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Change code so it uses 2 adds instead of one FFABS.

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About 1% faster ff_ac3_bit_alloc_calc_psd on Intel Atom, overall speedup
not measurable though.
Should have a bigger effect on systems without cmov or with very slow cmov.

Originally committed as revision 21214 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Reimar Döffinger 2010-01-14 17:50:33 +00:00
parent 574b183d64
commit 29b75f0b67
1 changed files with 3 additions and 2 deletions
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5
libavcodec/ac3.c
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@ -112,9 +112,10 @@ void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
int v = psd[bin++];
int band_end = FFMIN(band_start_tab[band+1], end);
for (; bin < band_end; bin++) {
int max = FFMAX(v, psd[bin]);
/* logadd */
int adr = FFMIN(FFABS(v - psd[bin]) >> 1, 255);
v = FFMAX(v, psd[bin]) + ff_ac3_log_add_tab[adr];
int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);
v = max + ff_ac3_log_add_tab[adr];
}
band_psd[band++] = v;
} while (end > band_start_tab[band]);