Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 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( |
| 21 | float *In, /* (i) Signal to be filtered */ |
| 22 | float *a, /* (i) LP parameters */ |
| 23 | int len,/* (i) Length of signal */ |
| 24 | float *Out, /* (o) Filtered signal */ |
| 25 | float *mem /* (i/o) Filter state */ |
| 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 | } |
| 72 | |