1/*
2 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11/*
12 * Contains the core loop function for the lattice filter AR routine
13 * for iSAC codec.
14 *
15 */
16
17#include "settings.h"
18#include "signal_processing_library.h"
19#include "typedefs.h"
20
21/* Filter ar_g_Q0[] and ar_f_Q0[] through an AR filter with coefficients
22 * cth_Q15[] and sth_Q15[].
23 */
24void WebRtcIsacfix_FilterArLoop(int16_t* ar_g_Q0,     // Input samples
25                                int16_t* ar_f_Q0,     // Input samples
26                                int16_t* cth_Q15,     // Filter coefficients
27                                int16_t* sth_Q15,     // Filter coefficients
28                                int16_t order_coef) { // order of the filter
29  int n = 0;
30
31  for (n = 0; n < HALF_SUBFRAMELEN - 1; n++) {
32    int k = 0;
33    int16_t tmpAR = 0;
34    int32_t tmp32 = 0;
35    int32_t tmp32_2 = 0;
36
37    tmpAR = ar_f_Q0[n + 1];
38    for (k = order_coef - 1; k >= 0; k--) {
39      tmp32 = WEBRTC_SPL_RSHIFT_W32(((WEBRTC_SPL_MUL_16_16(cth_Q15[k], tmpAR))
40              - (WEBRTC_SPL_MUL_16_16(sth_Q15[k], ar_g_Q0[k])) + 16384), 15);
41      tmp32_2 = WEBRTC_SPL_RSHIFT_W32(((WEBRTC_SPL_MUL_16_16(sth_Q15[k], tmpAR))
42                + (WEBRTC_SPL_MUL_16_16(cth_Q15[k], ar_g_Q0[k])) + 16384), 15);
43      tmpAR   = (WebRtc_Word16)WebRtcSpl_SatW32ToW16(tmp32);
44      ar_g_Q0[k + 1] = (WebRtc_Word16)WebRtcSpl_SatW32ToW16(tmp32_2);
45    }
46    ar_f_Q0[n + 1] = tmpAR;
47    ar_g_Q0[0] = tmpAR;
48  }
49}
50