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ape: Unbreak adaptcoeffs computation

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And simplify and explain the expression.

Fault introduced in f3fdef108e

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
This commit is contained in:
Luca Barbato 2016-04-21 16:09:38 +02:00 committed by Derek Buitenhuis
parent 5b9a4476e3
commit dd4fb2339f
1 changed files with 10 additions and 2 deletions
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12
libavcodec/apedec.c
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@ -1284,8 +1284,16 @@ static void do_apply_filter(APEContext *ctx, int version, APEFilter *f,
/* Update the adaption coefficients */
absres = FFABS(res);
if (absres)
*f->adaptcoeffs = ((res & INT32_MIN) ^ ((~0UL) << 30)) >>
(25 + (absres <= f->avg*3) + (absres <= f->avg*4/3));
*f->adaptcoeffs = APESIGN(res) *
(8 << ((absres > f->avg * 3) + (absres > f->avg * 4 / 3)));
/* equivalent to the following code
if (absres <= f->avg * 4 / 3)
*f->adaptcoeffs = APESIGN(res) * 8;
else if (absres <= f->avg * 3)
*f->adaptcoeffs = APESIGN(res) * 16;
else
*f->adaptcoeffs = APESIGN(res) * 32;
*/
else
*f->adaptcoeffs = 0;