Fixing an overflow issue in NetEq::BackgroundNoise

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.
  */
 
@@ skipping 83 matching lines @@
                                 fiter_output, lpc_coefficients,
                                 kMaxLpcOrder + 1, kResidualLength);
       int32_t residual_energy = WebRtcSpl_DotProductWithScale(fiter_output,
                                                               fiter_output,
                                                               kResidualLength,
                                                               0);
 
       // Check spectral flatness.
       // Comparing the residual variance with the input signal variance tells
       // if the spectrum is flat or not.
-      // If 20 * residual_energy >= sample_energy << 6, the spectrum is flat
+      // If 5 * residual_energy >= 16 * sample_energy, the spectrum is flat
       // enough.  Also ensure that the energy is non-zero.
-      if ((residual_energy * 20 >= (sample_energy << 6)) &&
-          (sample_energy > 0)) {
+      if ((sample_energy > 0) &&
+          (int64_t{5} * residual_energy >= int64_t{16} * sample_energy)) {

[kwiberg-webrtc, 2017/02/28 12:19:58]

Optionally, remove the redundant parentheses.

         // Spectrum is flat enough; save filter parameters.
         // |temp_signal| + |kVecLen| - |kMaxLpcOrder| points at the first of the
         // |kMaxLpcOrder| samples in the residual signal, which will form the
         // filter state for the next noise generation.
         SaveParameters(channel_ix, lpc_coefficients,
                        temp_signal + kVecLen - kMaxLpcOrder, sample_energy,
                        residual_energy);
       }
     } else {
       // Will only happen if post-decode VAD is disabled and |sample_energy| is
@@ skipping 128 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