Make the nonlinear beamformer steerable

webrtc/modules/audio_processing/beamformer/array_util.h

 /*
  *  Copyright (c) 2015 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.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_BEAMFORMER_ARRAY_UTIL_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_BEAMFORMER_ARRAY_UTIL_H_
 
 #include <cmath>
 #include <vector>
 
 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) {
     c[0] = x;
     c[1] = y;
     c[2] = z;
   }
   T x() const { return c[0]; }
   T y() const { return c[1]; }
   T z() const { return c[2]; }
   T c[3];
 };
 
 using Point = CartesianPoint<float>;
 
 float GetMinimumSpacing(const std::vector<Point>& array_geometry);
 
 template<typename T>
 float Distance(CartesianPoint<T> a, CartesianPoint<T> b) {
   return std::sqrt((a.x() - b.x()) * (a.x() - b.x()) +
                    (a.y() - b.y()) * (a.y() - b.y()) +
                    (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) {
     s[0] = azimuth;
     s[1] = elevation;
     s[2] = radius;
   }
   T azimuth() const { return s[0]; }
   T elevation() const { return s[1]; }
   T distance() const { return s[2]; }
   T s[3];
 };
 
 using SphericalPointf = SphericalPoint<float>;
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_BEAMFORMER_ARRAY_UTIL_H_