PulseAudio: do not ignore latency updates before stream trigger

Such a latency update is an opportunity to reschedule the stream
trigger time, or to trigger immediately if late. That can reduce the
initial audio delay in some cases.
(cherry picked from commit 1b06737a297cc5b9c48dd12e2e456b45bc6891d2)

modules/audio_output/pulse.c

@@ -203,10 +203,7 @@ static void stream_start(pa_stream *s, audio_output_t *aout)
     aout_sys_t *sys = aout->sys;
     pa_operation *op;
 
-    if (sys->trigger != NULL) {
-        vlc_pa_rttime_free(sys->mainloop, sys->trigger);
-        sys->trigger = NULL;
-    }
+    assert (sys->trigger == NULL);
 
     op = pa_stream_cork(s, 0, NULL, NULL);
     if (op != NULL)
@@ -237,8 +234,11 @@ static void stream_trigger_cb(pa_mainloop_api *api, pa_time_event *e,
     audio_output_t *aout = userdata;
     aout_sys_t *sys = aout->sys;
 
-    msg_Dbg(aout, "starting deferred");
     assert (sys->trigger == e);
+
+    msg_Dbg(aout, "starting deferred");
+    vlc_pa_rttime_free(sys->mainloop, sys->trigger);
+    sys->trigger = NULL;
     stream_start(sys->stream, aout);
     (void) api; (void) e; (void) tv;
 }
@@ -256,18 +256,21 @@ static void stream_resync(audio_output_t *aout, pa_stream *s)
 
     assert (sys->pts != VLC_TS_INVALID);
 
+    if (sys->trigger != NULL) {
+        vlc_pa_rttime_free(sys->mainloop, sys->trigger);
+        sys->trigger = NULL;
+    }
+
     delta = vlc_pa_get_latency(aout, sys->context, s);
     if (unlikely(delta == VLC_TS_INVALID))
         delta = 0; /* screwed */
 
     delta = (sys->pts - mdate()) - delta;
     if (delta > 0) {
-        if (sys->trigger == NULL) {
         msg_Dbg(aout, "deferring start (%"PRId64" us)", delta);
         delta += pa_rtclock_now();
         sys->trigger = pa_context_rttime_new(sys->context, delta,
                                              stream_trigger_cb, aout);
-        }
     } else {
         msg_Warn(aout, "starting late (%"PRId64" us)", delta);
         stream_start(s, aout);
@@ -280,13 +283,16 @@ static void stream_latency_cb(pa_stream *s, void *userdata)
     aout_sys_t *sys = aout->sys;
     mtime_t delta, change;
 
-    if (pa_stream_is_corked(s))
-        return;
-    if (sys->pts == VLC_TS_INVALID)
-    {
+    if (sys->paused != VLC_TS_INVALID)
+        return; /* nothing to do while paused */
+    if (sys->pts == VLC_TS_INVALID) {
         msg_Dbg(aout, "missing latency from input");
         return;
     }
+    if (pa_stream_is_corked(s) > 0) {
+        stream_resync(aout, s);
+        return;
+    }
 
     /* Compute lip desynchronization */
     delta = vlc_pa_get_latency(aout, sys->context, s);