams.
-class AudioManager {
- public:
-  enum Format {
-    AUDIO_PCM_LINEAR = 0,     // PCM is 'raw' amplitude samples.
-    AUDIO_PCM_LOW_LATENCY,    // Linear PCM, low latency requested.
-    AUDIO_MOCK,               // Creates a dummy AudioOutputStream object.
-    AUDIO_LAST_FORMAT         // Only used for validation of format.
-  };
-
-  // Telephone quality sample rate, mostly for speech-only audio.
-  static const uint32 kTelephoneSampleRate = 8000;
-  // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
-  static const uint32 kAudioCDSampleRate = 44100;
-  // Digital Audio Tape sample rate.
-  static const uint32 kAudioDATSampleRate = 48000;
-
-  // Returns true if the OS reports existence of audio devices. This does not
-  // guarantee that the existing devices support all formats and sample rates.
-  virtual bool HasAudioOutputDevices() = 0;
-
-  // Returns true if the OS reports existence of audio recording devices. This
-  // does not guarantee that the existing devices support all formats and
-  // sample rates.
-  virtual bool HasAudioInputDevices() = 0;
-
-  // Factory for all the supported stream formats. The |channels| can be 1 to 5.
-  // The |sample_rate| is in hertz and can be any value supported by the
-  // platform. For some future formats the |sample_rate| and |bits_per_sample|
-  // can take special values.
-  // Returns NULL if the combination of the parameters is not supported, or if
-  // we have reached some other platform specific limit.
-  //
-  // AUDIO_PCM_LOW_LATENCY can be passed to this method and it has two effects:
-  // 1- Instead of triple buffered the audio will be double buffered.
-  // 2- A low latency driver or alternative audio subsystem will be used when
-  //    available.
-  //
-  // Do not free the returned AudioOutputStream. It is owned by AudioManager.
-  virtual AudioOutputStream* MakeAudioOutputStream(Format format, int channels,
-                                                   int sample_rate,
-                                                   char bits_per_sample) = 0;
-
-  // Factory to create audio recording streams.
-  // |channels| can be 1 or 2.
-  // |sample_rate| is in hertz and can be any value supported by the platform.
-  // |bits_per_sample| can be any value supported by the platform.
-  // |samples_per_packet| is in hertz as well and can be 0 to |sample_rate|,
-  // with 0 suggesting that the implementation use a default value for that
-  // platform.
-  // Returns NULL if the combination of the parameters is not supported, or if
-  // we have reached some other platform specific limit.
-  //
-  // Do not free the returned AudioInputStream. It is owned by AudioManager.
-  // When you are done with it, call |Stop()| and |Close()| to release it.
-  virtual AudioInputStream* MakeAudioInputStream(Format format, int channels,
-                                                 int sample_rate,
-                                                 char bits_per_sample,
-                                                 uint32 samples_per_packet) = 0;
-
-  // Muting continues playback but effectively the volume is set to zero.
-  // Un-muting returns the volume to the previous level.
-  virtual void MuteAll() = 0;
-  virtual void UnMuteAll() = 0;
-
-  // Get AudioManager singleton.
-  // TODO(cpu): Define threading requirements for interacting with AudioManager.
-  static AudioManager* GetAudioManager();
-
- protected:
-  virtual ~AudioManager() {}
-};
-
-
 #endif  // MEDIA_AUDIO_AUDIO_IO_H_