Allow more than 2 input channels in AudioProcessing.

webrtc/common_audio/audio_util.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 21 matching lines @@
 void FloatToFloatS16(const float* src, size_t size, float* dest) {
   for (size_t i = 0; i < size; ++i)
     dest[i] = FloatToFloatS16(src[i]);
 }
 
 void FloatS16ToFloat(const float* src, size_t size, float* dest) {
   for (size_t i = 0; i < size; ++i)
     dest[i] = FloatS16ToFloat(src[i]);
 }
 
+template <>
+void DownmixInterleavedToMono<int16_t>(const int16_t* interleaved,
+                                       int num_multichannel_frames,
+                                       int num_channels,
+                                       int16_t* deinterleaved) {
+  DownmixInterleavedToMonoImpl<int16_t, int32_t>(
+      interleaved, num_multichannel_frames, num_channels, deinterleaved);
+}
+
 }  // namespace webrtc