utils/fallbacksrc: Fix debug output in pad probe callback

Let's print the name of the source's srcpad that is going to be blocked
instead of the "src" pad of the following queue. Without this it's hard
to distinguish the different streams from the logs.

utils/fallbackswitch/src/fallbacksrc.rs

@@ -1325,8 +1325,7 @@ impl FallbackSrc {
         }
 
         stream.source_srcpad = Some(pad.clone());
-        stream.source_srcpad_block =
-            Some(self.add_pad_probe(element, &stream.clocksync_queue_srcpad));
+        stream.source_srcpad_block = Some(self.add_pad_probe(element, stream));
 
         drop(state_guard);
         element.notify("status");
@@ -1334,11 +1333,21 @@ impl FallbackSrc {
         Ok(())
     }
 
-    fn add_pad_probe(&self, element: &gst::Bin, pad: &gst::Pad) -> Block {
-        gst_debug!(CAT, obj: element, "Adding probe to pad {}", pad.get_name());
+    fn add_pad_probe(&self, element: &gst::Bin, stream: &mut Stream) -> Block {
+        // FIXME: Not literally correct as we add the probe to the queue source pad but that's only
+        // a workaround until
+        //     https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/800
+        // is fixed.
+        gst_debug!(
+            CAT,
+            obj: element,
+            "Adding probe to pad {}",
+            stream.source_srcpad.as_ref().unwrap().get_name()
+        );
 
         let element_weak = element.downgrade();
-        let probe_id = pad
+        let probe_id = stream
+            .clocksync_queue_srcpad
             .add_probe(
                 gst::PadProbeType::BLOCK
                     | gst::PadProbeType::BUFFER
@@ -1369,7 +1378,7 @@ impl FallbackSrc {
             .unwrap();
 
         Block {
-            pad: pad.clone(),
+            pad: stream.clocksync_queue_srcpad.clone(),
             probe_id,
             running_time: gst::CLOCK_TIME_NONE,
         }
@@ -1381,8 +1390,6 @@ impl FallbackSrc {
         pad: &gst::Pad,
         pts: gst::ClockTime,
     ) -> Result<(), gst::ErrorMessage> {
-        gst_debug!(CAT, obj: element, "Called probe on pad {}", pad.get_name());
-
         let mut state_guard = self.state.lock().unwrap();
         let state = match &mut *state_guard {
             None => {
@@ -1391,6 +1398,39 @@ impl FallbackSrc {
             Some(state) => state,
         };
 
+        // FIXME: Not literally correct as we added the probe to the queue source pad but that's only
+        // a workaround until
+        //     https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/800
+        // is fixed.
+
+        let stream = if let Some(stream) = state
+            .audio_stream
+            .as_mut()
+            .filter(|s| &s.clocksync_queue_srcpad == pad)
+        {
+            gst_debug!(
+                CAT,
+                obj: element,
+                "Called probe on pad {}",
+                stream.source_srcpad.as_ref().unwrap().get_name()
+            );
+            stream
+        } else if let Some(stream) = state
+            .video_stream
+            .as_mut()
+            .filter(|s| &s.clocksync_queue_srcpad == pad)
+        {
+            gst_debug!(
+                CAT,
+                obj: element,
+                "Called probe on pad {}",
+                stream.source_srcpad.as_ref().unwrap().get_name()
+            );
+            stream
+        } else {
+            unreachable!();
+        };
+
         // Directly unblock for live streams
         if state.source_is_live {
             for block in [state.video_stream.as_mut(), state.audio_stream.as_mut()]
@@ -1410,22 +1450,6 @@ impl FallbackSrc {
         }
 
         // Update running time for this block
-        let stream = if let Some(stream) = state
-            .audio_stream
-            .as_mut()
-            .filter(|s| &s.clocksync_queue_srcpad == pad)
-        {
-            stream
-        } else if let Some(stream) = state
-            .video_stream
-            .as_mut()
-            .filter(|s| &s.clocksync_queue_srcpad == pad)
-        {
-            stream
-        } else {
-            unreachable!();
-        };
-
         let block = match stream.source_srcpad_block {
             Some(ref mut block) => block,
             None => return Ok(()),
@@ -1459,9 +1483,8 @@ impl FallbackSrc {
         gst_debug!(
             CAT,
             obj: element,
-            "Have block running time {} for pad {}",
+            "Have block running time {}",
             running_time,
-            pad.get_name()
         );
 
         block.running_time = running_time;
@@ -1728,14 +1751,12 @@ impl FallbackSrc {
             // Block source pads if needed to pause
             if let Some(ref mut stream) = state.audio_stream {
                 if stream.source_srcpad_block.is_none() && stream.source_srcpad.is_some() {
-                    stream.source_srcpad_block =
-                        Some(self.add_pad_probe(element, &stream.clocksync_queue_srcpad));
+                    stream.source_srcpad_block = Some(self.add_pad_probe(element, stream));
                 }
             }
             if let Some(ref mut stream) = state.video_stream {
                 if stream.source_srcpad_block.is_none() && stream.source_srcpad.is_some() {
-                    stream.source_srcpad_block =
-                        Some(self.add_pad_probe(element, &stream.clocksync_queue_srcpad));
+                    stream.source_srcpad_block = Some(self.add_pad_probe(element, stream));
                 }
             }
 
@@ -1800,8 +1821,7 @@ impl FallbackSrc {
             .filter_map(|v| v.as_mut())
         {
             if stream.source_srcpad.is_some() && stream.source_srcpad_block.is_none() {
-                stream.source_srcpad_block =
-                    Some(self.add_pad_probe(element, &stream.clocksync_queue_srcpad));
+                stream.source_srcpad_block = Some(self.add_pad_probe(element, stream));
             }
         }