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 #include "cng_helpfuns.h"
12 
13 #include "signal_processing_library.h"
14 #include "webrtc/typedefs.h"
15 #include "webrtc_cng.h"
16 
17 /* Values in |k| are Q15, and |a| Q12. */
WebRtcCng_K2a16(int16_t * k,int useOrder,int16_t * a)18 void WebRtcCng_K2a16(int16_t* k, int useOrder, int16_t* a) {
19   int16_t any[WEBRTC_SPL_MAX_LPC_ORDER + 1];
20   int16_t *aptr, *aptr2, *anyptr;
21   const int16_t *kptr;
22   int m, i;
23 
24   kptr = k;
25   *a = 4096;  /* i.e., (Word16_MAX >> 3) + 1 */
26   *any = *a;
27   a[1] = (*k + 4) >> 3;
28   for (m = 1; m < useOrder; m++) {
29     kptr++;
30     aptr = a;
31     aptr++;
32     aptr2 = &a[m];
33     anyptr = any;
34     anyptr++;
35 
36     any[m + 1] = (*kptr + 4) >> 3;
37     for (i = 0; i < m; i++) {
38       *anyptr++ = (*aptr++) +
39           (int16_t)((((int32_t)(*aptr2--) * (int32_t) * kptr) + 16384) >> 15);
40     }
41 
42     aptr = a;
43     anyptr = any;
44     for (i = 0; i < (m + 2); i++) {
45       *aptr++ = *anyptr++;
46     }
47   }
48 }
49