--- a/dom/media/AudioStream.cpp
+++ b/dom/media/AudioStream.cpp
@@ -349,16 +349,21 @@ AudioStream::Init(uint32_t aNumChannels,
 
   cubeb* cubebContext = CubebUtils::GetCubebContext();
   if (!cubebContext) {
     NS_WARNING("Can't get cubeb context!");
     CubebUtils::ReportCubebStreamInitFailure(true);
     return NS_ERROR_DOM_MEDIA_CUBEB_INITIALIZATION_ERR;
   }
 
+  cubeb_channel_layout layout;
+  int r = cubeb_get_preferred_channel_layout(cubebContext, &layout);
+  MOZ_ASSERT(r == CUBEB_OK || r == CUBEB_ERROR_NOT_SUPPORTED);
+  params.layout = (r == CUBEB_OK) ? layout : CUBEB_LAYOUT_UNDEFINED;
+
   return OpenCubeb(cubebContext, params, startTime, CubebUtils::GetFirstStream());
 }
 
 nsresult
 AudioStream::OpenCubeb(cubeb* aContext, cubeb_stream_params& aParams,
                        TimeStamp aStartTime, bool aIsFirst)
 {
   MOZ_ASSERT(aContext);

--- a/dom/media/GraphDriver.cpp
+++ b/dom/media/GraphDriver.cpp
@@ -634,16 +634,21 @@ AudioCallbackDriver::Init()
 
   output.channels = mGraphImpl->AudioChannelCount();
   if (AUDIO_OUTPUT_FORMAT == AUDIO_FORMAT_S16) {
     output.format = CUBEB_SAMPLE_S16NE;
   } else {
     output.format = CUBEB_SAMPLE_FLOAT32NE;
   }
 
+  cubeb_channel_layout layout;
+  int r = cubeb_get_preferred_channel_layout(cubebContext, &layout);
+  MOZ_ASSERT(r == CUBEB_OK || r == CUBEB_ERROR_NOT_SUPPORTED);
+  output.layout = (r == CUBEB_OK) ? layout : CUBEB_LAYOUT_UNDEFINED;
+
   Maybe<uint32_t> latencyPref = CubebUtils::GetCubebMSGLatencyInFrames();
   if (latencyPref) {
     latency_frames = latencyPref.value();
   } else {
     if (cubeb_get_min_latency(cubebContext, output, &latency_frames) != CUBEB_OK) {
       NS_WARNING("Could not get minimal latency from cubeb.");
       return false;
     }
@@ -653,16 +658,17 @@ AudioCallbackDriver::Init()
   // MediaStreamGraphs, cap the minimal latency to 512 frames int this case.
   if (IsMacbookOrMacbookAir()) {
     latency_frames = std::max((uint32_t) 512, latency_frames);
   }
 
 
   input = output;
   input.channels = mInputChannels; // change to support optional stereo capture
+  input.layout = CUBEB_LAYOUT_MONO;
 
   cubeb_stream* stream = nullptr;
   CubebUtils::AudioDeviceID input_id = nullptr, output_id = nullptr;
   // We have to translate the deviceID values to cubeb devid's since those can be
   // freed whenever enumerate is called.
   {
 #ifdef MOZ_WEBRTC
     StaticMutexAutoLock lock(AudioInputCubeb::Mutex());