1 files changed, 60 insertions, 0 deletions
diff --git a/media/libcubeb/src/cubeb_panner.cpp b/media/libcubeb/src/cubeb_panner.cpp
new file mode 100644
index 000000000..bd96ed6ef
--- /dev/null
+++ b/media/libcubeb/src/cubeb_panner.cpp
@@ -0,0 +1,60 @@
+/*
+ * Copyright © 2014 Mozilla Foundation
+ *
+ * This program is made available under an ISC-style license.  See the
+ * accompanying file LICENSE for details.
+ */
+
+#define _USE_MATH_DEFINES
+#include <math.h>
+#include <stdint.h>
+
+#include "cubeb_panner.h"
+
+#ifndef M_PI
+#define M_PI 3.14159263
+#endif
+
+/**
+ * We use a cos/sin law.
+ */
+
+namespace {
+template<typename T>
+void cubeb_pan_stereo_buffer(T * buf, uint32_t frames, float pan)
+{
+  if (pan == 0.0) {
+    return;
+  }
+  /* rescale in [0; 1] */
+  pan += 1;
+  pan /= 2;
+  float left_gain  = float(cos(pan * M_PI * 0.5));
+  float right_gain = float(sin(pan * M_PI * 0.5));
+
+  /* In we are panning on the left, pan the right channel into the left one and
+   * vice-versa. */
+  if (pan < 0.5) {
+    for (uint32_t i = 0; i < frames * 2; i+=2) {
+      buf[i]     = T(buf[i] + buf[i + 1] * left_gain);
+      buf[i + 1] = T(buf[i + 1] * right_gain);
+    }
+  } else {
+    for (uint32_t i = 0; i < frames * 2; i+=2) {
+      buf[i]     = T(buf[i] * left_gain);
+      buf[i + 1] = T(buf[i + 1] + buf[i] * right_gain);
+    }
+  }
+}
+}
+
+void cubeb_pan_stereo_buffer_float(float * buf, uint32_t frames, float pan)
+{
+  cubeb_pan_stereo_buffer(buf, frames, pan);
+}
+
+void cubeb_pan_stereo_buffer_int(short * buf, uint32_t frames, float pan)
+{
+  cubeb_pan_stereo_buffer(buf, frames, pan);
+}
+