videoaggregator: add "ignore-eos" property for input pads

When set, it causes videoaggregator to repeatedly aggregate the last buffer on
an EOS pad instead of skipping it and outputting silence. This is useful, for
instance, while playing back files seamless one after the other, to avoid
videoaggregator ever outputting silence (the checkerboard pattern).

It is to be noted that if all the pads on videoaggregator have this property set
on them, the mixer will never forward EOS downstream for obvious reasons. Hence,
at least one pad with 'ignore-eos' set to FALSE must send EOS to the mixer
before it will be forwarded downstream.

https://bugzilla.gnome.org/show_bug.cgi?id=748946

gst-libs/gst/video/gstvideoaggregator.c

@@ -54,10 +54,12 @@ static void gst_videoaggregator_reset_qos (GstVideoAggregator * vagg);
  ****************************************/
 
 #define DEFAULT_PAD_ZORDER 0
+#define DEFAULT_PAD_IGNORE_EOS FALSE
 enum
 {
   PROP_PAD_0,
   PROP_PAD_ZORDER,
+  PROP_PAD_IGNORE_EOS,
 };
 
 
@@ -87,6 +89,9 @@ gst_videoaggregator_pad_get_property (GObject * object, guint prop_id,
     case PROP_PAD_ZORDER:
       g_value_set_uint (value, pad->zorder);
       break;
+    case PROP_PAD_IGNORE_EOS:
+      g_value_set_boolean (value, pad->ignore_eos);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -116,6 +121,9 @@ gst_videoaggregator_pad_set_property (GObject * object, guint prop_id,
           (GCompareFunc) pad_zorder_compare);
       GST_OBJECT_UNLOCK (vagg);
       break;
+    case PROP_PAD_IGNORE_EOS:
+      pad->ignore_eos = g_value_get_boolean (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -304,6 +312,11 @@ gst_videoaggregator_pad_class_init (GstVideoAggregatorPadClass * klass)
       g_param_spec_uint ("zorder", "Z-Order", "Z Order of the picture",
           0, 10000, DEFAULT_PAD_ZORDER,
           G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));
+  g_object_class_install_property (gobject_class, PROP_PAD_IGNORE_EOS,
+      g_param_spec_boolean ("ignore-eos", "Ignore EOS", "Aggregate the last "
+          "frame on pads that are EOS till they are released",
+          DEFAULT_PAD_IGNORE_EOS,
+          G_PARAM_READWRITE | GST_PARAM_CONTROLLABLE | G_PARAM_STATIC_STRINGS));
 
   g_type_class_add_private (klass, sizeof (GstVideoAggregatorPadPrivate));
 
@@ -322,6 +335,7 @@ gst_videoaggregator_pad_init (GstVideoAggregatorPad * vaggpad)
       GstVideoAggregatorPadPrivate);
 
   vaggpad->zorder = DEFAULT_PAD_ZORDER;
+  vaggpad->ignore_eos = DEFAULT_PAD_IGNORE_EOS;
   vaggpad->aggregated_frame = NULL;
   vaggpad->priv->converted_buffer = NULL;
 
@@ -1112,6 +1126,12 @@ gst_videoaggregator_fill_queues (GstVideoAggregator * vagg,
         continue;
       }
     } else {
+      if (is_eos && pad->ignore_eos) {
+        eos = FALSE;
+        GST_DEBUG_OBJECT (pad, "ignoring EOS and re-using previous buffer");
+        continue;
+      }
+
       if (pad->priv->end_time != -1) {
         if (pad->priv->end_time <= output_start_time) {
           pad->priv->start_time = pad->priv->end_time = -1;

gst-libs/gst/video/gstvideoaggregatorpad.h

@@ -73,6 +73,7 @@ struct _GstVideoAggregatorPad
 
   /* properties */
   guint zorder;
+  gboolean ignore_eos;
 
   /* < private > */
   GstVideoAggregatorPadPrivate *priv;