Support 4 channel mic in Windows Core Audio

webrtc/audio/utility/audio_frame_operations.h

 /*
  *  Copyright (c) 2012 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 22 matching lines @@
   // |result_frame| is empty.
   static void Add(const AudioFrame& frame_to_add, AudioFrame* result_frame);
 
   // Upmixes mono |src_audio| to stereo |dst_audio|. This is an out-of-place
   // operation, meaning src_audio and dst_audio must point to different
   // buffers. It is the caller's responsibility to ensure that |dst_audio| is
   // sufficiently large.
   static void MonoToStereo(const int16_t* src_audio,
                            size_t samples_per_channel,
                            int16_t* dst_audio);
+
   // |frame.num_channels_| will be updated. This version checks for sufficient
   // buffer size and that |num_channels_| is mono.
   static int MonoToStereo(AudioFrame* frame);
 
   // Downmixes stereo |src_audio| to mono |dst_audio|. This is an in-place
   // operation, meaning |src_audio| and |dst_audio| may point to the same
   // buffer.
   static void StereoToMono(const int16_t* src_audio,
                            size_t samples_per_channel,
                            int16_t* dst_audio);
+
   // |frame.num_channels_| will be updated. This version checks that
   // |num_channels_| is stereo.
   static int StereoToMono(AudioFrame* frame);
 
+  // Downmixes 4 channels |src_audio| to stereo |dst_audio|. This is an in-place
+  // operation, meaning |src_audio| and |dst_audio| may point to the same
+  // buffer.
+  static void QuadToStereo(const int16_t* src_audio,
+                           size_t samples_per_channel,
+                           int16_t* dst_audio);
+
+  // |frame.num_channels_| will be updated. This version checks that
+  // |num_channels_| is 4 channels.
+  static int QuadToStereo(AudioFrame* frame);
+
+  // Downmixes 4 channels |src_audio| to mono |dst_audio|. This is an in-place
+  // operation, meaning |src_audio| and |dst_audio| may point to the same
+  // buffer.
+  static void QuadToMono(const int16_t* src_audio,
+                         size_t samples_per_channel,
+                         int16_t* dst_audio);
+
+  // |frame.num_channels_| will be updated. This version checks that
+  // |num_channels_| is 4 channels.
+  static int QuadToMono(AudioFrame* frame);
+
+  // Downmixes |src_channels| |src_audio| to |dst_channels| |dst_audio|.
+  // This is an in-place operation, meaning |src_audio| and |dst_audio|
+  // may point to the same buffer. Supported channel combinations are
+  // Stereo to Mono, Quad to Mono, and Quad to Stereo.
+  static void DownmixChannels(const int16_t* src_audio,
+                              size_t src_channels,
+                              size_t samples_per_channel,
+                              size_t dst_channels,
+                              int16_t* dst_audio);
+
+  // |frame.num_channels_| will be updated. This version checks that
+  // |num_channels_| and |dst_channels| are valid and performs relevant
+  // downmix.  Supported channel combinations are Stereo to Mono, Quad to Mono,
+  // and Quad to Stereo.
+  static int DownmixChannels(size_t dst_channels, AudioFrame* frame);
+
   // Swap the left and right channels of |frame|. Fails silently if |frame| is
   // not stereo.
   static void SwapStereoChannels(AudioFrame* frame);
 
   // Conditionally zero out contents of |frame| for implementing audio mute:
   //  |previous_frame_muted| &&  |current_frame_muted| - Zero out whole frame.
   //  |previous_frame_muted| && !|current_frame_muted| - Fade-in at frame start.
   // !|previous_frame_muted| &&  |current_frame_muted| - Fade-out at frame end.
   // !|previous_frame_muted| && !|current_frame_muted| - Leave frame untouched.
   static void Mute(AudioFrame* frame,
                    bool previous_frame_muted,
                    bool current_frame_muted);
 
   // Zero out contents of frame.
   static void Mute(AudioFrame* frame);
 
   // Halve samples in |frame|.
   static void ApplyHalfGain(AudioFrame* frame);
 
   static int Scale(float left, float right, AudioFrame& frame);
 
   static int ScaleWithSat(float scale, AudioFrame& frame);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_AUDIO_UTILITY_AUDIO_FRAME_OPERATIONS_H_