Prevent AudioLowLatencyInputMac from changing frame sizes.

media/audio/mac/audio_low_latency_input_mac.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/mac/audio_low_latency_input_mac.h"
 
 #include <CoreServices/CoreServices.h>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
@@ skipping 177 matching lines @@
                                 kAudioUnitScope_Output,
                                 1,
                                 &format_,
                                 sizeof(format_));
   if (result) {
     HandleError(result);
     return false;
   }
 
   // Set the desired number of frames in the IO buffer (output scope).
+  // WARNING: Setting this value changes the frame size for all audio units in
+  // the current process.  It's imperative that the input and output frame sizes
+  // be the same as audio_util::GetAudioHardwareBufferSize().
+  // TODO(henrika): Due to http://crrev.com/159666 this is currently not true
+  // and should be fixed, a CHECK() should be added at that time.
   result = AudioUnitSetProperty(audio_unit_,
                                 kAudioDevicePropertyBufferFrameSize,
                                 kAudioUnitScope_Output,
                                 1,
                                 &number_of_frames_,  // size is set in the ctor
                                 sizeof(number_of_frames_));
   if (result) {
     HandleError(result);
     return false;
   }
@@ skipping 245 matching lines @@
   QueryAgcVolume(&normalized_volume);
 
   AudioBuffer& buffer = io_data->mBuffers[0];
   uint8* audio_data = reinterpret_cast<uint8*>(buffer.mData);
   uint32 capture_delay_bytes = static_cast<uint32>
       ((capture_latency_frames + 0.5) * format_.mBytesPerFrame);
   DCHECK(audio_data);
   if (!audio_data)
     return kAudioUnitErr_InvalidElement;
 
+  // Unfortunately AUAudioInputStream and AUAudioOutputStream share the frame
+  // size set by kAudioDevicePropertyBufferFrameSize above on a per process

[Chris Rogers, 2012/10/08 22:14:31]

nit: "process process"

[DaleCurtis, 2012/10/08 22:21:56]

Done.

+  // process basis.  What this means is that the |number_of_frames| value may be
+  // larger or smaller than the value set during Configure().  In this case
+  // either audio input or audio output will be broken, so just do nothing.
+  // TODO(henrika): This should never happen so long as we're always using the
+  // hardware sample rate and the input/output streams configure the same frame
+  // size.  This is currently not true.  See http://crbug.com/154352.  Once
+  // fixed, a CHECK() should be added and this wall of text removed.
+  if (number_of_frames != static_cast<UInt32>(number_of_frames_))
+    return noErr;
+
   // Deliver data packet, delay estimation and volume level to the user.
   sink_->OnData(this,
                 audio_data,
                 buffer.mDataByteSize,
                 capture_delay_bytes,
                 normalized_volume);
 
   return noErr;
 }
 
@@ skipping 128 matching lines @@
     kAudioDevicePropertyScopeInput,
     static_cast<UInt32>(channel)
   };
   OSStatus result = AudioObjectIsPropertySettable(input_device_id_,
                                                   &property_address,
                                                   &is_settable);
   return (result == noErr) ? is_settable : false;
 }
 
 }  // namespace media