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6031b74664
Finding the array element with the largest argmax is a fairly common operation, so it makes sense to have a Neon optimized version. The implementation is done by first finding both the min and max value, and then returning whichever has the largest argmax. Bug: chromium:12355 Change-Id: I088bd4f7d469b2424a7265de10fffb42764567a1 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/201622 Commit-Queue: Ivo Creusen <ivoc@webrtc.org> Reviewed-by: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33052}
55 lines
2.3 KiB
C++
55 lines
2.3 KiB
C++
/*
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* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "modules/audio_coding/neteq/cross_correlation.h"
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#include <cstdlib>
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#include <limits>
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#include "common_audio/signal_processing/include/signal_processing_library.h"
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namespace webrtc {
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// This function decides the overflow-protecting scaling and calls
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// WebRtcSpl_CrossCorrelation.
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int CrossCorrelationWithAutoShift(const int16_t* sequence_1,
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const int16_t* sequence_2,
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size_t sequence_1_length,
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size_t cross_correlation_length,
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int cross_correlation_step,
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int32_t* cross_correlation) {
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// Find the element that has the maximum absolute value of sequence_1 and 2.
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// Note that these values may be negative.
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const int16_t max_1 =
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WebRtcSpl_MaxAbsElementW16(sequence_1, sequence_1_length);
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const int sequence_2_shift =
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cross_correlation_step * (static_cast<int>(cross_correlation_length) - 1);
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const int16_t* sequence_2_start =
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sequence_2_shift >= 0 ? sequence_2 : sequence_2 + sequence_2_shift;
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const size_t sequence_2_length =
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sequence_1_length + std::abs(sequence_2_shift);
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const int16_t max_2 =
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WebRtcSpl_MaxAbsElementW16(sequence_2_start, sequence_2_length);
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// In order to avoid overflow when computing the sum we should scale the
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// samples so that (in_vector_length * max_1 * max_2) will not overflow.
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const int64_t max_value =
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abs(max_1 * max_2) * static_cast<int64_t>(sequence_1_length);
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const int32_t factor = max_value >> 31;
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const int scaling = factor == 0 ? 0 : 31 - WebRtcSpl_NormW32(factor);
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WebRtcSpl_CrossCorrelation(cross_correlation, sequence_1, sequence_2,
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sequence_1_length, cross_correlation_length,
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scaling, cross_correlation_step);
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return scaling;
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}
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} // namespace webrtc
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