Mercurial > hg > audiostuff
comparison intercom/ilbc/syntFilter.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 syntFilter.c | |
| 7 | |
| 8 Copyright (C) The Internet Society (2004). | |
| 9 All Rights Reserved. | |
| 10 | |
| 11 ******************************************************************/ | |
| 12 | |
| 13 #include "iLBC_define.h" | |
| 14 | |
| 15 /*----------------------------------------------------------------* | |
| 16 * LP synthesis filter. | |
| 17 *---------------------------------------------------------------*/ | |
| 18 | |
| 19 void syntFilter(float *Out, /* (i/o) Signal to be filtered */ | |
| 20 float *a, /* (i) LP parameters */ | |
| 21 int len, /* (i) Length of signal */ | |
| 22 float *mem /* (i/o) Filter state */ | |
| 23 ) | |
| 24 { | |
| 25 int i, j; | |
| 26 float *po, *pi, *pa, *pm; | |
| 27 | |
| 28 po = Out; | |
| 29 | |
| 30 /* Filter first part using memory from past */ | |
| 31 | |
| 32 for (i = 0; i < LPC_FILTERORDER; i++) { | |
| 33 pi = &Out[i - 1]; | |
| 34 pa = &a[1]; | |
| 35 pm = &mem[LPC_FILTERORDER - 1]; | |
| 36 for (j = 1; j <= i; j++) { | |
| 37 *po -= (*pa++) * (*pi--); | |
| 38 } | |
| 39 for (j = i + 1; j < LPC_FILTERORDER + 1; j++) { | |
| 40 *po -= (*pa++) * (*pm--); | |
| 41 } | |
| 42 po++; | |
| 43 } | |
| 44 | |
| 45 /* Filter last part where the state is entirely in | |
| 46 the output vector */ | |
| 47 | |
| 48 for (i = LPC_FILTERORDER; i < len; i++) { | |
| 49 pi = &Out[i - 1]; | |
| 50 pa = &a[1]; | |
| 51 for (j = 1; j < LPC_FILTERORDER + 1; j++) { | |
| 52 *po -= (*pa++) * (*pi--); | |
| 53 } | |
| 54 po++; | |
| 55 } | |
| 56 | |
| 57 /* Update state vector */ | |
| 58 | |
| 59 memcpy(mem, &Out[len - LPC_FILTERORDER], | |
| 60 LPC_FILTERORDER * sizeof(float)); | |
| 61 } |