From 0712c230ae8b15f920e877e680e0fa6e856e8006 Mon Sep 17 00:00:00 2001
From: Nick Brereton
Date: Mon, 5 Jul 2010 08:16:43 +0000
Subject: DCA: Occasionally a false XCH sync word can turn up after the core
 DTS data, to verify the sync word the extension fsize field should be
 compared to the core data length field.

Patch by nick.nbrereton@net

Originally committed as revision 24054 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/dca.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'libavcodec/dca.c')

diff --git a/libavcodec/dca.c b/libavcodec/dca.c
index 989c6a286e..4b232c7006 100644
--- a/libavcodec/dca.c
+++ b/libavcodec/dca.c
@@ -1298,7 +1298,13 @@ static int dca_decode_frame(AVCodecContext * avctx,
         switch(bits) {
         case 0x5a5a5a5a: {
             int ext_base_ch = s->prim_channels;
-            int ext_amode;
+            int ext_amode, xch_fsize;
+
+            /* validate sync word using XCHFSIZE field */
+            xch_fsize = show_bits(&s->gb, 10);
+            if((s->frame_size != (get_bits_count(&s->gb) >> 3) - 4 + xch_fsize) &&
+               (s->frame_size != (get_bits_count(&s->gb) >> 3) - 4 + xch_fsize + 1))
+                continue;
 
             /* skip length-to-end-of-frame field for the moment */
             skip_bits(&s->gb, 10);
-- 
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