1 files changed, 52 insertions, 0 deletions
diff --git a/src/3rdparty/resonance-audio/resonance_audio/ambisonics/stereo_from_soundfield_converter.cc b/src/3rdparty/resonance-audio/resonance_audio/ambisonics/stereo_from_soundfield_converter.cc
new file mode 100644
index 000000000..94462a445
--- /dev/null
+++ b/src/3rdparty/resonance-audio/resonance_audio/ambisonics/stereo_from_soundfield_converter.cc
@@ -0,0 +1,52 @@
+/*
+Copyright 2018 Google Inc. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS-IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include "ambisonics/stereo_from_soundfield_converter.h"
+
+#include "base/constants_and_types.h"
+#include "dsp/gain.h"
+
+namespace vraudio {
+
+namespace {
+
+const float kMidSideChannelGain = 0.5f;
+
+}  // namespace
+
+void StereoFromSoundfield(const AudioBuffer& soundfield_input,
+                          AudioBuffer* stereo_output) {
+  DCHECK(stereo_output);
+  DCHECK_EQ(kNumStereoChannels, stereo_output->num_channels());
+  DCHECK_EQ(soundfield_input.num_frames(), stereo_output->num_frames());
+  DCHECK_GE(soundfield_input.num_channels(), kNumFirstOrderAmbisonicChannels);
+  const AudioBuffer::Channel& channel_audio_space_w = soundfield_input[0];
+  const AudioBuffer::Channel& channel_audio_space_y = soundfield_input[1];
+  AudioBuffer::Channel* left_channel_output = &(*stereo_output)[0];
+  AudioBuffer::Channel* right_channel_output = &(*stereo_output)[1];
+  // Left = 0.5 * (Mid + Side).
+  *left_channel_output = channel_audio_space_w;
+  *left_channel_output += channel_audio_space_y;
+  ConstantGain(0 /* no offset */, kMidSideChannelGain, *left_channel_output,
+               left_channel_output, false /* accumulate_output */);
+  // Right = 0.5 * (Mid - Side).
+  *right_channel_output = channel_audio_space_w;
+  *right_channel_output -= channel_audio_space_y;
+  ConstantGain(0 /* no offset */, kMidSideChannelGain, *right_channel_output,
+               right_channel_output, false /* accumulate_output */);
+}
+
+}  // namespace vraudio