multiqueue: Don't reduce single queue visible size below its current level

If the multiqueue has automatically grown chances are good that
we will cause the pipeline to starve if the maximum level is reduced
below that automatically grown size.

https://bugzilla.gnome.org/show_bug.cgi?id=707156

diff --git a/plugins/elements/gstmultiqueue.c b/plugins/elements/gstmultiqueue.c
index a83220d..8a7a45e 100644 (file)
--- a/plugins/elements/gstmultiqueue.c
+++ b/plugins/elements/gstmultiqueue.c
@@ -495,11 +495,30 @@ gst_multi_queue_set_property (GObject * object, guint prop_id,
       GST_MULTI_QUEUE_MUTEX_UNLOCK (mq);
       break;
     case PROP_MAX_SIZE_BUFFERS:
+    {
+      GList *tmp;
+      gint new_size = g_value_get_uint (value);
+
       GST_MULTI_QUEUE_MUTEX_LOCK (mq);
-      mq->max_size.visible = g_value_get_uint (value);
-      SET_CHILD_PROPERTY (mq, visible);
+
+      tmp = mq->queues;
+      while (tmp) {
+        GstDataQueueSize size;
+        GstSingleQueue *q = (GstSingleQueue *) tmp->data;
+        gst_data_queue_get_level (q->queue, &size);
+
+        /* do not reduce max size below current level if the single queue has grown because of empty queue */
+        if (new_size >= size.visible && size.visible <= mq->max_size.visible)
+          q->max_size.visible = new_size;
+        tmp = g_list_next (tmp);
+      };
+
+      mq->max_size.visible = new_size;
+
       GST_MULTI_QUEUE_MUTEX_UNLOCK (mq);
+
       break;
+    }
     case PROP_MAX_SIZE_TIME:
       GST_MULTI_QUEUE_MUTEX_LOCK (mq);
       mq->max_size.time = g_value_get_uint64 (value);
@@ -704,7 +723,12 @@ gst_multi_queue_change_state (GstElement * element, GstStateChange transition)
         sq = (GstSingleQueue *) tmp->data;
         sq->flushing = FALSE;
       }
+
+      /* the visible limit might not have been set on single queues that have grown because of other queueus were empty */
+      SET_CHILD_PROPERTY (mqueue, visible);
+
       GST_MULTI_QUEUE_MUTEX_UNLOCK (mqueue);
+
       break;
     }
     case GST_STATE_CHANGE_PAUSED_TO_READY:{