<p>Hugo Beauzée-Luyseen found an off-by-one error in the patch in which this email is a reply to, see attachment for one that has fixed this issue.</p>
<p>The new patch effectively differs (in terms of result) from the previous patch in the following way:</p>
<pre><code>index 01ba53a..c49ddb0 100644
--- a/modules/demux/mkv/matroska_segment.cpp
+++ b/modules/demux/mkv/matroska_segment.cpp
@@ -848,7 +848,7 @@ void matroska_segment_c::Seek( mtime_t i_mk_date, mtime_t i_mk_time_offset, int6
         EbmlElement *el = NULL;
 
         /* Start from the last known index instead of the beginning eachtime */
-        if(index_idx())
+        if(index_idx() == 0)
             es.I_O().setFilePointer( i_start_pos, seek_beginning );
         else
             es.I_O().setFilePointer( prev_index().i_position,
@@ -864,7 +864,7 @@ void matroska_segment_c::Seek( mtime_t i_mk_date, mtime_t i_mk_time_offset, int6
             {
                 cluster = kc_ptr;
                 i_cluster_pos = cluster->GetElementPosition();
-                if( index_idx() ||
+                if( index_idx() == 0 ||
                     ( prev_index().i_position < (int64_t)cluster->GetElementPosition() ) )
                 {
                     ParseCluster( cluster, false, SCOPE_NO_DATA );
@@ -1424,7 +1424,7 @@ int matroska_segment_c::BlockGet( KaxBlock * & pp_block, KaxSimpleBlock * & pp_s
                         cluster->InitTimecode( uint64( *kct_ptr ), i_timescale );
 
                         /* add it to the index */
-                        if( index_idx() ||
+                        if( index_idx() == 0 ||
                             ( prev_index().i_position < (int64_t)cluster->GetElementPosition() ) )
                         {
                             IndexAppendCluster( cluster );</code></pre>
<p>Thanks Hugo!</p>