Linking Gstrplaybin to custom video sink videoconvert and sink not linking gstreamer - c

Question

Trying to make gstreamer application from the pipeline: gst-launch-1.0 playbin uri=rtsp:// video-sink="videoconvert ! video/x-raw,width=720, height=480 ! ximagesink"
Getting error to link elements. Posting my code:
#include <gst/gst.h>
int main(int argc, char *argv[]) {
GstElement *source, *videosink, *pipeline, *videoconvert;
GstCaps *capsFilter;
GstBus *bus;
GstMessage *msg;
GstPad *pad;
gboolean link_ok;
/* Initialize GStreamer */
gst_init (&argc, &argv);
/* Create Elements */
pipeline = gst_pipeline_new("my-pipeline");
source = gst_element_factory_make ("playbin", "source");
videoconvert = gst_element_factory_make("videoconvert", "convert");
videosink = gst_element_factory_make("ximagesink", "autovideosink");
/* set property value */
g_object_set (source, "uri", "rtsp:<file location>", NULL);
if (!pipeline || !source || !videoconvert || !videosink)
{
g_printerr ("Not all elements could be created.\n");
return;
}
gst_bin_add_many (GST_BIN(pipeline), videoconvert, videosink, NULL);
capsFilter = gst_caps_new_simple("video/x-raw",
"width", G_TYPE_INT, 176,
"height", G_TYPE_INT, 144,
NULL);
link_ok = gst_element_link_filtered(videoconvert,videosink, capsFilter);
gst_caps_unref (capsFilter);
if (!link_ok) {
g_warning ("Failed to link element1 and element2!");
}
if (gst_element_link_many( videoconvert, videosink, NULL) != TRUE) {
g_print ("Failed to link some elements .....1 !\n");
gst_object_unref (pipeline);
return -1;
}
/* Start playing */
gst_element_set_state (source, GST_STATE_PLAYING);
/* Wait until error or EOS */
bus = gst_element_get_bus (source);
msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,
GST_MESSAGE_ERROR | GST_MESSAGE_EOS);

Answer 1

It should be noted that the playbin element gives a full pipeline from src to sink, so the pipeline without the sink stuff would play perfectly:
gst-launch-1.0 playbin uri=rtsp://127.0.0.1:8551/test
The correct pipeline that you want to create is next:
gst-launch-1.0 playbin uri=rtsp://127.0.0.1:8551/test video-sink="videoconvert ! video/x-raw,width=320,height=240 ! ximagesink"
In order to embed this into GStreamer application, it is not necessary to link all the elements. Instead of that, the necessary steps to make are to build a custom video output bin and set it to playbin's video-sink property. In other words, the way to go is create a bin and link the necessary elements and then tell playbin to use it via it's video-sink property. It is also necessary to create a GhostPad for the bin and point it to the sink pad of the first element within the bin.
This is the result:
#include <gst/gst.h>
int main(int argc, char *argv[]) {
GstElement *source, *videosink, *pipeline, *videoconvert, *customoutput;
GstCaps *capsFilter;
GstBus *bus;
GstMessage *msg;
GstPad *pad;
gboolean add_ok;
gboolean link_ok;
GstStateChangeReturn ret;
GMainLoop *loop;
/* Initialize GStreamer */
gst_init (&argc, &argv);
loop = g_main_loop_new (NULL, FALSE);
/* Create Elements */
pipeline = gst_pipeline_new("my-pipeline");
source = gst_element_factory_make ("playbin", "source");
videoconvert = gst_element_factory_make("videoconvert", "videoconvert");
capsFilter = gst_caps_new_simple("video/x-raw",
"width", G_TYPE_INT, 320,
"height", G_TYPE_INT, 240,
NULL);
videosink = gst_element_factory_make("ximagesink", "videosink");
customoutput = gst_bin_new("customoutput");
// It is possible to create the bin like this
// Ghost pads on the bin for unlinked source or sink pads within the bin can automatically be created
// customoutput = gst_parse_bin_from_description ("videoconvert ! video/x-raw,width=320 ! ximagesink", TRUE, NULL);
gst_bin_add_many (GST_BIN (customoutput), videoconvert, videosink, NULL);
link_ok = gst_element_link_filtered(videoconvert,videosink, capsFilter);
gst_caps_unref (capsFilter);
if (!link_ok) {
g_warning ("Failed to link element1 and element2!");
}
GstPad *sinkpad,*ghost_sinkpad;
sinkpad = gst_element_get_static_pad (videoconvert, "sink");
ghost_sinkpad = gst_ghost_pad_new ("sink", sinkpad);
gst_pad_set_active (ghost_sinkpad, TRUE);
gst_element_add_pad (customoutput, ghost_sinkpad);
/* set property value */
g_object_set (source, "video-sink", customoutput, NULL);
g_object_set (source, "uri", "rtsp://127.0.0.1:8551/test", NULL);
if (!pipeline || !source || !videoconvert || !capsFilter || !videosink || !customoutput)
{
g_printerr ("Not all elements could be created.\n");
return -1;
}
gst_bin_add_many (GST_BIN(pipeline), source,NULL);
// Start playing */
ret = gst_element_set_state (pipeline, GST_STATE_PLAYING);
g_print ("Running...\n");
g_main_loop_run (loop);
if (ret == GST_STATE_CHANGE_FAILURE) {
g_printerr ("Unable to set the pipeline to the playing state.\n");
gst_object_unref (pipeline);
return -1;
}
/* Wait until error or EOS */
//bus = gst_element_get_bus (pipeline);
//msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,GST_MESSAGE_ERROR | GST_MESSAGE_EOS);
/* Free resources */
gst_object_unref (bus);
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (pipeline);
g_main_loop_unref (loop);
return 0;
}