[MPlayer-dev-eng] MS-ADPCM/Stereo Works
Michael Niedermayer
michaelni at gmx.at
Fri Dec 28 04:26:20 CET 2001
Hi
On Friday 28 December 2001 04:05, Michael Niedermayer wrote:
[...]
> ... cool, we r trying to optimize a adpcm decoder wich needs perhaps 1% of
> the cpu time
that following could be replaced with a simple look up table i think
sign = delta & 8;
delta = delta & 7;
diff = step[channel_number] >> 3;
if (delta & 4) diff += step[channel_number];
if (delta & 2) diff += step[channel_number] >> 1;
if (delta & 1) diff += step[channel_number] >> 2;
if (sign)
predictor[channel_number] -= diff;
...
step[channel_number] = adpcm_step[index[channel_number]];
----------
diff= lut[delta]
...
lut= adpcm_step_lut[index[channel_number]];
CLAMP_0_TO_88 could allso be replaced with a look up table
Michael
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