Avoiding overflow in cross correlation in NetEq.

webrtc/modules/audio_coding/neteq/background_noise.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
 #include "webrtc/modules/audio_coding/neteq/background_noise.h"
 
 #include <assert.h>
 #include <string.h>  // memcpy
 
 #include <algorithm>  // min, max
 
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 #include "webrtc/modules/audio_coding/neteq/audio_multi_vector.h"
+#include "webrtc/modules/audio_coding/neteq/cross_correlation.h"
 #include "webrtc/modules/audio_coding/neteq/post_decode_vad.h"
 
 namespace webrtc {
 
 // static
 const size_t BackgroundNoise::kMaxLpcOrder;
 
 BackgroundNoise::BackgroundNoise(size_t num_channels)
     : num_channels_(num_channels),
       channel_parameters_(new ChannelParameters[num_channels_]),
@@ skipping 132 matching lines @@
   assert(channel < num_channels_);
   return channel_parameters_[channel].scale;
 }
 int16_t BackgroundNoise::ScaleShift(size_t channel) const {
   assert(channel < num_channels_);
   return channel_parameters_[channel].scale_shift;
 }
 
 int32_t BackgroundNoise::CalculateAutoCorrelation(
     const int16_t* signal, size_t length, int32_t* auto_correlation) const {
-  int16_t signal_max = WebRtcSpl_MaxAbsValueW16(signal, length);
-  int correlation_scale = kLogVecLen -
-      WebRtcSpl_NormW32(signal_max * signal_max);
-  correlation_scale = std::max(0, correlation_scale);
-
   static const int kCorrelationStep = -1;
-  WebRtcSpl_CrossCorrelation(auto_correlation, signal, signal, length,
-                             kMaxLpcOrder + 1, correlation_scale,
-                             kCorrelationStep);
+  const int correlation_scale =
+      CrossCorrelationWithAutoShift(auto_correlation, signal, signal, length,
+                                    kMaxLpcOrder + 1, kCorrelationStep);
 
   // Number of shifts to normalize energy to energy/sample.
   int energy_sample_shift = kLogVecLen - correlation_scale;
   return auto_correlation[0] >> energy_sample_shift;
 }
 
 void BackgroundNoise::IncrementEnergyThreshold(size_t channel,
                                                int32_t sample_energy) {
   // TODO(hlundin): Simplify the below threshold update. What this code
   // does is simply "threshold += (increment * threshold) >> 16", but due
@@ skipping 62 matching lines @@
   // Add 13 to the |scale_shift_|, since the random numbers table is in
   // Q13.
   // TODO(hlundin): Move the "13" to where the |scale_shift_| is used?
   parameters.scale_shift =
       static_cast<int16_t>(13 + ((kLogResidualLength + norm_shift) / 2));
 
   initialized_ = true;
 }
 
 }  // namespace webrtc