mirror of
https://github.com/mollyim/webrtc.git
synced 2025-05-13 05:40:42 +01:00
665174fdbb
Running clang-format with chromium's style guide. The goal is n-fold: * providing consistency and readability (that's what code guidelines are for) * preventing noise with presubmit checks and git cl format * building on the previous point: making it easier to automatically fix format issues * you name it Please consider using git-hyper-blame to ignore this commit. Bug: webrtc:9340 Change-Id: I694567c4cdf8cee2860958cfe82bfaf25848bb87 Reviewed-on: https://webrtc-review.googlesource.com/81185 Reviewed-by: Patrik Höglund <phoglund@webrtc.org> Cr-Commit-Position: refs/heads/master@{#23660}
63 lines
2.7 KiB
C++
63 lines
2.7 KiB
C++
/*
|
|
* 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 "modules/audio_coding/neteq/cross_correlation.h"
|
|
|
|
#include <cstdlib>
|
|
#include <limits>
|
|
|
|
#include "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
|