Handle near-colinear case in WSOLAS QuadraticInterpolation better.

media/filters/audio_renderer_algorithm_unittest.cc

Index: media/filters/audio_renderer_algorithm_unittest.cc
diff --git a/media/filters/audio_renderer_algorithm_unittest.cc b/media/filters/audio_renderer_algorithm_unittest.cc
index bde07a23f8439e7900ee2b610dd1fbba8d4d4fce..11a844adb9afab6a024957973e8dd8b5c835bf40 100644
--- a/media/filters/audio_renderer_algorithm_unittest.cc
+++ b/media/filters/audio_renderer_algorithm_unittest.cc
@@ -590,7 +590,7 @@ TEST_F(AudioRendererAlgorithmTest, FullAndDecimatedSearch) {
                                       exclude_interval));
 }
 
-TEST_F(AudioRendererAlgorithmTest, CubicInterpolation) {
+TEST_F(AudioRendererAlgorithmTest, QuadraticInterpolation) {
   // Arbitrary coefficients.
   const float kA = 0.7f;
   const float kB = 1.2f;
@@ -604,7 +604,7 @@ TEST_F(AudioRendererAlgorithmTest, CubicInterpolation) {
   float extremum;
   float extremum_value;
 
-  internal::CubicInterpolation(y_values, &extremum, &extremum_value);
+  internal::QuadraticInterpolation(y_values, &extremum, &extremum_value);
 
   float x_star = -kB / (2.f * kA);
   float y_star = kA * x_star * x_star + kB * x_star + kC;
@@ -613,6 +613,21 @@ TEST_F(AudioRendererAlgorithmTest, CubicInterpolation) {
   EXPECT_FLOAT_EQ(y_star, extremum_value);
 }
 
+TEST_F(AudioRendererAlgorithmTest, QuadraticInterpolation_Colinear) {
+  float y_values[3];
+  y_values[0] = 1.0;
+  y_values[1] = 1.0;
+  y_values[2] = 1.0;
+
+  float extremum;
+  float extremum_value;
+
+  internal::QuadraticInterpolation(y_values, &extremum, &extremum_value);
+
+  EXPECT_NEAR(extremum, 0.0, 1.0);

[DaleCurtis, 2014/03/29 01:10:01]

within 1 seems pretty large?

[sandersd (OOO until July 31), 2014/03/29 01:19:37]

Since the choice of x = 0 was arbitrary, I'm only testing that the returned
value satisfies -1 <= x <= 1.

+  EXPECT_FLOAT_EQ(extremum_value, 1.0);
+}
+
 TEST_F(AudioRendererAlgorithmTest, WsolaSlowdown) {
   WsolaTest(0.6f);
 }