aacsbr: change order of operation to prevent out of array read

CC: libav-stable@libav.org
Bug-Id: CID 732250

diff --git a/libavcodec/aacsbr.c b/libavcodec/aacsbr.c
index 4d2ac6c..dbfb167 100644 (file)
--- a/libavcodec/aacsbr.c
+++ b/libavcodec/aacsbr.c
@@ -549,7 +549,8 @@ static int sbr_hf_calc_npatches(AACContext *ac, SpectralBandReplication *sbr)
             k = sbr->n_master;
     } while (sb != sbr->kx[1] + sbr->m[1]);
 
-    if (sbr->patch_num_subbands[sbr->num_patches-1] < 3 && sbr->num_patches > 1)
+    if (sbr->num_patches > 1 &&
+        sbr->patch_num_subbands[sbr->num_patches - 1] < 3)
         sbr->num_patches--;
 
     return 0;