wait won't wake up other threads, so notify first. Since we have the lock, this should be ok

src/zm_packetqueue.cpp

@@ -133,6 +133,7 @@ bool PacketQueue::queuePacket(std::shared_ptr<ZMPacket> add_packet) {
       if (max_video_packet_count > 0) {
         while (packet_counts[video_stream_id] > max_video_packet_count) {
           Error("Unable to free up older packets.  Waiting.");
+          condition.notify_all();
           condition.wait(lck);
           if (deleting or zm_terminate)
             return false;