Add m-esr52 at 52.6.0

1 files changed, 2734 insertions, 0 deletions

diff --git a/media/libcubeb/src/cubeb_audiounit.cpp b/media/libcubeb/src/cubeb_audiounit.cpp
new file mode 100644
index 000000000..f24dfbff2
--- /dev/null
+++ b/media/libcubeb/src/cubeb_audiounit.cpp
@@ -0,0 +1,2734 @@
+/*
+ * Copyright © 2011 Mozilla Foundation
+ *
+ * This program is made available under an ISC-style license.  See the
+ * accompanying file LICENSE for details.
+ */
+#undef NDEBUG
+
+#include <TargetConditionals.h>
+#include <assert.h>
+#include <mach/mach_time.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <AudioUnit/AudioUnit.h>
+#if !TARGET_OS_IPHONE
+#include <AvailabilityMacros.h>
+#include <CoreAudio/AudioHardware.h>
+#include <CoreAudio/HostTime.h>
+#include <CoreFoundation/CoreFoundation.h>
+#endif
+#include <CoreAudio/CoreAudioTypes.h>
+#include <AudioToolbox/AudioToolbox.h>
+#include "cubeb/cubeb.h"
+#include "cubeb-internal.h"
+#include "cubeb_panner.h"
+#if !TARGET_OS_IPHONE
+#include "cubeb_osx_run_loop.h"
+#endif
+#include "cubeb_resampler.h"
+#include "cubeb_ring_array.h"
+#include "cubeb_utils.h"
+#include <algorithm>
+#include <atomic>
+
+#if !defined(kCFCoreFoundationVersionNumber10_7)
+/* From CoreFoundation CFBase.h */
+#define kCFCoreFoundationVersionNumber10_7 635.00
+#endif
+
+#if !TARGET_OS_IPHONE && MAC_OS_X_VERSION_MIN_REQUIRED < 1060
+#define AudioComponent Component
+#define AudioComponentDescription ComponentDescription
+#define AudioComponentFindNext FindNextComponent
+#define AudioComponentInstanceNew OpenAComponent
+#define AudioComponentInstanceDispose CloseComponent
+#endif
+
+#if MAC_OS_X_VERSION_MIN_REQUIRED < 101000
+typedef UInt32  AudioFormatFlags;
+#endif
+
+#define CUBEB_STREAM_MAX 8
+
+#define AU_OUT_BUS    0
+#define AU_IN_BUS     1
+
+#define PRINT_ERROR_CODE(str, r) do {                                \
+  LOG("System call failed: %s (rv: %d)", str, r);                    \
+} while(0)
+
+const char * DISPATCH_QUEUE_LABEL = "org.mozilla.cubeb";
+
+/* Testing empirically, some headsets report a minimal latency that is very
+ * low, but this does not work in practice. Lie and say the minimum is 256
+ * frames. */
+const uint32_t SAFE_MIN_LATENCY_FRAMES = 256;
+const uint32_t SAFE_MAX_LATENCY_FRAMES = 512;
+
+void audiounit_stream_stop_internal(cubeb_stream * stm);
+void audiounit_stream_start_internal(cubeb_stream * stm);
+static void audiounit_close_stream(cubeb_stream *stm);
+static int audiounit_setup_stream(cubeb_stream *stm);
+
+extern cubeb_ops const audiounit_ops;
+
+struct cubeb {
+  cubeb_ops const * ops;
+  owned_critical_section mutex;
+  std::atomic<int> active_streams;
+  uint32_t global_latency_frames = 0;
+  int limit_streams;
+  cubeb_device_collection_changed_callback collection_changed_callback;
+  void * collection_changed_user_ptr;
+  /* Differentiate input from output devices. */
+  cubeb_device_type collection_changed_devtype;
+  uint32_t devtype_device_count;
+  AudioObjectID * devtype_device_array;
+  // The queue is asynchronously deallocated once all references to it are released
+  dispatch_queue_t serial_queue = dispatch_queue_create(DISPATCH_QUEUE_LABEL, DISPATCH_QUEUE_SERIAL);
+};
+
+class auto_array_wrapper
+{
+public:
+  explicit auto_array_wrapper(auto_array<float> * ar)
+  : float_ar(ar)
+  , short_ar(nullptr)
+  {assert((float_ar && !short_ar) || (!float_ar && short_ar));}
+
+  explicit auto_array_wrapper(auto_array<short> * ar)
+  : float_ar(nullptr)
+  , short_ar(ar)
+  {assert((float_ar && !short_ar) || (!float_ar && short_ar));}
+
+  ~auto_array_wrapper() {
+    auto_lock l(lock);
+    assert((float_ar && !short_ar) || (!float_ar && short_ar));
+    delete float_ar;
+    delete short_ar;
+  }
+
+  void push(void * elements, size_t length){
+    assert((float_ar && !short_ar) || (!float_ar && short_ar));
+    auto_lock l(lock);
+    if (float_ar)
+      return float_ar->push(static_cast<float*>(elements), length);
+    return short_ar->push(static_cast<short*>(elements), length);
+  }
+
+  size_t length() {
+    assert((float_ar && !short_ar) || (!float_ar && short_ar));
+    auto_lock l(lock);
+    if (float_ar)
+      return float_ar->length();
+    return short_ar->length();
+  }
+
+  void push_silence(size_t length) {
+    assert((float_ar && !short_ar) || (!float_ar && short_ar));
+    auto_lock l(lock);
+    if (float_ar)
+      return float_ar->push_silence(length);
+    return short_ar->push_silence(length);
+  }
+
+  bool pop(void * elements, size_t length) {
+    assert((float_ar && !short_ar) || (!float_ar && short_ar));
+    auto_lock l(lock);
+    if (float_ar)
+      return float_ar->pop(static_cast<float*>(elements), length);
+    return short_ar->pop(static_cast<short*>(elements), length);
+  }
+
+  void * data() {
+    assert((float_ar && !short_ar) || (!float_ar && short_ar));
+    auto_lock l(lock);
+    if (float_ar)
+      return float_ar->data();
+    return short_ar->data();
+  }
+
+  void clear() {
+    assert((float_ar && !short_ar) || (!float_ar && short_ar));
+    auto_lock l(lock);
+    if (float_ar) {
+      float_ar->clear();
+    } else {
+      short_ar->clear();
+    }
+  }
+
+private:
+  auto_array<float> * float_ar;
+  auto_array<short> * short_ar;
+  owned_critical_section lock;
+};
+
+struct cubeb_stream {
+  cubeb * context;
+  cubeb_data_callback data_callback;
+  cubeb_state_callback state_callback;
+  cubeb_device_changed_callback device_changed_callback;
+  /* Stream creation parameters */
+  cubeb_stream_params input_stream_params;
+  cubeb_stream_params output_stream_params;
+  cubeb_devid input_device;
+  bool is_default_input;
+  cubeb_devid output_device;
+  /* User pointer of data_callback */
+  void * user_ptr;
+  /* Format descriptions */
+  AudioStreamBasicDescription input_desc;
+  AudioStreamBasicDescription output_desc;
+  /* I/O AudioUnits */
+  AudioUnit input_unit;
+  AudioUnit output_unit;
+  /* I/O device sample rate */
+  Float64 input_hw_rate;
+  Float64 output_hw_rate;
+  /* Expected I/O thread interleave,
+   * calculated from I/O hw rate. */
+  int expected_output_callbacks_in_a_row;
+  owned_critical_section mutex;
+  /* Hold the input samples in every
+   * input callback iteration */
+  auto_array_wrapper * input_linear_buffer;
+  /* Frames on input buffer */
+  std::atomic<uint32_t> input_buffer_frames;
+  /* Frame counters */
+  uint64_t frames_played;
+  uint64_t frames_queued;
+  std::atomic<int64_t> frames_read;
+  std::atomic<bool> shutdown;
+  std::atomic<bool> draining;
+  /* Latency requested by the user. */
+  uint32_t latency_frames;
+  std::atomic<uint64_t> current_latency_frames;
+  uint64_t hw_latency_frames;
+  std::atomic<float> panning;
+  cubeb_resampler * resampler;
+  /* This is the number of output callback we got in a row. This is usually one,
+   * but can be two when the input and output rate are different, and more when
+   * a device has been plugged or unplugged, as there can be some time before
+   * the device is ready. */
+  std::atomic<int> output_callback_in_a_row;
+  /* This is true if a device change callback is currently running.  */
+  std::atomic<bool> switching_device;
+  std::atomic<bool> buffer_size_change_state{ false };
+};
+
+bool has_input(cubeb_stream * stm)
+{
+  return stm->input_stream_params.rate != 0;
+}
+
+bool has_output(cubeb_stream * stm)
+{
+  return stm->output_stream_params.rate != 0;
+}
+
+#if TARGET_OS_IPHONE
+typedef UInt32 AudioDeviceID;
+typedef UInt32 AudioObjectID;
+
+#define AudioGetCurrentHostTime mach_absolute_time
+
+uint64_t
+AudioConvertHostTimeToNanos(uint64_t host_time)
+{
+  static struct mach_timebase_info timebase_info;
+  static bool initialized = false;
+  if (!initialized) {
+    mach_timebase_info(&timebase_info);
+    initialized = true;
+  }
+
+  long double answer = host_time;
+  if (timebase_info.numer != timebase_info.denom) {
+    answer *= timebase_info.numer;
+    answer /= timebase_info.denom;
+  }
+  return (uint64_t)answer;
+}
+#endif
+
+static int64_t
+audiotimestamp_to_latency(AudioTimeStamp const * tstamp, cubeb_stream * stream)
+{
+  if (!(tstamp->mFlags & kAudioTimeStampHostTimeValid)) {
+    return 0;
+  }
+
+  uint64_t pres = AudioConvertHostTimeToNanos(tstamp->mHostTime);
+  uint64_t now = AudioConvertHostTimeToNanos(AudioGetCurrentHostTime());
+
+  return ((pres - now) * stream->output_desc.mSampleRate) / 1000000000LL;
+}
+
+static void
+audiounit_set_global_latency(cubeb_stream * stm, uint32_t latency_frames)
+{
+  stm->mutex.assert_current_thread_owns();
+  assert(stm->context->active_streams == 1);
+  stm->context->global_latency_frames = latency_frames;
+}
+
+static void
+audiounit_make_silent(AudioBuffer * ioData)
+{
+  assert(ioData);
+  assert(ioData->mData);
+  memset(ioData->mData, 0, ioData->mDataByteSize);
+}
+
+static OSStatus
+audiounit_render_input(cubeb_stream * stm,
+                       AudioUnitRenderActionFlags * flags,
+                       AudioTimeStamp const * tstamp,
+                       UInt32 bus,
+                       UInt32 input_frames)
+{
+  /* Create the AudioBufferList to store input. */
+  AudioBufferList input_buffer_list;
+  input_buffer_list.mBuffers[0].mDataByteSize =
+      stm->input_desc.mBytesPerFrame * input_frames;
+  input_buffer_list.mBuffers[0].mData = nullptr;
+  input_buffer_list.mBuffers[0].mNumberChannels = stm->input_desc.mChannelsPerFrame;
+  input_buffer_list.mNumberBuffers = 1;
+
+  /* Render input samples */
+  OSStatus r = AudioUnitRender(stm->input_unit,
+                               flags,
+                               tstamp,
+                               bus,
+                               input_frames,
+                               &input_buffer_list);
+
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitRender", r);
+    return r;
+  }
+
+  /* Copy input data in linear buffer. */
+  stm->input_linear_buffer->push(input_buffer_list.mBuffers[0].mData,
+                                 input_frames * stm->input_desc.mChannelsPerFrame);
+
+  LOGV("(%p) input:  buffers %d, size %d, channels %d, frames %d.",
+       stm, input_buffer_list.mNumberBuffers,
+       input_buffer_list.mBuffers[0].mDataByteSize,
+       input_buffer_list.mBuffers[0].mNumberChannels,
+       input_frames);
+
+  /* Advance input frame counter. */
+  assert(input_frames > 0);
+  stm->frames_read += input_frames;
+
+  return noErr;
+}
+
+static OSStatus
+audiounit_input_callback(void * user_ptr,
+                         AudioUnitRenderActionFlags * flags,
+                         AudioTimeStamp const * tstamp,
+                         UInt32 bus,
+                         UInt32 input_frames,
+                         AudioBufferList * /* bufs */)
+{
+  cubeb_stream * stm = static_cast<cubeb_stream *>(user_ptr);
+  long outframes;
+
+  assert(stm->input_unit != NULL);
+  assert(AU_IN_BUS == bus);
+
+  if (stm->shutdown) {
+    LOG("(%p) input shutdown", stm);
+    return noErr;
+  }
+
+  // This happens when we're finally getting a new input callback after having
+  // switched device, we can clear the input buffer now, only keeping the data
+  // we just got.
+  if (stm->output_callback_in_a_row > stm->expected_output_callbacks_in_a_row) {
+    stm->input_linear_buffer->pop(
+        nullptr,
+        stm->input_linear_buffer->length() -
+        input_frames * stm->input_stream_params.channels);
+  }
+
+  OSStatus r = audiounit_render_input(stm, flags, tstamp, bus, input_frames);
+  if (r != noErr) {
+    return r;
+  }
+
+  // Full Duplex. We'll call data_callback in the AudioUnit output callback.
+  if (stm->output_unit != NULL) {
+    stm->output_callback_in_a_row = 0;
+    return noErr;
+  }
+
+  /* Input only. Call the user callback through resampler.
+     Resampler will deliver input buffer in the correct rate. */
+  assert(input_frames <= stm->input_linear_buffer->length() / stm->input_desc.mChannelsPerFrame);
+  long total_input_frames = stm->input_linear_buffer->length() / stm->input_desc.mChannelsPerFrame;
+  outframes = cubeb_resampler_fill(stm->resampler,
+                                   stm->input_linear_buffer->data(),
+                                   &total_input_frames,
+                                   NULL,
+                                   0);
+  // Reset input buffer
+  stm->input_linear_buffer->clear();
+
+  if (outframes < 0 || outframes != input_frames) {
+    stm->shutdown = true;
+    return noErr;
+  }
+
+  return noErr;
+}
+
+static bool
+is_extra_input_needed(cubeb_stream * stm)
+{
+  /* If the output callback came first and this is a duplex stream, we need to
+    * fill in some additional silence in the resampler.
+    * Otherwise, if we had more than expected callbacks in a row, or we're currently
+    * switching, we add some silence as well to compensate for the fact that
+    * we're lacking some input data. */
+
+  /* If resampling is taking place after every output callback
+   * the input buffer expected to be empty.  Any frame left over
+   * from resampling is stored inside the resampler available to
+   * be used in next iteration as needed.
+   * BUT when noop_resampler is operating we have left over
+   * frames since it does not store anything internally. */
+  return stm->frames_read == 0 ||
+         (stm->input_linear_buffer->length() == 0 &&
+         (stm->output_callback_in_a_row > stm->expected_output_callbacks_in_a_row ||
+         stm->switching_device));
+}
+
+static OSStatus
+audiounit_output_callback(void * user_ptr,
+                          AudioUnitRenderActionFlags * /* flags */,
+                          AudioTimeStamp const * tstamp,
+                          UInt32 bus,
+                          UInt32 output_frames,
+                          AudioBufferList * outBufferList)
+{
+  assert(AU_OUT_BUS == bus);
+  assert(outBufferList->mNumberBuffers == 1);
+
+  cubeb_stream * stm = static_cast<cubeb_stream *>(user_ptr);
+
+  stm->output_callback_in_a_row++;
+
+  LOGV("(%p) output: buffers %d, size %d, channels %d, frames %d.",
+       stm, outBufferList->mNumberBuffers,
+       outBufferList->mBuffers[0].mDataByteSize,
+       outBufferList->mBuffers[0].mNumberChannels, output_frames);
+
+  long outframes = 0, input_frames = 0;
+  void * output_buffer = NULL, * input_buffer = NULL;
+
+  if (stm->shutdown) {
+    LOG("(%p) output shutdown.", stm);
+    audiounit_make_silent(&outBufferList->mBuffers[0]);
+    return noErr;
+  }
+
+  stm->current_latency_frames = audiotimestamp_to_latency(tstamp, stm);
+  if (stm->draining) {
+    OSStatus r = AudioOutputUnitStop(stm->output_unit);
+    assert(r == 0);
+    if (stm->input_unit) {
+      r = AudioOutputUnitStop(stm->input_unit);
+      assert(r == 0);
+    }
+    stm->state_callback(stm, stm->user_ptr, CUBEB_STATE_DRAINED);
+    audiounit_make_silent(&outBufferList->mBuffers[0]);
+    return noErr;
+  }
+  /* Get output buffer. */
+  output_buffer = outBufferList->mBuffers[0].mData;
+  /* If Full duplex get also input buffer */
+  if (stm->input_unit != NULL) {
+    if (is_extra_input_needed(stm)) {
+      uint32_t min_input_frames_required = ceilf(stm->input_hw_rate / stm->output_hw_rate *
+                                                                      stm->input_buffer_frames);
+      stm->input_linear_buffer->push_silence(min_input_frames_required * stm->input_desc.mChannelsPerFrame);
+      LOG("(%p) %s pushed %u frames of input silence.", stm, stm->frames_read == 0 ? "Input hasn't started," :
+          stm->switching_device ? "Device switching," : "Drop out,", min_input_frames_required);
+    }
+    // The input buffer
+    input_buffer = stm->input_linear_buffer->data();
+    // Number of input frames in the buffer
+    input_frames = stm->input_linear_buffer->length() / stm->input_desc.mChannelsPerFrame;
+  }
+
+  /* Call user callback through resampler. */
+  outframes = cubeb_resampler_fill(stm->resampler,
+                                   input_buffer,
+                                   input_buffer ? &input_frames : NULL,
+                                   output_buffer,
+                                   output_frames);
+
+  if (input_buffer) {
+    stm->input_linear_buffer->pop(nullptr, input_frames * stm->input_desc.mChannelsPerFrame);
+  }
+
+  if (outframes < 0) {
+    stm->shutdown = true;
+    return noErr;
+  }
+
+  size_t outbpf = stm->output_desc.mBytesPerFrame;
+  stm->draining = outframes < output_frames;
+  stm->frames_played = stm->frames_queued;
+  stm->frames_queued += outframes;
+
+  AudioFormatFlags outaff = stm->output_desc.mFormatFlags;
+  float panning = (stm->output_desc.mChannelsPerFrame == 2) ?
+      stm->panning.load(std::memory_order_relaxed) : 0.0f;
+
+  /* Post process output samples. */
+  if (stm->draining) {
+    /* Clear missing frames (silence) */
+    memset((uint8_t*)output_buffer + outframes * outbpf, 0, (output_frames - outframes) * outbpf);
+  }
+  /* Pan stereo. */
+  if (panning != 0.0f) {
+    if (outaff & kAudioFormatFlagIsFloat) {
+      cubeb_pan_stereo_buffer_float((float*)output_buffer, outframes, panning);
+    } else if (outaff & kAudioFormatFlagIsSignedInteger) {
+      cubeb_pan_stereo_buffer_int((short*)output_buffer, outframes, panning);
+    }
+  }
+  return noErr;
+}
+
+extern "C" {
+int
+audiounit_init(cubeb ** context, char const * /* context_name */)
+{
+  cubeb * ctx;
+
+  *context = NULL;
+
+  ctx = (cubeb *)calloc(1, sizeof(cubeb));
+  assert(ctx);
+  // Placement new to call the ctors of cubeb members.
+  new (ctx) cubeb();
+
+  ctx->ops = &audiounit_ops;
+
+  ctx->active_streams = 0;
+
+  ctx->limit_streams = kCFCoreFoundationVersionNumber < kCFCoreFoundationVersionNumber10_7;
+#if !TARGET_OS_IPHONE
+  cubeb_set_coreaudio_notification_runloop();
+#endif
+
+  *context = ctx;
+
+  return CUBEB_OK;
+}
+}
+
+static char const *
+audiounit_get_backend_id(cubeb * /* ctx */)
+{
+  return "audiounit";
+}
+
+#if !TARGET_OS_IPHONE
+static int
+audiounit_get_output_device_id(AudioDeviceID * device_id)
+{
+  UInt32 size;
+  OSStatus r;
+  AudioObjectPropertyAddress output_device_address = {
+    kAudioHardwarePropertyDefaultOutputDevice,
+    kAudioObjectPropertyScopeGlobal,
+    kAudioObjectPropertyElementMaster
+  };
+
+  size = sizeof(*device_id);
+
+  r = AudioObjectGetPropertyData(kAudioObjectSystemObject,
+                                 &output_device_address,
+                                 0,
+                                 NULL,
+                                 &size,
+                                 device_id);
+  if (r != noErr) {
+    PRINT_ERROR_CODE("output_device_id", r);
+    return CUBEB_ERROR;
+  }
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_get_input_device_id(AudioDeviceID * device_id)
+{
+  UInt32 size;
+  OSStatus r;
+  AudioObjectPropertyAddress input_device_address = {
+    kAudioHardwarePropertyDefaultInputDevice,
+    kAudioObjectPropertyScopeGlobal,
+    kAudioObjectPropertyElementMaster
+  };
+
+  size = sizeof(*device_id);
+
+  r = AudioObjectGetPropertyData(kAudioObjectSystemObject,
+                                 &input_device_address,
+                                 0,
+                                 NULL,
+                                 &size,
+                                 device_id);
+  if (r != noErr) {
+    return CUBEB_ERROR;
+  }
+
+  return CUBEB_OK;
+}
+
+static int audiounit_stream_get_volume(cubeb_stream * stm, float * volume);
+static int audiounit_stream_set_volume(cubeb_stream * stm, float volume);
+static int audiounit_uninstall_device_changed_callback(cubeb_stream * stm);
+
+static int
+audiounit_reinit_stream(cubeb_stream * stm)
+{
+  auto_lock context_lock(stm->context->mutex);
+  if (!stm->shutdown) {
+    audiounit_stream_stop_internal(stm);
+  }
+
+  int r = audiounit_uninstall_device_changed_callback(stm);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Could not uninstall the device changed callback", stm);
+  }
+
+  {
+    auto_lock lock(stm->mutex);
+    float volume = 0.0;
+    int vol_rv = audiounit_stream_get_volume(stm, &volume);
+
+    audiounit_close_stream(stm);
+
+    if (audiounit_setup_stream(stm) != CUBEB_OK) {
+      LOG("(%p) Stream reinit failed.", stm);
+      return CUBEB_ERROR;
+    }
+
+    if (vol_rv == CUBEB_OK) {
+      audiounit_stream_set_volume(stm, volume);
+    }
+
+    // Reset input frames to force new stream pre-buffer
+    // silence if needed, check `is_extra_input_needed()`
+    stm->frames_read = 0;
+
+    // If the stream was running, start it again.
+    if (!stm->shutdown) {
+      audiounit_stream_start_internal(stm);
+    }
+  }
+  return CUBEB_OK;
+}
+
+static OSStatus
+audiounit_property_listener_callback(AudioObjectID /* id */, UInt32 address_count,
+                                     const AudioObjectPropertyAddress * addresses,
+                                     void * user)
+{
+  cubeb_stream * stm = (cubeb_stream*) user;
+  stm->switching_device = true;
+
+  LOG("(%p) Audio device changed, %d events.", stm, address_count);
+  for (UInt32 i = 0; i < address_count; i++) {
+    switch(addresses[i].mSelector) {
+      case kAudioHardwarePropertyDefaultOutputDevice: {
+          LOG("Event[%d] - mSelector == kAudioHardwarePropertyDefaultOutputDevice", i);
+          // Allow restart to choose the new default
+          stm->output_device = nullptr;
+        }
+        break;
+      case kAudioHardwarePropertyDefaultInputDevice: {
+          LOG("Event[%d] - mSelector == kAudioHardwarePropertyDefaultInputDevice", i);
+          // Allow restart to choose the new default
+          stm->input_device = nullptr;
+        }
+      break;
+      case kAudioDevicePropertyDeviceIsAlive: {
+          LOG("Event[%d] - mSelector == kAudioDevicePropertyDeviceIsAlive", i);
+          // If this is the default input device ignore the event,
+          // kAudioHardwarePropertyDefaultInputDevice will take care of the switch
+          if (stm->is_default_input) {
+            LOG("It's the default input device, ignore the event");
+            return noErr;
+          }
+          // Allow restart to choose the new default. Event register only for input.
+          stm->input_device = nullptr;
+        }
+        break;
+      case kAudioDevicePropertyDataSource: {
+          LOG("Event[%d] - mSelector == kAudioHardwarePropertyDataSource", i);
+          return noErr;
+        }
+    }
+  }
+
+  for (UInt32 i = 0; i < address_count; i++) {
+    switch(addresses[i].mSelector) {
+    case kAudioHardwarePropertyDefaultOutputDevice:
+    case kAudioHardwarePropertyDefaultInputDevice:
+    case kAudioDevicePropertyDeviceIsAlive:
+      /* fall through */
+    case kAudioDevicePropertyDataSource: {
+        auto_lock lock(stm->mutex);
+        if (stm->device_changed_callback) {
+          stm->device_changed_callback(stm->user_ptr);
+        }
+        break;
+      }
+    }
+  }
+
+  // Use a new thread, through the queue, to avoid deadlock when calling
+  // Get/SetProperties method from inside notify callback
+  dispatch_async(stm->context->serial_queue, ^() {
+    if (audiounit_reinit_stream(stm) != CUBEB_OK) {
+      stm->state_callback(stm, stm->user_ptr, CUBEB_STATE_STOPPED);
+      LOG("(%p) Could not reopen the stream after switching.", stm);
+    }
+    stm->switching_device = false;
+  });
+
+  return noErr;
+}
+
+OSStatus
+audiounit_add_listener(cubeb_stream * stm, AudioDeviceID id, AudioObjectPropertySelector selector,
+    AudioObjectPropertyScope scope, AudioObjectPropertyListenerProc listener)
+{
+  AudioObjectPropertyAddress address = {
+      selector,
+      scope,
+      kAudioObjectPropertyElementMaster
+  };
+
+  return AudioObjectAddPropertyListener(id, &address, listener, stm);
+}
+
+OSStatus
+audiounit_remove_listener(cubeb_stream * stm, AudioDeviceID id,
+                          AudioObjectPropertySelector selector,
+                          AudioObjectPropertyScope scope,
+                          AudioObjectPropertyListenerProc listener)
+{
+  AudioObjectPropertyAddress address = {
+      selector,
+      scope,
+      kAudioObjectPropertyElementMaster
+  };
+
+  return AudioObjectRemovePropertyListener(id, &address, listener, stm);
+}
+
+static AudioObjectID audiounit_get_default_device_id(cubeb_device_type type);
+
+static int
+audiounit_install_device_changed_callback(cubeb_stream * stm)
+{
+  OSStatus r;
+
+  if (stm->output_unit) {
+    /* This event will notify us when the data source on the same device changes,
+     * for example when the user plugs in a normal (non-usb) headset in the
+     * headphone jack. */
+    AudioDeviceID output_dev_id;
+    r = audiounit_get_output_device_id(&output_dev_id);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+
+    r = audiounit_add_listener(stm, output_dev_id, kAudioDevicePropertyDataSource,
+        kAudioDevicePropertyScopeOutput, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioObjectAddPropertyListener/output/kAudioDevicePropertyDataSource", r);
+      return CUBEB_ERROR;
+    }
+  }
+
+  if (stm->input_unit) {
+    /* This event will notify us when the data source on the input device changes. */
+    AudioDeviceID input_dev_id;
+    r = audiounit_get_input_device_id(&input_dev_id);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+
+    r = audiounit_add_listener(stm, input_dev_id, kAudioDevicePropertyDataSource,
+        kAudioDevicePropertyScopeInput, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioObjectAddPropertyListener/input/kAudioDevicePropertyDataSource", r);
+      return CUBEB_ERROR;
+    }
+
+    /* Event to notify when the input is going away. */
+    AudioDeviceID dev = stm->input_device ? reinterpret_cast<intptr_t>(stm->input_device) :
+                                            audiounit_get_default_device_id(CUBEB_DEVICE_TYPE_INPUT);
+    r = audiounit_add_listener(stm, dev, kAudioDevicePropertyDeviceIsAlive,
+        kAudioObjectPropertyScopeGlobal, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioObjectAddPropertyListener/input/kAudioDevicePropertyDeviceIsAlive", r);
+      return CUBEB_ERROR;
+    }
+  }
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_install_system_changed_callback(cubeb_stream * stm)
+{
+  OSStatus r;
+
+  if (stm->output_unit) {
+    /* This event will notify us when the default audio device changes,
+     * for example when the user plugs in a USB headset and the system chooses it
+     * automatically as the default, or when another device is chosen in the
+     * dropdown list. */
+    r = audiounit_add_listener(stm, kAudioObjectSystemObject, kAudioHardwarePropertyDefaultOutputDevice,
+                               kAudioObjectPropertyScopeGlobal, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      LOG("AudioObjectAddPropertyListener/output/kAudioHardwarePropertyDefaultOutputDevice rv=%d", r);
+      return CUBEB_ERROR;
+    }
+  }
+
+  if (stm->input_unit) {
+    /* This event will notify us when the default input device changes. */
+    r = audiounit_add_listener(stm, kAudioObjectSystemObject, kAudioHardwarePropertyDefaultInputDevice,
+                               kAudioObjectPropertyScopeGlobal, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      LOG("AudioObjectAddPropertyListener/input/kAudioHardwarePropertyDefaultInputDevice rv=%d", r);
+      return CUBEB_ERROR;
+    }
+  }
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_uninstall_device_changed_callback(cubeb_stream * stm)
+{
+  OSStatus r;
+
+  if (stm->output_unit) {
+    AudioDeviceID output_dev_id;
+    r = audiounit_get_output_device_id(&output_dev_id);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+
+    r = audiounit_remove_listener(stm, output_dev_id, kAudioDevicePropertyDataSource,
+        kAudioDevicePropertyScopeOutput, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+  }
+
+  if (stm->input_unit) {
+    AudioDeviceID input_dev_id;
+    r = audiounit_get_input_device_id(&input_dev_id);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+
+    r = audiounit_remove_listener(stm, input_dev_id, kAudioDevicePropertyDataSource,
+        kAudioDevicePropertyScopeInput, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+  }
+  return CUBEB_OK;
+}
+
+static int
+audiounit_uninstall_system_changed_callback(cubeb_stream * stm)
+{
+  OSStatus r;
+
+  if (stm->output_unit) {
+    r = audiounit_remove_listener(stm, kAudioObjectSystemObject, kAudioHardwarePropertyDefaultOutputDevice,
+                                  kAudioObjectPropertyScopeGlobal, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+  }
+
+  if (stm->input_unit) {
+    r = audiounit_remove_listener(stm, kAudioObjectSystemObject, kAudioHardwarePropertyDefaultInputDevice,
+                                  kAudioObjectPropertyScopeGlobal, &audiounit_property_listener_callback);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+  }
+  return CUBEB_OK;
+}
+
+/* Get the acceptable buffer size (in frames) that this device can work with. */
+static int
+audiounit_get_acceptable_latency_range(AudioValueRange * latency_range)
+{
+  UInt32 size;
+  OSStatus r;
+  AudioDeviceID output_device_id;
+  AudioObjectPropertyAddress output_device_buffer_size_range = {
+    kAudioDevicePropertyBufferFrameSizeRange,
+    kAudioDevicePropertyScopeOutput,
+    kAudioObjectPropertyElementMaster
+  };
+
+  if (audiounit_get_output_device_id(&output_device_id) != CUBEB_OK) {
+    LOG("Could not get default output device id.");
+    return CUBEB_ERROR;
+  }
+
+  /* Get the buffer size range this device supports */
+  size = sizeof(*latency_range);
+
+  r = AudioObjectGetPropertyData(output_device_id,
+                                 &output_device_buffer_size_range,
+                                 0,
+                                 NULL,
+                                 &size,
+                                 latency_range);
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioObjectGetPropertyData/buffer size range", r);
+    return CUBEB_ERROR;
+  }
+
+  return CUBEB_OK;
+}
+#endif /* !TARGET_OS_IPHONE */
+
+static AudioObjectID
+audiounit_get_default_device_id(cubeb_device_type type)
+{
+  AudioObjectPropertyAddress adr = { 0, kAudioObjectPropertyScopeGlobal, kAudioObjectPropertyElementMaster };
+  AudioDeviceID devid;
+  UInt32 size;
+
+  if (type == CUBEB_DEVICE_TYPE_OUTPUT) {
+    adr.mSelector = kAudioHardwarePropertyDefaultOutputDevice;
+  } else if (type == CUBEB_DEVICE_TYPE_INPUT) {
+    adr.mSelector = kAudioHardwarePropertyDefaultInputDevice;
+  } else {
+    return kAudioObjectUnknown;
+  }
+
+  size = sizeof(AudioDeviceID);
+  if (AudioObjectGetPropertyData(kAudioObjectSystemObject, &adr, 0, NULL, &size, &devid) != noErr) {
+    return kAudioObjectUnknown;
+  }
+
+  return devid;
+}
+
+int
+audiounit_get_max_channel_count(cubeb * ctx, uint32_t * max_channels)
+{
+#if TARGET_OS_IPHONE
+  //TODO: [[AVAudioSession sharedInstance] maximumOutputNumberOfChannels]
+  *max_channels = 2;
+#else
+  UInt32 size;
+  OSStatus r;
+  AudioDeviceID output_device_id;
+  AudioStreamBasicDescription stream_format;
+  AudioObjectPropertyAddress stream_format_address = {
+    kAudioDevicePropertyStreamFormat,
+    kAudioDevicePropertyScopeOutput,
+    kAudioObjectPropertyElementMaster
+  };
+
+  assert(ctx && max_channels);
+
+  if (audiounit_get_output_device_id(&output_device_id) != CUBEB_OK) {
+    return CUBEB_ERROR;
+  }
+
+  size = sizeof(stream_format);
+
+  r = AudioObjectGetPropertyData(output_device_id,
+                                 &stream_format_address,
+                                 0,
+                                 NULL,
+                                 &size,
+                                 &stream_format);
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioObjectPropertyAddress/StreamFormat", r);
+    return CUBEB_ERROR;
+  }
+
+  *max_channels = stream_format.mChannelsPerFrame;
+#endif
+  return CUBEB_OK;
+}
+
+static int
+audiounit_get_min_latency(cubeb * /* ctx */,
+                          cubeb_stream_params /* params */,
+                          uint32_t * latency_frames)
+{
+#if TARGET_OS_IPHONE
+  //TODO: [[AVAudioSession sharedInstance] inputLatency]
+  return CUBEB_ERROR_NOT_SUPPORTED;
+#else
+  AudioValueRange latency_range;
+  if (audiounit_get_acceptable_latency_range(&latency_range) != CUBEB_OK) {
+    LOG("Could not get acceptable latency range.");
+    return CUBEB_ERROR;
+  }
+
+  *latency_frames = std::max<uint32_t>(latency_range.mMinimum,
+                                       SAFE_MIN_LATENCY_FRAMES);
+#endif
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_get_preferred_sample_rate(cubeb * /* ctx */, uint32_t * rate)
+{
+#if TARGET_OS_IPHONE
+  //TODO
+  return CUBEB_ERROR_NOT_SUPPORTED;
+#else
+  UInt32 size;
+  OSStatus r;
+  Float64 fsamplerate;
+  AudioDeviceID output_device_id;
+  AudioObjectPropertyAddress samplerate_address = {
+    kAudioDevicePropertyNominalSampleRate,
+    kAudioObjectPropertyScopeGlobal,
+    kAudioObjectPropertyElementMaster
+  };
+
+  if (audiounit_get_output_device_id(&output_device_id) != CUBEB_OK) {
+    return CUBEB_ERROR;
+  }
+
+  size = sizeof(fsamplerate);
+  r = AudioObjectGetPropertyData(output_device_id,
+                                 &samplerate_address,
+                                 0,
+                                 NULL,
+                                 &size,
+                                 &fsamplerate);
+
+  if (r != noErr) {
+    return CUBEB_ERROR;
+  }
+
+  *rate = static_cast<uint32_t>(fsamplerate);
+#endif
+  return CUBEB_OK;
+}
+
+static OSStatus audiounit_remove_device_listener(cubeb * context);
+
+static void
+audiounit_destroy(cubeb * ctx)
+{
+  // Disabling this assert for bug 1083664 -- we seem to leak a stream
+  // assert(ctx->active_streams == 0);
+
+  {
+    auto_lock lock(ctx->mutex);
+    /* Unregister the callback if necessary. */
+    if(ctx->collection_changed_callback) {
+      audiounit_remove_device_listener(ctx);
+    }
+  }
+
+  ctx->~cubeb();
+  free(ctx);
+}
+
+static void audiounit_stream_destroy(cubeb_stream * stm);
+
+static int
+audio_stream_desc_init(AudioStreamBasicDescription * ss,
+                       const cubeb_stream_params * stream_params)
+{
+  switch (stream_params->format) {
+  case CUBEB_SAMPLE_S16LE:
+    ss->mBitsPerChannel = 16;
+    ss->mFormatFlags = kAudioFormatFlagIsSignedInteger;
+    break;
+  case CUBEB_SAMPLE_S16BE:
+    ss->mBitsPerChannel = 16;
+    ss->mFormatFlags = kAudioFormatFlagIsSignedInteger |
+      kAudioFormatFlagIsBigEndian;
+    break;
+  case CUBEB_SAMPLE_FLOAT32LE:
+    ss->mBitsPerChannel = 32;
+    ss->mFormatFlags = kAudioFormatFlagIsFloat;
+    break;
+  case CUBEB_SAMPLE_FLOAT32BE:
+    ss->mBitsPerChannel = 32;
+    ss->mFormatFlags = kAudioFormatFlagIsFloat |
+      kAudioFormatFlagIsBigEndian;
+    break;
+  default:
+    return CUBEB_ERROR_INVALID_FORMAT;
+  }
+
+  ss->mFormatID = kAudioFormatLinearPCM;
+  ss->mFormatFlags |= kLinearPCMFormatFlagIsPacked;
+  ss->mSampleRate = stream_params->rate;
+  ss->mChannelsPerFrame = stream_params->channels;
+
+  ss->mBytesPerFrame = (ss->mBitsPerChannel / 8) * ss->mChannelsPerFrame;
+  ss->mFramesPerPacket = 1;
+  ss->mBytesPerPacket = ss->mBytesPerFrame * ss->mFramesPerPacket;
+
+  ss->mReserved = 0;
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_create_unit(AudioUnit * unit,
+                      bool is_input,
+                      const cubeb_stream_params * /* stream_params */,
+                      cubeb_devid device)
+{
+  AudioComponentDescription desc;
+  AudioComponent comp;
+  UInt32 enable;
+  AudioDeviceID devid;
+  OSStatus rv;
+
+  desc.componentType = kAudioUnitType_Output;
+#if TARGET_OS_IPHONE
+  bool use_default_output = false;
+  desc.componentSubType = kAudioUnitSubType_RemoteIO;
+#else
+  // Use the DefaultOutputUnit for output when no device is specified
+  // so we retain automatic output device switching when the default
+  // changes.  Once we have complete support for device notifications
+  // and switching, we can use the AUHAL for everything.
+  bool use_default_output = device == NULL && !is_input;
+  if (use_default_output) {
+    desc.componentSubType = kAudioUnitSubType_DefaultOutput;
+  } else {
+    desc.componentSubType = kAudioUnitSubType_HALOutput;
+  }
+#endif
+  desc.componentManufacturer = kAudioUnitManufacturer_Apple;
+  desc.componentFlags = 0;
+  desc.componentFlagsMask = 0;
+  comp = AudioComponentFindNext(NULL, &desc);
+  if (comp == NULL) {
+    LOG("Could not find matching audio hardware.");
+    return CUBEB_ERROR;
+  }
+
+  rv = AudioComponentInstanceNew(comp, unit);
+  if (rv != noErr) {
+    PRINT_ERROR_CODE("AudioComponentInstanceNew", rv);
+    return CUBEB_ERROR;
+  }
+
+  if (!use_default_output) {
+    enable = 1;
+    rv = AudioUnitSetProperty(*unit, kAudioOutputUnitProperty_EnableIO,
+                              is_input ? kAudioUnitScope_Input : kAudioUnitScope_Output,
+                              is_input ? AU_IN_BUS : AU_OUT_BUS, &enable, sizeof(UInt32));
+    if (rv != noErr) {
+      PRINT_ERROR_CODE("AudioUnitSetProperty/kAudioOutputUnitProperty_EnableIO", rv);
+      return CUBEB_ERROR;
+    }
+
+    enable = 0;
+    rv = AudioUnitSetProperty(*unit, kAudioOutputUnitProperty_EnableIO,
+                              is_input ? kAudioUnitScope_Output : kAudioUnitScope_Input,
+                              is_input ? AU_OUT_BUS : AU_IN_BUS, &enable, sizeof(UInt32));
+    if (rv != noErr) {
+      PRINT_ERROR_CODE("AudioUnitSetProperty/kAudioOutputUnitProperty_EnableIO", rv);
+      return CUBEB_ERROR;
+    }
+
+    if (device == NULL) {
+      assert(is_input);
+      devid = audiounit_get_default_device_id(CUBEB_DEVICE_TYPE_INPUT);
+    } else {
+      devid = reinterpret_cast<intptr_t>(device);
+    }
+    rv = AudioUnitSetProperty(*unit, kAudioOutputUnitProperty_CurrentDevice,
+                              kAudioUnitScope_Global,
+                              is_input ? AU_IN_BUS : AU_OUT_BUS,
+                              &devid, sizeof(AudioDeviceID));
+    if (rv != noErr) {
+      PRINT_ERROR_CODE("AudioUnitSetProperty/kAudioOutputUnitProperty_CurrentDevice", rv);
+      return CUBEB_ERROR;
+    }
+  }
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_init_input_linear_buffer(cubeb_stream * stream, uint32_t capacity)
+{
+  if (stream->input_desc.mFormatFlags & kAudioFormatFlagIsSignedInteger) {
+    stream->input_linear_buffer = new auto_array_wrapper(
+        new auto_array<short>(capacity *
+                              stream->input_buffer_frames *
+                              stream->input_desc.mChannelsPerFrame) );
+  } else {
+    stream->input_linear_buffer = new auto_array_wrapper(
+        new auto_array<float>(capacity *
+                              stream->input_buffer_frames *
+                              stream->input_desc.mChannelsPerFrame) );
+  }
+
+  if (!stream->input_linear_buffer) {
+    return CUBEB_ERROR;
+  }
+
+  assert(stream->input_linear_buffer->length() == 0);
+
+  // Pre-buffer silence if needed
+  if (capacity != 1) {
+    size_t silence_size = stream->input_buffer_frames *
+                          stream->input_desc.mChannelsPerFrame;
+    stream->input_linear_buffer->push_silence(silence_size);
+
+    assert(stream->input_linear_buffer->length() == silence_size);
+  }
+
+  return CUBEB_OK;
+}
+
+static void
+audiounit_destroy_input_linear_buffer(cubeb_stream * stream)
+{
+  delete stream->input_linear_buffer;
+}
+
+static uint32_t
+audiounit_clamp_latency(cubeb_stream * stm, uint32_t latency_frames)
+{
+  // For the 1st stream set anything within safe min-max
+  assert(stm->context->active_streams > 0);
+  if (stm->context->active_streams == 1) {
+    return std::max(std::min<uint32_t>(latency_frames, SAFE_MAX_LATENCY_FRAMES),
+                    SAFE_MIN_LATENCY_FRAMES);
+  }
+
+  // If more than one stream operates in parallel
+  // allow only lower values of latency
+  int r;
+  UInt32 output_buffer_size = 0;
+  UInt32 size = sizeof(output_buffer_size);
+  if (stm->output_unit) {
+    r = AudioUnitGetProperty(stm->output_unit,
+                            kAudioDevicePropertyBufferFrameSize,
+                            kAudioUnitScope_Output,
+                            AU_OUT_BUS,
+                            &output_buffer_size,
+                            &size);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioUnitGetProperty/output/kAudioDevicePropertyBufferFrameSize", r);
+      return 0;
+    }
+
+    output_buffer_size = std::max(std::min<uint32_t>(output_buffer_size, SAFE_MAX_LATENCY_FRAMES),
+                                  SAFE_MIN_LATENCY_FRAMES);
+  }
+
+  UInt32 input_buffer_size = 0;
+  if (stm->input_unit) {
+    r = AudioUnitGetProperty(stm->input_unit,
+                            kAudioDevicePropertyBufferFrameSize,
+                            kAudioUnitScope_Input,
+                            AU_IN_BUS,
+                            &input_buffer_size,
+                            &size);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioUnitGetProperty/input/kAudioDevicePropertyBufferFrameSize", r);
+      return 0;
+    }
+
+    input_buffer_size = std::max(std::min<uint32_t>(input_buffer_size, SAFE_MAX_LATENCY_FRAMES),
+                                 SAFE_MIN_LATENCY_FRAMES);
+  }
+
+  // Every following active streams can only set smaller latency
+  UInt32 upper_latency_limit = 0;
+  if (input_buffer_size != 0 && output_buffer_size != 0) {
+    upper_latency_limit = std::min<uint32_t>(input_buffer_size, output_buffer_size);
+  } else if (input_buffer_size != 0) {
+    upper_latency_limit = input_buffer_size;
+  } else if (output_buffer_size != 0) {
+    upper_latency_limit = output_buffer_size;
+  } else {
+    upper_latency_limit = SAFE_MAX_LATENCY_FRAMES;
+  }
+
+  return std::max(std::min<uint32_t>(latency_frames, upper_latency_limit),
+                  SAFE_MIN_LATENCY_FRAMES);
+}
+
+/*
+ * Change buffer size is prone to deadlock thus we change it
+ * following the steps:
+ * - register a listener for the buffer size property
+ * - change the property
+ * - wait until the listener is executed
+ * - property has changed, remove the listener
+ * */
+static void
+buffer_size_changed_callback(void * inClientData,
+                             AudioUnit inUnit,
+                             AudioUnitPropertyID	inPropertyID,
+                             AudioUnitScope		inScope,
+                             AudioUnitElement	inElement)
+{
+  cubeb_stream * stm = (cubeb_stream *)inClientData;
+
+  AudioUnit au = inUnit;
+  AudioUnitScope au_scope = kAudioUnitScope_Input;
+  AudioUnitElement au_element = inElement;
+  const char * au_type = "output";
+
+  if (au == stm->input_unit) {
+    au_scope = kAudioUnitScope_Output;
+    au_type = "input";
+  }
+
+  switch (inPropertyID) {
+
+    case kAudioDevicePropertyBufferFrameSize: {
+      if (inScope != au_scope) {
+        break;
+      }
+      UInt32 new_buffer_size;
+      UInt32 outSize = sizeof(UInt32);
+      OSStatus r = AudioUnitGetProperty(au,
+                                        kAudioDevicePropertyBufferFrameSize,
+                                        au_scope,
+                                        au_element,
+                                        &new_buffer_size,
+                                        &outSize);
+      if (r != noErr) {
+        LOG("(%p) Event: kAudioDevicePropertyBufferFrameSize: Cannot get current buffer size", stm);
+      } else {
+        LOG("(%p) Event: kAudioDevicePropertyBufferFrameSize: New %s buffer size = %d for scope %d", stm,
+            au_type, new_buffer_size, inScope);
+      }
+      stm->buffer_size_change_state = true;
+      break;
+    }
+  }
+}
+
+enum set_buffer_size_side {
+  INPUT,
+  OUTPUT,
+};
+
+static int
+audiounit_set_buffer_size(cubeb_stream * stm, uint32_t new_size_frames, set_buffer_size_side set_side)
+{
+  AudioUnit au = stm->output_unit;
+  AudioUnitScope au_scope = kAudioUnitScope_Input;
+  AudioUnitElement au_element = AU_OUT_BUS;
+  const char * au_type = "output";
+
+  if (set_side == INPUT) {
+    au = stm->input_unit;
+    au_scope = kAudioUnitScope_Output;
+    au_element = AU_IN_BUS;
+    au_type = "input";
+  }
+
+  uint32_t buffer_frames = 0;
+  UInt32 size = sizeof(buffer_frames);
+  int r = AudioUnitGetProperty(au,
+                               kAudioDevicePropertyBufferFrameSize,
+                               au_scope,
+                               au_element,
+                               &buffer_frames,
+                               &size);
+  if (r != noErr) {
+    if (set_side == INPUT) {
+      PRINT_ERROR_CODE("AudioUnitGetProperty/input/kAudioDevicePropertyBufferFrameSize", r);
+    } else {
+      PRINT_ERROR_CODE("AudioUnitGetProperty/output/kAudioDevicePropertyBufferFrameSize", r);
+    }
+    return CUBEB_ERROR;
+  }
+
+  if (new_size_frames == buffer_frames) {
+    LOG("(%p) No need to update %s buffer size already %u frames", stm, au_type, buffer_frames);
+    return CUBEB_OK;
+  }
+
+  r = AudioUnitAddPropertyListener(au,
+                                   kAudioDevicePropertyBufferFrameSize,
+                                   buffer_size_changed_callback,
+                                   stm);
+  if (r != noErr) {
+    if (set_side == INPUT) {
+      PRINT_ERROR_CODE("AudioUnitAddPropertyListener/input/kAudioDevicePropertyBufferFrameSize", r);
+    } else {
+      PRINT_ERROR_CODE("AudioUnitAddPropertyListener/output/kAudioDevicePropertyBufferFrameSize", r);
+    }
+    return CUBEB_ERROR;
+  }
+
+  stm->buffer_size_change_state = false;
+
+  r = AudioUnitSetProperty(au,
+                           kAudioDevicePropertyBufferFrameSize,
+                           au_scope,
+                           au_element,
+                           &new_size_frames,
+                           sizeof(new_size_frames));
+  if (r != noErr) {
+    if (set_side == INPUT) {
+      PRINT_ERROR_CODE("AudioUnitSetProperty/input/kAudioDevicePropertyBufferFrameSize", r);
+    } else {
+      PRINT_ERROR_CODE("AudioUnitSetProperty/output/kAudioDevicePropertyBufferFrameSize", r);
+    }
+
+    r = AudioUnitRemovePropertyListenerWithUserData(au,
+                                                    kAudioDevicePropertyBufferFrameSize,
+                                                    buffer_size_changed_callback,
+                                                    stm);
+    if (r != noErr) {
+      if (set_side == INPUT) {
+        PRINT_ERROR_CODE("AudioUnitAddPropertyListener/input/kAudioDevicePropertyBufferFrameSize", r);
+      } else {
+        PRINT_ERROR_CODE("AudioUnitAddPropertyListener/output/kAudioDevicePropertyBufferFrameSize", r);
+      }
+    }
+
+    return CUBEB_ERROR;
+  }
+
+  int count = 0;
+  while (!stm->buffer_size_change_state && count++ < 30) {
+    struct timespec req, rem;
+    req.tv_sec = 0;
+    req.tv_nsec = 100000000L; // 0.1 sec
+    if (nanosleep(&req , &rem) < 0 ) {
+      LOG("(%p) Warning: nanosleep call failed or interrupted. Remaining time %ld nano secs \n", stm, rem.tv_nsec);
+    }
+    LOG("(%p) audiounit_set_buffer_size : wait count = %d", stm, count);
+  }
+
+  r = AudioUnitRemovePropertyListenerWithUserData(au,
+                                                  kAudioDevicePropertyBufferFrameSize,
+                                                  buffer_size_changed_callback,
+                                                  stm);
+  if (r != noErr) {
+    return CUBEB_ERROR;
+    if (set_side == INPUT) {
+      PRINT_ERROR_CODE("AudioUnitAddPropertyListener/input/kAudioDevicePropertyBufferFrameSize", r);
+    } else {
+      PRINT_ERROR_CODE("AudioUnitAddPropertyListener/output/kAudioDevicePropertyBufferFrameSize", r);
+    }
+  }
+
+  if (!stm->buffer_size_change_state && count >= 30) {
+    LOG("(%p) Error, did not get buffer size change callback ...", stm);
+    return CUBEB_ERROR;
+  }
+
+  LOG("(%p) %s buffer size changed to %u frames.", stm, au_type, new_size_frames);
+  return CUBEB_OK;
+}
+
+static int
+audiounit_configure_input(cubeb_stream * stm)
+{
+  int r = 0;
+  UInt32 size;
+  AURenderCallbackStruct aurcbs_in;
+
+  LOG("(%p) Opening input side: rate %u, channels %u, format %d, latency in frames %u.",
+      stm, stm->input_stream_params.rate, stm->input_stream_params.channels,
+      stm->input_stream_params.format, stm->latency_frames);
+
+  /* Get input device sample rate. */
+  AudioStreamBasicDescription input_hw_desc;
+  size = sizeof(AudioStreamBasicDescription);
+  r = AudioUnitGetProperty(stm->input_unit,
+                           kAudioUnitProperty_StreamFormat,
+                           kAudioUnitScope_Input,
+                           AU_IN_BUS,
+                           &input_hw_desc,
+                           &size);
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitGetProperty/input/kAudioUnitProperty_StreamFormat", r);
+    return CUBEB_ERROR;
+  }
+  stm->input_hw_rate = input_hw_desc.mSampleRate;
+  LOG("(%p) Input device sampling rate: %.2f", stm, stm->input_hw_rate);
+
+  /* Set format description according to the input params. */
+  r = audio_stream_desc_init(&stm->input_desc, &stm->input_stream_params);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Setting format description for input failed.", stm);
+    return r;
+  }
+
+  // Use latency to set buffer size
+  stm->input_buffer_frames = stm->latency_frames;
+  r = audiounit_set_buffer_size(stm, stm->input_buffer_frames, INPUT);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Error in change input buffer size.", stm);
+    return CUBEB_ERROR;
+  }
+
+  AudioStreamBasicDescription src_desc = stm->input_desc;
+  /* Input AudioUnit must be configured with device's sample rate.
+     we will resample inside input callback. */
+  src_desc.mSampleRate = stm->input_hw_rate;
+
+  r = AudioUnitSetProperty(stm->input_unit,
+                           kAudioUnitProperty_StreamFormat,
+                           kAudioUnitScope_Output,
+                           AU_IN_BUS,
+                           &src_desc,
+                           sizeof(AudioStreamBasicDescription));
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitSetProperty/input/kAudioUnitProperty_StreamFormat", r);
+    return CUBEB_ERROR;
+  }
+
+  /* Frames per buffer in the input callback. */
+  r = AudioUnitSetProperty(stm->input_unit,
+                           kAudioUnitProperty_MaximumFramesPerSlice,
+                           kAudioUnitScope_Global,
+                           AU_IN_BUS,
+                           &stm->input_buffer_frames,
+                           sizeof(UInt32));
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitSetProperty/input/kAudioUnitProperty_MaximumFramesPerSlice", r);
+    return CUBEB_ERROR;
+  }
+
+  // Input only capacity
+  unsigned int array_capacity = 1;
+  if (has_output(stm)) {
+    // Full-duplex increase capacity
+    array_capacity = 8;
+  }
+  if (audiounit_init_input_linear_buffer(stm, array_capacity) != CUBEB_OK) {
+    return CUBEB_ERROR;
+  }
+
+  assert(stm->input_unit != NULL);
+  aurcbs_in.inputProc = audiounit_input_callback;
+  aurcbs_in.inputProcRefCon = stm;
+
+  r = AudioUnitSetProperty(stm->input_unit,
+                           kAudioOutputUnitProperty_SetInputCallback,
+                           kAudioUnitScope_Global,
+                           AU_OUT_BUS,
+                           &aurcbs_in,
+                           sizeof(aurcbs_in));
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitSetProperty/input/kAudioOutputUnitProperty_SetInputCallback", r);
+    return CUBEB_ERROR;
+  }
+  LOG("(%p) Input audiounit init successfully.", stm);
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_configure_output(cubeb_stream * stm)
+{
+  int r;
+  AURenderCallbackStruct aurcbs_out;
+  UInt32 size;
+
+
+  LOG("(%p) Opening output side: rate %u, channels %u, format %d, latency in frames %u.",
+      stm, stm->output_stream_params.rate, stm->output_stream_params.channels,
+      stm->output_stream_params.format, stm->latency_frames);
+
+  r = audio_stream_desc_init(&stm->output_desc, &stm->output_stream_params);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Could not initialize the audio stream description.", stm);
+    return r;
+  }
+
+  /* Get output device sample rate. */
+  AudioStreamBasicDescription output_hw_desc;
+  size = sizeof(AudioStreamBasicDescription);
+  memset(&output_hw_desc, 0, size);
+  r = AudioUnitGetProperty(stm->output_unit,
+                           kAudioUnitProperty_StreamFormat,
+                           kAudioUnitScope_Output,
+                           AU_OUT_BUS,
+                           &output_hw_desc,
+                           &size);
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitGetProperty/output/tkAudioUnitProperty_StreamFormat", r);
+    return CUBEB_ERROR;
+  }
+  stm->output_hw_rate = output_hw_desc.mSampleRate;
+  LOG("(%p) Output device sampling rate: %.2f", stm, output_hw_desc.mSampleRate);
+
+  r = AudioUnitSetProperty(stm->output_unit,
+                           kAudioUnitProperty_StreamFormat,
+                           kAudioUnitScope_Input,
+                           AU_OUT_BUS,
+                           &stm->output_desc,
+                           sizeof(AudioStreamBasicDescription));
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitSetProperty/output/kAudioUnitProperty_StreamFormat", r);
+    return CUBEB_ERROR;
+  }
+
+  r = audiounit_set_buffer_size(stm, stm->latency_frames, OUTPUT);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Error in change output buffer size.", stm);
+    return CUBEB_ERROR;
+  }
+
+  /* Frames per buffer in the input callback. */
+  r = AudioUnitSetProperty(stm->output_unit,
+                           kAudioUnitProperty_MaximumFramesPerSlice,
+                           kAudioUnitScope_Global,
+                           AU_OUT_BUS,
+                           &stm->latency_frames,
+                           sizeof(UInt32));
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitSetProperty/output/kAudioUnitProperty_MaximumFramesPerSlice", r);
+    return CUBEB_ERROR;
+  }
+
+  assert(stm->output_unit != NULL);
+  aurcbs_out.inputProc = audiounit_output_callback;
+  aurcbs_out.inputProcRefCon = stm;
+  r = AudioUnitSetProperty(stm->output_unit,
+                           kAudioUnitProperty_SetRenderCallback,
+                           kAudioUnitScope_Global,
+                           AU_OUT_BUS,
+                           &aurcbs_out,
+                           sizeof(aurcbs_out));
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitSetProperty/output/kAudioUnitProperty_SetRenderCallback", r);
+    return CUBEB_ERROR;
+  }
+
+  LOG("(%p) Output audiounit init successfully.", stm);
+  return CUBEB_OK;
+}
+
+static int
+audiounit_setup_stream(cubeb_stream * stm)
+{
+  stm->mutex.assert_current_thread_owns();
+
+  int r = 0;
+  if (has_input(stm)) {
+    r = audiounit_create_unit(&stm->input_unit, true,
+                              &stm->input_stream_params,
+                              stm->input_device);
+    if (r != CUBEB_OK) {
+      LOG("(%p) AudioUnit creation for input failed.", stm);
+      return r;
+    }
+  }
+
+  if (has_output(stm)) {
+    r = audiounit_create_unit(&stm->output_unit, false,
+                              &stm->output_stream_params,
+                              stm->output_device);
+    if (r != CUBEB_OK) {
+      LOG("(%p) AudioUnit creation for output failed.", stm);
+      return r;
+    }
+  }
+
+  /* Latency cannot change if another stream is operating in parallel. In this case
+  * latecy is set to the other stream value. */
+  if (stm->context->active_streams > 1) {
+    LOG("(%p) More than one active stream, use global latency.", stm);
+    stm->latency_frames = stm->context->global_latency_frames;
+  } else {
+    /* Silently clamp the latency down to the platform default, because we
+    * synthetize the clock from the callbacks, and we want the clock to update
+    * often. */
+    stm->latency_frames = audiounit_clamp_latency(stm, stm->latency_frames);
+    assert(stm->latency_frames); // Ungly error check
+    audiounit_set_global_latency(stm, stm->latency_frames);
+  }
+
+  /* Setup Input Stream! */
+  if (has_input(stm)) {
+    r = audiounit_configure_input(stm);
+    if (r != CUBEB_OK) {
+      LOG("(%p) Configure audiounit input failed.", stm);
+      return r;
+    }
+  }
+
+  /* Setup Output Stream! */
+  if (has_output(stm)) {
+    r = audiounit_configure_output(stm);
+    if (r != CUBEB_OK) {
+      LOG("(%p) Configure audiounit output failed.", stm);
+      return r;
+    }
+  }
+
+  // Setting the latency doesn't work well for USB headsets (eg. plantronics).
+  // Keep the default latency for now.
+#if 0
+  buffer_size = latency;
+
+  /* Get the range of latency this particular device can work with, and clamp
+   * the requested latency to this acceptable range. */
+#if !TARGET_OS_IPHONE
+  if (audiounit_get_acceptable_latency_range(&latency_range) != CUBEB_OK) {
+    return CUBEB_ERROR;
+  }
+
+  if (buffer_size < (unsigned int) latency_range.mMinimum) {
+    buffer_size = (unsigned int) latency_range.mMinimum;
+  } else if (buffer_size > (unsigned int) latency_range.mMaximum) {
+    buffer_size = (unsigned int) latency_range.mMaximum;
+  }
+
+  /**
+   * Get the default buffer size. If our latency request is below the default,
+   * set it. Otherwise, use the default latency.
+   **/
+  size = sizeof(default_buffer_size);
+  if (AudioUnitGetProperty(stm->output_unit, kAudioDevicePropertyBufferFrameSize,
+        kAudioUnitScope_Output, 0, &default_buffer_size, &size) != 0) {
+    return CUBEB_ERROR;
+  }
+
+  if (buffer_size < default_buffer_size) {
+    /* Set the maximum number of frame that the render callback will ask for,
+     * effectively setting the latency of the stream. This is process-wide. */
+    if (AudioUnitSetProperty(stm->output_unit, kAudioDevicePropertyBufferFrameSize,
+          kAudioUnitScope_Output, 0, &buffer_size, sizeof(buffer_size)) != 0) {
+      return CUBEB_ERROR;
+    }
+  }
+#else  // TARGET_OS_IPHONE
+  //TODO: [[AVAudioSession sharedInstance] inputLatency]
+  // http://stackoverflow.com/questions/13157523/kaudiodevicepropertybufferframesize-replacement-for-ios
+#endif
+#endif
+
+  /* We use a resampler because input AudioUnit operates
+   * reliable only in the capture device sample rate.
+   * Resampler will convert it to the user sample rate
+   * and deliver it to the callback. */
+  uint32_t target_sample_rate;
+  if (has_input(stm)) {
+    target_sample_rate = stm->input_stream_params.rate;
+  } else {
+    assert(has_output(stm));
+    target_sample_rate = stm->output_stream_params.rate;
+  }
+
+  cubeb_stream_params input_unconverted_params;
+  if (has_input(stm)) {
+    input_unconverted_params = stm->input_stream_params;
+    /* Use the rate of the input device. */
+    input_unconverted_params.rate = stm->input_hw_rate;
+  }
+
+  /* Create resampler. Output params are unchanged
+   * because we do not need conversion on the output. */
+  stm->resampler = cubeb_resampler_create(stm,
+                                          has_input(stm) ? &input_unconverted_params : NULL,
+                                          has_output(stm) ? &stm->output_stream_params : NULL,
+                                          target_sample_rate,
+                                          stm->data_callback,
+                                          stm->user_ptr,
+                                          CUBEB_RESAMPLER_QUALITY_DESKTOP);
+  if (!stm->resampler) {
+    LOG("(%p) Could not create resampler.", stm);
+    return CUBEB_ERROR;
+  }
+
+  if (stm->input_unit != NULL) {
+    r = AudioUnitInitialize(stm->input_unit);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioUnitInitialize/input", r);
+      return CUBEB_ERROR;
+    }
+  }
+
+  if (stm->output_unit != NULL) {
+    r = AudioUnitInitialize(stm->output_unit);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioUnitInitialize/output", r);
+      return CUBEB_ERROR;
+    }
+  }
+
+  if (stm->input_unit && stm->output_unit) {
+    // According to the I/O hardware rate it is expected a specific pattern of callbacks
+    // for example is input is 44100 and output is 48000 we expected no more than 2
+    // out callback in a row.
+    stm->expected_output_callbacks_in_a_row = ceilf(stm->output_hw_rate / stm->input_hw_rate);
+  }
+
+  r = audiounit_install_device_changed_callback(stm);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Could not install the device change callback.", stm);
+    return r;
+  }
+
+  return CUBEB_OK;
+}
+
+static int
+audiounit_stream_init(cubeb * context,
+                      cubeb_stream ** stream,
+                      char const * /* stream_name */,
+                      cubeb_devid input_device,
+                      cubeb_stream_params * input_stream_params,
+                      cubeb_devid output_device,
+                      cubeb_stream_params * output_stream_params,
+                      unsigned int latency_frames,
+                      cubeb_data_callback data_callback,
+                      cubeb_state_callback state_callback,
+                      void * user_ptr)
+{
+  cubeb_stream * stm;
+  int r;
+
+  assert(context);
+  *stream = NULL;
+
+  assert(latency_frames > 0);
+  if (context->limit_streams && context->active_streams >= CUBEB_STREAM_MAX) {
+    LOG("Reached the stream limit of %d", CUBEB_STREAM_MAX);
+    return CUBEB_ERROR;
+  }
+
+  stm = (cubeb_stream *) calloc(1, sizeof(cubeb_stream));
+  assert(stm);
+  // Placement new to call the ctors of cubeb_stream members.
+  new (stm) cubeb_stream();
+
+  /* These could be different in the future if we have both
+   * full-duplex stream and different devices for input vs output. */
+  stm->context = context;
+  stm->data_callback = data_callback;
+  stm->state_callback = state_callback;
+  stm->user_ptr = user_ptr;
+  stm->latency_frames = latency_frames;
+  stm->device_changed_callback = NULL;
+  if (input_stream_params) {
+    stm->input_stream_params = *input_stream_params;
+    stm->input_device = input_device;
+    stm->is_default_input = input_device == nullptr ||
+                            (audiounit_get_default_device_id(CUBEB_DEVICE_TYPE_INPUT) ==
+                                                  reinterpret_cast<intptr_t>(input_device));
+  }
+  if (output_stream_params) {
+    stm->output_stream_params = *output_stream_params;
+    stm->output_device = output_device;
+  }
+
+  /* Init data members where necessary */
+  stm->hw_latency_frames = UINT64_MAX;
+
+  stm->switching_device = false;
+
+  auto_lock context_lock(context->mutex);
+  {
+    // It's not critical to lock here, because no other thread has been started
+    // yet, but it allows to assert that the lock has been taken in
+    // `audiounit_setup_stream`.
+    context->active_streams += 1;
+    auto_lock lock(stm->mutex);
+    r = audiounit_setup_stream(stm);
+  }
+
+  if (r != CUBEB_OK) {
+    LOG("(%p) Could not setup the audiounit stream.", stm);
+    audiounit_stream_destroy(stm);
+    return r;
+  }
+
+  r = audiounit_install_system_changed_callback(stm);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Could not install the device change callback.", stm);
+    return r;
+  }
+
+  *stream = stm;
+  LOG("Cubeb stream (%p) init successful.", stm);
+  return CUBEB_OK;
+}
+
+static void
+audiounit_close_stream(cubeb_stream *stm)
+{
+  stm->mutex.assert_current_thread_owns();
+
+  if (stm->input_unit) {
+    AudioUnitUninitialize(stm->input_unit);
+    AudioComponentInstanceDispose(stm->input_unit);
+  }
+
+  audiounit_destroy_input_linear_buffer(stm);
+
+  if (stm->output_unit) {
+    AudioUnitUninitialize(stm->output_unit);
+    AudioComponentInstanceDispose(stm->output_unit);
+  }
+
+  cubeb_resampler_destroy(stm->resampler);
+}
+
+static void
+audiounit_stream_destroy(cubeb_stream * stm)
+{
+  stm->shutdown = true;
+
+  int r = audiounit_uninstall_system_changed_callback(stm);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Could not uninstall the device changed callback", stm);
+  }
+
+  r = audiounit_uninstall_device_changed_callback(stm);
+  if (r != CUBEB_OK) {
+    LOG("(%p) Could not uninstall the device changed callback", stm);
+  }
+
+  auto_lock context_lock(stm->context->mutex);
+  audiounit_stream_stop_internal(stm);
+
+  // Execute close in serial queue to avoid collision
+  // with reinit when un/plug devices
+  dispatch_sync(stm->context->serial_queue, ^() {
+    auto_lock lock(stm->mutex);
+    audiounit_close_stream(stm);
+  });
+
+  assert(stm->context->active_streams >= 1);
+  stm->context->active_streams -= 1;
+
+  LOG("Cubeb stream (%p) destroyed successful.", stm);
+
+  stm->~cubeb_stream();
+  free(stm);
+}
+
+void
+audiounit_stream_start_internal(cubeb_stream * stm)
+{
+  OSStatus r;
+  if (stm->input_unit != NULL) {
+    r = AudioOutputUnitStart(stm->input_unit);
+    assert(r == 0);
+  }
+  if (stm->output_unit != NULL) {
+    r = AudioOutputUnitStart(stm->output_unit);
+    assert(r == 0);
+  }
+}
+
+static int
+audiounit_stream_start(cubeb_stream * stm)
+{
+  auto_lock context_lock(stm->context->mutex);
+  stm->shutdown = false;
+  stm->draining = false;
+
+  audiounit_stream_start_internal(stm);
+
+  stm->state_callback(stm, stm->user_ptr, CUBEB_STATE_STARTED);
+
+  LOG("Cubeb stream (%p) started successfully.", stm);
+  return CUBEB_OK;
+}
+
+void
+audiounit_stream_stop_internal(cubeb_stream * stm)
+{
+  OSStatus r;
+  if (stm->input_unit != NULL) {
+    r = AudioOutputUnitStop(stm->input_unit);
+    assert(r == 0);
+  }
+  if (stm->output_unit != NULL) {
+    r = AudioOutputUnitStop(stm->output_unit);
+    assert(r == 0);
+  }
+}
+
+static int
+audiounit_stream_stop(cubeb_stream * stm)
+{
+  auto_lock context_lock(stm->context->mutex);
+  stm->shutdown = true;
+
+  audiounit_stream_stop_internal(stm);
+
+  stm->state_callback(stm, stm->user_ptr, CUBEB_STATE_STOPPED);
+
+  LOG("Cubeb stream (%p) stopped successfully.", stm);
+  return CUBEB_OK;
+}
+
+static int
+audiounit_stream_get_position(cubeb_stream * stm, uint64_t * position)
+{
+  auto_lock lock(stm->mutex);
+
+  *position = stm->frames_played;
+  return CUBEB_OK;
+}
+
+int
+audiounit_stream_get_latency(cubeb_stream * stm, uint32_t * latency)
+{
+#if TARGET_OS_IPHONE
+  //TODO
+  return CUBEB_ERROR_NOT_SUPPORTED;
+#else
+  auto_lock lock(stm->mutex);
+  if (stm->hw_latency_frames == UINT64_MAX) {
+    UInt32 size;
+    uint32_t device_latency_frames, device_safety_offset;
+    double unit_latency_sec;
+    AudioDeviceID output_device_id;
+    OSStatus r;
+    AudioObjectPropertyAddress latency_address = {
+      kAudioDevicePropertyLatency,
+      kAudioDevicePropertyScopeOutput,
+      kAudioObjectPropertyElementMaster
+    };
+    AudioObjectPropertyAddress safety_offset_address = {
+      kAudioDevicePropertySafetyOffset,
+      kAudioDevicePropertyScopeOutput,
+      kAudioObjectPropertyElementMaster
+    };
+
+    r = audiounit_get_output_device_id(&output_device_id);
+    if (r != noErr) {
+      return CUBEB_ERROR;
+    }
+
+    size = sizeof(unit_latency_sec);
+    r = AudioUnitGetProperty(stm->output_unit,
+                             kAudioUnitProperty_Latency,
+                             kAudioUnitScope_Global,
+                             0,
+                             &unit_latency_sec,
+                             &size);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioUnitGetProperty/kAudioUnitProperty_Latency", r);
+      return CUBEB_ERROR;
+    }
+
+    size = sizeof(device_latency_frames);
+    r = AudioObjectGetPropertyData(output_device_id,
+                                   &latency_address,
+                                   0,
+                                   NULL,
+                                   &size,
+                                   &device_latency_frames);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioUnitGetPropertyData/latency_frames", r);
+      return CUBEB_ERROR;
+    }
+
+    size = sizeof(device_safety_offset);
+    r = AudioObjectGetPropertyData(output_device_id,
+                                   &safety_offset_address,
+                                   0,
+                                   NULL,
+                                   &size,
+                                   &device_safety_offset);
+    if (r != noErr) {
+      PRINT_ERROR_CODE("AudioUnitGetPropertyData/safety_offset", r);
+      return CUBEB_ERROR;
+    }
+
+    /* This part is fixed and depend on the stream parameter and the hardware. */
+    stm->hw_latency_frames =
+      static_cast<uint32_t>(unit_latency_sec * stm->output_desc.mSampleRate)
+      + device_latency_frames
+      + device_safety_offset;
+  }
+
+  *latency = stm->hw_latency_frames + stm->current_latency_frames;
+
+  return CUBEB_OK;
+#endif
+}
+
+static int
+audiounit_stream_get_volume(cubeb_stream * stm, float * volume)
+{
+  assert(stm->output_unit);
+  OSStatus r = AudioUnitGetParameter(stm->output_unit,
+                                     kHALOutputParam_Volume,
+                                     kAudioUnitScope_Global,
+                                     0, volume);
+  if (r != noErr) {
+    LOG("AudioUnitGetParameter/kHALOutputParam_Volume rv=%d", r);
+    return CUBEB_ERROR;
+  }
+  return CUBEB_OK;
+}
+
+int audiounit_stream_set_volume(cubeb_stream * stm, float volume)
+{
+  OSStatus r;
+
+  r = AudioUnitSetParameter(stm->output_unit,
+                            kHALOutputParam_Volume,
+                            kAudioUnitScope_Global,
+                            0, volume, 0);
+
+  if (r != noErr) {
+    PRINT_ERROR_CODE("AudioUnitSetParameter/kHALOutputParam_Volume", r);
+    return CUBEB_ERROR;
+  }
+  return CUBEB_OK;
+}
+
+int audiounit_stream_set_panning(cubeb_stream * stm, float panning)
+{
+  if (stm->output_desc.mChannelsPerFrame > 2) {
+    return CUBEB_ERROR_INVALID_PARAMETER;
+  }
+
+  stm->panning.store(panning, std::memory_order_relaxed);
+  return CUBEB_OK;
+}
+
+int audiounit_stream_get_current_device(cubeb_stream * stm,
+                                        cubeb_device ** const  device)
+{
+#if TARGET_OS_IPHONE
+  //TODO
+  return CUBEB_ERROR_NOT_SUPPORTED;
+#else
+  OSStatus r;
+  UInt32 size;
+  UInt32 data;
+  char strdata[4];
+  AudioDeviceID output_device_id;
+  AudioDeviceID input_device_id;
+
+  AudioObjectPropertyAddress datasource_address = {
+    kAudioDevicePropertyDataSource,
+    kAudioDevicePropertyScopeOutput,
+    kAudioObjectPropertyElementMaster
+  };
+
+  AudioObjectPropertyAddress datasource_address_input = {
+    kAudioDevicePropertyDataSource,
+    kAudioDevicePropertyScopeInput,
+    kAudioObjectPropertyElementMaster
+  };
+
+  *device = NULL;
+
+  if (audiounit_get_output_device_id(&output_device_id) != CUBEB_OK) {
+    return CUBEB_ERROR;
+  }
+
+  *device = new cubeb_device;
+  if (!*device) {
+    return CUBEB_ERROR;
+  }
+  PodZero(*device, 1);
+
+  size = sizeof(UInt32);
+  /* This fails with some USB headset, so simply return an empty string. */
+  r = AudioObjectGetPropertyData(output_device_id,
+                                 &datasource_address,
+                                 0, NULL, &size, &data);
+  if (r != noErr) {
+    size = 0;
+    data = 0;
+  }
+
+  (*device)->output_name = new char[size + 1];
+  if (!(*device)->output_name) {
+    return CUBEB_ERROR;
+  }
+
+  // Turn the four chars packed into a uint32 into a string
+  strdata[0] = (char)(data >> 24);
+  strdata[1] = (char)(data >> 16);
+  strdata[2] = (char)(data >> 8);
+  strdata[3] = (char)(data);
+
+  memcpy((*device)->output_name, strdata, size);
+  (*device)->output_name[size] = '\0';
+
+  if (audiounit_get_input_device_id(&input_device_id) != CUBEB_OK) {
+    return CUBEB_ERROR;
+  }
+
+  size = sizeof(UInt32);
+  r = AudioObjectGetPropertyData(input_device_id, &datasource_address_input, 0, NULL, &size, &data);
+  if (r != noErr) {
+    LOG("(%p) Error when getting device !", stm);
+    size = 0;
+    data = 0;
+  }
+
+  (*device)->input_name = new char[size + 1];
+  if (!(*device)->input_name) {
+    return CUBEB_ERROR;
+  }
+
+  // Turn the four chars packed into a uint32 into a string
+  strdata[0] = (char)(data >> 24);
+  strdata[1] = (char)(data >> 16);
+  strdata[2] = (char)(data >> 8);
+  strdata[3] = (char)(data);
+
+  memcpy((*device)->input_name, strdata, size);
+  (*device)->input_name[size] = '\0';
+
+  return CUBEB_OK;
+#endif
+}
+
+int audiounit_stream_device_destroy(cubeb_stream * /* stream */,
+                                    cubeb_device * device)
+{
+  delete [] device->output_name;
+  delete [] device->input_name;
+  delete device;
+  return CUBEB_OK;
+}
+
+int audiounit_stream_register_device_changed_callback(cubeb_stream * stream,
+                                                      cubeb_device_changed_callback device_changed_callback)
+{
+  /* Note: second register without unregister first causes 'nope' error.
+   * Current implementation requires unregister before register a new cb. */
+  assert(!stream->device_changed_callback);
+
+  auto_lock lock(stream->mutex);
+
+  stream->device_changed_callback = device_changed_callback;
+
+  return CUBEB_OK;
+}
+
+static OSStatus
+audiounit_get_devices(AudioObjectID ** devices, uint32_t * count)
+{
+  OSStatus ret;
+  UInt32 size = 0;
+  AudioObjectPropertyAddress adr = { kAudioHardwarePropertyDevices,
+                                     kAudioObjectPropertyScopeGlobal,
+                                     kAudioObjectPropertyElementMaster };
+
+  ret = AudioObjectGetPropertyDataSize(kAudioObjectSystemObject, &adr, 0, NULL, &size);
+  if (ret != noErr) {
+    return ret;
+  }
+
+  *count = static_cast<uint32_t>(size / sizeof(AudioObjectID));
+  if (size >= sizeof(AudioObjectID)) {
+    if (*devices != NULL) {
+      delete [] (*devices);
+    }
+    *devices = new AudioObjectID[*count];
+    PodZero(*devices, *count);
+
+    ret = AudioObjectGetPropertyData(kAudioObjectSystemObject, &adr, 0, NULL, &size, (void *)*devices);
+    if (ret != noErr) {
+      delete [] (*devices);
+      *devices = NULL;
+    }
+  } else {
+    *devices = NULL;
+    ret = -1;
+  }
+
+  return ret;
+}
+
+static char *
+audiounit_strref_to_cstr_utf8(CFStringRef strref)
+{
+  CFIndex len, size;
+  char * ret;
+  if (strref == NULL) {
+    return NULL;
+  }
+
+  len = CFStringGetLength(strref);
+  size = CFStringGetMaximumSizeForEncoding(len, kCFStringEncodingUTF8);
+  ret = static_cast<char *>(malloc(size));
+
+  if (!CFStringGetCString(strref, ret, size, kCFStringEncodingUTF8)) {
+    free(ret);
+    ret = NULL;
+  }
+
+  return ret;
+}
+
+static uint32_t
+audiounit_get_channel_count(AudioObjectID devid, AudioObjectPropertyScope scope)
+{
+  AudioObjectPropertyAddress adr = { 0, scope, kAudioObjectPropertyElementMaster };
+  UInt32 size = 0;
+  uint32_t i, ret = 0;
+
+  adr.mSelector = kAudioDevicePropertyStreamConfiguration;
+
+  if (AudioObjectGetPropertyDataSize(devid, &adr, 0, NULL, &size) == noErr && size > 0) {
+    AudioBufferList * list = static_cast<AudioBufferList *>(alloca(size));
+    if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, list) == noErr) {
+      for (i = 0; i < list->mNumberBuffers; i++)
+        ret += list->mBuffers[i].mNumberChannels;
+    }
+  }
+
+  return ret;
+}
+
+static void
+audiounit_get_available_samplerate(AudioObjectID devid, AudioObjectPropertyScope scope,
+                                   uint32_t * min, uint32_t * max, uint32_t * def)
+{
+  AudioObjectPropertyAddress adr = { 0, scope, kAudioObjectPropertyElementMaster };
+
+  adr.mSelector = kAudioDevicePropertyNominalSampleRate;
+  if (AudioObjectHasProperty(devid, &adr)) {
+    UInt32 size = sizeof(Float64);
+    Float64 fvalue = 0.0;
+    if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &fvalue) == noErr) {
+      *def = fvalue;
+    }
+  }
+
+  adr.mSelector = kAudioDevicePropertyAvailableNominalSampleRates;
+  UInt32 size = 0;
+  AudioValueRange range;
+  if (AudioObjectHasProperty(devid, &adr) &&
+      AudioObjectGetPropertyDataSize(devid, &adr, 0, NULL, &size) == noErr) {
+    uint32_t i, count = size / sizeof(AudioValueRange);
+    AudioValueRange * ranges = new AudioValueRange[count];
+    range.mMinimum = 9999999999.0;
+    range.mMaximum = 0.0;
+    if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, ranges) == noErr) {
+      for (i = 0; i < count; i++) {
+        if (ranges[i].mMaximum > range.mMaximum)
+          range.mMaximum = ranges[i].mMaximum;
+        if (ranges[i].mMinimum < range.mMinimum)
+          range.mMinimum = ranges[i].mMinimum;
+      }
+    }
+    delete [] ranges;
+    *max = static_cast<uint32_t>(range.mMaximum);
+    *min = static_cast<uint32_t>(range.mMinimum);
+  } else {
+    *min = *max = 0;
+  }
+
+}
+
+static UInt32
+audiounit_get_device_presentation_latency(AudioObjectID devid, AudioObjectPropertyScope scope)
+{
+  AudioObjectPropertyAddress adr = { 0, scope, kAudioObjectPropertyElementMaster };
+  UInt32 size, dev, stream = 0, offset;
+  AudioStreamID sid[1];
+
+  adr.mSelector = kAudioDevicePropertyLatency;
+  size = sizeof(UInt32);
+  if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &dev) != noErr) {
+    dev = 0;
+  }
+
+  adr.mSelector = kAudioDevicePropertyStreams;
+  size = sizeof(sid);
+  if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, sid) == noErr) {
+    adr.mSelector = kAudioStreamPropertyLatency;
+    size = sizeof(UInt32);
+    AudioObjectGetPropertyData(sid[0], &adr, 0, NULL, &size, &stream);
+  }
+
+  adr.mSelector = kAudioDevicePropertySafetyOffset;
+  size = sizeof(UInt32);
+  if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &offset) != noErr) {
+    offset = 0;
+  }
+
+  return dev + stream + offset;
+}
+
+static cubeb_device_info *
+audiounit_create_device_from_hwdev(AudioObjectID devid, cubeb_device_type type)
+{
+  AudioObjectPropertyAddress adr = { 0, 0, kAudioObjectPropertyElementMaster };
+  UInt32 size, ch, latency;
+  cubeb_device_info * ret;
+  CFStringRef str = NULL;
+  AudioValueRange range;
+
+  if (type == CUBEB_DEVICE_TYPE_OUTPUT) {
+    adr.mScope = kAudioDevicePropertyScopeOutput;
+  } else if (type == CUBEB_DEVICE_TYPE_INPUT) {
+    adr.mScope = kAudioDevicePropertyScopeInput;
+  } else {
+    return NULL;
+  }
+
+  ch = audiounit_get_channel_count(devid, adr.mScope);
+  if (ch == 0) {
+    return NULL;
+  }
+
+  ret = new cubeb_device_info;
+  PodZero(ret, 1);
+
+  size = sizeof(CFStringRef);
+  adr.mSelector = kAudioDevicePropertyDeviceUID;
+  if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &str) == noErr && str != NULL) {
+    ret->device_id = audiounit_strref_to_cstr_utf8(str);
+    ret->devid = (cubeb_devid)(size_t)devid;
+    ret->group_id = strdup(ret->device_id);
+    CFRelease(str);
+  }
+
+  size = sizeof(CFStringRef);
+  adr.mSelector = kAudioObjectPropertyName;
+  if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &str) == noErr && str != NULL) {
+    UInt32 ds;
+    size = sizeof(UInt32);
+    adr.mSelector = kAudioDevicePropertyDataSource;
+    if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &ds) == noErr) {
+      CFStringRef dsname;
+      AudioValueTranslation trl = { &ds, sizeof(ds), &dsname, sizeof(dsname) };
+      adr.mSelector = kAudioDevicePropertyDataSourceNameForIDCFString;
+      size = sizeof(AudioValueTranslation);
+      // If there is a datasource for this device, use it instead of the device
+      // name.
+      if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &trl) == noErr) {
+        CFRelease(str);
+        str = dsname;
+      }
+    }
+
+    ret->friendly_name = audiounit_strref_to_cstr_utf8(str);
+    CFRelease(str);
+  }
+
+  size = sizeof(CFStringRef);
+  adr.mSelector = kAudioObjectPropertyManufacturer;
+  if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &str) == noErr && str != NULL) {
+    ret->vendor_name = audiounit_strref_to_cstr_utf8(str);
+    CFRelease(str);
+  }
+
+  ret->type = type;
+  ret->state = CUBEB_DEVICE_STATE_ENABLED;
+  ret->preferred = (devid == audiounit_get_default_device_id(type)) ?
+    CUBEB_DEVICE_PREF_ALL : CUBEB_DEVICE_PREF_NONE;
+
+  ret->max_channels = ch;
+  ret->format = (cubeb_device_fmt)CUBEB_DEVICE_FMT_ALL; /* CoreAudio supports All! */
+  /* kAudioFormatFlagsAudioUnitCanonical is deprecated, prefer floating point */
+  ret->default_format = CUBEB_DEVICE_FMT_F32NE;
+  audiounit_get_available_samplerate(devid, adr.mScope,
+      &ret->min_rate, &ret->max_rate, &ret->default_rate);
+
+  latency = audiounit_get_device_presentation_latency(devid, adr.mScope);
+
+  adr.mSelector = kAudioDevicePropertyBufferFrameSizeRange;
+  size = sizeof(AudioValueRange);
+  if (AudioObjectGetPropertyData(devid, &adr, 0, NULL, &size, &range) == noErr) {
+    ret->latency_lo = latency + range.mMinimum;
+    ret->latency_hi = latency + range.mMaximum;
+  } else {
+    ret->latency_lo = 10 * ret->default_rate / 1000;  /* Default to  10ms */
+    ret->latency_hi = 100 * ret->default_rate / 1000; /* Default to 100ms */
+  }
+
+  return ret;
+}
+
+static int
+audiounit_enumerate_devices(cubeb * /* context */, cubeb_device_type type,
+                            cubeb_device_collection ** collection)
+{
+  AudioObjectID * hwdevs = NULL;
+  uint32_t i, hwdevcount = 0;
+  OSStatus err;
+
+  if ((err = audiounit_get_devices(&hwdevs, &hwdevcount)) != noErr) {
+    return CUBEB_ERROR;
+  }
+
+  *collection = static_cast<cubeb_device_collection *>(malloc(sizeof(cubeb_device_collection) +
+      sizeof(cubeb_device_info*) * (hwdevcount > 0 ? hwdevcount - 1 : 0)));
+  (*collection)->count = 0;
+
+  if (hwdevcount > 0) {
+    cubeb_device_info * cur;
+
+    if (type & CUBEB_DEVICE_TYPE_OUTPUT) {
+      for (i = 0; i < hwdevcount; i++) {
+        if ((cur = audiounit_create_device_from_hwdev(hwdevs[i], CUBEB_DEVICE_TYPE_OUTPUT)) != NULL)
+          (*collection)->device[(*collection)->count++] = cur;
+      }
+    }
+
+    if (type & CUBEB_DEVICE_TYPE_INPUT) {
+      for (i = 0; i < hwdevcount; i++) {
+        if ((cur = audiounit_create_device_from_hwdev(hwdevs[i], CUBEB_DEVICE_TYPE_INPUT)) != NULL)
+          (*collection)->device[(*collection)->count++] = cur;
+      }
+    }
+  }
+
+  delete [] hwdevs;
+
+  return CUBEB_OK;
+}
+
+/* qsort compare method. */
+int compare_devid(const void * a, const void * b)
+{
+  return (*(AudioObjectID*)a - *(AudioObjectID*)b);
+}
+
+static uint32_t
+audiounit_get_devices_of_type(cubeb_device_type devtype, AudioObjectID ** devid_array)
+{
+  assert(devid_array == NULL || *devid_array == NULL);
+
+  AudioObjectPropertyAddress adr = { kAudioHardwarePropertyDevices,
+                                     kAudioObjectPropertyScopeGlobal,
+                                     kAudioObjectPropertyElementMaster };
+  UInt32 size = 0;
+  OSStatus ret = AudioObjectGetPropertyDataSize(kAudioObjectSystemObject, &adr, 0, NULL, &size);
+  if (ret != noErr) {
+    return 0;
+  }
+  /* Total number of input and output devices. */
+  uint32_t count = (uint32_t)(size / sizeof(AudioObjectID));
+
+  AudioObjectID devices[count];
+  ret = AudioObjectGetPropertyData(kAudioObjectSystemObject, &adr, 0, NULL, &size, &devices);
+  if (ret != noErr) {
+    return 0;
+  }
+  /* Expected sorted but did not find anything in the docs. */
+  qsort(devices, count, sizeof(AudioObjectID), compare_devid);
+
+  if (devtype == (CUBEB_DEVICE_TYPE_INPUT | CUBEB_DEVICE_TYPE_OUTPUT)) {
+    if (devid_array) {
+      *devid_array = new AudioObjectID[count];
+      assert(*devid_array);
+      memcpy(*devid_array, &devices, count * sizeof(AudioObjectID));
+    }
+    return count;
+  }
+
+  AudioObjectPropertyScope scope = (devtype == CUBEB_DEVICE_TYPE_INPUT) ?
+                                         kAudioDevicePropertyScopeInput :
+                                         kAudioDevicePropertyScopeOutput;
+
+  uint32_t dev_count = 0;
+  AudioObjectID devices_in_scope[count];
+  for(uint32_t i = 0; i < count; ++i) {
+    /* For device in the given scope channel must be > 0. */
+    if (audiounit_get_channel_count(devices[i], scope) > 0) {
+      devices_in_scope[dev_count] = devices[i];
+      ++dev_count;
+    }
+  }
+
+  if (devid_array && dev_count > 0) {
+    *devid_array = new AudioObjectID[dev_count];
+    assert(*devid_array);
+    memcpy(*devid_array, &devices_in_scope, dev_count * sizeof(AudioObjectID));
+  }
+  return dev_count;
+}
+
+static uint32_t
+audiounit_equal_arrays(AudioObjectID * left, AudioObjectID * right, uint32_t size)
+{
+  /* Expected sorted arrays. */
+  for (uint32_t i = 0; i < size; ++i) {
+    if (left[i] != right[i]) {
+      return 0;
+    }
+  }
+  return 1;
+}
+
+static OSStatus
+audiounit_collection_changed_callback(AudioObjectID /* inObjectID */,
+                                      UInt32 /* inNumberAddresses */,
+                                      const AudioObjectPropertyAddress * /* inAddresses */,
+                                      void * inClientData)
+{
+  cubeb * context = static_cast<cubeb *>(inClientData);
+  auto_lock lock(context->mutex);
+
+  if (context->collection_changed_callback == NULL) {
+    /* Listener removed while waiting in mutex, abort. */
+    return noErr;
+  }
+
+  /* Differentiate input from output changes. */
+  if (context->collection_changed_devtype == CUBEB_DEVICE_TYPE_INPUT ||
+      context->collection_changed_devtype == CUBEB_DEVICE_TYPE_OUTPUT) {
+    AudioObjectID * devices = NULL;
+    uint32_t new_number_of_devices = audiounit_get_devices_of_type(context->collection_changed_devtype, &devices);
+    /* When count is the same examine the devid for the case of coalescing. */
+    if (context->devtype_device_count == new_number_of_devices &&
+        audiounit_equal_arrays(devices, context->devtype_device_array, new_number_of_devices)) {
+      /* Device changed for the other scope, ignore. */
+      delete [] devices;
+      return noErr;
+    }
+    /* Device on desired scope changed, reset counter and array. */
+    context->devtype_device_count = new_number_of_devices;
+    /* Free the old array before replace. */
+    delete [] context->devtype_device_array;
+    context->devtype_device_array = devices;
+  }
+
+  context->collection_changed_callback(context, context->collection_changed_user_ptr);
+  return noErr;
+}
+
+static OSStatus
+audiounit_add_device_listener(cubeb * context,
+                              cubeb_device_type devtype,
+                              cubeb_device_collection_changed_callback collection_changed_callback,
+                              void * user_ptr)
+{
+  /* Note: second register without unregister first causes 'nope' error.
+   * Current implementation requires unregister before register a new cb. */
+  assert(context->collection_changed_callback == NULL);
+
+  AudioObjectPropertyAddress devAddr;
+  devAddr.mSelector = kAudioHardwarePropertyDevices;
+  devAddr.mScope = kAudioObjectPropertyScopeGlobal;
+  devAddr.mElement = kAudioObjectPropertyElementMaster;
+
+  OSStatus ret = AudioObjectAddPropertyListener(kAudioObjectSystemObject,
+                                                &devAddr,
+                                                audiounit_collection_changed_callback,
+                                                context);
+  if (ret == noErr) {
+    /* Expected zero after unregister. */
+    assert(context->devtype_device_count == 0);
+    assert(context->devtype_device_array == NULL);
+    /* Listener works for input and output.
+     * When requested one of them we need to differentiate. */
+    if (devtype == CUBEB_DEVICE_TYPE_INPUT ||
+        devtype == CUBEB_DEVICE_TYPE_OUTPUT) {
+      /* Used to differentiate input from output device changes. */
+      context->devtype_device_count = audiounit_get_devices_of_type(devtype, &context->devtype_device_array);
+    }
+    context->collection_changed_devtype = devtype;
+    context->collection_changed_callback = collection_changed_callback;
+    context->collection_changed_user_ptr = user_ptr;
+  }
+  return ret;
+}
+
+static OSStatus
+audiounit_remove_device_listener(cubeb * context)
+{
+  AudioObjectPropertyAddress devAddr;
+  devAddr.mSelector = kAudioHardwarePropertyDevices;
+  devAddr.mScope = kAudioObjectPropertyScopeGlobal;
+  devAddr.mElement = kAudioObjectPropertyElementMaster;
+
+  /* Note: unregister a non registered cb is not a problem, not checking. */
+  OSStatus ret = AudioObjectRemovePropertyListener(kAudioObjectSystemObject,
+                                                   &devAddr,
+                                                   audiounit_collection_changed_callback,
+                                                   context);
+  if (ret == noErr) {
+    /* Reset all values. */
+    context->collection_changed_devtype = CUBEB_DEVICE_TYPE_UNKNOWN;
+    context->collection_changed_callback = NULL;
+    context->collection_changed_user_ptr = NULL;
+    context->devtype_device_count = 0;
+    if (context->devtype_device_array) {
+      delete [] context->devtype_device_array;
+      context->devtype_device_array = NULL;
+    }
+  }
+  return ret;
+}
+
+int audiounit_register_device_collection_changed(cubeb * context,
+                                                 cubeb_device_type devtype,
+                                                 cubeb_device_collection_changed_callback collection_changed_callback,
+                                                 void * user_ptr)
+{
+  OSStatus ret;
+  auto_lock lock(context->mutex);
+  if (collection_changed_callback) {
+    ret = audiounit_add_device_listener(context, devtype,
+                                        collection_changed_callback,
+                                        user_ptr);
+  } else {
+    ret = audiounit_remove_device_listener(context);
+  }
+  return (ret == noErr) ? CUBEB_OK : CUBEB_ERROR;
+}
+
+cubeb_ops const audiounit_ops = {
+  /*.init =*/ audiounit_init,
+  /*.get_backend_id =*/ audiounit_get_backend_id,
+  /*.get_max_channel_count =*/ audiounit_get_max_channel_count,
+  /*.get_min_latency =*/ audiounit_get_min_latency,
+  /*.get_preferred_sample_rate =*/ audiounit_get_preferred_sample_rate,
+  /*.enumerate_devices =*/ audiounit_enumerate_devices,
+  /*.destroy =*/ audiounit_destroy,
+  /*.stream_init =*/ audiounit_stream_init,
+  /*.stream_destroy =*/ audiounit_stream_destroy,
+  /*.stream_start =*/ audiounit_stream_start,
+  /*.stream_stop =*/ audiounit_stream_stop,
+  /*.stream_get_position =*/ audiounit_stream_get_position,
+  /*.stream_get_latency =*/ audiounit_stream_get_latency,
+  /*.stream_set_volume =*/ audiounit_stream_set_volume,
+  /*.stream_set_panning =*/ audiounit_stream_set_panning,
+  /*.stream_get_current_device =*/ audiounit_stream_get_current_device,
+  /*.stream_device_destroy =*/ audiounit_stream_device_destroy,
+  /*.stream_register_device_changed_callback =*/ audiounit_stream_register_device_changed_callback,
+  /*.register_device_collection_changed =*/ audiounit_register_device_collection_changed
+};