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adpcmenc:Optimize adpcm_ima_qt_compress_sample()

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Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer 2011-05-08 13:20:22 +02:00
parent 35d3d44a84
commit af3c8f8230
1 changed files with 18 additions and 15 deletions
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33
libavcodec/adpcm.c
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@ -274,24 +274,27 @@ static inline unsigned char adpcm_ima_compress_sample(ADPCMChannelStatus *c, sho
static inline unsigned char adpcm_ima_qt_compress_sample(ADPCMChannelStatus *c, short sample)
{
int delta = sample - c->prev_sample;
int mask, step = step_table[c->step_index];
int diff = step >> 3;
int nibble = 0;
int diff, step = step_table[c->step_index];
int nibble = 8*(delta < 0);
if (delta < 0) {
nibble = 8;
delta = -delta;
}
delta= abs(delta);
diff = delta + (step >> 3);
for (mask = 4; mask;) {
if (delta >= step) {
nibble |= mask;
delta -= step;
diff += step;
}
step >>= 1;
mask >>= 1;
if (delta >= step) {
nibble |= 4;
delta -= step;
}
step >>= 1;
if (delta >= step) {
nibble |= 2;
delta -= step;
}
step >>= 1;
if (delta >= step) {
nibble |= 1;
delta -= step;
}
diff -= delta;
if (nibble & 8)
c->prev_sample -= diff;