clock: document internal functions

src/clock/clock.h

@@ -74,8 +74,19 @@ void vlc_clock_main_Abort(vlc_clock_main_t *main_clock);
  */
 void vlc_clock_main_Reset(vlc_clock_main_t *main_clock);
 
+/**
+ * Set the first PCR of the input
+ *
+ * It is used to calculate the input delay when output clocks are starting.
+ */
 void vlc_clock_main_SetFirstPcr(vlc_clock_main_t *main_clock,
                                 vlc_tick_t system_now, vlc_tick_t ts);
+
+/**
+ * Set the input dejitter (or pts_delay)
+ *
+ * It is used to calculate the input delay when output clocks are starting.
+ */
 void vlc_clock_main_SetInputDejitter(vlc_clock_main_t *main_clock,
                                      vlc_tick_t delay);