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
13 iLBC Speech Coder ANSI-C Source Code
14
15 WebRtcIlbcfix_SimpleLpcAnalysis.c
16
17 ******************************************************************/
18
19 #include "modules/audio_coding/codecs/ilbc/simple_lpc_analysis.h"
20
21 #include "modules/audio_coding/codecs/ilbc/bw_expand.h"
22 #include "modules/audio_coding/codecs/ilbc/constants.h"
23 #include "modules/audio_coding/codecs/ilbc/defines.h"
24 #include "modules/audio_coding/codecs/ilbc/poly_to_lsf.h"
25 #include "modules/audio_coding/codecs/ilbc/window32_w32.h"
26
27 /*----------------------------------------------------------------*
28 * lpc analysis (subrutine to LPCencode)
29 *---------------------------------------------------------------*/
30
WebRtcIlbcfix_SimpleLpcAnalysis(int16_t * lsf,int16_t * data,IlbcEncoder * iLBCenc_inst)31 void WebRtcIlbcfix_SimpleLpcAnalysis(
32 int16_t *lsf, /* (o) lsf coefficients */
33 int16_t *data, /* (i) new block of speech */
34 IlbcEncoder *iLBCenc_inst
35 /* (i/o) the encoder state structure */
36 ) {
37 int k;
38 int scale;
39 size_t is;
40 int16_t stability;
41 /* Stack based */
42 int16_t A[LPC_FILTERORDER + 1];
43 int32_t R[LPC_FILTERORDER + 1];
44 int16_t windowedData[BLOCKL_MAX];
45 int16_t rc[LPC_FILTERORDER];
46
47 is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
48 WEBRTC_SPL_MEMCPY_W16(iLBCenc_inst->lpc_buffer+is,data,iLBCenc_inst->blockl);
49
50 /* No lookahead, last window is asymmetric */
51
52 for (k = 0; k < iLBCenc_inst->lpc_n; k++) {
53
54 is = LPC_LOOKBACK;
55
56 if (k < (iLBCenc_inst->lpc_n - 1)) {
57
58 /* Hanning table WebRtcIlbcfix_kLpcWin[] is in Q15-domain so the output is right-shifted 15 */
59 WebRtcSpl_ElementwiseVectorMult(windowedData, iLBCenc_inst->lpc_buffer, WebRtcIlbcfix_kLpcWin, BLOCKL_MAX, 15);
60 } else {
61
62 /* Hanning table WebRtcIlbcfix_kLpcAsymWin[] is in Q15-domain so the output is right-shifted 15 */
63 WebRtcSpl_ElementwiseVectorMult(windowedData, iLBCenc_inst->lpc_buffer+is, WebRtcIlbcfix_kLpcAsymWin, BLOCKL_MAX, 15);
64 }
65
66 /* Compute autocorrelation */
67 WebRtcSpl_AutoCorrelation(windowedData, BLOCKL_MAX, LPC_FILTERORDER, R, &scale);
68
69 /* Window autocorrelation vector */
70 WebRtcIlbcfix_Window32W32(R, R, WebRtcIlbcfix_kLpcLagWin, LPC_FILTERORDER + 1 );
71
72 /* Calculate the A coefficients from the Autocorrelation using Levinson Durbin algorithm */
73 stability=WebRtcSpl_LevinsonDurbin(R, A, rc, LPC_FILTERORDER);
74
75 /*
76 Set the filter to {1.0, 0.0, 0.0,...} if filter from Levinson Durbin algorithm is unstable
77 This should basically never happen...
78 */
79 if (stability!=1) {
80 A[0]=4096;
81 WebRtcSpl_MemSetW16(&A[1], 0, LPC_FILTERORDER);
82 }
83
84 /* Bandwidth expand the filter coefficients */
85 WebRtcIlbcfix_BwExpand(A, A, (int16_t*)WebRtcIlbcfix_kLpcChirpSyntDenum, LPC_FILTERORDER+1);
86
87 /* Convert from A to LSF representation */
88 WebRtcIlbcfix_Poly2Lsf(lsf + k*LPC_FILTERORDER, A);
89 }
90
91 is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
92 WEBRTC_SPL_MEMCPY_W16(iLBCenc_inst->lpc_buffer,
93 iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is, is);
94
95 return;
96 }
97