audioparams: move calculate_channel_count definition to source file

app/render/audioparams.cpp

@@ -350,4 +350,9 @@ AudioParams::Format AudioParams::GetPlanarEquivalent(Format fmt)
   return kFormatInvalid;
 }
 
+void AudioParams::calculate_channel_count()
+{
+  channel_count_ = av_get_channel_layout_nb_channels(channel_layout());
+}
+
 }

app/render/audioparams.h

@@ -256,10 +256,7 @@ private:
     duration_ = 0;
   }
 
-  void calculate_channel_count()
-  {
-    channel_count_ = av_get_channel_layout_nb_channels(channel_layout());
-  }
+  void calculate_channel_count();
 
   int sample_rate_;