blob: e02ab1f76db4ea7b74b726a10f3e26b4a56f0ce8 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
implement IDCT;
include "sys.m";
include "math.m";
include "mpegio.m";
sys: Sys;
math: Math;
#
# Reference IDCT. Full expanded 2-d IDCT.
#
coeff: array of array of real;
init()
{
sys = load Sys Sys->PATH;
math = load Math Math->PATH;
if (math == nil) {
sys->fprint(sys->fildes(2), "could not load %s: %r\n", Math->PATH);
exit;
}
init_idct();
}
init_idct()
{
coeff = array[8] of array of real;
for (f := 0; f < 8; f++) {
coeff[f] = array[8] of real;
s := 0.5;
if (f == 0)
s = math->sqrt(0.125);
a := real f * (Math->Pi / 8.0);
for (t := 0; t < 8; t++)
coeff[f][t] = s * math->cos(a * (real t + 0.5));
}
}
idct(block: array of int)
{
tmp := array[64] of real;
for (i := 0; i < 8; i++)
for (j := 0; j < 8; j++) {
p := 0.0;
for (k := 0; k < 8; k++)
p += coeff[k][j] * real block[8 * i + k];
tmp[8 * i + j] = p;
}
for (j = 0; j < 8; j++)
for (i = 0; i < 8; i++) {
p := 0.0;
for (k := 0; k < 8; k++)
p += coeff[k][i] * tmp[8 * k + j];
block[8 * i + j] = int p;
}
}
|
