libvlc_clock, libvlc_delay: expose LibVLC clock for audio sync

include/vlc/libvlc.h

@@ -448,6 +448,34 @@ LIBVLC_API
 libvlc_module_description_t *libvlc_video_filter_list_get( libvlc_instance_t *p_instance );
 
 /** @} */
+
+/** \defgroup libvlc_clock LibVLC time
+ * These functions provide access to the LibVLC time/clock.
+ * @{
+ */
+
+/**
+ * Return the current time as defined by LibVLC. The unit is the microsecond.
+ * Time increases monotonically (regardless of time zone changes and RTC
+ * adjustements).
+ * The origin is arbitrary but consistent across the whole system
+ * (e.g. the system uptim, the time since the system was booted).
+ * \note On systems that support it, the POSIX monotonic clock is used.
+ */
+LIBVLC_API
+int64_t libvlc_clock(void);
+
+/**
+ * Return the delay (in microseconds) until a certain timestamp.
+ * \param pts timestamp
+ * \return negative if timestamp is in the past,
+ * positive if it is in the future
+ */
+static inline int64_t libvlc_delay(int64_t pts)
+{
+    return pts - libvlc_clock();
+}
+
 /** @} */
 
 # ifdef __cplusplus

src/control/core.c

@@ -238,3 +238,8 @@ libvlc_module_description_t *libvlc_video_filter_list_get( libvlc_instance_t *p_
 {
     return libvlc_module_description_list_get( p_instance, "video filter2" );
 }
+
+int64_t libvlc_clock(void)
+{
+    return mdate();
+}

src/libvlc.sym

@@ -25,6 +25,7 @@ libvlc_audio_set_mute
 libvlc_audio_set_track
 libvlc_audio_set_volume
 libvlc_audio_toggle_mute
+libvlc_clock
 libvlc_event_attach
 libvlc_event_detach
 libvlc_event_manager_new