[FFmpeg-cvslog] ape: Unbreak adaptcoeffs computation

[Luca Barbato]

ffmpeg | branch: master | Luca Barbato <lu_zero at gentoo.org> | Thu Apr 21 16:09:38 2016 +0200| [4012fe1ee819edc7689e182189e66c5401fb4b41] | committer: Luca Barbato

ape: Unbreak adaptcoeffs computation

And simplify and explain the expression.

Fault introduced in f3fdef108eb06b1e71b29152bf6822519e787efe

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=4012fe1ee819edc7689e182189e66c5401fb4b41
---

 libavcodec/apedec.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c
index 85d26ae..d7cf8a2 100644
--- a/libavcodec/apedec.c
+++ b/libavcodec/apedec.c
@@ -1305,8 +1305,16 @@ static void do_apply_filter(APEContext *ctx, int version, APEFilter *f,
             /* Update the adaption coefficients */
             absres = FFABS(res);
             if (absres)
-                *f->adaptcoeffs = ((res & ((~0UL) << 31)) ^ ((~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;