[vlc-devel] Re: Clock synchro problems - proposed solution

[Marian Durkovic]

Hi Sigmund,

> The clock drift calculation smoothing algorithm is basically a running
> average with cr-average being by default 40. This means that even though
> the calculation is performed at every pcr at least 40 pcr periods are
> taken into account. Increasing cr-average will increase the period. The
> computation is indeed subject to rounding error, and I have a still
> uncommited patch that fixes this.

  thanks for commiting the rounding-error fix. Indeed, with this fix, it's
enough to change the computation interval to 1 second, and my test streams
play all fine. 

  Please find the new - now much simpler version of my synchro patch in the 
attachment. 


	With kind regards,

		M.
-------------- next part --------------
Index: src/input/input_internal.h
===================================================================
--- src/input/input_internal.h	(revision 13166)
+++ src/input/input_internal.h	(working copy)
@@ -133,6 +133,7 @@
     /* 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;
Index: src/input/clock.c
===================================================================
--- src/input/clock.c	(revision 13166)
+++ src/input/clock.c	(working copy)
@@ -133,6 +133,7 @@
 
     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 @@
         else
         {
             cl->last_cr = 0;
+            cl->last_sysdate = 0;
             cl->delta_cr = 0;
             cl->i_delta_cr_residue = 0;
         }
@@ -308,7 +310,7 @@
             input_ClockManageControl( p_input, cl, i_clock );
 #endif
         }
-        else
+        else if ( mdate() - cl->last_sysdate > 1000000 )
         {
             /* Smooth clock reference variations. */
             mtime_t i_extrapoled_clock = ClockCurrent( p_input, cl );
@@ -324,6 +326,7 @@
                                        + cl->i_delta_cr_residue )
                                     % cl->i_cr_average;
             cl->delta_cr = delta_cr;
+            cl->last_sysdate = mdate();
         }
     }
 }