blob: 6bab912f84b233869a95320adc9b7dfe76b1627b (
plain) (
blame)
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
59
60
61
62
63
64
65
66
|
#include "idctref.h"
#include <math.h>
#ifndef PI
# ifdef M_PI
# define PI M_PI
# else
# define PI 3.14159265358979323846
# endif
#endif
bool IDCTRef::initted = false;
double IDCTRef::c[8][8]; /* cosine transform matrix for 8x1 IDCT */
/* initialize DCT coefficient matrix */
void IDCTRef::init()
{
if (!initted)
{
int freq, time;
for (freq=0; freq < 8; freq++)
{
double scale = (freq == 0) ? sqrt(0.125) : 0.5;
for (time=0; time<8; time++)
c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5));
}
initted=true;
}
}
/* perform IDCT matrix multiply for 8x8 coefficient block */
void IDCTRef::idct(short *block)
{
int i, j, k, v;
double partial_product;
double tmp[64];
for (i=0; i<8; i++)
for (j=0; j<8; j++)
{
partial_product = 0.0;
for (k=0; k<8; k++)
partial_product+= c[k][j]*block[8*i+k];
tmp[8*i+j] = partial_product;
}
/* Transpose operation is integrated into address mapping by switching
loop order of i and j */
for (j=0; j<8; j++)
for (i=0; i<8; i++)
{
partial_product = 0.0;
for (k=0; k<8; k++)
partial_product+= c[k][i]*tmp[8*k+j];
v = (int)floor(partial_product+0.5);
block[8*i+j] = (v<-256) ? -256 : ((v>255) ? 255 : v);
}
}
|
