BadShmSeg when adding textoverlay dynamically

[Francisco Velázquez]

Dear GStreamer community,

I'm trying to add a text overlay on-the-fly but I am getting BadShmSeg error. The most simple pipeline to reproduce this error changes from:

videotestsrc ! ximagesink 

to: 

videotestsrc ! textoverlay text="Hello World!" ! imagesink.

The code is:
---------------------------

#include <gst/gst.h>

static GstPad *videosrc_blockpad;
static GstElement *videosrc, *videosink, *pipeline, *textoverlay;

static GstPadProbeReturn pad_probe_videosrc_cb(GstPad * videosrc_pad, GstPadProbeInfo * info, gpointer user_data){
    
    /* unlink videotestsrc from ximagesink */
    gst_element_set_state(videosink, GST_STATE_NULL);
    gst_bin_remove(GST_BIN(pipeline), videosink);

    /* adding the textoverlay */
    textoverlay = gst_element_factory_make("textoverlay", NULL);
    g_object_set(G_OBJECT (textoverlay), "text", "Hello World!", NULL);
    gst_bin_add_many(GST_BIN(pipeline), textoverlay, videosink, NULL);
    
    /* inserting the text overlay */
    gst_element_link_many(videosrc, textoverlay, videosink, NULL);
    
    /* I might need to setup a GST_STATE_PLAYING again. */
    gst_element_set_state(textoverlay, GST_STATE_PLAYING);
    gst_element_set_state(videosink, GST_STATE_PLAYING);
    
    gst_debug_set_threshold_from_string ("*:5", TRUE);
    
    return GST_PAD_PROBE_REMOVE;
}

static gboolean timeout_cb (gpointer user_data){
    
    gst_pad_add_probe (videosrc_blockpad, GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM, pad_probe_videosrc_cb, user_data, NULL);
    return FALSE;
}

int main (int argc, char **argv){
    GMainLoop *loop;
    
    /* init GStreamer */
    gst_init (&argc, &argv);
    loop = g_main_loop_new (NULL, FALSE);
    
    videosrc = gst_element_factory_make("videotestsrc", NULL);
    videosrc_blockpad = gst_element_get_static_pad(videosrc, "src");

    videosink = gst_element_factory_make("ximagesink", NULL);
    
    pipeline = gst_pipeline_new("pipeline");
    
    gst_bin_add_many(GST_BIN(pipeline), videosrc, videosink, NULL);
    
    gst_element_link_many(videosrc, videosink, NULL);

    gst_element_set_state(pipeline, GST_STATE_PLAYING);

    g_timeout_add_seconds (5, timeout_cb, loop);
    
    g_main_loop_run (loop);
    
    gst_element_set_state (pipeline, GST_STATE_NULL);
    
    gst_object_unref (pipeline);
    
    return 0;
}
—————————

The error log:

….

0:00:06.233014000 43633    0x1020ea230 DEBUG              videosink gstvideosink.c:117:void gst_video_sink_center_rect(GstVideoRectangle, GstVideoRectangle, GstVideoRectangle *, gboolean): source is 320x240 dest is 320x240, result is 320x240 with x,y 0x0
X Error of failed request:  BadShmSeg (invalid shared segment parameter)
  Major opcode of failed request:  132 (MIT-SHM)
  Minor opcode of failed request:  3 (X_ShmPutImage)
  Segment id in failed request:  0x600003
  Serial number of failed request:  41
  Current serial number in output stream:  42
Program ended with exit code: 1
———————————————————————————————————————————

Can somebody help me to find out what I'm doing wrong?

Thank you!

Francisco