Handle near-colinear case in WSOLAS QuadraticInterpolation better.

media/filters/audio_renderer_algorithm_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // The format of these tests are to enqueue a known amount of data and then
 // request the exact amount we expect in order to dequeue the known amount of
 // data.  This ensures that for any rate we are consuming input data at the
 // correct rate.  We always pass in a very large destination buffer with the
 // expectation that FillBuffer() will fill as much as it can but no more.
 
@@ skipping 572 matching lines @@
   // An interval which is of no effect.
   exclude_interval = std::make_pair(-100, -10);
   EXPECT_EQ(4, internal::DecimatedSearch(
       4, exclude_interval, target.get(), search_region.get(),
       energy_target.get(), energy_candid_blocks.get()));
 
   EXPECT_EQ(5, internal::OptimalIndex(search_region.get(), target.get(),
                                       exclude_interval));
 }
 
-TEST_F(AudioRendererAlgorithmTest, CubicInterpolation) {
+TEST_F(AudioRendererAlgorithmTest, QuadraticInterpolation) {
   // Arbitrary coefficients.
   const float kA = 0.7f;
   const float kB = 1.2f;
   const float kC = 0.8f;
 
   float y_values[3];
   y_values[0] = kA - kB + kC;
   y_values[1] = kC;
   y_values[2] = kA + kB + kC;
 
   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;
 
   EXPECT_FLOAT_EQ(x_star, extremum);
   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);
 }
 
 TEST_F(AudioRendererAlgorithmTest, WsolaSpeedup) {
   WsolaTest(1.6f);
 }
 
 }  // namespace media