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added idct reference code

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Originally committed as revision 46 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Fabrice Bellard 2001-08-07 22:43:37 +00:00
parent e0eac44e82
commit dc541ee74b
1 changed files with 36 additions and 0 deletions
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36
libavcodec/fdctref.c
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@ -116,3 +116,39 @@ short *block;
*/
}
}
/* perform IDCT matrix multiply for 8x8 coefficient block */
void idct(block)
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;
}
}