Add ms_ticker_synchronizer functions

include/mediastreamer2/msticker.h

@@ -89,6 +89,19 @@ struct _MSTickerParams{
 
 typedef struct _MSTickerParams MSTickerParams;
 
+
+struct _MSTickerSynchronizer
+{
+	uint64_t offset; /**<the default offset of ticker*/
+	double av_skew; /**< mean skew */
+};
+
+/**
+ * Structure for ticker synchronizer object.
+ * @var MSTickerSynchronizer
+ */
+typedef struct _MSTickerSynchronizer MSTickerSynchronizer;
+
 #ifdef __cplusplus
 extern "C"{
 #endif
@@ -144,6 +157,7 @@ MS2_PUBLIC int ms_ticker_attach(MSTicker *ticker,MSFilter *f);
  * Returns: 0 if successfull, -1 otherwise.
  */
 MS2_PUBLIC int ms_ticker_attach_multiple(MSTicker *ticker,MSFilter *f,...);
+
 /**
  * Dettach a chain of filters to a ticker.
  * The processing chain will no more be executed.
@@ -190,7 +204,42 @@ MS2_PUBLIC void ms_ticker_print_graphs(MSTicker *ticker);
  * A load greater than 100% clearly means that the ticker is over loaded and runs late.
 **/
 MS2_PUBLIC float ms_ticker_get_average_load(MSTicker *ticker);
-	
+
+/**
+ * Create a ticker synchronizer.
+ *
+ * Returns: MSTickerSynchronizer * if successfull, NULL otherwise.
+ */
+MS2_PUBLIC MSTickerSynchronizer* ms_ticker_synchronizer_new(void);
+
+/**
+ * Set the current external time.
+ *
+ * @param ts  A #MSTickerSynchronizer object.
+ * @param time  A #MSTimeSpec object.
+ *
+ * Returns: Average skew.
+ */
+MS2_PUBLIC double ms_ticker_synchronizer_set_external_time(MSTickerSynchronizer* ts, const MSTimeSpec *time);
+
+/**
+ * Get the corrected current time following the set external times.
+ *
+ * @param ts  A #MSTickerSynchronizer object.
+ *
+ *
+ * Returns: A corrected current time.
+ */
+MS2_PUBLIC uint64_t ms_ticker_synchronizer_get_corrected_time(MSTickerSynchronizer* ts);
+
+/**
+ * Destroy a ticker synchronizer.
+ *
+ * @param ts  A #MSTickerSynchronizer object.
+ *
+ */
+MS2_PUBLIC void ms_ticker_synchronizer_destroy(MSTickerSynchronizer* ts);
+
 /* private functions:*/
 
 #ifdef __cplusplus

src/msticker.c

@@ -482,3 +482,42 @@ float ms_ticker_get_average_load(MSTicker *ticker){
 	return ticker->av_load;
 }
 
+
+static uint64_t get_ms(const MSTimeSpec *ts){
+	return (ts->tv_sec*1000LL) + ((ts->tv_nsec+500000LL)/1000000LL);
+}
+
+static uint64_t get_wallclock_ms(void){
+	MSTimeSpec ts;
+	ms_get_cur_time(&ts);
+	return get_ms(&ts);
+}
+
+static const double clock_coef = .01;
+
+MSTickerSynchronizer* ms_ticker_synchronizer_new(void) {
+	MSTickerSynchronizer *obj=(MSTickerSynchronizer *)ms_new(MSTickerSynchronizer,1);
+	obj->av_skew = 0;
+	obj->offset = 0;
+	return obj;
+}
+
+double ms_ticker_synchronizer_set_external_time(MSTickerSynchronizer* ts, const MSTimeSpec *time) {
+	uint64_t wc = get_wallclock_ms();
+	uint64_t ms = get_ms(time);
+	if (ts->offset == 0) {
+		ts->offset = wc - ms;
+	}
+	int64_t sound_time = ts->offset + ms;
+	int64_t diff = wc - sound_time;
+	ts->av_skew = (ts->av_skew * (1.0 - clock_coef)) + ((double) diff * clock_coef);
+	return ts->av_skew;
+}
+
+uint64_t ms_ticker_synchronizer_get_corrected_time(MSTickerSynchronizer* ts) {
+	return get_wallclock_ms() - ts->av_skew;
+}
+
+void ms_ticker_synchronizer_destroy(MSTickerSynchronizer* ts) {
+	ms_free(ts);
+}