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mss12: avoid unnecessary division in arith*_get_bit() 

That division can be replaced with a comparison:
((c->value - c->low) << 1) + 1 >= range

By expanding 'range' definition and simplifying this inequation we obtain
the final expression.

Suggested by Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>
This commit is contained in:
Alberto Delmás 2012-09-03 17:32:01 +02:00 committed by Kostya Shishkov
parent 6ceef07b21
commit 9699b3a2d7
1 changed files with 1 additions and 1 deletions
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2
libavcodec/mss12.h
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@ -103,7 +103,7 @@ av_cold int ff_mss12_decode_end(MSS12Context *ctx);
static int arith ## VERSION ## _get_bit(ArithCoder *c) \ static int arith ## VERSION ## _get_bit(ArithCoder *c) \
{ \ { \
int range = c->high - c->low + 1; \ int range = c->high - c->low + 1; \
int bit = (((c->value - c->low) << 1) + 1) / range; \ int bit = 2 * c->value - c->low >= c->high; \
\ \
if (bit) \ if (bit) \
c->low += range >> 1; \ c->low += range >> 1; \