diff options
Diffstat (limited to 'third_party/ilbc/syntFilter.c')
-rw-r--r-- | third_party/ilbc/syntFilter.c | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/third_party/ilbc/syntFilter.c b/third_party/ilbc/syntFilter.c new file mode 100644 index 00000000..190eb009 --- /dev/null +++ b/third_party/ilbc/syntFilter.c @@ -0,0 +1,80 @@ + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + syntFilter.c + + Copyright (C) The Internet Society (2004). + 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 entirely 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)); + } + + + + + + + + + + + + + + |