1. ffmpeg
  2. Commit 29b75f0b673d92364c57bf3926a8b9168ea0a05b
Browse code

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

Reimar Döffinger authored on 2010/01/15 02:50:33
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libavcodec/ac3.c
History View file @ 29b75f0
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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,
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         int v = psd[bin++];
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         int band_end = FFMIN(band_start_tab[band+1], end);
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         for (; bin < band_end; bin++) {
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+            int max = FFMAX(v, psd[bin]);
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             /* logadd */
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-            int adr = FFMIN(FFABS(v - psd[bin]) >> 1, 255);
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-            v = FFMAX(v, psd[bin]) + ff_ac3_log_add_tab[adr];
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+            int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);
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+            v = max + ff_ac3_log_add_tab[adr];
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         }
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         band_psd[band++] = v;
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     } while (end > band_start_tab[band]);