deps-libff: Add master/slave deferred clock methods

Enables clocks to wait if the main sync clock has not been started yet.  An example of this is a video stream (video/audio) being synced to the video clock.  If an audio frame gets produced before the video clock has started it will wait.

deps/libff/libff/ff-clock.c

@@ -18,12 +18,78 @@
 #include "ff-threading.h"
 
 #include <libavutil/avutil.h>
+#include <libavutil/time.h>
+
+// Amount of microseconds between checks to see if a clock has started
+#define CLOCK_START_CHECK_INTERVAL 100
 
 double ff_get_sync_clock(struct ff_clock *clock)
 {
 	return clock->sync_clock(clock->opaque);
 }
 
+int64_t ff_clock_start_time(struct ff_clock *clock)
+{
+	int64_t start_time = AV_NOPTS_VALUE;
+
+	pthread_mutex_lock(&clock->mutex);
+	if (clock->started)
+		start_time = clock->start_time;
+	pthread_mutex_unlock(&clock->mutex);
+
+	return start_time;
+}
+
+bool ff_clock_start(struct ff_clock *clock, enum ff_av_sync_type sync_type,
+		const bool *abort)
+{
+	bool release = false;
+	bool aborted = false;
+
+	if (clock->sync_type == sync_type && !clock->started) {
+		pthread_mutex_lock(&clock->mutex);
+		if (!clock->started) {
+			clock->start_time = av_gettime();
+			clock->started = true;
+		}
+		pthread_cond_signal(&clock->cond);
+		pthread_mutex_unlock(&clock->mutex);
+	} else {
+		while (!clock->started) {
+			pthread_mutex_lock(&clock->mutex);
+			int64_t current_time = av_gettime()
+					+ CLOCK_START_CHECK_INTERVAL;
+			struct timespec sleep_time = {
+				.tv_sec = current_time / AV_TIME_BASE,
+				.tv_nsec = (current_time % AV_TIME_BASE) * 1000
+			};
+			pthread_cond_timedwait(&clock->cond, &clock->mutex,
+					&sleep_time);
+
+			aborted = *abort;
+
+			// There is no way anyone can signal us since we are
+			// the only reference
+			if (clock->retain == 1)
+				release = true;
+			pthread_mutex_unlock(&clock->mutex);
+
+			if (aborted || release) {
+				av_log(NULL, AV_LOG_ERROR, "could not start "
+						"slave clock as master clock "
+						"was never started before "
+						"being released or aborted");
+				break;
+			}
+		}
+	}
+
+	if (release)
+		ff_clock_release(&clock);
+
+	return !release && !aborted;
+}
+
 struct ff_clock *ff_clock_init(struct ff_clock *clock)
 {
 	clock = av_mallocz(sizeof(struct ff_clock));

deps/libff/libff/ff-clock.h

@@ -20,6 +20,7 @@
 #define AV_NOSYNC_THRESHOLD 10.0
 
 #include <stdbool.h>
+#include <stdint.h>
 #include <pthread.h>
 
 enum ff_av_sync_type {
@@ -33,10 +34,12 @@ typedef double (*ff_sync_clock)(void *opaque);
 struct ff_clock {
 	ff_sync_clock sync_clock;
 	enum ff_av_sync_type sync_type;
+	uint64_t start_time;
 
 	pthread_mutex_t mutex;
 	pthread_cond_t cond;
 	volatile long retain;
+	bool started;
 
 	void *opaque;
 };
@@ -48,3 +51,7 @@ double ff_get_sync_clock(struct ff_clock *clock);
 struct ff_clock *ff_clock_retain(struct ff_clock *clock);
 struct ff_clock *ff_clock_move(struct ff_clock **clock);
 void ff_clock_release(struct ff_clock **clock);
+
+int64_t ff_clock_start_time(struct ff_clock *clock);
+bool ff_clock_start(struct ff_clock *clock, enum ff_av_sync_type sync_type,
+		const bool *abort);