1 /* Copyright (C) 2004 Jean-Marc Valin
2 File medfilter.c
3 Median filter
4
5
6 Redistribution and use in source and binary forms, with or without
7 modification, are permitted provided that the following conditions
8 are met:
9
10 - Redistributions of source code must retain the above copyright
11 notice, this list of conditions and the following disclaimer.
12
13 - Redistributions in binary form must reproduce the above copyright
14 notice, this list of conditions and the following disclaimer in the
15 documentation and/or other materials provided with the distribution.
16
17 - Neither the name of the Xiph.org Foundation nor the names of its
18 contributors may be used to endorse or promote products derived from
19 this software without specific prior written permission.
20
21 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
24 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
25 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
26 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
27 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
28 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
29 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
30 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
31 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32
33 */
34
35 #include "medfilter.h"
36 #include "misc.h"
37
median_filter_new(int N)38 MedianFilter *median_filter_new(int N)
39 {
40 MedianFilter *f = speex_alloc(sizeof(MedianFilter));
41 f->N = N;
42 f->ids = speex_alloc(sizeof(int)*N);
43 f->val = speex_alloc(sizeof(float)*N);
44 f->filled = 0;
45 return f;
46 }
47
median_filter_update(MedianFilter * f,float val)48 void median_filter_update(MedianFilter *f, float val)
49 {
50 int i=0;
51 int insert = 0;
52 while (insert<f->filled && f->val[insert] < val)
53 {
54 insert++;
55 }
56 if (f->filled == f->N)
57 {
58 int remove;
59 for (remove=0;remove<f->N;remove++)
60 if (f->ids[remove] == 0)
61 break;
62 if (insert>remove)
63 insert--;
64 if (insert > remove)
65 {
66 for (i=remove;i<insert;i++)
67 {
68 f->val[i] = f->val[i+1];
69 f->ids[i] = f->ids[i+1];
70 }
71 } else if (insert < remove)
72 {
73 for (i=remove;i>insert;i--)
74 {
75 f->val[i] = f->val[i-1];
76 f->ids[i] = f->ids[i-1];
77 }
78 }
79 for (i=0;i<f->filled;i++)
80 f->ids[i]--;
81 } else {
82 for (i=f->filled;i>insert;i--)
83 {
84 f->val[i] = f->val[i-1];
85 f->ids[i] = f->ids[i-1];
86 }
87 f->filled++;
88 }
89 f->val[insert]=val;
90 f->ids[insert]=f->filled-1;
91 }
92
median_filter_get(MedianFilter * f)93 float median_filter_get(MedianFilter *f)
94 {
95 return f->val[f->filled>>1];
96 }
97
98