From 69a5c189ad088715d1fac7140c57248d747d6a2a Mon Sep 17 00:00:00 2001
From: Fraunhofer IIS FDK <audio-fdk@iis.fraunhofer.de>
Date: Fri, 8 Mar 2019 16:09:45 +0100
Subject: [PATCH] Improve accuracy of division in calcSubbandGain().

Bug: 132641988
Test: atest DecoderTestXheAac ; atest DecoderTestAacDrc

Change-Id: I3beeda23355ae1200d9f55c9e8cd1cc6bc899153
---
 libSBRdec/src/env_calc.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/libSBRdec/src/env_calc.cpp b/libSBRdec/src/env_calc.cpp
index cb1474f..11b7eca 100644
--- a/libSBRdec/src/env_calc.cpp
+++ b/libSBRdec/src/env_calc.cpp
@@ -1,7 +1,7 @@
 /* -----------------------------------------------------------------------------
 Software License for The Fraunhofer FDK AAC Codec Library for Android
 
-© Copyright  1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
+© Copyright  1995 - 2019 Fraunhofer-Gesellschaft zur Förderung der angewandten
 Forschung e.V. All rights reserved.
 
  1.    INTRODUCTION
@@ -2325,7 +2325,15 @@ static void calcSubbandGain(
     }
 
     /*  gain = nrgRef / B */
-    FDK_divide_MantExp(nrgRef, nrgRef_e, b, b_e, ptrNrgGain, ptrNrgGain_e);
+    INT result_exp = 0;
+    *ptrNrgGain = fDivNorm(nrgRef, b, &result_exp);
+    *ptrNrgGain_e = (SCHAR)result_exp + (nrgRef_e - b_e);
+
+    /* There could be a one bit diffs. This is important to compensate,
+       because later in the code values are compared by exponent only. */
+    int headroom = CountLeadingBits(*ptrNrgGain);
+    *ptrNrgGain <<= headroom;
+    *ptrNrgGain_e -= headroom;
   }
 }