Edinburgh Speech Tools 2.4-release
EST_filter_design.h
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33
34#ifndef __EST_FILTER_DESIGN_H__
35#define __EST_FILTER_DESIGN_H__
36
37#include "EST_Wave.h"
38#include "EST_FMatrix.h"
39#include "EST_Track.h"
40
41/**@name Filter Design
42
43FIR Filtering is a 2 stage process, first involving design and then
44the filtering itself. As the design is somewhat costly, it is usually
45desirable to design a filter outside the main loop.
46
47For one off filtering operations, functions are
48provided which design and filter the waveform in a single go.
49
50It is impossible to design an ideal filter, i.e. one which exactly
51obeys the desired frequency response. The "quality" of a filter is
52given by the order parameter, with high values indicating good
53approximations to desired responses. High orders are slower. The
54default is 199 which gives a pretty good filter, but a value as low as
5519 is still usable if speech is important.
56
57*/
58//@{
59
60/** Create an arbitrary filter or order {\tt order} that attempts to
61give the frequency response given by {\tt freq_response}. The vector
62{\tt freq_response} should be any size 2**N and contain a plot of the
63desired frequency response with values ranging between 0.0 and
641.0. The actual filtering is done by \Ref{FIRfilter}.
65
66@see design_lowpass_FIR_filter, design_highpass_FIR_filter
67@see FIRfilter, FIRlowpass_filter, FIRhighpass_filter
68
69*/
70EST_FVector design_FIR_filter(const EST_FVector &freq_response, int
71 filter_order);
72
73/** Design a FIR lowpass filter of order {\tt order} and cut-off
74frequency {\tt freq}. The filter coefficients are returned in the
75FVector and should be used in conjunction with \Ref{FIRfilter}.
76
77@see design_FIR_filter, design_highpass_FIR_filter, FIRfilter,
78FIRlowpass_filter, FIRhighpass_filter
79*/
80
81EST_FVector design_lowpass_FIR_filter(int sample_rate, int freq, int
82 order);
83
84/** Design a FIR highpass filter of order {\tt order} and cut-off frequency
85{\tt freq}. The filter coefficients are returned in the FVector and should be used in conjunction with \Ref{FIRfilter}
86@see design_FIR_filter, design_lowpass_FIR_filter, design_highpass_FIR_filter
87@see FIRfilter, FIRlowpass_filter, FIRhighpass_filter
88
89*/
90EST_FVector design_highpass_FIR_filter(int sample_rate, int
91 freq, int order);
92
93//@}
94
95
96#endif /* __EST_FILTER_DESIGN_H__ */
97