Alexandre Lision | 8af73cb | 2013-12-10 14:11:20 -0500 | [diff] [blame] | 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( |
| 20 | float *Out, /* (i/o) Signal to be filtered */ |
| 21 | float *a, /* (i) LP parameters */ |
| 22 | int len, /* (i) Length of signal */ |
| 23 | |
| 24 | |
| 25 | |
| 26 | |
| 27 | |
| 28 | float *mem /* (i/o) Filter state */ |
| 29 | ){ |
| 30 | int i, j; |
| 31 | float *po, *pi, *pa, *pm; |
| 32 | |
| 33 | po=Out; |
| 34 | |
| 35 | /* Filter first part using memory from past */ |
| 36 | |
| 37 | for (i=0; i<LPC_FILTERORDER; i++) { |
| 38 | pi=&Out[i-1]; |
| 39 | pa=&a[1]; |
| 40 | pm=&mem[LPC_FILTERORDER-1]; |
| 41 | for (j=1; j<=i; j++) { |
| 42 | *po-=(*pa++)*(*pi--); |
| 43 | } |
| 44 | for (j=i+1; j<LPC_FILTERORDER+1; j++) { |
| 45 | *po-=(*pa++)*(*pm--); |
| 46 | } |
| 47 | po++; |
| 48 | } |
| 49 | |
| 50 | /* Filter last part where the state is entirely in |
| 51 | the output vector */ |
| 52 | |
| 53 | for (i=LPC_FILTERORDER; i<len; i++) { |
| 54 | pi=&Out[i-1]; |
| 55 | pa=&a[1]; |
| 56 | for (j=1; j<LPC_FILTERORDER+1; j++) { |
| 57 | *po-=(*pa++)*(*pi--); |
| 58 | } |
| 59 | po++; |
| 60 | } |
| 61 | |
| 62 | /* Update state vector */ |
| 63 | |
| 64 | memcpy(mem, &Out[len-LPC_FILTERORDER], |
| 65 | LPC_FILTERORDER*sizeof(float)); |
| 66 | } |
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