libvoipcodecs 0.0.1
filter.h
1/*
2 * iLBC - a library for the iLBC codec
3 *
4 * filter.h - The iLBC low bit rate speech codec.
5 *
6 * Adapted by Steve Underwood <steveu@coppice.org> from the reference
7 * iLBC code supplied in RFC3951.
8 *
9 * Original code Copyright (C) The Internet Society (2004).
10 * All changes to produce this version Copyright (C) 2008 by Steve Underwood
11 * All Rights Reserved.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
16 *
17 * $Id: filter.h,v 1.2 2008/03/06 12:27:38 steveu Exp $
18 */
19
20#ifndef __iLBC_FILTER_H
21#define __iLBC_FILTER_H
22
23void AllPoleFilter(float *InOut, /* (i/o) on entrance InOut[-orderCoef] to
24 InOut[-1] contain the state of the
25 filter (delayed samples). InOut[0] to
26 InOut[lengthInOut-1] contain the filter
27 input, on en exit InOut[-orderCoef] to
28 InOut[-1] is unchanged and InOut[0] to
29 InOut[lengthInOut-1] contain filtered
30 samples */
31 const float *Coef, /* (i) filter coefficients, Coef[0] is assumed to be 1.0 */
32 int lengthInOut, /* (i) number of input/output samples */
33 int orderCoef); /* (i) number of filter coefficients */
34
35void AllZeroFilter(float *In, /* (i) In[0] to In[lengthInOut-1] contain
36 filter input samples */
37 const float *Coef, /* (i) filter coefficients (Coef[0] is assumed to be 1.0) */
38 int lengthInOut, /* (i) number of input/output samples */
39 int orderCoef, /* (i) number of filter coefficients */
40 float *Out); /* (i/o) on entrance Out[-orderCoef] to Out[-1]
41 contain the filter state, on exit Out[0]
42 to Out[lengthInOut-1] contain filtered
43 samples */
44
45void ZeroPoleFilter(float *In, /* (i) In[0] to In[lengthInOut-1] contain filter
46 input samples In[-orderCoef] to In[-1]
47 contain state of all-zero section */
48 const float *ZeroCoef, /* (i) filter coefficients for all-zero
49 section (ZeroCoef[0] is assumed to
50 be 1.0) */
51 const float *PoleCoef, /* (i) filter coefficients for all-pole section
52 (ZeroCoef[0] is assumed to be 1.0) */
53 int lengthInOut, /* (i) number of input/output samples */
54 int orderCoef, /* (i) number of filter coefficients */
55 float *Out); /* (i/o) on entrance Out[-orderCoef] to Out[-1]
56 contain state of all-pole section. On
57 exit Out[0] to Out[lengthInOut-1]
58 contain filtered samples */
59
60void DownSample(const float *In, /* (i) input samples */
61 const float *Coef, /* (i) filter coefficients */
62 int lengthIn, /* (i) number of input samples */
63 float *state, /* (i) filter state */
64 float *Out); /* (o) downsampled output */
65
66#endif