From affa49e62f974f5ed6207730817bc8cc56a09da6 Mon Sep 17 00:00:00 2001
From: Moritz Bunkus <moritz@bunkus.org>
Date: Sat, 12 Nov 2005 19:25:13 +0000
Subject: [PATCH] Check for resetting timecodes in the middle of Ogg/OGM files.
 Fixes Anthill bug #166.

---
 ChangeLog           |  6 +++++-
 src/input/r_ogm.cpp | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index cda052c51..2049d029a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,11 @@
 2005-11-12  Moritz Bunkus  <moritz@bunkus.org>
 
+	* mkvmerge: bug fix: Fixed a crash If the granulepos (the
+	timecodes) reset in the middle of an Ogg/OGM file. Fixes Anthill
+	bug #166.
+
 	* mkvmerge: bug fix: Fixed a division-by-zero error in the
-	RealMedia demuxer.
+	RealMedia demuxer. Fixes Anthill bug #161.
 
 	* mkvmerge: bug fix: Fixed a couple of potential (and actual)
 	segmentation faults by accessing invalid memory addresses. Initial
diff --git a/src/input/r_ogm.cpp b/src/input/r_ogm.cpp
index cc7c6ec0f..764a56c8a 100644
--- a/src/input/r_ogm.cpp
+++ b/src/input/r_ogm.cpp
@@ -802,14 +802,26 @@ ogm_reader_c::process_page(ogg_page *og) {
   ogg_packet op;
   int duration_len, eos, i;
   long duration;
+  bool last_granulepos_set;
 
   duration = 0;
   dmx = find_demuxer(ogg_page_serialno(og));
   if ((NULL == dmx) || (-1 == dmx->ptzr))
     return;
 
+  if ((-1 != ogg_page_granulepos(og)) &&
+      (ogg_page_granulepos(og) < dmx->last_granulepos)) {
+    mxwarn(FMT_TID "The timecodes for this stream have been reset in the "
+           "middle of the file. This is not supported. The current packet "
+           "will be discarded.\n", ti.fname.c_str(),
+           (int64_t)dmx->serialno);
+    return;
+  }
+
   debug_enter("ogm_reader_c::process_page");
 
+  last_granulepos_set = false;
+
   ogg_stream_pagein(&dmx->os, og);
   while (ogg_stream_packetout(&dmx->os, &op) == 1) {
     eos = op.e_o_s;
@@ -841,6 +853,8 @@ ogm_reader_c::process_page(ogg_page *og) {
         return;
       }
 
+      last_granulepos_set = true;
+
       continue;
     }
 #endif
@@ -878,6 +892,8 @@ ogm_reader_c::process_page(ogg_page *og) {
         return;
       }
 
+      last_granulepos_set = true;
+
       continue;
     }
 
@@ -933,6 +949,9 @@ ogm_reader_c::process_page(ogg_page *og) {
     }
   }
 
+  if (!last_granulepos_set)
+    dmx->last_granulepos = ogg_page_granulepos(og);
+
   debug_leave("ogm_reader_c::process_page");
 }