--- a/dom/media/webrtc/MediaEngineWebRTC.h
+++ b/dom/media/webrtc/MediaEngineWebRTC.h
@@ -179,16 +179,18 @@ public:
                         uint32_t aChannels) override;
 
   void NotifyInputData(MediaStreamGraph* aGraph,
                        const AudioDataValue* aBuffer,
                        size_t aFrames,
                        TrackRate aRate,
                        uint32_t aChannels) override;
 
+  uint32_t InputChannelCount() override;
+
   void DeviceChanged() override;
 
   void Shutdown();
 
 private:
   Mutex mMutex;
   RefPtr<MediaEngineWebRTCMicrophoneSource> mAudioSource;
 };

--- a/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
+++ b/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
@@ -82,16 +82,26 @@ void
 WebRTCAudioDataListener::DeviceChanged()
 {
   MutexAutoLock lock(mMutex);
   if (mAudioSource) {
     mAudioSource->DeviceChanged();
   }
 }
 
+uint32_t
+WebRTCAudioDataListener::InputChannelCount()
+{
+ MutexAutoLock lock(mMutex);
+ if (mAudioSource) {
+   return mAudioSource->InputChannelCount();
+ }
+ return 0;
+}
+
 void
 WebRTCAudioDataListener::Shutdown()
 {
   MutexAutoLock lock(mMutex);
   mAudioSource = nullptr;
 }
 
 /**