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first version of IDCT248 for DV decoding support

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Originally committed as revision 994 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Fabrice Bellard 2002-10-03 13:41:33 +00:00
parent 3a3d3a42c2
commit 9bf71516b1
2 changed files with 82 additions and 1 deletions
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81
libavcodec/simple_idct.c
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@ -659,4 +659,83 @@ void simple_idct(INT16 *block)
#endif
#undef COL_SHIFT
/* 2x4x8 idct */
#define CN_SHIFT 12
#define C_FIX(x) ((int)((x) * (1 << CN_SHIFT) + 0.5))
#define C0 C_FIX(0.7071067811)
#define C1 C_FIX(0.9238795324)
#define C2 C_FIX(0.3826834324)
/* row idct is multiple by 16 * sqrt(2.0), col idct4 is multiplied by
sqrt(2). An extra division by two is needed for the first butterfly
stage */
#define C_SHIFT (4+1+12+1)
static inline void idct4col(UINT8 *dest, int line_size, const INT16 *col)
{
int c0, c1, c2, c3, a0, a1, a2, a3;
const UINT8 *cm = cropTbl + MAX_NEG_CROP;
a0 = col[8*0];
a1 = col[8*2];
a2 = col[8*4];
a3 = col[8*6];
c0 = (a0 + a2) * C0 + (1 << (C_SHIFT - 1)) + (128 << C_SHIFT);
c2 = (a0 - a2) * C0 + (1 << (C_SHIFT - 1)) + (128 << C_SHIFT);
c1 = a1 * C1 + a3 * C2;
c3 = a1 * C2 - a3 * C1;
dest[0] = cm[(c0 + c1) >> C_SHIFT];
dest += line_size;
dest[0] = cm[(c2 + c3) >> C_SHIFT];
dest += line_size;
dest[0] = cm[(c2 - c3) >> C_SHIFT];
dest += line_size;
dest[0] = cm[(c0 - c1) >> C_SHIFT];
}
#define BF(k) \
{\
int a0, a1;\
a0 = ptr[k];\
a1 = ptr[8 + k];\
ptr[k] = a0 + a1;\
ptr[8 + k] = a0 - a1;\
}
/* only used by DV codec. The input must be interlaced. 128 is added
to the pixels before clamping to avoid systematic error
(1024*sqrt(2)) offset would be needed otherwise. */
/* XXX: I think a 1.0/sqrt(2) normalization should be needed to
compensate the extra butterfly stage - I don't have the full DV
specification */
void simple_idct248_put(UINT8 *dest, int line_size, INT16 *block)
{
int i;
INT16 *ptr;
/* butterfly */
ptr = block;
for(i=0;i<4;i++) {
BF(0);
BF(1);
BF(2);
BF(3);
BF(4);
BF(5);
BF(6);
BF(7);
ptr += 2 * 8;
}
/* IDCT8 on each line */
for(i=0; i<8; i++) {
idctRowCondDC(block + i*8);
}
/* IDCT4 and store */
for(i=0;i<8;i++) {
idct4col(dest + i, 2 * line_size, block + i);
idct4col(dest + line_size + i, 2 * line_size, block + 8 + i);
}
}

2
libavcodec/simple_idct.h
View File

@ -24,3 +24,5 @@ void ff_simple_idct_mmx(short *block);
void ff_simple_idct_add_mmx(UINT8 *dest, int line_size, INT16 *block);
void ff_simple_idct_put_mmx(UINT8 *dest, int line_size, INT16 *block);
void simple_idct(short *block);
void simple_idct248_put(UINT8 *dest, int line_size, INT16 *block);