Allow timespans to vary.

No change in performance if they do not vary.

Originally committed as revision 17840 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/timefilter.c

@@ -34,10 +34,10 @@ struct TimeFilter {
     double integrator2_state;
 };
 
-TimeFilter * ff_timefilter_new(double period, double feedback2_factor, double feedback3_factor)
+TimeFilter * ff_timefilter_new(double feedback2_factor, double feedback3_factor)
 {
     TimeFilter *self        = av_mallocz(sizeof(TimeFilter));
-    self->integrator2_state = period;
+    self->integrator2_state = 1.0;
     self->feedback2_factor  = feedback2_factor;
     self->feedback3_factor  = feedback3_factor;
     return self;
@@ -53,20 +53,20 @@ void ff_timefilter_reset(TimeFilter *self)
     self->cycle_time = 0;
 }
 
-void ff_timefilter_update(TimeFilter *self, double system_time)
+void ff_timefilter_update(TimeFilter *self, double system_time, double period)
 {
     if (!self->cycle_time) {
         /// init loop
         self->cycle_time        = system_time;
     } else {
         double loop_error;
-        self->cycle_time+= self->integrator2_state;
+        self->cycle_time+= self->integrator2_state * period;
         /// calculate loop error
         loop_error = system_time - self->cycle_time;
 
         /// update loop
         self->cycle_time        += self->feedback2_factor * loop_error;
-        self->integrator2_state += self->feedback3_factor * loop_error;
+        self->integrator2_state += self->feedback3_factor * loop_error / period;
     }
 }
 

libavformat/timefilter.h

@@ -37,10 +37,6 @@ typedef struct TimeFilter TimeFilter;
 /**
  * Create a new Delay Locked Loop time filter
  *
- * period is the device cycle duration in seconds. For example, at
- * 44.1Hz and a buffer size of 512 frames, period = 512 / 44100. The filter
- * only works if the cycle duration is fixed.
- *
  * feedback2_factor and feedback3_factor are the factors used for the
  * multiplications that are respectively performed in the second and third
  * feedback paths of the loop.
@@ -58,19 +54,22 @@ typedef struct TimeFilter TimeFilter;
  * For more details about these parameters and background concepts please see:
  * http://www.kokkinizita.net/papers/usingdll.pdf
  */
-TimeFilter * ff_timefilter_new(double period, double feedback2_factor, double feedback3_factor);
+TimeFilter * ff_timefilter_new(double feedback2_factor, double feedback3_factor);
 
 /**
  * Update the filter
  *
  * This function must be called in real time, at each process cycle.
  *
+ * period is the device cycle duration in seconds. For example, at
+ * 44.1Hz and a buffer size of 512 frames, period = 512 / 44100.
+ *
  * system_time, in seconds, should be the value of the system clock time,
  * at (or as close as possible to) the moment the device hardware interrupt
  * occured (or any other event the device clock raises at the beginning of a
  * cycle).
  */
-void ff_timefilter_update(TimeFilter *self, double system_time);
+void ff_timefilter_update(TimeFilter *self, double system_time, double period);
 
 /**
  * Retrieve the filtered time