Allow pass through buffer sizes on OSX.

media/audio/mac/audio_manager_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_manager_mac.h"
 
 #include <CoreAudio/AudioHardware.h>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 654 matching lines @@
   const AudioDeviceID device = GetAudioDeviceIdByUId(false, output_device_id);
   if (device == kAudioObjectUnknown) {
     DLOG(ERROR) << "Invalid output device " << output_device_id;
     return input_params.IsValid() ? input_params : AudioParameters(
         AudioParameters::AUDIO_PCM_LOW_LATENCY, CHANNEL_LAYOUT_STEREO,
         kFallbackSampleRate, 16, ChooseBufferSize(kFallbackSampleRate));
   }
 
   const bool has_valid_input_params = input_params.IsValid();
   const int hardware_sample_rate = HardwareSampleRateForDevice(device);
-  const int buffer_size = ChooseBufferSize(hardware_sample_rate);
+
+  // Allow pass through buffer sizes.  If concurrent input and output streams
+  // exist, they will use the smallest buffer size amongst them.  As such, each
+  // stream must be able to FIFO requests appropriately when this happens.
+  int buffer_size = ChooseBufferSize(hardware_sample_rate);
+  if (has_valid_input_params)
+    buffer_size = std::max(input_params.frames_per_buffer(), buffer_size);
 
   int hardware_channels;
   if (!GetDeviceChannels(device, kAudioDevicePropertyScopeOutput,
                          &hardware_channels)) {
     hardware_channels = 2;
   }
 
   // Use the input channel count and channel layout if possible.  Let OSX take
   // care of remapping the channels; this lets user specified channel layouts
   // work correctly.
@@ skipping 90 matching lines @@
 void AudioManagerMac::ReleaseInputStream(AudioInputStream* stream) {
   input_streams_.remove(stream);
   AudioManagerBase::ReleaseInputStream(stream);
 }
 
 AudioManager* CreateAudioManager(AudioLogFactory* audio_log_factory) {
   return new AudioManagerMac(audio_log_factory);
 }
 
 }  // namespace media