Override PulseAudio input buffer attributes and watch them

Since VLC allows the input format to differ from the requested one, it
needs to recompute the buffer attributes after the stream is connected.
Otherwise, we would get different timing than intended.

modules/access/pulse.c

@@ -78,6 +78,24 @@ static void stream_state_cb(pa_stream *s, void *userdata)
     }
 }
 
+static void stream_success_cb (pa_stream *s, int success, void *userdata)
+{
+    pa_threaded_mainloop *mainloop = userdata;
+
+    pa_threaded_mainloop_signal(mainloop, 0);
+    (void) s;
+    (void) success;
+}
+
+static void stream_buffer_attr_cb(pa_stream *s, void *userdata)
+{
+    demux_t *demux = userdata;
+    const struct pa_buffer_attr *pba = pa_stream_get_buffer_attr(s);
+
+    msg_Dbg(demux, "using buffer metrics: maxlength=%"PRIu32", "
+            "fragsize=%"PRIu32, pba->maxlength, pba->fragsize);
+}
+
 static void stream_moved_cb(pa_stream *s, void *userdata)
 {
     demux_t *demux = userdata;
@@ -85,6 +103,7 @@ static void stream_moved_cb(pa_stream *s, void *userdata)
 
     msg_Dbg(demux, "connected to source %"PRIu32": %s", idx,
                   pa_stream_get_device_name(s));
+    stream_buffer_attr_cb(s, userdata);
 }
 
 static void stream_overflow_cb(pa_stream *s, void *userdata)
@@ -276,7 +295,7 @@ static int Open(vlc_object_t *obj)
     if (demux->psz_location != NULL && demux->psz_location[0] != '\0')
         dev = demux->psz_location;
 
-    const struct pa_buffer_attr attr = {
+    struct pa_buffer_attr attr = {
         .maxlength = -1,
         .fragsize = pa_usec_to_bytes(sys->caching, &ss) / 2,
     };
@@ -285,6 +304,7 @@ static int Open(vlc_object_t *obj)
 
     /* Create record stream */
     pa_stream *s;
+    pa_operation *op;
 
     pa_threaded_mainloop_lock(sys->mainloop);
     s = pa_stream_new(sys->context, "audio stream", &ss, &map);
@@ -294,6 +314,7 @@ static int Open(vlc_object_t *obj)
     sys->stream = s;
     pa_stream_set_state_callback(s, stream_state_cb, sys->mainloop);
     pa_stream_set_read_callback(s, stream_read_cb, demux);
+    pa_stream_set_buffer_attr_callback(s, stream_buffer_attr_cb, demux);
     pa_stream_set_moved_callback(s, stream_moved_cb, demux);
     pa_stream_set_overflow_callback(s, stream_overflow_cb, demux);
     pa_stream_set_started_callback(s, stream_started_cb, demux);
@@ -332,9 +353,15 @@ static int Open(vlc_object_t *obj)
     sys->framesize = fmt.audio.i_blockalign;
     sys->es = es_out_Add (demux->out, &fmt);
 
-    const struct pa_buffer_attr *pba = pa_stream_get_buffer_attr(s);
-    msg_Dbg(obj, "using buffer metrics: maxlength=%"PRIu32", fragsize=%"PRIu32,
-            pba->maxlength, pba->fragsize);
+    /* Update the buffer attributes according to actual format */
+    attr.fragsize = pa_usec_to_bytes(sys->caching, pss) / 2;
+    op = pa_stream_set_buffer_attr(s, &attr, stream_success_cb, sys->mainloop);
+    if (likely(op != NULL)) {
+        while (pa_operation_get_state(op) == PA_OPERATION_RUNNING)
+            pa_threaded_mainloop_wait(sys->mainloop);
+        pa_operation_unref(op);
+    }
+    stream_buffer_attr_cb(s, demux);
     pa_threaded_mainloop_unlock(sys->mainloop);
 
     demux->pf_demux = NULL;
@@ -358,6 +385,7 @@ static void Close (vlc_object_t *obj)
         pa_stream_disconnect(s);
         pa_stream_set_state_callback(s, NULL, NULL);
         pa_stream_set_read_callback(s, NULL, NULL);
+        pa_stream_set_buffer_attr_callback(s, NULL, NULL);
         pa_stream_set_moved_callback(s, NULL, NULL);
         pa_stream_set_overflow_callback(s, NULL, NULL);
         pa_stream_set_started_callback(s, NULL, NULL);