Mercurial > hg > audiostuff
comparison intercom/ilbc/anaFilter.c @ 2:13be24d74cd2
import intercom-0.4.1
| author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
|---|---|
| date | Fri, 25 Jun 2010 09:57:52 +0200 |
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| 1:9cadc470e3da | 2:13be24d74cd2 |
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| 1 | |
| 2 /****************************************************************** | |
| 3 | |
| 4 iLBC Speech Coder ANSI-C Source Code | |
| 5 | |
| 6 anaFilter.c | |
| 7 | |
| 8 Copyright (C) The Internet Society (2004). | |
| 9 All Rights Reserved. | |
| 10 | |
| 11 ******************************************************************/ | |
| 12 | |
| 13 #include <string.h> | |
| 14 #include "iLBC_define.h" | |
| 15 | |
| 16 /*----------------------------------------------------------------* | |
| 17 * LP analysis filter. | |
| 18 *---------------------------------------------------------------*/ | |
| 19 | |
| 20 void anaFilter(float *In, /* (i) Signal to be filtered */ | |
| 21 float *a, /* (i) LP parameters */ | |
| 22 int len, /* (i) Length of signal */ | |
| 23 float *Out, /* (o) Filtered signal */ | |
| 24 float *mem /* (i/o) Filter state */ | |
| 25 ) | |
| 26 { | |
| 27 int i, j; | |
| 28 float *po, *pi, *pm, *pa; | |
| 29 | |
| 30 po = Out; | |
| 31 | |
| 32 /* Filter first part using memory from past */ | |
| 33 | |
| 34 for (i = 0; i < LPC_FILTERORDER; i++) { | |
| 35 pi = &In[i]; | |
| 36 pm = &mem[LPC_FILTERORDER - 1]; | |
| 37 pa = a; | |
| 38 *po = 0.0; | |
| 39 | |
| 40 | |
| 41 | |
| 42 | |
| 43 | |
| 44 for (j = 0; j <= i; j++) { | |
| 45 *po += (*pa++) * (*pi--); | |
| 46 } | |
| 47 for (j = i + 1; j < LPC_FILTERORDER + 1; j++) { | |
| 48 | |
| 49 *po += (*pa++) * (*pm--); | |
| 50 } | |
| 51 po++; | |
| 52 } | |
| 53 | |
| 54 /* Filter last part where the state is entirely | |
| 55 in the input vector */ | |
| 56 | |
| 57 for (i = LPC_FILTERORDER; i < len; i++) { | |
| 58 pi = &In[i]; | |
| 59 pa = a; | |
| 60 *po = 0.0; | |
| 61 for (j = 0; j < LPC_FILTERORDER + 1; j++) { | |
| 62 *po += (*pa++) * (*pi--); | |
| 63 } | |
| 64 po++; | |
| 65 } | |
| 66 | |
| 67 /* Update state vector */ | |
| 68 | |
| 69 memcpy(mem, &In[len - LPC_FILTERORDER], | |
| 70 LPC_FILTERORDER * sizeof(float)); | |
| 71 } |