From 72941b5dc5db729577441fac209bce974a3b81be Mon Sep 17 00:00:00 2001
From: "Jan Alexander Steffens (heftig)" <jan.steffens@ltnglobal.com>
Date: Wed, 8 Feb 2023 20:33:29 +0100
Subject: livesync: Improve EOS handling

I've looked at the GstQueue code again and tried making livesync behave
better with EOS. This isn't very well tested, though. My goal was to
make this look saner but I think this should be reviewed by someone who
knows the queue code.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1267>
---
 utils/livesync/src/livesync/imp.rs | 65 ++++++++++++++++++++++++++++----------
 1 file changed, 48 insertions(+), 17 deletions(-)

diff --git a/utils/livesync/src/livesync/imp.rs b/utils/livesync/src/livesync/imp.rs
index 99eac29f3..d5de74eef 100644
--- a/utils/livesync/src/livesync/imp.rs
+++ b/utils/livesync/src/livesync/imp.rs
@@ -598,6 +598,9 @@ impl LiveSync {
             }
         }
 
+        let mut is_restart = false;
+        let mut is_eos = false;
+
         match event.view() {
             gst::EventView::FlushStart(_) => {
                 let ret = self.srcpad.push_event(event);
@@ -637,13 +640,11 @@ impl LiveSync {
                 return ret;
             }
 
-            gst::EventView::StreamStart(_) => {
-                let mut state = self.state.lock();
-                state.srcresult = Ok(gst::FlowSuccess::Ok);
-                state.eos = false;
-            }
+            gst::EventView::StreamStart(_) => is_restart = true,
 
             gst::EventView::Segment(e) => {
+                is_restart = true;
+
                 let segment = match e.segment().downcast_ref() {
                     Some(s) => s,
                     None => {
@@ -656,17 +657,7 @@ impl LiveSync {
                 state.in_segment = Some(segment.clone());
             }
 
-            gst::EventView::Eos(_) => {
-                let mut state = self.state.lock();
-
-                if let Err(err) = state.srcresult {
-                    if matches!(err, gst::FlowError::Flushing | gst::FlowError::Eos) {
-                        self.flow_error(err);
-                    }
-                }
-
-                state.eos = true;
-            }
+            gst::EventView::Eos(_) => is_eos = true,
 
             gst::EventView::Caps(c) => {
                 let caps = c.caps_owned();
@@ -698,7 +689,33 @@ impl LiveSync {
         }
 
         let mut state = self.state.lock();
-        if state.srcresult.is_err() {
+
+        if is_restart {
+            if state.srcresult == Err(gst::FlowError::Eos) {
+                state.srcresult = Ok(gst::FlowSuccess::Ok);
+            }
+
+            state.eos = false;
+            let _ = self.start_src_task();
+        }
+
+        if state.eos {
+            gst::trace!(CAT, imp: self, "Refusing event, we are EOS: {:?}", event);
+            return false;
+        }
+
+        if is_eos {
+            state.eos = true;
+        }
+
+        if let Err(err) = state.srcresult {
+            // Following GstQueue's behavior:
+            // > For EOS events, that are not followed by data flow, we still
+            // > return FALSE here though and report an error.
+            if is_eos && !matches!(err, gst::FlowError::Flushing | gst::FlowError::Eos) {
+                self.flow_error(err);
+            }
+
             return false;
         }
 
@@ -792,6 +809,11 @@ impl LiveSync {
 
         let mut state = self.state.lock();
 
+        if state.eos {
+            gst::debug!(CAT, imp: self, "Refusing buffer, we are EOS");
+            return Err(gst::FlowError::Eos);
+        }
+
         if state.upstream_latency.is_none() {
             gst::debug!(CAT, imp: self, "Have no upstream latency yet, querying");
             let mut q = gst::query::Latency::new();
@@ -988,6 +1010,9 @@ impl LiveSync {
             self.cond.notify_all();
         }
 
+        // Following GstQueue's behavior:
+        // > let app know about us giving up if upstream is not expected to do so
+        // > EOS is already taken care of elsewhere
         if eos && !matches!(err, gst::FlowError::Flushing | gst::FlowError::Eos) {
             self.flow_error(err);
             pad.push_event(gst::event::Eos::new());
@@ -1032,6 +1057,12 @@ impl LiveSync {
                         push = false;
                     }
 
+                    gst::EventView::Eos(_) => {
+                        state.out_buffer = None;
+                        state.out_timestamp = None;
+                        state.srcresult = Err(gst::FlowError::Eos);
+                    }
+
                     gst::EventView::Caps(e) => {
                         state.pending_caps = Some(e.caps_owned());
                         state.update_fallback_duration();
-- 
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