update cl->delta_cr only once per 200 msec to ensure better refclock

stability and mitigate temporary OS/network jitter problems

src/input/clock.c

@@ -133,6 +133,7 @@ void input_ClockInit( input_clock_t *cl, vlc_bool_t b_master, int i_cr_average )
 
     cl->last_cr = 0;
     cl->last_pts = 0;
+    cl->last_sysdate = 0;
     cl->cr_ref = 0;
     cl->sysdate_ref = 0;
     cl->delta_cr = 0;
@@ -264,6 +265,7 @@ void input_ClockSetPCR( input_thread_t *p_input,
         else
         {
             cl->last_cr = 0;
+            cl->last_sysdate = 0;
             cl->delta_cr = 0;
             cl->i_delta_cr_residue = 0;
         }
@@ -308,7 +310,7 @@ void input_ClockSetPCR( input_thread_t *p_input,
             input_ClockManageControl( p_input, cl, i_clock );
 #endif
         }
-        else
+        else if ( mdate() - cl->last_sysdate > 200000 )
         {
             /* Smooth clock reference variations. */
             mtime_t i_extrapoled_clock = ClockCurrent( p_input, cl );
@@ -324,6 +326,7 @@ void input_ClockSetPCR( input_thread_t *p_input,
                                        + cl->i_delta_cr_residue )
                                     % cl->i_cr_average;
             cl->delta_cr = delta_cr;
+            cl->last_sysdate = mdate();
         }
     }
 }

src/input/input_internal.h

@@ -133,6 +133,7 @@ typedef struct
     /* Synchronization information */
     mtime_t                 delta_cr;
     mtime_t                 cr_ref, sysdate_ref;
+    mtime_t                 last_sysdate;
     mtime_t                 last_cr; /* reference to detect unexpected stream
                                       * discontinuities                      */
     mtime_t                 last_pts;