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Code Issues Releases Activity

add rounding bias earlier in the idct, avoids many adds

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Originally committed as revision 5618 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2006-07-04 22:43:35 +00:00
parent 959e63c9ba
commit 05e7e64d1a
1 changed files with 20 additions and 18 deletions
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38
libavcodec/cavsdsp.c
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@ -184,6 +184,8 @@ static void cavs_idct8_add_c(uint8_t *dst, DCTELEM *block, int stride) {
DCTELEM (*src)[8] = (DCTELEM(*)[8])block;
uint8_t *cm = cropTbl + MAX_NEG_CROP;
src[0][0] += 8;
for( i = 0; i < 8; i++ ) {
const int a0 = 3*src[i][1] - (src[i][7]<<1);
const int a1 = 3*src[i][3] + (src[i][5]<<1);
@ -197,22 +199,22 @@ static void cavs_idct8_add_c(uint8_t *dst, DCTELEM *block, int stride) {
const int a7 = (src[i][2]<<2) - 10*src[i][6];
const int a6 = (src[i][6]<<2) + 10*src[i][2];
const int a5 = (src[i][0] - src[i][4]) << 3;
const int a4 = (src[i][0] + src[i][4]) << 3;
const int a5 = ((src[i][0] - src[i][4]) << 3) + 4;
const int a4 = ((src[i][0] + src[i][4]) << 3) + 4;
const int b0 = a4 + a6;
const int b1 = a5 + a7;
const int b2 = a5 - a7;
const int b3 = a4 - a6;
src[i][0] = (b0 + b4 + 4) >> 3;
src[i][1] = (b1 + b5 + 4) >> 3;
src[i][2] = (b2 + b6 + 4) >> 3;
src[i][3] = (b3 + b7 + 4) >> 3;
src[i][4] = (b3 - b7 + 4) >> 3;
src[i][5] = (b2 - b6 + 4) >> 3;
src[i][6] = (b1 - b5 + 4) >> 3;
src[i][7] = (b0 - b4 + 4) >> 3;
src[i][0] = (b0 + b4) >> 3;
src[i][1] = (b1 + b5) >> 3;
src[i][2] = (b2 + b6) >> 3;
src[i][3] = (b3 + b7) >> 3;
src[i][4] = (b3 - b7) >> 3;
src[i][5] = (b2 - b6) >> 3;
src[i][6] = (b1 - b5) >> 3;
src[i][7] = (b0 - b4) >> 3;
}
for( i = 0; i < 8; i++ ) {
const int a0 = 3*src[1][i] - (src[7][i]<<1);
@ -235,14 +237,14 @@ static void cavs_idct8_add_c(uint8_t *dst, DCTELEM *block, int stride) {
const int b2 = a5 - a7;
const int b3 = a4 - a6;
dst[i + 0*stride] = cm[ dst[i + 0*stride] + ((b0 + b4 + 64) >> 7)];
dst[i + 1*stride] = cm[ dst[i + 1*stride] + ((b1 + b5 + 64) >> 7)];
dst[i + 2*stride] = cm[ dst[i + 2*stride] + ((b2 + b6 + 64) >> 7)];
dst[i + 3*stride] = cm[ dst[i + 3*stride] + ((b3 + b7 + 64) >> 7)];
dst[i + 4*stride] = cm[ dst[i + 4*stride] + ((b3 - b7 + 64) >> 7)];
dst[i + 5*stride] = cm[ dst[i + 5*stride] + ((b2 - b6 + 64) >> 7)];
dst[i + 6*stride] = cm[ dst[i + 6*stride] + ((b1 - b5 + 64) >> 7)];
dst[i + 7*stride] = cm[ dst[i + 7*stride] + ((b0 - b4 + 64) >> 7)];
dst[i + 0*stride] = cm[ dst[i + 0*stride] + ((b0 + b4) >> 7)];
dst[i + 1*stride] = cm[ dst[i + 1*stride] + ((b1 + b5) >> 7)];
dst[i + 2*stride] = cm[ dst[i + 2*stride] + ((b2 + b6) >> 7)];
dst[i + 3*stride] = cm[ dst[i + 3*stride] + ((b3 + b7) >> 7)];
dst[i + 4*stride] = cm[ dst[i + 4*stride] + ((b3 - b7) >> 7)];
dst[i + 5*stride] = cm[ dst[i + 5*stride] + ((b2 - b6) >> 7)];
dst[i + 6*stride] = cm[ dst[i + 6*stride] + ((b1 - b5) >> 7)];
dst[i + 7*stride] = cm[ dst[i + 7*stride] + ((b0 - b4) >> 7)];
}
}