diff options
Diffstat (limited to 'codecs/ilbc/syntFilter.c')
-rwxr-xr-x | codecs/ilbc/syntFilter.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/codecs/ilbc/syntFilter.c b/codecs/ilbc/syntFilter.c new file mode 100755 index 000000000..fe61eaa46 --- /dev/null +++ b/codecs/ilbc/syntFilter.c @@ -0,0 +1,65 @@ + +/****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + syntFilter.c + + Copyright (c) 2001, + Global IP Sound AB. + All rights reserved. + +******************************************************************/ + +#include "iLBC_define.h" + +/*----------------------------------------------------------------* + * LP synthesis filter. + *---------------------------------------------------------------*/ + +void syntFilter( + float *Out, /* (i/o) Signal to be filtered */ + float *a, /* (i) LP parameters */ + int len, /* (i) Length of signal */ + float *mem /* (i/o) Filter state */ +){ + int i, j; + float *po, *pi, *pa, *pm; + + po=Out; + + /* Filter first part using memory from past */ + + for (i=0;i<LPC_FILTERORDER;i++) { + pi=&Out[i-1]; + pa=&a[1]; + pm=&mem[LPC_FILTERORDER-1]; + for (j=1;j<=i;j++) { + *po-=(*pa++)*(*pi--); + } + for (j=i+1;j<LPC_FILTERORDER+1;j++) { + *po-=(*pa++)*(*pm--); + } + po++; + } + + /* Filter last part where the state is entierly in + the output vector */ + + for (i=LPC_FILTERORDER;i<len;i++) { + pi=&Out[i-1]; + pa=&a[1]; + for (j=1;j<LPC_FILTERORDER+1;j++) { + *po-=(*pa++)*(*pi--); + } + po++; + } + + /* Update state vector */ + + memcpy(mem, &Out[len-LPC_FILTERORDER], + LPC_FILTERORDER*sizeof(float)); +} + + + |