Used VLC_TS_INVALID/0 in vobsub demuxer.

modules/demux/vobsub.c

@@ -408,7 +408,7 @@ static int Demux( demux_t *p_demux )
             p_block->i_buffer = i_read;
 
             /* pts */
-            p_block->i_pts = tk.p_subtitles[tk.i_current_subtitle].i_start;
+            p_block->i_pts = VLC_TS_0 + tk.p_subtitles[tk.i_current_subtitle].i_start;
 
             /* demux this block */
             DemuxVobSub( p_demux, p_block );
@@ -701,7 +701,7 @@ static int DemuxVobSub( demux_t *p_demux, block_t *p_bk )
             if( p_tk->p_es && p_tk->i_track_id == i_spu )
             {
                 es_out_Send( p_demux->out, p_tk->p_es, p_pkt );
-                p_bk->i_pts = 0;     /*only first packet has a pts */
+                p_bk->i_pts = VLC_TS_INVALID;     /*only first packet has a pts */
                 break;
             }
         }