Adds support for OpenSL ES based audio capture on Android

webrtc/modules/audio_device/android/opensles_recorder.h

Index: webrtc/modules/audio_device/android/opensles_recorder.h
diff --git a/webrtc/modules/audio_device/android/opensles_recorder.h b/webrtc/modules/audio_device/android/opensles_recorder.h
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+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_DEVICE_ANDROID_OPENSLES_RECORDER_H_
+#define WEBRTC_MODULES_AUDIO_DEVICE_ANDROID_OPENSLES_RECORDER_H_
+
+#include <SLES/OpenSLES.h>
+#include <SLES/OpenSLES_Android.h>
+#include <SLES/OpenSLES_AndroidConfiguration.h>
+
+#include <memory>
+
+#include "webrtc/base/thread_checker.h"
+#include "webrtc/modules/audio_device/android/audio_common.h"
+#include "webrtc/modules/audio_device/android/audio_manager.h"
+#include "webrtc/modules/audio_device/android/opensles_common.h"
+#include "webrtc/modules/audio_device/include/audio_device_defines.h"
+#include "webrtc/modules/audio_device/audio_device_generic.h"
+#include "webrtc/modules/utility/include/helpers_android.h"
+
+namespace webrtc {
+
+class FineAudioBuffer;
+
+// Implements 16-bit mono PCM audio input support for Android using the
+// C based OpenSL ES API. No calls from C/C++ to Java using JNI is done.
+//
+// An instance must be created and destroyed on one and the same thread.
+// All public methods must also be called on the same thread. A thread checker
+// will RTC_DCHECK if any method is called on an invalid thread. Recorded audio
+// buffers are provided on a dedicated internal thread managed by the OpenSL
+// ES layer.
+//
+// The existing design forces the user to call InitRecording() after
+// StopRecording() to be able to call StartRecording() again. This is inline
+// with how the Java-based implementation works.
+//
+// As of API level 21, lower latency audio input is supported on select devices.
+// To take advantage of this feature, first confirm that lower latency output is
+// available. The capability for lower latency output is a prerequisite for the
+// lower latency input feature. Then, create an AudioRecorder with the same
+// sample rate and buffer size as would be used for output. OpenSL ES interfaces
+// for input effects preclude the lower latency path.
+// See https://developer.android.com/ndk/guides/audio/opensl-prog-notes.html
+// for more details.
+class OpenSLESRecorder {
+ public:
+  // Beginning with API level 17 (Android 4.2), a buffer count of 2 or more is
+  // required for lower latency. Beginning with API level 18 (Android 4.3), a
+  // buffer count of 1 is sufficient for lower latency. In addition, the buffer
+  // size and sample rate must be compatible with the device's native input
+  // configuration provided via the audio manager at construction.
+  // TODO(henrika): perhaps set this value dynamically based on OS version.
+  static const int kNumOfOpenSLESBuffers = 2;
+
+  explicit OpenSLESRecorder(AudioManager* audio_manager);
+  ~OpenSLESRecorder();
+
+  int Init();
+  int Terminate();
+
+  int InitRecording();
+  bool RecordingIsInitialized() const { return initialized_; }
+
+  int StartRecording();
+  int StopRecording();
+  bool Recording() const { return recording_; }
+
+  void AttachAudioBuffer(AudioDeviceBuffer* audio_buffer);
+
+  // TODO(henrika): add support using OpenSL ES APIs when available.
+  int EnableBuiltInAEC(bool enable);
+  int EnableBuiltInAGC(bool enable);
+  int EnableBuiltInNS(bool enable);
+
+ private:
+  // Obtaines the SL Engine Interface from the existing global Engine object.
+  // The interface exposes creation methods of all the OpenSL ES object types.
+  // This method defines the |engine_| member variable.
+  bool ObtainEngineInterface();
+
+  // Creates/destroys the audio recorder and the simple-buffer queue object.
+  bool CreateAudioRecorder();
+  void DestroyAudioRecorder();
+
+  // Allocate memory for audio buffers which will be used to capture audio
+  // via the SLAndroidSimpleBufferQueueItf interface.
+  void AllocateDataBuffers();
+
+  // These callback methods are called when data has been written to the input
+  // buffer queue. They are both called from an internal "OpenSL ES thread"
+  // which is not attached to the Dalvik VM.
+  static void SimpleBufferQueueCallback(SLAndroidSimpleBufferQueueItf caller,
+                                        void* context);
+  void ReadBufferQueue();
+
+  // Wraps calls to SLAndroidSimpleBufferQueueState::Enqueue() and it can be
+  // called both on the main thread (but before recording has started) and from
+  // the internal audio thread while input streaming is active. It uses
+  // |simple_buffer_queue_| but no lock is needed since the initial calls from
+  // the main thread and the native callback thread are mutually exclusive.
+  bool EnqueueAudioBuffer();
+
+  // Returns the current recorder state.
+  SLuint32 GetRecordState() const;
+
+  // Returns the current buffer queue state.
+  SLAndroidSimpleBufferQueueState GetBufferQueueState() const;
+
+  // Number of buffers currently in the queue.
+  SLuint32 GetBufferCount();
+
+  // Prints a log message of the current queue state. Can be used for debugging
+  // purposes.
+  void LogBufferState() const;
+
+  // Ensures that methods are called from the same thread as this object is
+  // created on.
+  rtc::ThreadChecker thread_checker_;
+
+  // Stores thread ID in first call to SimpleBufferQueueCallback() from internal
+  // non-application thread which is not attached to the Dalvik JVM.
+  // Detached during construction of this object.
+  rtc::ThreadChecker thread_checker_opensles_;
+
+  // Raw pointer to the audio manager injected at construction. Used to cache
+  // audio parameters and to access the global SL engine object needed by the
+  // ObtainEngineInterface() method. The audio manager outlives any instance of
+  // this class.
+  AudioManager* const audio_manager_;
+
+  // Contains audio parameters provided to this class at construction by the
+  // AudioManager.
+  const AudioParameters audio_parameters_;
+
+  // Raw pointer handle provided to us in AttachAudioBuffer(). Owned by the
+  // AudioDeviceModuleImpl class and called by AudioDeviceModule::Create().
+  AudioDeviceBuffer* audio_device_buffer_;
+
+  // PCM-type format definition.
+  // TODO(henrika): add support for SLAndroidDataFormat_PCM_EX (android-21) if
+  // 32-bit float representation is needed.
+  SLDataFormat_PCM pcm_format_;
+
+  bool initialized_;
+  bool recording_;
+
+  // This interface exposes creation methods for all the OpenSL ES object types.
+  // It is the OpenSL ES API entry point.
+  SLEngineItf engine_;
+
+  // The audio recorder media object records audio to the destination specified
+  // by the data sink capturing it from the input specified by the data source.
+  webrtc::ScopedSLObjectItf recorder_object_;
+
+  // This interface is supported on the audio recorder object and it controls
+  // the state of the audio recorder.
+  SLRecordItf recorder_;
+
+  // The Android Simple Buffer Queue interface is supported on the audio
+  // recorder. For recording, an app should enqueue empty buffers. When a
+  // registered callback sends notification that the system has finished writing
+  // data to the buffer, the app can read the buffer.
+  SLAndroidSimpleBufferQueueItf simple_buffer_queue_;
+
+  // Consumes audio of native buffer size and feeds the WebRTC layer with 10ms
+  // chunks of audio.
+  std::unique_ptr<FineAudioBuffer> fine_audio_buffer_;
+
+  // Queue of audio buffers to be used by the recorder object for capturing
+  // audio. They will be used in a Round-robin way and the size of each buffer
+  // is given by AudioParameters::GetBytesPerBuffer(), i.e., it corresponds to
+  // the native OpenSL ES buffer size.
+  std::unique_ptr<std::unique_ptr<SLint8[]>[]> audio_buffers_;
+
+  // Keeps track of active audio buffer 'n' in the audio_buffers_[n] queue.
+  // Example (kNumOfOpenSLESBuffers = 2): counts 0, 1, 0, 1, ...
+  int buffer_index_;
+
+  // Last time the OpenSL ES layer delivered recorded audio data.
+  uint32_t last_rec_time_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_DEVICE_ANDROID_OPENSLES_RECORDER_H_