media/audio/win/audio_low_latency_input_win.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 // Implementation of AudioInputStream for Windows using Windows Core Audio
   6 // WASAPI for low latency capturing.
   7 //
   8 // Overview of operation:
   9 //
  10 // - An object of WASAPIAudioInputStream is created by the AudioManager
  11 //   factory.
  12 // - Next some thread will call Open(), at that point the underlying
  13 //   Core Audio APIs are utilized to create two WASAPI interfaces called
  14 //   IAudioClient and IAudioCaptureClient.
  15 // - Then some thread will call Start(sink).
  16 //   A thread called "wasapi_capture_thread" is started and this thread listens
  17 //   on an event signal which is set periodically by the audio engine for
  18 //   each recorded data packet. As a result, data samples will be provided
  19 //   to the registered sink.
  20 // - At some point, a thread will call Stop(), which stops and joins the
  21 //   capture thread and at the same time stops audio streaming.
  22 // - The same thread that called stop will call Close() where we cleanup
  23 //   and notify the audio manager, which likely will destroy this object.
  24 //
  25 // Implementation notes:
  26 //
  27 // - The minimum supported client is Windows Vista.
  28 // - This implementation is single-threaded, hence:
  29 //    o Construction and destruction must take place from the same thread.
  30 //    o It is recommended to call all APIs from the same thread as well.
  31 // - It is recommended to first acquire the native sample rate of the default
  32 //   input device and then use the same rate when creating this object. Use
  33 //   WASAPIAudioInputStream::HardwareSampleRate() to retrieve the sample rate.
  34 // - Calling Close() also leads to self destruction.
  35 //
  36 // Core Audio API details:
  37 //
  38 // - Utilized MMDevice interfaces:
  39 //     o IMMDeviceEnumerator
  40 //     o IMMDevice
  41 // - Utilized WASAPI interfaces:
  42 //     o IAudioClient
  43 //     o IAudioCaptureClient
  44 // - The stream is initialized in shared mode and the processing of the
  45 //   audio buffer is event driven.
  46 // - The Multimedia Class Scheduler service (MMCSS) is utilized to boost
  47 //   the priority of the capture thread.
  48 // - Audio applications that use the MMDevice API and WASAPI typically use
  49 //   the ISimpleAudioVolume interface to manage stream volume levels on a
  50 //   per-session basis. It is also possible to use of the IAudioEndpointVolume
  51 //   interface to control the master volume level of an audio endpoint device.
  52 //   This implementation is using the ISimpleAudioVolume interface.
  53 //   MSDN states that "In rare cases, a specialized audio application might
  54 //   require the use of the IAudioEndpointVolume".
  55 //
  56 #ifndef MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_INPUT_WIN_H_
  57 #define MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_INPUT_WIN_H_
  58
  59 #include <Audioclient.h>
  60 #include <MMDeviceAPI.h>
  61
  62 #include <string>
  63
  64 #include "base/compiler_specific.h"
  65 #include "base/threading/non_thread_safe.h"
  66 #include "base/threading/platform_thread.h"
  67 #include "base/threading/simple_thread.h"
  68 #include "base/win/scoped_co_mem.h"
  69 #include "base/win/scoped_com_initializer.h"
  70 #include "base/win/scoped_comptr.h"
  71 #include "base/win/scoped_handle.h"
  72 #include "media/audio/audio_input_stream_impl.h"
  73 #include "media/audio/audio_parameters.h"
  74 #include "media/base/media_export.h"
  75
  76 namespace media {
  77
  78 class AudioManagerWin;
  79
  80 // AudioInputStream implementation using Windows Core Audio APIs.
  81 class MEDIA_EXPORT WASAPIAudioInputStream
  82     : public AudioInputStreamImpl,
  83       public base::DelegateSimpleThread::Delegate,
  84       NON_EXPORTED_BASE(public base::NonThreadSafe) {
  85  public:
  86   // The ctor takes all the usual parameters, plus |manager| which is the
  87   // the audio manager who is creating this object.
  88   WASAPIAudioInputStream(AudioManagerWin* manager,
  89                          const AudioParameters& params,
  90                          const std::string& device_id);
  91   // The dtor is typically called by the AudioManager only and it is usually
  92   // triggered by calling AudioInputStream::Close().
  93   virtual ~WASAPIAudioInputStream();
  94
  95   // Implementation of AudioInputStream.
  96   virtual bool Open() OVERRIDE;
  97   virtual void Start(AudioInputCallback* callback) OVERRIDE;
  98   virtual void Stop() OVERRIDE;
  99   virtual void Close() OVERRIDE;
 100   virtual double GetMaxVolume() OVERRIDE;
 101   virtual void SetVolume(double volume) OVERRIDE;
 102   virtual double GetVolume() OVERRIDE;
 103
 104   // Retrieves the sample rate used by the audio engine for its internal
 105   // processing/mixing of shared-mode streams given a specifed device.
 106   static int HardwareSampleRate(const std::string& device_id);
 107
 108   // Retrieves the number of audio channels used by the audio engine for its
 109   // internal processing/mixing of shared-mode streams given a specified device.
 110   static uint32 HardwareChannelCount(const std::string& device_id);
 111
 112   bool started() const { return started_; }
 113
 114  private:
 115   // DelegateSimpleThread::Delegate implementation.
 116   virtual void Run() OVERRIDE;
 117
 118   // Issues the OnError() callback to the |sink_|.
 119   void HandleError(HRESULT err);
 120
 121   // The Open() method is divided into these sub methods.
 122   HRESULT SetCaptureDevice();
 123   HRESULT ActivateCaptureDevice();
 124   HRESULT GetAudioEngineStreamFormat();
 125   bool DesiredFormatIsSupported();
 126   HRESULT InitializeAudioEngine();
 127
 128   // Retrieves the stream format that the audio engine uses for its internal
 129   // processing/mixing of shared-mode streams.
 130   static HRESULT GetMixFormat(const std::string& device_id,
 131                               WAVEFORMATEX** device_format);
 132
 133   // Our creator, the audio manager needs to be notified when we close.
 134   AudioManagerWin* manager_;
 135
 136   // Capturing is driven by this thread (which has no message loop).
 137   // All OnData() callbacks will be called from this thread.
 138   base::DelegateSimpleThread* capture_thread_;
 139
 140   // Contains the desired audio format which is set up at construction.
 141   WAVEFORMATEX format_;
 142
 143   bool opened_;
 144   bool started_;
 145
 146   // Size in bytes of each audio frame (4 bytes for 16-bit stereo PCM)
 147   size_t frame_size_;
 148
 149   // Size in audio frames of each audio packet where an audio packet
 150   // is defined as the block of data which the user received in each
 151   // OnData() callback.
 152   size_t packet_size_frames_;
 153
 154   // Size in bytes of each audio packet.
 155   size_t packet_size_bytes_;
 156
 157   // Length of the audio endpoint buffer.
 158   uint32 endpoint_buffer_size_frames_;
 159
 160   // Contains the unique name of the selected endpoint device.
 161   // Note that AudioManagerBase::kDefaultDeviceId represents the default
 162   // device role and is not a valid ID as such.
 163   std::string device_id_;
 164
 165   // Conversion factor used in delay-estimation calculations.
 166   // Converts a raw performance counter value to 100-nanosecond unit.
 167   double perf_count_to_100ns_units_;
 168
 169   // Conversion factor used in delay-estimation calculations.
 170   // Converts from milliseconds to audio frames.
 171   double ms_to_frame_count_;
 172
 173   // Pointer to the object that will receive the recorded audio samples.
 174   AudioInputCallback* sink_;
 175
 176   // Windows Multimedia Device (MMDevice) API interfaces.
 177
 178   // An IMMDevice interface which represents an audio endpoint device.
 179   base::win::ScopedComPtr<IMMDevice> endpoint_device_;
 180
 181   // Windows Audio Session API (WASAP) interfaces.
 182
 183   // An IAudioClient interface which enables a client to create and initialize
 184   // an audio stream between an audio application and the audio engine.
 185   base::win::ScopedComPtr<IAudioClient> audio_client_;
 186
 187   // The IAudioCaptureClient interface enables a client to read input data
 188   // from a capture endpoint buffer.
 189   base::win::ScopedComPtr<IAudioCaptureClient> audio_capture_client_;
 190
 191   // The ISimpleAudioVolume interface enables a client to control the
 192   // master volume level of an audio session.
 193   // The volume-level is a value in the range 0.0 to 1.0.
 194   // This interface does only work with shared-mode streams.
 195   base::win::ScopedComPtr<ISimpleAudioVolume> simple_audio_volume_;
 196
 197   // The audio engine will signal this event each time a buffer has been
 198   // recorded.
 199   base::win::ScopedHandle audio_samples_ready_event_;
 200
 201   // This event will be signaled when capturing shall stop.
 202   base::win::ScopedHandle stop_capture_event_;
 203
 204   DISALLOW_COPY_AND_ASSIGN(WASAPIAudioInputStream);
 205 };
 206
 207 }  // namespace media
 208
 209 #endif  // MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_INPUT_WIN_H_