Gstreamer splitmuxsink callback when a new file is created - callback

Question

I have a gst pipeline for recording video with splitmuxsink set to create new file every hour. I would like to have some callback when the new file is created.
I have tried
GstElement *sink = gst_element_factory_make ("splitmuxsink", "sink");
g_object_set (sink, "max-size-bytes", 4294967295, NULL);
g_object_set (sink, "max-size-time", 3600000000000, NULL); // 3600000000000 - 1 hour
g_signal_connect (sink, "split-now",G_CALLBACK(split_now_callback_test), &data);
However i found out, that "split-now" is signal which I can pass to the splitmuxsink and not the other way around. Is there a relatively easy way to have some callback a new target file is created?

Answer 1

There is a message that is emitted by the splitmuxsink element when it opens or closes a new fragment: "splitmuxsink-fragment-opened" or "splitmuxsink-fragment-closed". I found these messages in the splitmuxsink source code (search for the gst_element_post_message function call to see where the message is sent).
Here's an SO question about of listening for element messages (from the multifilesink element, which is very similar to the splitmuxsink element). In particular, see this gist from the OP on that question for an example of how to implement this in C.
I didn't validate that the approach above works in C, as I used this splitmuxsink message in a Rust implementation of the pipeline, but I think the general idea, translated to C, is something like this (adapted from GStreamer basic tutorial #3):
/* Listen to the bus */
bus = gst_element_get_bus (data.pipeline);
do {
msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,
GST_MESSAGE_ELEMENT | GST_MESSAGE_ERROR | GST_MESSAGE_EOS);
/* Parse message */
if (msg != NULL) {
GError *err;
gchar *debug_info;
switch (GST_MESSAGE_TYPE (msg)) {
case GST_MESSAGE_ERROR:
gst_message_parse_error (msg, &err, &debug_info);
g_printerr ("Error received from element %s: %s\n", GST_OBJECT_NAME (msg->src), err->message);
g_printerr ("Debugging information: %s\n", debug_info ? debug_info : "none");
g_clear_error (&err);
g_free (debug_info);
terminate = TRUE;
break;
case GST_MESSAGE_EOS:
g_print ("End-Of-Stream reached.\n");
terminate = TRUE;
break;
case GST_MESSAGE_ELEMENT:
/* Handle element-specific message here */
break;
default:
/* We should not reach here */
g_printerr ("Unexpected message received.\n");
break;
}
gst_message_unref (msg);
}
} while (!terminate);
For more info on element messages and the GstBus, see this page of the GStreamer docs