net: hlssink3: Use closed fragment location in playlist generation

Currently, we incorrectly use the last location we generated, which is
the current in-flight fragment while generating a new playlist. Instead,
the playlist should use the fragment that was just close (i.e. the
previous fragment), so it does not refer to a fragment we have not yet
uploaded.

This is a bug that was copied over from how hlssink2 does things.

Fixes: https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/issues/701
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/2324>

net/hlssink3/src/hlsbasesink.rs

@@ -350,6 +350,20 @@ impl HlsBaseSink {
         }
     }
 
+    pub fn get_location(&self, fragment_id: u32) -> Option<String> {
+        let mut state = self.state.lock().unwrap();
+        let context = match state.context.as_mut() {
+            Some(context) => context,
+            None => {
+                gst::error!(CAT, imp = self, "Playlist is not configured",);
+
+                return None;
+            }
+        };
+
+        sprintf::sprintf!(&context.segment_template, fragment_id).ok()
+    }
+
     pub fn get_fragment_stream(&self, fragment_id: u32) -> Option<(gio::OutputStream, String)> {
         let mut state = self.state.lock().unwrap();
         let context = match state.context.as_mut() {

net/hlssink3/src/hlssink3/imp.rs

@@ -583,15 +583,28 @@ impl HlsSink3 {
             CAT,
             imp = self,
             "New segment location: {:?}",
-            state.current_segment_location.as_ref()
+            segment_file_location,
         );
 
         Ok(segment_file_location)
     }
 
     fn on_fragment_closed(&self, s: &gst::StructureRef, closed_at: gst::ClockTime) {
+        let obj = self.obj();
+        let base_imp = obj.upcast_ref::<HlsBaseSink>().imp();
+
         let mut state = self.state.lock().unwrap();
-        let location = match state.current_segment_location.take() {
+
+        let location = match s
+            .get::<u32>("fragment-id")
+            .ok()
+            // Try to get the location of the fragment we just closed, if splitmuxsink gave us the
+            // fragment id (1.26+)
+            .and_then(|fragment_id| base_imp.get_location(fragment_id))
+            // Else fallback to the last fragment location we generated, which is techincally wrong
+            // (because this is the current fragment in progress, not the last fragment closed)
+            .or_else(|| state.current_segment_location.take())
+        {
             Some(location) => location,
             None => {
                 gst::error!(CAT, imp = self, "Unknown segment location");
@@ -628,8 +641,6 @@ impl HlsSink3 {
 
         drop(state);
 
-        let obj = self.obj();
-        let base_imp = obj.upcast_ref::<HlsBaseSink>().imp();
         let uri = base_imp.get_segment_uri(&location, None);
         let _ = base_imp.add_segment(
             &location,