[wsola] Rename misleading "symmetric" Hanning window function.

This function actually produces a periodic Hanning window instead of a
symmetric one.

Change-Id: If921c08d990eafe3e9475de2fbf7b6a64c7879f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2211363
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Thomas Guilbert <tguilbert@chromium.org>
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771085}

media/filters/audio_renderer_algorithm.cc

@@ -272,11 +272,11 @@ int AudioRendererAlgorithm::FillBuffer(AudioBus* dest,
   // chunk of memory. ~56kB for stereo 48kHz, up to ~765kB for 7.1 192kHz.
   if (!ola_window_) {
     ola_window_.reset(new float[ola_window_size_]);
-    internal::GetSymmetricHanningWindow(ola_window_size_, ola_window_.get());
+    internal::GetPeriodicHanningWindow(ola_window_size_, ola_window_.get());
 
     transition_window_.reset(new float[ola_window_size_ * 2]);
-    internal::GetSymmetricHanningWindow(2 * ola_window_size_,
-                                        transition_window_.get());
+    internal::GetPeriodicHanningWindow(2 * ola_window_size_,
+                                       transition_window_.get());
 
     // Initialize for overlap-and-add of the first block.
     wsola_output_ =

media/filters/wsola_internals.cc

@@ -308,7 +308,7 @@ int OptimalIndex(const AudioBus* search_block,
                     energy_candidate_blocks.get());
 }
 
-void GetSymmetricHanningWindow(int window_length, float* window) {
+void GetPeriodicHanningWindow(int window_length, float* window) {
   const float scale = 2.0f * base::kPiFloat / window_length;
   for (int n = 0; n < window_length; ++n)
     window[n] = 0.5f * (1.0f - std::cos(n * scale));

media/filters/wsola_internals.h

@@ -78,7 +78,7 @@ MEDIA_EXPORT int OptimalIndex(const AudioBus* search_block,
 
 // Return a "periodic" Hann window. This is the first L samples of an L+1
 // Hann window. It is perfect reconstruction for overlap-and-add.
-MEDIA_EXPORT void GetSymmetricHanningWindow(int window_length, float* window);
+MEDIA_EXPORT void GetPeriodicHanningWindow(int window_length, float* window);
 
 }  // namespace internal