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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_DownsampleFast().
* The description header can be found in signal_processing_library.h
*
*/
#include "signal_processing_library.h"
int WebRtcSpl_DownsampleFast(WebRtc_Word16 *in_ptr, WebRtc_Word16 in_length,
WebRtc_Word16 *out_ptr, WebRtc_Word16 out_length,
WebRtc_Word16 *B, WebRtc_Word16 B_length, WebRtc_Word16 factor,
WebRtc_Word16 delay)
{
WebRtc_Word32 o;
int i, j;
WebRtc_Word16 *downsampled_ptr = out_ptr;
WebRtc_Word16 *b_ptr;
WebRtc_Word16 *x_ptr;
WebRtc_Word16 endpos = delay
+ (WebRtc_Word16)WEBRTC_SPL_MUL_16_16(factor, (out_length - 1)) + 1;
if (in_length < endpos)
{
return -1;
}
for (i = delay; i < endpos; i += factor)
{
b_ptr = &B[0];
x_ptr = &in_ptr[i];
o = (WebRtc_Word32)2048; // Round val
for (j = 0; j < B_length; j++)
{
o += WEBRTC_SPL_MUL_16_16(*b_ptr++, *x_ptr--);
}
o = WEBRTC_SPL_RSHIFT_W32(o, 12);
// If output is higher than 32768, saturate it. Same with negative side
*downsampled_ptr++ = WebRtcSpl_SatW32ToW16(o);
}
return 0;
}
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