diff options
Diffstat (limited to 'third_party/ilbc/anaFilter.c')
-rw-r--r-- | third_party/ilbc/anaFilter.c | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/third_party/ilbc/anaFilter.c b/third_party/ilbc/anaFilter.c new file mode 100644 index 00000000..c161f98a --- /dev/null +++ b/third_party/ilbc/anaFilter.c @@ -0,0 +1,72 @@ + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + anaFilter.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <string.h> + #include "iLBC_define.h" + + /*----------------------------------------------------------------* + * LP analysis filter. + *---------------------------------------------------------------*/ + + void anaFilter( + float *In, /* (i) Signal to be filtered */ + float *a, /* (i) LP parameters */ + int len,/* (i) Length of signal */ + float *Out, /* (o) Filtered signal */ + float *mem /* (i/o) Filter state */ + ){ + int i, j; + float *po, *pi, *pm, *pa; + + po = Out; + + /* Filter first part using memory from past */ + + for (i=0; i<LPC_FILTERORDER; i++) { + pi = &In[i]; + pm = &mem[LPC_FILTERORDER-1]; + pa = a; + *po=0.0; + + + + + + for (j=0; 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 input vector */ + + for (i=LPC_FILTERORDER; i<len; i++) { + pi = &In[i]; + pa = a; + *po=0.0; + for (j=0; j<LPC_FILTERORDER+1; j++) { + *po+=(*pa++)*(*pi--); + } + po++; + } + + /* Update state vector */ + + memcpy(mem, &In[len-LPC_FILTERORDER], + LPC_FILTERORDER*sizeof(float)); + } + |