gst_parse_launch differs output from command line gst_launch

I have a pipeline like this, which works with gst-launch-1.0

gst-launch-1.0 v4l2src device='/dev/video0' ! 'video/x-raw,format=(string)YUY2,width=(int)640,height=(int)480' ! nvvidconv ! 'video/x-raw(memory:NVMM),format=(string)NV12,width=(int)640,height=(int)480' ! nvvidconv ! 'video/x-raw,format=(string)NV12,width=(int)640,height=(int)480' ! nvvideoconvert ! 'video/x-raw(memory:NVMM),format=(string)NV12,width=(int)640,height=(int)480' ! mux.sink_0 nvstreammux live-source=1 name=mux batch-size=1 width=640 height=480 ! nvinfer config-file-path=/opt/nvidia/deepstream/deepstream-4.0/sources/apps/sample_apps/deepstream-test1/dstest1_pgie_config.txt batch-size=1 ! nvmultistreamtiler rows=1 columns=1 width=640 height=480 ! nvvideoconvert ! nvdsosd ! nvegltransform ! nveglglessink sync=false -v

In my c application, such as below which executes the same command line, it doesn't display any window.

#include <gst/gst.h>

int
main (int argc, char *argv[])
{
  GstElement *pipeline;
  GstBus *bus;
  GstMessage *msg;

  /* Initialize GStreamer */
  gst_init (&argc, &argv);

  /* Build the pipeline */
  pipeline =
      gst_parse_launch
      ("v4l2src device='/dev/video0' ! 'video/x-raw,format=(string)YUY2,width=(int)640,height=(int)480' ! nvvidconv ! 'video/x-raw(memory:NVMM),format=(string)NV12,width=(int)640,height=(int)480' ! nvvidconv ! 'video/x-raw,format=(string)NV12,width=(int)640,height=(int)480' ! nvvideoconvert ! 'video/x-raw(memory:NVMM),format=(string)NV12,width=(int)640,height=(int)480' ! mux.sink_0 nvstreammux live-source=1 name=mux batch-size=1 width=640 height=480 ! nvinfer config-file-path=/opt/nvidia/deepstream/deepstream-4.0/sources/apps/sample_apps/deepstream-test1/dstest1_pgie_config.txt batch-size=1 ! nvmultistreamtiler rows=1 columns=1 width=640 height=480 ! nvvideoconvert ! nvdsosd ! nvegltransform ! nveglglessink sync=false -v",
      NULL);

  /* Start playing */
  gst_element_set_state (pipeline, GST_STATE_PLAYING);

  /* 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 */
  if (msg != NULL)
    gst_message_unref (msg);
  gst_object_unref (bus);
  gst_element_set_state (pipeline, GST_STATE_NULL);
  gst_object_unref (pipeline);
  return 0;
}

Solution

That's why you should check for errors. You pipeline description has a -v at the end which is an option to the gst-launch-1.0 application but is not part of a valid pipeline description.