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/*
* Copyright (c) 2011 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.
*/
/*
* This file contains the function WebRtcSpl_AutoCorrelation().
* The description header can be found in signal_processing_library.h
*
*/
#include "signal_processing_library.h"
int WebRtcSpl_AutoCorrelation(G_CONST WebRtc_Word16* in_vector,
int in_vector_length,
int order,
WebRtc_Word32* result,
int* scale)
{
WebRtc_Word32 sum;
int i, j;
WebRtc_Word16 smax; // Sample max
G_CONST WebRtc_Word16* xptr1;
G_CONST WebRtc_Word16* xptr2;
WebRtc_Word32* resultptr;
int scaling = 0;
#ifdef _ARM_OPT_
#pragma message("NOTE: _ARM_OPT_ optimizations are used")
WebRtc_Word16 loops4;
#endif
if (order < 0)
order = in_vector_length;
// Find the max. sample
smax = WebRtcSpl_MaxAbsValueW16(in_vector, in_vector_length);
// In order to avoid overflow when computing the sum we should scale the samples so that
// (in_vector_length * smax * smax) will not overflow.
if (smax == 0)
{
scaling = 0;
} else
{
int nbits = WebRtcSpl_GetSizeInBits(in_vector_length); // # of bits in the sum loop
int t = WebRtcSpl_NormW32(WEBRTC_SPL_MUL(smax, smax)); // # of bits to normalize smax
if (t > nbits)
{
scaling = 0;
} else
{
scaling = nbits - t;
}
}
resultptr = result;
// Perform the actual correlation calculation
for (i = 0; i < order + 1; i++)
{
int loops = (in_vector_length - i);
sum = 0;
xptr1 = in_vector;
xptr2 = &in_vector[i];
#ifndef _ARM_OPT_
for (j = loops; j > 0; j--)
{
sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1++, *xptr2++, scaling);
}
#else
loops4 = (loops >> 2) << 2;
if (scaling == 0)
{
for (j = 0; j < loops4; j = j + 4)
{
sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
xptr1++;
xptr2++;
sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
xptr1++;
xptr2++;
sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
xptr1++;
xptr2++;
sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
xptr1++;
xptr2++;
}
for (j = loops4; j < loops; j++)
{
sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
xptr1++;
xptr2++;
}
}
else
{
for (j = 0; j < loops4; j = j + 4)
{
sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
xptr1++;
xptr2++;
sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
xptr1++;
xptr2++;
sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
xptr1++;
xptr2++;
sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
xptr1++;
xptr2++;
}
for (j = loops4; j < loops; j++)
{
sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
xptr1++;
xptr2++;
}
}
#endif
*resultptr++ = sum;
}
*scale = scaling;
return order + 1;
}
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