Revert of Avoiding overflow in cross correlation in NetEq.

webrtc/modules/audio_coding/neteq/cross_correlation.cc

Index: webrtc/modules/audio_coding/neteq/cross_correlation.cc
diff --git a/webrtc/modules/audio_coding/neteq/cross_correlation.cc b/webrtc/modules/audio_coding/neteq/cross_correlation.cc
deleted file mode 100644
index ad89ab8a139eafadafb27632de5e9bc3ddbc5376..0000000000000000000000000000000000000000
--- a/webrtc/modules/audio_coding/neteq/cross_correlation.cc
+++ /dev/null
@@ -1,62 +0,0 @@
-/*
- *  Copyright (c) 2016 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/cross_correlation.h"
-
-#include <cstdlib>
-#include <limits>
-
-#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
-
-namespace webrtc {
-
-// This function decides the overflow-protecting scaling and calls
-// WebRtcSpl_CrossCorrelation.
-int CrossCorrelationWithAutoShift(const int16_t* sequence_1,
-                                  const int16_t* sequence_2,
-                                  size_t sequence_1_length,
-                                  size_t cross_correlation_length,
-                                  int cross_correlation_step,
-                                  int32_t* cross_correlation) {
-  // Find the maximum absolute value of sequence_1 and 2.
-  const int16_t max_1 = WebRtcSpl_MaxAbsValueW16(sequence_1, sequence_1_length);
-  const int sequence_2_shift =
-      cross_correlation_step * (static_cast<int>(cross_correlation_length) - 1);
-  const int16_t* sequence_2_start =
-      sequence_2_shift >= 0 ? sequence_2 : sequence_2 + sequence_2_shift;
-  const size_t sequence_2_length =
-      sequence_1_length + std::abs(sequence_2_shift);
-  const int16_t max_2 =
-      WebRtcSpl_MaxAbsValueW16(sequence_2_start, sequence_2_length);
-
-  // In order to avoid overflow when computing the sum we should scale the
-  // samples so that (in_vector_length * max_1 * max_2) will not overflow.
-  // Expected scaling fulfills
-  // 1) sufficient:
-  //    sequence_1_length * (max_1 * max_2 >> scaling) <= 0x7fffffff;
-  // 2) necessary:
-  //    if (scaling > 0)
-  //      sequence_1_length * (max_1 * max_2 >> (scaling - 1)) > 0x7fffffff;
-  // The following calculation fulfills 1) and almost fulfills 2).
-  // There are some corner cases that 2) is not satisfied, e.g.,
-  // max_1 = 17, max_2 = 30848, sequence_1_length = 4095, in such case,
-  // optimal scaling is 0, while the following calculation results in 1.
-  const int32_t factor = (max_1 * max_2) / (std::numeric_limits<int32_t>::max()
-      / static_cast<int32_t>(sequence_1_length));
-  const int scaling = factor == 0 ? 0 : 31 - WebRtcSpl_NormW32(factor);
-
-  WebRtcSpl_CrossCorrelation(cross_correlation, sequence_1, sequence_2,
-                             sequence_1_length, cross_correlation_length,
-                             scaling, cross_correlation_step);
-
-  return scaling;
-}
-
-}  // namespace webrtc