commit e9f70f8f10638ecc5e931cfe6cf5ffc9a19f3a8d
author Alex Converse <aconverse@google.com> Mon Aug 22 12:44:16 2016 -0700
committer Alex Converse <aconverse@google.com> Wed Oct 12 17:41:01 2016 -0700
tree f119261c34966f8b8f00115eb3d9062a32b080bf
parent a1ac972867570fdfc2bda28daf0316b8ecc9a266

Remove the starting zero from ANS CDFs.

This brings it in line with the Daala CDFs and will make it easier to
share code.

Change-Id: Idfd2d2b33c3b9b2c4e72ce72fb3d8039013448b9
(cherry picked from aom/master commit af98507ca928afe33e9f88fdd2ca168379528d6a)

aom_dsp/bitwriter.h

diff --git a/aom_dsp/bitwriter.h b/aom_dsp/bitwriter.h
index 4aa7f88..d6937aa 100644
--- a/aom_dsp/bitwriter.h
+++ b/aom_dsp/bitwriter.h
@@ -92,8 +92,8 @@
   struct rans_sym s;
   (void)nsymbs;
   assert(cdf);
-  s.cum_prob = cdf[symb];
-  s.prob = cdf[symb + 1] - s.cum_prob;
+  s.cum_prob = symb > 0 ? cdf[symb - 1] : 0;
+  s.prob = cdf[symb] - s.cum_prob;
   buf_rans_write(w, &s);
 #else
   (void)w;