Udpsrc to autovideosink

[Ian Davidson]

Hi Christian,

Some elements have Dynamic Source Pads - so they do not have the source 
pad until they have examined what is coming in to them. Such elements 
cannot be linked until the element has created the pad.

You need to examine the documentation for each element to see whether 
the pads are static or dynamic.  If it is a dynamic pad, you need to 
watch for messages from that element - and then dynamically link when 
the pad has been created.

gst-launch is clever enough to know that it has to do that!


On 13/09/2017 08:49, chrplus3 wrote:
> I've just seen, that raw text is not working in this mailing list.
>
> Here is the code again:
> Working:
> gst-launch-1.0 -v \
> udpsrc port=5016 caps="application/x-rtp,encoding-name=JPEG,payload=26" ! \
> rtpjpegdepay ! jpegparse ! queue max-size-time=0 max-size-buffers=0 !
> jpegdec ! autovideosink
>
> Not working (because element link failed):
> ...
> GstElement *pipeline, *source, *depay, *parse, *queue, *decode, *sink;
> GstCaps *caps;
> gst_init(&argc, &argv);
> pipeline = gst_pipeline_new("pipe");
> source = gst_element_factory_make("udpsrc", "source");
> depay = gst_element_factory_make("rtpjpegdepay", "depay");
> parse = gst_element_factory_make("jpegparse", "parse");
> queue = gst_element_factory_make("queue", "queue");
> decode = gst_element_factory_make("jpegdec", "decode");
> sink = gst_element_factory_make("autovideosink", "sink");
> caps = gst_caps_new_simple(
> 	"video/x-rtp",
> 	"encoding-name", G_TYPE_STRING, "JPEG",
> 	"payload", G_TYPE_INT, 26, NULL);
> g_object_set(G_OBJECT(source),
> 	"port", 5016,
> 	"caps", caps, NULL);
> g_object_set(G_OBJECT(queue),
> 	"max-size-time", 0,
> 	"max-size-buffers", 0, NULL);
> gst_bin_add_many(GST_BIN(pipeline), source, depay, parse, queue, decode,
> sink, NULL);
> if(!gst_element_link_many(source, depay, parse, queue, decode, sink, NULL))
> {
> 	g_printerr("Elements could not be linked.\n");
> 	gst_object_unref(pipeline);
> 	return -1;
> }
> gst_element_set_state(pipeline, GST_STATE_PLAYING);
> ...
>
> --
Ian Davidson