virtualenv/FFmpeg
1
0
Fork 0
mirror of https://github.com/FFmpeg/FFmpeg.git synced 2024-12-23 12:43:46 +02:00
Code Issues Releases Activity

(commit by michael)

Browse Source 
16-bit divide instead of 32-bit on x86 in msmpeg_pred_dc()

Originally committed as revision 264 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2002-01-14 04:34:52 +00:00
parent 8bdbae01fe
commit 6f903d8e27
1 changed files with 25 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
libavcodec/msmpeg4.c
View File

@ -411,10 +411,34 @@ static int msmpeg4_pred_dc(MpegEncContext * s, int n,
necessitate to modify mpegvideo.c. The problem comes from the
fact they decided to store the quantized DC (which would lead
to problems if Q could vary !) */
#ifdef ARCH_X86
/* using 16bit divisions as they are large enough and 2x as fast */
asm volatile(
"movl %3, %%eax \n\t"
"shrl $1, %%eax \n\t"
"addl %%eax, %2 \n\t"
"addl %%eax, %1 \n\t"
"addl %0, %%eax \n\t"
"xorl %%edx, %%edx \n\t"
"divw %w3 \n\t"
"movzwl %%ax, %0 \n\t"
"movl %1, %%eax \n\t"
"xorl %%edx, %%edx \n\t"
"divw %w3 \n\t"
"movzwl %%ax, %1 \n\t"
"movl %2, %%eax \n\t"
"xorl %%edx, %%edx \n\t"
"divw %w3 \n\t"
"movzwl %%ax, %2 \n\t"
: "+r" (a), "+r" (b), "+r" (c)
: "r" (scale)
: "%eax", "%edx"
);
#else
a = (a + (scale >> 1)) / scale;
b = (b + (scale >> 1)) / scale;
c = (c + (scale >> 1)) / scale;
#endif
/* XXX: WARNING: they did not choose the same test as MPEG4. This
is very important ! */
if (abs(a - b) <= abs(b - c)) {