Restores larger output buffer size when output stream requiring smaller size is closed

media/audio/mac/audio_auhal_mac.cc

Index: media/audio/mac/audio_auhal_mac.cc
diff --git a/media/audio/mac/audio_auhal_mac.cc b/media/audio/mac/audio_auhal_mac.cc
index d71673fd12ae517dd61f0fdedabda64d2e7e4077..8bb62e809ecb08be16817bb5389d1b44d657a506 100644
--- a/media/audio/mac/audio_auhal_mac.cc
+++ b/media/audio/mac/audio_auhal_mac.cc
@@ -44,6 +44,7 @@ AUHALStream::AUHALStream(AudioManagerMac* manager,
       params_(params),
       output_channels_(params_.channels()),
       number_of_frames_(params_.frames_per_buffer()),
+      actual_io_buffer_frame_size_(0),
       number_of_frames_requested_(0),
       source_(NULL),
       device_(device),
@@ -115,6 +116,12 @@ bool AUHALStream::Open() {
   if (configured)
     hardware_latency_frames_ = GetHardwareLatency();
 
+#if !defined(NDEBUG)
+  // Print a list of all existing output streams and there current buffer size
+  // state (required and actual). Does nothing in Release builds.
+  manager_->PrintOutputBufferSizes();
+#endif
+
   return configured;
 }
 
@@ -175,6 +182,7 @@ void AUHALStream::Stop() {
   if (stopped_)
     return;
   DVLOG(1) << "Stop";
+  DVLOG(2) << "number_of_frames: " << number_of_frames_;
   OSStatus result = AudioOutputUnitStop(audio_unit_);
   OSSTATUS_DLOG_IF(ERROR, result != noErr, result)
       << "AudioOutputUnitStop() failed.";
@@ -217,13 +225,16 @@ OSStatus AUHALStream::Render(
       // any further changes will be ignored. It would be nice to have all
       // changes reflected in UMA stats.
       number_of_frames_requested_ = number_of_frames;
+      actual_io_buffer_frame_size_ = number_of_frames;

[Henrik Grunell, 2016/04/27 08:59:28]

Is the intention that only the first time the requested number of frames differ
from what we request should update |actual_io_buffer_frame_size_|? That's what
will happen now.

[henrika (OOO until Aug 14), 2016/04/27 12:12:30]

Good point. I can move it up one scope instead. That should do it.
But on the other hand, the existing implementation is broken for this case
anyhow since the FIFO will not be updated. So, not sure if my change helps.

       DVLOG(1) << "Audio frame size changed from " << number_of_frames_
-               << " to " << number_of_frames
-               << "; adding FIFO to compensate.";
+               << " to " << number_of_frames << " adding FIFO to compensate.";
       audio_fifo_.reset(new AudioPullFifo(
           output_channels_,
           number_of_frames_,
           base::Bind(&AUHALStream::ProvideInput, base::Unretained(this))));
+#if !defined(NDEBUG)
+      manager_->PrintOutputBufferSizes();
+#endif
     }
   }
 
@@ -512,6 +523,26 @@ bool AUHALStream::ConfigureAUHAL() {
     return false;
   }
 
+  // Get the actual number of frames in the IO buffers after the audio manager
+  // has tried to set the requested size. We could use |io_buffer_frame_size|
+  // here instead of doing these extra steps but I prefer to play it safe and
+  // to ensure that the change done by the audio manager is really active.
+  // TODO(henrika): it might be possible to remove this part.
+  UInt32 actual_io_buffer_frame_size;
+  UInt32 property_size = sizeof(actual_io_buffer_frame_size);
+  result = AudioUnitGetProperty(
+      audio_unit_, kAudioDevicePropertyBufferFrameSize, kAudioUnitScope_Global,
+      0, &actual_io_buffer_frame_size, &property_size);
+  LOG_IF(WARNING, result != noErr)
+      << "Failed to get the actual I/O buffer size";
+  if (result == noErr) {
+    actual_io_buffer_frame_size_ = actual_io_buffer_frame_size;
+    DVLOG(1) << "actual_io_buffer_frame_size: " << actual_io_buffer_frame_size_;
+  }
+  LOG_IF(WARNING, actual_io_buffer_frame_size_ != number_of_frames_)
+      << "Failed to set the requested buffer frame size exactly";
+  DCHECK_EQ(io_buffer_frame_size, actual_io_buffer_frame_size);
+
   // Setup callback.
   AURenderCallbackStruct callback;
   callback.inputProc = InputProc;