Revert "RNN VAD: pitch search optimizations (part 3)"

This reverts commit ea89f2a447c514b73da2ed6189fe4b8485f123c6.

Reason for revert: bug in ancestor CL https://webrtc-review.googlesource.com/c/src/+/191320

Original change's description:
> RNN VAD: pitch search optimizations (part 3)
>
> `ComputeSlidingFrameSquareEnergies()` which computes the energy of a
> sliding 20 ms frame in the pitch buffer has been switched from backward
> to forward.
>
> The benchmark has shown a slight improvement (about +6x).
>
> This change is not bit exact but all the tolerance tests still pass
> except for one single case in `RnnVadTest,PitchSearchWithinTolerance`
> for which the tolerance has been slightly increased. Note that the pitch
> estimation is still bit-exact.
>
> Benchmarked as follows:
> ```
> out/release/modules_unittests \
>   --gtest_filter=*RnnVadTest.DISABLED_RnnVadPerformance* \
>   --gtest_also_run_disabled_tests --logs
> ```
>
> Results:
>
>       | baseline             | this CL
> ------+----------------------+------------------------
> run 1 | 22.8319 +/- 1.46554  | 22.087 +/- 0.552932
>       | 389.367x             | 402.499x
> ------+----------------------+------------------------
> run 2 | 22.4286 +/- 0.726449 | 22.216 +/- 0.916222
>       | 396.369x             | 400.162x
> ------+----------------------+------------------------
> run 2 | 22.5688 +/- 0.831341 | 22.4902 +/- 1.04881
>       | 393.906x             | 395.283x
>
> Bug: webrtc:10480
> Change-Id: I1fd54077a32e25e46196c8e18f003cd0ffd503e1
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/191703
> Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#32572}

TBR=alessiob@webrtc.org,kwiberg@webrtc.org

Change-Id: I57a8f937ade0a35e1ccf0e229c391cc3a10e7c48
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:10480
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/192621
Reviewed-by: Alessio Bazzica <alessiob@webrtc.org>
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32578}

modules/audio_processing/agc2/rnn_vad/pitch_search_internal.cc

@@ -169,7 +169,7 @@ int ComputePitchPeriod24kHz(
       // Auto-correlation energy normalized by frame energy.
       const float numerator =
           auto_correlation[inverted_lag] * auto_correlation[inverted_lag];
-      const float denominator = y_energy[inverted_lag];
+      const float denominator = y_energy[kMaxPitch24kHz - inverted_lag];
       // Compare numerator/denominator ratios without using divisions.
       if (numerator * best_denominator > best_numerator * denominator) {
         best_inverted_lag = inverted_lag;
@@ -253,19 +253,19 @@ void Decimate2x(rtc::ArrayView<const float, kBufSize24kHz> src,
 
 void ComputeSlidingFrameSquareEnergies24kHz(
     rtc::ArrayView<const float, kBufSize24kHz> pitch_buffer,
-    rtc::ArrayView<float, kRefineNumLags24kHz> y_energy) {
+    rtc::ArrayView<float, kRefineNumLags24kHz> yy_values) {
-  float yy = std::inner_product(pitch_buffer.begin(),
+  float yy = ComputeAutoCorrelation(kMaxPitch24kHz, pitch_buffer);
-                                pitch_buffer.begin() + kFrameSize20ms24kHz,
+  yy_values[0] = yy;
-                                pitch_buffer.begin(), 0.f);
+  static_assert(kMaxPitch24kHz - (kRefineNumLags24kHz - 1) >= 0, "");
-  y_energy[0] = yy;
   static_assert(kMaxPitch24kHz - 1 + kFrameSize20ms24kHz < kBufSize24kHz, "");
-  static_assert(kMaxPitch24kHz < kRefineNumLags24kHz, "");
+  for (int lag = 1; lag < kRefineNumLags24kHz; ++lag) {
-  for (int inverted_lag = 0; inverted_lag < kMaxPitch24kHz; ++inverted_lag) {
+    const int inverted_lag = kMaxPitch24kHz - lag;
-    yy -= pitch_buffer[inverted_lag] * pitch_buffer[inverted_lag];
+    const float y_old = pitch_buffer[inverted_lag + kFrameSize20ms24kHz];
-    yy += pitch_buffer[inverted_lag + kFrameSize20ms24kHz] *
+    const float y_new = pitch_buffer[inverted_lag];
-          pitch_buffer[inverted_lag + kFrameSize20ms24kHz];
+    yy -= y_old * y_old;
-    yy = std::max(1.f, yy);
+    yy += y_new * y_new;
-    y_energy[inverted_lag + 1] = yy;
+    yy = std::max(0.f, yy);
+    yy_values[lag] = yy;
   }
 }
 
@@ -375,7 +375,7 @@ PitchInfo ComputeExtendedPitchPeriod48kHz(
     float y_energy;  // Energy of the sliding frame `y`.
   };
 
-  const float x_energy = y_energy[kMaxPitch24kHz];
+  const float x_energy = y_energy[0];
   const auto pitch_strength = [x_energy](float xy, float y_energy) {
     RTC_DCHECK_GE(x_energy * y_energy, 0.f);
     return xy / std::sqrt(1.f + x_energy * y_energy);
@@ -387,7 +387,7 @@ PitchInfo ComputeExtendedPitchPeriod48kHz(
       std::min(initial_pitch_period_48kHz / 2, kMaxPitch24kHz - 1);
   best_pitch.xy =
       ComputeAutoCorrelation(kMaxPitch24kHz - best_pitch.period, pitch_buffer);
-  best_pitch.y_energy = y_energy[kMaxPitch24kHz - best_pitch.period];
+  best_pitch.y_energy = y_energy[best_pitch.period];
   best_pitch.strength = pitch_strength(best_pitch.xy, best_pitch.y_energy);
   // Keep a copy of the initial pitch candidate.
   const PitchInfo initial_pitch{best_pitch.period, best_pitch.strength};
@@ -428,9 +428,8 @@ PitchInfo ComputeExtendedPitchPeriod48kHz(
     const float xy_secondary_period = ComputeAutoCorrelation(
         kMaxPitch24kHz - dual_alternative_period, pitch_buffer);
     const float xy = 0.5f * (xy_primary_period + xy_secondary_period);
-    const float yy =
+    const float yy = 0.5f * (y_energy[alternative_pitch.period] +
-        0.5f * (y_energy[kMaxPitch24kHz - alternative_pitch.period] +
+                             y_energy[dual_alternative_period]);
-                y_energy[kMaxPitch24kHz - dual_alternative_period]);
     alternative_pitch.strength = pitch_strength(xy, yy);
 
     // Maybe update best period.

modules/audio_processing/agc2/rnn_vad/pitch_search_internal.h

@@ -62,10 +62,10 @@ void Decimate2x(rtc::ArrayView<const float, kBufSize24kHz> src,
 // corresponding pitch period.
 
 // Computes the sum of squared samples for every sliding frame `y` in the pitch
-// buffer. The indexes of `y_energy` are inverted lags.
+// buffer. The indexes of `yy_values` are lags.
 void ComputeSlidingFrameSquareEnergies24kHz(
     rtc::ArrayView<const float, kBufSize24kHz> pitch_buffer,
-    rtc::ArrayView<float, kRefineNumLags24kHz> y_energy);
+    rtc::ArrayView<float, kRefineNumLags24kHz> yy_values);
 
 // Top-2 pitch period candidates. Unit: number of samples - i.e., inverted lags.
 struct CandidatePitchPeriods {

modules/audio_processing/agc2/rnn_vad/pitch_search_internal_unittest.cc

@@ -42,7 +42,7 @@ TEST(RnnVadTest, ComputeSlidingFrameSquareEnergies24kHzWithinTolerance) {
                                          computed_output);
   auto square_energies_view = test_data.GetPitchBufSquareEnergiesView();
   ExpectNearAbsolute({square_energies_view.data(), square_energies_view.size()},
-                     computed_output, 1e-3f);
+                     computed_output, 3e-2f);
 }
 
 // Checks that the estimated pitch period is bit-exact given test input data.

modules/audio_processing/agc2/rnn_vad/pitch_search_unittest.cc

@@ -42,7 +42,7 @@ TEST(RnnVadTest, PitchSearchWithinTolerance) {
           pitch_estimator.Estimate({lp_residual.data(), kBufSize24kHz});
       EXPECT_EQ(expected_pitch_period, pitch_period);
       EXPECT_NEAR(expected_pitch_strength,
-                  pitch_estimator.GetLastPitchStrengthForTesting(), 15e-6f);
+                  pitch_estimator.GetLastPitchStrengthForTesting(), 1e-5f);
     }
   }
 }

modules/audio_processing/agc2/rnn_vad/test_utils.cc

@@ -10,7 +10,6 @@
 
 #include "modules/audio_processing/agc2/rnn_vad/test_utils.h"
 
-#include <algorithm>
 #include <memory>
 
 #include "rtc_base/checks.h"
@@ -87,10 +86,6 @@ PitchTestData::PitchTestData() {
       ResourcePath("audio_processing/agc2/rnn_vad/pitch_search_int", "dat"),
       1396);
   test_data_reader.ReadChunk(test_data_);
-  // Reverse the order of the squared energy values.
-  // Required after the WebRTC CL 191703 which switched to forward computation.
-  std::reverse(test_data_.begin() + kBufSize24kHz,
-               test_data_.begin() + kBufSize24kHz + kNumPitchBufSquareEnergies);
 }
 
 PitchTestData::~PitchTestData() = default;