1% spec.m
2% Jean Marc Valin
3%
4% Spectrogram function for Octave
5%
6%   Copyright (c) John-Marc Valin 2012
7%
8%   Redistribution and use in source and binary forms, with or without
9%   modification, are permitted provided that the following conditions
10%   are met:
11%
12%   - Redistributions of source code must retain the above copyright
13%   notice, this list of conditions and the following disclaimer.
14%
15%   - Redistributions in binary form must reproduce the above copyright
16%   notice, this list of conditions and the following disclaimer in the
17%   documentation and/or other materials provided with the distribution.
18%
19%   - Neither the name of Jean Marc Valin nor the names of its
20%   contributors may be used to endorse or promote products derived from
21%   this software without specific prior written permission.
22%
23%   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24%   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25%   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
26%   A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
27%   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
28%   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
29%   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
30%   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
31%   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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33%   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34
35function X = spec(x, Fs, framesize, start, stop)
36
37
38gr=[zeros(1024,1),[0:1023]'/1023,.68*[0:1023]'/1023];
39
40%gr=[.4*[0:1023]'/1023,[0:1023]'/1023,.68*[0:1023]'/1023];
41
42%t=[0:1023]'/1023;
43%t=(1+.25*t-cos(pi*t))/2.25;
44%gr = [zeros(1024,1),t,.68*t];
45
46
47%colormap(gr);
48
49if nargin < 2 || isempty(Fs)
50   Fs = 44100;
51end
52
53if nargin < 3 || isempty(framesize)
54   framesize = 2048;
55endif
56
57offset = framesize/8;
58
59X = 20*log10(abs(specgram(x, framesize, 48000, blackmanharris(framesize)', framesize-offset)));
60
61XM=max(max(X));
62X = max(XM-30,X);
63%size(X)
64F = -[framesize/2-1:-1:0]/framesize*Fs;
65%F = [0:127]/128*24000;
66T=[1:size(X,2)]/Fs*offset;
67%imagesc(X(end:-1:1,:));
68
69if nargin < 4 || isempty(start)
70   istart=1;
71else
72   istart = round(start*Fs/offset);
73end
74
75if nargin < 5 || isempty(stop)
76   istop = size(X,2);
77else
78   istop = round(stop*Fs/offset);
79endif
80
81istart = max(1,istart);
82istop = min(istop, size(X,2));
83
84imagesc(T(1+istart:istop), F, X(end:-1:1,1+istart:istop));
85
86X = X(:,1+istart:istop);
87