Make the nonlinear beamformer steerable

webrtc/modules/audio_processing/beamformer/array_util.h

Index: webrtc/modules/audio_processing/beamformer/array_util.h
diff --git a/webrtc/modules/audio_processing/beamformer/array_util.h b/webrtc/modules/audio_processing/beamformer/array_util.h
index 64a9ca37f92dfefff8c5b95e35683677e7bf098e..63b0131aae07ebc4877e2ca886267c749025e917 100644
--- a/webrtc/modules/audio_processing/beamformer/array_util.h
+++ b/webrtc/modules/audio_processing/beamformer/array_util.h
@@ -16,7 +16,12 @@
 
 namespace webrtc {
 
-// Coordinates in meters.
+// Coordinates in meters. The convention used is:
+// x: the horizontal dimension, with positive to the right from the camera's
+//    perspective.
+// y: the depth dimension, with positive forward from the camera's
+//    perspective.
+// z: the vertical dimension, with positive upwards.
 template<typename T>
 struct CartesianPoint {
   CartesianPoint(T x, T y, T z) {
@@ -41,6 +46,11 @@ float Distance(CartesianPoint<T> a, CartesianPoint<T> b) {
                    (a.z() - b.z()) * (a.z() - b.z()));
 }
 
+// The convention used:
+// azimuth: Zero is to the right from the camera's perspective, with positive

[Andrew MacDonald, 2015/10/20 03:00:08]

nit: to be consistent with above, no capitalization ("azimuth: zero...")

[aluebs-webrtc, 2015/10/21 01:41:40]

Done.

+//          angles in radians towards the front of the camera.

[Andrew MacDonald, 2015/10/20 03:00:08]

with positive angles counter-clockwise.

[aluebs-webrtc, 2015/10/21 01:41:40]

My only concern with using "counter-clockwise" is that this depends if you are
looking from above or below. But if you think it is clearer I am changing it.
Done.

[Andrew MacDonald, 2015/10/21 22:59:46]

Right. Another option is to define these in terms of the Cartesian coordinates
rather than the camera. So:

azimuth: the angle from the positive x-axis towards the positive y-axis in
radians.
elevation: the angle from the xy projection towards the positive z-axis in
radians.
radius: distance from the origin in meters.

WDYT?

+// elevation: Zero is horizontal, with positive angles in radians upwards.
+// radius: Distance from the camera in meters.
 template <typename T>
 struct SphericalPoint {
   SphericalPoint(T azimuth, T elevation, T radius) {