Asterisk - The Open Source Telephony Project  21.4.1
LPCencode.c
1 
2  /******************************************************************
3 
4  iLBC Speech Coder ANSI-C Source Code
5 
6  LPCencode.c
7 
8  Copyright (C) The Internet Society (2004).
9  All Rights Reserved.
10 
11  ******************************************************************/
12 
13  #include <string.h>
14 
15  #include "iLBC_define.h"
16  #include "helpfun.h"
17  #include "lsf.h"
18  #include "constants.h"
19 
20 
21 
22 
23 
24  /*----------------------------------------------------------------*
25  * lpc analysis (subroutine to LPCencode)
26  *---------------------------------------------------------------*/
27 
28  void SimpleAnalysis(
29  float *lsf, /* (o) lsf coefficients */
30  float *data, /* (i) new data vector */
31  iLBC_Enc_Inst_t *iLBCenc_inst
32  /* (i/o) the encoder state structure */
33  ){
34  int k, is;
35  float temp[BLOCKL_MAX], lp[LPC_FILTERORDER + 1];
36  float lp2[LPC_FILTERORDER + 1];
37  float r[LPC_FILTERORDER + 1];
38 
39  is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
40  memcpy(iLBCenc_inst->lpc_buffer+is,data,
41  iLBCenc_inst->blockl*sizeof(float));
42 
43  /* No lookahead, last window is asymmetric */
44 
45  for (k = 0; k < iLBCenc_inst->lpc_n; k++) {
46 
47  is = LPC_LOOKBACK;
48 
49  if (k < (iLBCenc_inst->lpc_n - 1)) {
50  window(temp, lpc_winTbl,
51  iLBCenc_inst->lpc_buffer, BLOCKL_MAX);
52  } else {
53  window(temp, lpc_asymwinTbl,
54  iLBCenc_inst->lpc_buffer + is, BLOCKL_MAX);
55  }
56 
57  autocorr(r, temp, BLOCKL_MAX, LPC_FILTERORDER);
58  window(r, r, lpc_lagwinTbl, LPC_FILTERORDER + 1);
59 
60  levdurb(lp, temp, r, LPC_FILTERORDER);
61  bwexpand(lp2, lp, LPC_CHIRP_SYNTDENUM, LPC_FILTERORDER+1);
62 
63  a2lsf(lsf + k*LPC_FILTERORDER, lp2);
64  }
65  is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
66  memmove(iLBCenc_inst->lpc_buffer,
67  iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is,
68  is*sizeof(float));
69  }
70 
71  /*----------------------------------------------------------------*
72 
73 
74 
75 
76 
77  * lsf interpolator and conversion from lsf to a coefficients
78  * (subroutine to SimpleInterpolateLSF)
79  *---------------------------------------------------------------*/
80 
81  void LSFinterpolate2a_enc(
82  float *a, /* (o) lpc coefficients */
83  float *lsf1,/* (i) first set of lsf coefficients */
84  float *lsf2,/* (i) second set of lsf coefficients */
85  float coef, /* (i) weighting coefficient to use between
86  lsf1 and lsf2 */
87  long length /* (i) length of coefficient vectors */
88  ){
89  float lsftmp[LPC_FILTERORDER];
90 
91  interpolate(lsftmp, lsf1, lsf2, coef, length);
92  lsf2a(a, lsftmp);
93  }
94 
95  /*----------------------------------------------------------------*
96  * lsf interpolator (subroutine to LPCencode)
97  *---------------------------------------------------------------*/
98 
99  void SimpleInterpolateLSF(
100  float *syntdenum, /* (o) the synthesis filter denominator
101  resulting from the quantized
102  interpolated lsf */
103  float *weightdenum, /* (o) the weighting filter denominator
104  resulting from the unquantized
105  interpolated lsf */
106  float *lsf, /* (i) the unquantized lsf coefficients */
107  float *lsfdeq, /* (i) the dequantized lsf coefficients */
108  float *lsfold, /* (i) the unquantized lsf coefficients of
109  the previous signal frame */
110  float *lsfdeqold, /* (i) the dequantized lsf coefficients of
111  the previous signal frame */
112  int length, /* (i) should equate LPC_FILTERORDER */
113  iLBC_Enc_Inst_t *iLBCenc_inst
114  /* (i/o) the encoder state structure */
115  ){
116  int i, pos, lp_length;
117  float lp[LPC_FILTERORDER + 1], *lsf2, *lsfdeq2;
118 
119  lsf2 = lsf + length;
120  lsfdeq2 = lsfdeq + length;
121  lp_length = length + 1;
122 
123  if (iLBCenc_inst->mode==30) {
124  /* sub-frame 1: Interpolation between old and first
125 
126 
127 
128 
129 
130  set of lsf coefficients */
131 
132  LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq,
133  lsf_weightTbl_30ms[0], length);
134  memcpy(syntdenum,lp,lp_length*sizeof(float));
135  LSFinterpolate2a_enc(lp, lsfold, lsf,
136  lsf_weightTbl_30ms[0], length);
137  bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, lp_length);
138 
139  /* sub-frame 2 to 6: Interpolation between first
140  and second set of lsf coefficients */
141 
142  pos = lp_length;
143  for (i = 1; i < iLBCenc_inst->nsub; i++) {
144  LSFinterpolate2a_enc(lp, lsfdeq, lsfdeq2,
145  lsf_weightTbl_30ms[i], length);
146  memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
147 
148  LSFinterpolate2a_enc(lp, lsf, lsf2,
149  lsf_weightTbl_30ms[i], length);
150  bwexpand(weightdenum + pos, lp,
151  LPC_CHIRP_WEIGHTDENUM, lp_length);
152  pos += lp_length;
153  }
154  }
155  else {
156  pos = 0;
157  for (i = 0; i < iLBCenc_inst->nsub; i++) {
158  LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq,
159  lsf_weightTbl_20ms[i], length);
160  memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
161  LSFinterpolate2a_enc(lp, lsfold, lsf,
162  lsf_weightTbl_20ms[i], length);
163  bwexpand(weightdenum+pos, lp,
164  LPC_CHIRP_WEIGHTDENUM, lp_length);
165  pos += lp_length;
166  }
167  }
168 
169  /* update memory */
170 
171  if (iLBCenc_inst->mode==30) {
172  memcpy(lsfold, lsf2, length*sizeof(float));
173  memcpy(lsfdeqold, lsfdeq2, length*sizeof(float));
174  }
175  else {
176  memcpy(lsfold, lsf, length*sizeof(float));
177  memcpy(lsfdeqold, lsfdeq, length*sizeof(float));
178 
179 
180 
181 
182 
183  }
184  }
185 
186  /*----------------------------------------------------------------*
187  * lsf quantizer (subroutine to LPCencode)
188  *---------------------------------------------------------------*/
189 
190  void SimplelsfQ(
191  float *lsfdeq, /* (o) dequantized lsf coefficients
192  (dimension FILTERORDER) */
193  int *index, /* (o) quantization index */
194  float *lsf, /* (i) the lsf coefficient vector to be
195  quantized (dimension FILTERORDER ) */
196  int lpc_n /* (i) number of lsf sets to quantize */
197  ){
198  /* Quantize first LSF with memoryless split VQ */
199  SplitVQ(lsfdeq, index, lsf, lsfCbTbl, LSF_NSPLIT,
200  dim_lsfCbTbl, size_lsfCbTbl);
201 
202  if (lpc_n==2) {
203  /* Quantize second LSF with memoryless split VQ */
204  SplitVQ(lsfdeq + LPC_FILTERORDER, index + LSF_NSPLIT,
205  lsf + LPC_FILTERORDER, lsfCbTbl, LSF_NSPLIT,
206  dim_lsfCbTbl, size_lsfCbTbl);
207  }
208  }
209 
210  /*----------------------------------------------------------------*
211  * lpc encoder
212  *---------------------------------------------------------------*/
213 
214  void LPCencode(
215  float *syntdenum, /* (i/o) synthesis filter coefficients
216  before/after encoding */
217  float *weightdenum, /* (i/o) weighting denumerator
218  coefficients before/after
219  encoding */
220  int *lsf_index, /* (o) lsf quantization index */
221  float *data, /* (i) lsf coefficients to quantize */
222  iLBC_Enc_Inst_t *iLBCenc_inst
223  /* (i/o) the encoder state structure */
224  ){
225  float lsf[LPC_FILTERORDER * LPC_N_MAX];
226  float lsfdeq[LPC_FILTERORDER * LPC_N_MAX];
227 
228  SimpleAnalysis(lsf, data, iLBCenc_inst);
229  SimplelsfQ(lsfdeq, lsf_index, lsf, iLBCenc_inst->lpc_n);
230 
231 
232 
233 
234  LSF_check(lsfdeq, LPC_FILTERORDER, iLBCenc_inst->lpc_n);
235  SimpleInterpolateLSF(syntdenum, weightdenum,
236  lsf, lsfdeq, iLBCenc_inst->lsfold,
237  iLBCenc_inst->lsfdeqold, LPC_FILTERORDER, iLBCenc_inst);
238  }