Support for remote audio into tracks

webrtc/voice_engine/channel.cc

Index: webrtc/voice_engine/channel.cc
diff --git a/webrtc/voice_engine/channel.cc b/webrtc/voice_engine/channel.cc
index 37dc3b685b9243d7c31bdf35cb7b2ee9ce79ccc0..a36b13e566a3d1915c971ed5f456cbfdff48633b 100644
--- a/webrtc/voice_engine/channel.cc
+++ b/webrtc/voice_engine/channel.cc
@@ -560,6 +560,29 @@ int32_t Channel::GetAudioFrame(int32_t id, AudioFrame* audioFrame)
       }
     }
 
+    // External media.
+    // Pass the audio buffers to the external media callback, if set, before
+    // applying scaling/panning, as that applies to the mix operation.

[the sun, 2015/12/10 12:36:32]

Does this break any of our tests? It might break 3rd party code using the
processing API and relying on scaling etc being applied.

If you pick option b) in the previous comment you'd keep the external media code
in its original place for now, and add a new hook for AudioRenderer::Sink in
this place.

+    // External recipients of the audio (e.g. via AudioTrack), will do their own
+    // mixing.
+    if (_outputExternalMedia)
+    {
+        CriticalSectionScoped cs(&_callbackCritSect);
+        const bool isStereo = (audioFrame->num_channels_ == 2);
+        if (_outputExternalMediaCallbackPtr)
+        {
+            // TODO(tommi, hlundin): There's no timestamp information that
+            // accompanies the audio data.  Fix pwetty pwease.
+            _outputExternalMediaCallbackPtr->Process(
+                _channelId,
+                kPlaybackPerChannel,
+                reinterpret_cast<int16_t*>(audioFrame->data_),
+                audioFrame->samples_per_channel_,
+                audioFrame->sample_rate_hz_,
+                isStereo);
+        }
+    }
+
     float output_gain = 1.0f;
     float left_pan =  1.0f;
     float right_pan =  1.0f;
@@ -601,23 +624,6 @@ int32_t Channel::GetAudioFrame(int32_t id, AudioFrame* audioFrame)
         MixAudioWithFile(*audioFrame, audioFrame->sample_rate_hz_);
     }
 
-    // External media
-    if (_outputExternalMedia)
-    {
-        CriticalSectionScoped cs(&_callbackCritSect);
-        const bool isStereo = (audioFrame->num_channels_ == 2);
-        if (_outputExternalMediaCallbackPtr)
-        {
-            _outputExternalMediaCallbackPtr->Process(
-                _channelId,
-                kPlaybackPerChannel,
-                (int16_t*)audioFrame->data_,
-                audioFrame->samples_per_channel_,
-                audioFrame->sample_rate_hz_,
-                isStereo);
-        }
-    }
-
     // Record playout if enabled
     {
         CriticalSectionScoped cs(&_fileCritSect);