From 07fed1bf76ce38099d94e58770ca9db19fd772d3 Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date: Mon, 28 Dec 2009 07:59:42 -0500
Subject: Adding a safeguard against unstable LPC, so now there's no way (that
 I can think of) to produce NaNs in the new PLC.

---
 libcelt/celt.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/libcelt/celt.c b/libcelt/celt.c
index 41effc4..2e206e7 100644
--- a/libcelt/celt.c
+++ b/libcelt/celt.c
@@ -1347,13 +1347,20 @@ static void celt_decode_lost(CELTDecoder * restrict st, celt_word16 * restrict p
       iir(e, st->lpc, e, len+st->mode->overlap, LPC_ORDER, mem);
 
       {
-         float ratio, S2=0;
+         float S2=0;
          for (i=0;i<len+overlap;i++)
             S2 += e[i]*1.*e[i];
-         ratio = sqrt((S1+1)/(S2+1));
-         if (ratio < 1)
+         /* This checks for an "explosion" in the synthesis (including NaNs) */
+         if (!(S1 > 0.2f*S2))
+         {
+            for (i=0;i<len+overlap;i++)
+               e[i] = 0;
+         } else if (S1 < S2)
+         {
+            float ratio = sqrt((S1+1)/(S2+1));
             for (i=0;i<len+overlap;i++)
                e[i] *= ratio;
+         }
       }
 
       for (i=0;i<MAX_PERIOD+st->mode->overlap-N;i++)
-- 
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