From e73e6aaabc4af842be1f869e47d473ee76dfb130 Mon Sep 17 00:00:00 2001
From: Isaac Connor <isaac@zoneminder.com>
Date: Tue, 26 Jan 2021 12:23:44 -0500
Subject: [PATCH] check for terminating before locking packetqueue. Handle when
 pre_event_count==0

---
 src/zm_packetqueue.cpp | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/src/zm_packetqueue.cpp b/src/zm_packetqueue.cpp
index 366f308c2..1164f556f 100644
--- a/src/zm_packetqueue.cpp
+++ b/src/zm_packetqueue.cpp
@@ -428,6 +428,8 @@ int zm_packetqueue::packet_count(int stream_id) {
 
 // Returns a packet. Packet will be locked
 ZMPacket *zm_packetqueue::get_packet(packetqueue_iterator *it) {
+  if ( deleting or zm_terminate )
+    return nullptr;
 
   Debug(4, "Locking in get_packet using it %p queue end? %d, packet %p",
       *it, (*it == pktQueue.end()), *(*it));
@@ -494,20 +496,22 @@ std::list<ZMPacket *>::iterator zm_packetqueue::get_event_start_packet_it(
     ) {
 
   std::list<ZMPacket *>::iterator it = snapshot_it;
-  dumpPacket( &((*it)->packet ) );
+  dumpPacket(&((*it)->packet));
   // Step one count back pre_event_count frames as the minimum
   // Do not assume that snapshot_it is video
-  Debug(1, "Checking for keyframe %p", *it);
-  Debug(1, "Checking for keyframe begin %p", *(pktQueue.begin()));
   // snapshot it might already point to the beginning
   while ( ( it != pktQueue.begin() ) and pre_event_count ) {
-    Debug(1, "Previous packet pre %d index %d keyframe %d", pre_event_count, (*it)->packet.stream_index, (*it)->keyframe);
-    dumpPacket( &((*it)->packet ) );
-    if ( (*it)->packet.stream_index != video_stream_id ) {
+    Debug(1, "Previous packet pre_event_count %d stream_index %d keyframe %d", pre_event_count, (*it)->packet.stream_index, (*it)->keyframe);
+    dumpPacket(&((*it)->packet));
+    if ( (*it)->packet.stream_index == video_stream_id ) {
       pre_event_count --;
+      if ( ! pre_event_count )
+        break;
     }
     it--;
   }
+  // it either points to beginning or we have seen pre_event_count video packets.
+  
   if ( it == pktQueue.begin() ) {
     Debug(1, "Hit begin");
     // hit end, the first packet in the queue should ALWAYS be a video keyframe.
@@ -523,21 +527,20 @@ std::list<ZMPacket *>::iterator zm_packetqueue::get_event_start_packet_it(
     }
     return it;
   }
-  Debug(1, "Checking for keyframe %p", *it);
+
+  // Not at beginning, so must be pointing at a video keyframe or maybe pre_event_count == 0
   if ( (*it)->keyframe ) {
-    Debug(1, "Returning");
-    Debug(1, "Previous packet pre %d index %d keyframe %d", pre_event_count, (*it)->image_index, (*it)->keyframe);
+    dumpPacket(&((*it)->packet), "Found video keyframe, Returning");
     return it;
   }
-  Debug(1, "Wasnt Checking for keyframe");
 
-  while ( ( it-- != pktQueue.begin() ) and ! (*it)->keyframe ) {
-    Debug(1, "No keyframe");
-    dumpPacket( &((*it)->packet ) );
+  while ( it-- != pktQueue.begin() ) {
+    dumpPacket(&((*it)->packet), "No keyframe");
+    if ( (*it)->packet.stream_index == video_stream_id and (*it)->keyframe )
+      return it; // Success
   }
-  Debug(1, "Checking for keyframe");
   if ( !(*it)->keyframe ) {
-      Warning("Hit end of packetqueue before satisfying pre_event_count. Needed %d more video frames", pre_event_count);
+    Warning("Hit end of packetqueue before satisfying pre_event_count. Needed %d more video frames", pre_event_count);
   }
   return it;