gst-decoder.c: advertise support for GstVideoMeta

This way, upstream decoder the produce frame with special strides and
offsets won't have to copy the frames. This also ensure DMABuf can be
delivered to kmscube.

Signed-off-by: Nicolas Dufresne <nicolas@ndufresne.ca>

1 files changed, 25 insertions, 0 deletions

diff --git a/gst-decoder.c b/gst-decoder.c
index 17d5407..044c07d 100644
--- a/gst-decoder.c
+++ b/gst-decoder.c
@@ -234,11 +234,26 @@ bus_watch_cb(GstBus *bus, GstMessage *msg, gpointer user_data)
 	return TRUE;
 }
 
+static GstPadProbeReturn
+appsink_query_cb(GstPad *pad G_GNUC_UNUSED, GstPadProbeInfo *info,
+	gpointer user_data G_GNUC_UNUSED)
+{
+	GstQuery *query = info->data;
+
+	if (GST_QUERY_TYPE (query) != GST_QUERY_ALLOCATION)
+	  return GST_PAD_PROBE_OK;
+
+	gst_query_add_allocation_meta(query, GST_VIDEO_META_API_TYPE, NULL);
+
+	return GST_PAD_PROBE_HANDLED;
+}
+
 struct decoder *
 video_init(const struct egl *egl, const struct gbm *gbm, const char *filename)
 {
 	struct decoder *dec;
 	GstElement *src, *decodebin;
+	GstPad *pad;
 	GstBus *bus;
 
 	dec = calloc(1, sizeof(*dec));
@@ -253,6 +268,16 @@ video_init(const struct egl *egl, const struct gbm *gbm, const char *filename)
 
 	dec->sink = gst_bin_get_by_name(GST_BIN(dec->pipeline), "sink");
 
+	/* Implement the allocation query using a pad probe. This probe will
+	 * adverstize support for GstVideoMeta, which avoid hardware accelerated
+	 * decoder that produce special strides and offsets from having to
+	 * copy the buffers.
+	 */
+	pad = gst_element_get_static_pad(dec->sink, "sink");
+	gst_pad_add_probe(pad, GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM,
+		appsink_query_cb, NULL, NULL);
+	gst_object_unref(pad);
+
 	src = gst_bin_get_by_name(GST_BIN(dec->pipeline), "src");
 	g_object_set(G_OBJECT(src), "location", filename, NULL);
 	gst_object_unref(src);