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dnxhdenc: fixed signed multiplication overflow 

The low 32 bits of a multiplication are the same for signed
and unsigned operands.  Casting to unsigned before multiplying
is thus equivalent while avoiding signed overflow, which is
undefined by the C99 standard.

Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard 2011-10-08 01:37:20 +01:00
parent 05c8f119cc
commit d341d5fd2c
1 changed files with 1 additions and 1 deletions
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2
libavcodec/dnxhdenc.c
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@ -623,7 +623,7 @@ static int dnxhd_mb_var_thread(AVCodecContext *avctx, void *arg, int jobnr, int
for (mb_x = 0; mb_x < ctx->m.mb_width; ++mb_x, pix += 16) { for (mb_x = 0; mb_x < ctx->m.mb_width; ++mb_x, pix += 16) {
unsigned mb = mb_y * ctx->m.mb_width + mb_x; unsigned mb = mb_y * ctx->m.mb_width + mb_x;
int sum = ctx->m.dsp.pix_sum(pix, ctx->m.linesize); int sum = ctx->m.dsp.pix_sum(pix, ctx->m.linesize);
int varc = (ctx->m.dsp.pix_norm1(pix, ctx->m.linesize) - (((unsigned)(sum*sum))>>8)+128)>>8; int varc = (ctx->m.dsp.pix_norm1(pix, ctx->m.linesize) - (((unsigned)sum*sum)>>8)+128)>>8;
ctx->mb_cmp[mb].value = varc; ctx->mb_cmp[mb].value = varc;
ctx->mb_cmp[mb].mb = mb; ctx->mb_cmp[mb].mb = mb;
} }