Revert "MKV: Always set an i_pts in a lace otherwise it disturbs seeking performance"

This reverts commit 6a16055a.

Fixes #14194
Vorbis doesn't work properly with forced bogus PTS.

The seek issue in #13575 is solved with the DirectSound fixes from #14186
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/demux/mkv/mkv.cpp

@@ -719,8 +719,10 @@ msg_Dbg( p_demux, "block (track=%d) i_dts: %"PRId64" / i_pts: %"PRId64, tk->i_nu
 
         es_out_Send( p_demux->out, tk->p_es, p_block );
 
-        // prepare the pts for the next frame in the lace
-        i_pts += tk->i_default_duration ? tk->i_default_duration : 1;
+        /* use time stamp only for first block */
+        i_pts = ( tk->i_default_duration )?
+                 i_pts + ( mtime_t )tk->i_default_duration:
+                 VLC_TS_INVALID;
     }
 }