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