Support 4 channel mic in Windows Core Audio

webrtc/audio/utility/audio_frame_operations.cc

 /*
  *  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 81 matching lines @@
   MonoToStereo(data_copy, frame->samples_per_channel_, frame->data_);
   frame->num_channels_ = 2;
 
   return 0;
 }
 
 void AudioFrameOperations::StereoToMono(const int16_t* src_audio,
                                         size_t samples_per_channel,
                                         int16_t* dst_audio) {
   for (size_t i = 0; i < samples_per_channel; i++) {
-    dst_audio[i] = (src_audio[2 * i] + src_audio[2 * i + 1]) >> 1;
+    dst_audio[i] =
+        (static_cast<int32_t>(src_audio[2 * i]) + src_audio[2 * i + 1]) >> 1;
   }
 }
 
 int AudioFrameOperations::StereoToMono(AudioFrame* frame) {
   if (frame->num_channels_ != 2) {
     return -1;
   }
 
+  RTC_DCHECK_LE(frame->samples_per_channel_ * 2,
+                AudioFrame::kMaxDataSizeSamples);
+
   StereoToMono(frame->data_, frame->samples_per_channel_, frame->data_);
   frame->num_channels_ = 1;
 
   return 0;
 }
 
+void AudioFrameOperations::QuadToStereo(const int16_t* src_audio,
+                                        size_t samples_per_channel,
+                                        int16_t* dst_audio) {
+  for (size_t i = 0; i < samples_per_channel; i++) {
+    dst_audio[i * 2] =
+        (static_cast<int32_t>(src_audio[4 * i]) + src_audio[4 * i + 1]) >> 1;
+    dst_audio[i * 2 + 1] =
+        (static_cast<int32_t>(src_audio[4 * i + 2]) + src_audio[4 * i + 3]) >>
+        1;
+  }
+}
+
+int AudioFrameOperations::QuadToStereo(AudioFrame* frame) {
+  if (frame->num_channels_ != 4) {
+    return -1;
+  }
+
+  RTC_DCHECK_LE(frame->samples_per_channel_ * 4,
+                AudioFrame::kMaxDataSizeSamples);
+
+  QuadToStereo(frame->data_, frame->samples_per_channel_, frame->data_);
+  frame->num_channels_ = 2;
+
+  return 0;
+}
+
+void AudioFrameOperations::QuadToMono(const int16_t* src_audio,
+                                      size_t samples_per_channel,
+                                      int16_t* dst_audio) {
+  for (size_t i = 0; i < samples_per_channel; i++) {
+    dst_audio[i] =
+        (static_cast<int32_t>(src_audio[4 * i]) + src_audio[4 * i + 1] +
+         src_audio[4 * i + 2] + src_audio[4 * i + 3]) >> 2;
+  }
+}
+
+int AudioFrameOperations::QuadToMono(AudioFrame* frame) {
+  if (frame->num_channels_ != 4) {
+    return -1;
+  }
+
+  RTC_DCHECK_LE(frame->samples_per_channel_ * 4,
+                AudioFrame::kMaxDataSizeSamples);
+
+  QuadToMono(frame->data_, frame->samples_per_channel_, frame->data_);
+  frame->num_channels_ = 1;
+
+  return 0;
+}
+
+void AudioFrameOperations::DownmixChannels(const int16_t* src_audio,
+                                           size_t src_channels,
+                                           size_t samples_per_channel,
+                                           size_t dst_channels,
+                                           int16_t* dst_audio) {
+  if (src_channels == 2 && dst_channels == 1) {
+    StereoToMono(src_audio, samples_per_channel, dst_audio);
+    return;
+  } else if (src_channels == 4 && dst_channels == 2) {
+    QuadToStereo(src_audio, samples_per_channel, dst_audio);
+    return;
+  } else if (src_channels == 4 && dst_channels == 1) {
+    QuadToMono(src_audio, samples_per_channel, dst_audio);
+    return;
+  }
+
+  RTC_NOTREACHED() << "src_channels: " << src_channels
+                   << ", dst_channels: " << dst_channels;
+}
+
+int AudioFrameOperations::DownmixChannels(size_t dst_channels,
+                                          AudioFrame* frame) {
+  if (frame->num_channels_ == 2 && dst_channels == 1) {
+    return StereoToMono(frame);
+  } else if (frame->num_channels_ == 4 && dst_channels == 2) {
+    return QuadToStereo(frame);
+  } else if (frame->num_channels_ == 4 && dst_channels == 1) {
+    return QuadToMono(frame);
+  }
+
+  return -1;
+}
+
 void AudioFrameOperations::SwapStereoChannels(AudioFrame* frame) {
   RTC_DCHECK(frame);
   if (frame->num_channels_ != 2) {
     return;
   }
 
   for (size_t i = 0; i < frame->samples_per_channel_ * 2; i += 2) {
     int16_t temp_data = frame->data_[i];
     frame->data_[i] = frame->data_[i + 1];
     frame->data_[i + 1] = temp_data;
@@ skipping 90 matching lines @@
       frame.data_[i] = -32768;
     } else if (temp_data > 32767) {
       frame.data_[i] = 32767;
     } else {
       frame.data_[i] = static_cast<int16_t>(temp_data);
     }
   }
   return 0;
 }
 }  // namespace webrtc