Display no signal image if video sender is closed - c++

Question

If I close the sender in this example, the video displayed by the receiver freezes. Is there a way to display a static no signal image instead, for example an all blue image, and have the video return when the sender restarts?
Sender
gst-launch-1.0 videotestsrc ! video/x-raw,format=GRAY8 ! videoconvert ! x264enc pass=qual quantizer=20 tune=zerolatency ! rtph264pay ! udpsink host=127.0.0.1 port=5000
Receiver
gst-launch-1.0 udpsrc port=5000 ! application/x-rtp ! rtph264depay ! avdec_h264 ! videoconvert ! autovideosink
EDIT
This code seems to come close, but for some reason if I add in the videotestsrc by uncommenting the commented out lines, the udpsrc no longer calls the timeout callback:
// g++ gst_client.cpp `pkg-config --cflags gstreamer-1.0` `pkg-config --libs gstreamer-1.0`
#include <gst/gst.h>
#include <cstdlib>
#include <cstdio>
struct gstreamer_data {
GstElement* pipeline;
GstElement* no_signal_source;
GstElement* udp_source;
GstElement* rtp_decoder;
GstElement* video_decoder;
GstElement* input_selector;
GstElement* video_converter;
GstElement* video_sink;
gulong signal_handler_id;
GMainLoop* main_loop;
};
static void element_callback(GstBus* bus, GstMessage* message, gstreamer_data* data);
static GstPadProbeReturn have_data_callback(GstPad* pad, GstPadProbeInfo *info, gstreamer_data* user_data);
static GstPadProbeReturn have_data_callback(GstPad* pad, GstPadProbeInfo *info, gstreamer_data* user_data) {
GstBus* bus;
printf("have data\n");
bus = gst_element_get_bus(user_data->pipeline);
user_data->signal_handler_id = g_signal_connect(G_OBJECT(bus), "message::element", (GCallback) element_callback, user_data);
gst_object_unref(bus);
return GST_PAD_PROBE_REMOVE;
}
static void element_callback(GstBus* bus, GstMessage* message, gstreamer_data* data) {
const GstStructure* st = gst_message_get_structure(message);
GstPad* pad;
if (GST_MESSAGE_TYPE(message) == GST_MESSAGE_ELEMENT) {
if (gst_structure_has_name(st, "GstUDPSrcTimeout")) {
printf("Timeout received from udpsrc\n");
g_signal_handler_disconnect(G_OBJECT(bus), data->signal_handler_id);
pad = gst_element_get_static_pad(data->udp_source, "src");
gst_pad_add_probe(pad, GST_PAD_PROBE_TYPE_BUFFER, (GstPadProbeCallback) have_data_callback, data, NULL);
}
}
}
static void error_callback(GstBus* bus, GstMessage* message, gstreamer_data* data) {
(void) bus;
GError* err;
gchar* debug_info;
gst_message_parse_error(message, &err, &debug_info);
g_printerr("Error received from element %s: %s\n", GST_OBJECT_NAME(message->src), err->message);
g_printerr("Debugging information: %s\n", debug_info ? debug_info : "none");
g_clear_error(&err);
g_free(debug_info);
g_main_loop_quit(data->main_loop);
}
int main() {
gstreamer_data data;
GstStateChangeReturn ret;
GstBus* bus;
GstPad* pad;
gst_init(NULL, NULL);
data.no_signal_source = gst_element_factory_make("videotestsrc", "no_signal_source");
g_object_set(G_OBJECT(data.no_signal_source),
"pattern", 6,
NULL);
data.udp_source = gst_element_factory_make("udpsrc", "udp_source");
g_object_set(G_OBJECT(data.udp_source),
"port", 5000,
"caps", gst_caps_new_empty_simple("application/x-rtp"),
"timeout", 1000000000,
NULL);
data.rtp_decoder = gst_element_factory_make("rtph264depay", "rtp_decoder");
data.video_decoder = gst_element_factory_make("avdec_h264", "video_decoder");
data.input_selector = gst_element_factory_make("input-selector", "input_selector");
data.video_converter = gst_element_factory_make("videoconvert", "video_converter");
data.video_sink = gst_element_factory_make("autovideosink", "video_sink");
data.pipeline = gst_pipeline_new("pipeline");
if (
!data.pipeline ||
!data.no_signal_source ||
!data.udp_source ||
!data.rtp_decoder ||
!data.video_decoder ||
!data.input_selector ||
!data.video_converter ||
!data.video_sink
)
{
g_printerr("Not all elements could be created.\n");
exit(-1);
}
gst_bin_add_many(
GST_BIN(data.pipeline),
//data.no_signal_source,
data.udp_source,
data.rtp_decoder,
data.video_decoder,
data.input_selector,
data.video_converter,
data.video_sink,
NULL);
if (gst_element_link_many(
data.udp_source,
data.rtp_decoder,
data.video_decoder,
NULL) != TRUE)
{
g_printerr("Elements could not be linked.\n");
gst_object_unref(data.pipeline);
exit(-1);
}
GstPad* src_1 = gst_element_get_static_pad(data.video_decoder, "src");
GstPad* sink_1 = gst_element_get_request_pad(data.input_selector, "sink_%u");
gst_pad_link(src_1, sink_1);
/*
GstPad* src_2 = gst_element_get_static_pad(data.no_signal_source, "src");
GstPad* sink_2 = gst_element_get_request_pad(data.input_selector, "sink_%u");
gst_pad_link(src_2, sink_2);
*/
g_object_set(G_OBJECT(data.input_selector),
"active-pad", sink_1,
NULL);
if (gst_element_link_many(
data.input_selector,
data.video_converter,
data.video_sink,
NULL) != TRUE)
{
g_printerr("Elements could not be linked.\n");
gst_object_unref(data.pipeline);
exit(-1);
}
pad = gst_element_get_static_pad(data.udp_source, "src");
gst_pad_add_probe(pad, GST_PAD_PROBE_TYPE_BUFFER, (GstPadProbeCallback) have_data_callback, &data, NULL);
bus = gst_element_get_bus(data.pipeline);
gst_bus_add_signal_watch(bus);
data.signal_handler_id = g_signal_connect(G_OBJECT(bus), "message::error", (GCallback) error_callback, &data);
gst_object_unref(bus);
ret = gst_element_set_state(data.pipeline, GST_STATE_PLAYING);
if (ret == GST_STATE_CHANGE_FAILURE) {
g_printerr("Unable to set the pipeline to the playing state.\n");
gst_object_unref(data.pipeline);
exit(-1);
}
data.main_loop = g_main_loop_new(NULL, FALSE);
g_main_loop_run(data.main_loop);
return 0;
}
EDIT
This code seems fine until I uncomment the selection of the active pad in the callbacks. Do I need to do something before I change the active pad, like stop the pipeline?
// g++ gst_client.cpp `pkg-config --cflags gstreamer-1.0` `pkg-config --libs gstreamer-1.0`
#include <gst/gst.h>
#include <cstdlib>
#include <cstdio>
struct gstreamer_data {
GstElement* pipeline;
GstElement* video_source;
GstElement* udp_source;
GstElement* rtp_decoder;
GstElement* video_decoder;
GstElement* video_converter;
GstElement* input_selector;
GstPad* sink_1;
GstPad* sink_2;
GstElement* video_sink;
gulong signal_handler_id;
GMainLoop* main_loop;
};
static void element_callback(GstBus* bus, GstMessage* message, gstreamer_data* data);
static GstPadProbeReturn have_data_callback(GstPad* pad, GstPadProbeInfo *info, gstreamer_data* user_data);
static GstPadProbeReturn have_data_callback(GstPad* pad, GstPadProbeInfo *info, gstreamer_data* user_data) {
GstBus* bus;
printf("have data\n");
/*
g_object_set(G_OBJECT(user_data->input_selector),
"active-pad", user_data->sink_2,
NULL);
*/
bus = gst_element_get_bus(user_data->pipeline);
user_data->signal_handler_id = g_signal_connect(G_OBJECT(bus), "message::element", (GCallback) element_callback, user_data);
gst_object_unref(bus);
return GST_PAD_PROBE_REMOVE;
}
static void element_callback(GstBus* bus, GstMessage* message, gstreamer_data* data) {
const GstStructure* st = gst_message_get_structure(message);
GstPad* pad;
if (GST_MESSAGE_TYPE(message) == GST_MESSAGE_ELEMENT) {
if (gst_structure_has_name(st, "GstUDPSrcTimeout")) {
printf("no data\n");
/*
g_object_set(G_OBJECT(data->input_selector),
"active-pad", data->sink_1,
NULL);
*/
g_signal_handler_disconnect(G_OBJECT(bus), data->signal_handler_id);
pad = gst_element_get_static_pad(data->udp_source, "src");
gst_pad_add_probe(pad, GST_PAD_PROBE_TYPE_BUFFER, (GstPadProbeCallback) have_data_callback, data, NULL);
gst_object_unref(pad);
}
}
}
static void error_callback(GstBus* bus, GstMessage* message, gstreamer_data* data) {
(void) bus;
GError* err;
gchar* debug_info;
gst_message_parse_error(message, &err, &debug_info);
g_printerr("Error received from element %s: %s\n", GST_OBJECT_NAME(message->src), err->message);
g_printerr("Debugging information: %s\n", debug_info ? debug_info : "none");
g_clear_error(&err);
g_free(debug_info);
g_main_loop_quit(data->main_loop);
}
int main() {
gstreamer_data data;
GstStateChangeReturn ret;
GstBus* bus;
GstPad* pad;
gst_init(NULL, NULL);
data.video_source = gst_element_factory_make("videotestsrc", "video_source");
g_object_set(G_OBJECT(data.video_source),
"pattern", 6,
"is-live", true,
NULL);
data.udp_source = gst_element_factory_make("udpsrc", "udp_source");
g_object_set(G_OBJECT(data.udp_source),
"port", 5000,
"caps", gst_caps_new_empty_simple("application/x-rtp"),
"timeout", 1000000000,
NULL);
data.rtp_decoder = gst_element_factory_make("rtph264depay", "rtp_decoder");
data.video_decoder = gst_element_factory_make("avdec_h264", "video_decoder");
data.video_converter = gst_element_factory_make("videoconvert", "video_converter");
data.input_selector = gst_element_factory_make("input-selector", "input_selector");
data.video_sink = gst_element_factory_make("autovideosink", "video_sink");
data.pipeline = gst_pipeline_new("pipeline");
if (
!data.pipeline ||
!data.video_source ||
!data.udp_source ||
!data.rtp_decoder ||
!data.video_decoder ||
!data.video_converter ||
!data.input_selector ||
!data.video_sink
)
{
g_printerr("Not all elements could be created.\n");
exit(-1);
}
gst_bin_add_many(
GST_BIN(data.pipeline),
data.video_source,
data.udp_source,
data.rtp_decoder,
data.video_decoder,
data.video_converter,
data.input_selector,
data.video_sink,
NULL);
if (gst_element_link_many(
data.udp_source,
data.rtp_decoder,
data.video_decoder,
data.video_converter,
NULL) != TRUE)
{
g_printerr("Elements could not be linked.\n");
gst_object_unref(data.pipeline);
exit(-1);
}
GstPad* src_1 = gst_element_get_static_pad(data.video_source, "src");
data.sink_1 = gst_element_get_request_pad(data.input_selector, "sink_%u");
gst_pad_link(src_1, data.sink_1);
gst_object_unref(src_1);
GstPad* src_2 = gst_element_get_static_pad(data.video_converter, "src");
data.sink_2 = gst_element_get_request_pad(data.input_selector, "sink_%u");
gst_pad_link(src_2, data.sink_2);
gst_object_unref(src_2);
if (gst_element_link_many(
data.input_selector,
data.video_sink,
NULL) != TRUE)
{
g_printerr("Elements could not be linked.\n");
gst_object_unref(data.pipeline);
exit(-1);
}
pad = gst_element_get_static_pad(data.udp_source, "src");
gst_pad_add_probe(pad, GST_PAD_PROBE_TYPE_BUFFER, (GstPadProbeCallback) have_data_callback, &data, NULL);
gst_object_unref(pad);
bus = gst_element_get_bus(data.pipeline);
gst_bus_add_signal_watch(bus);
data.signal_handler_id = g_signal_connect(G_OBJECT(bus), "message::error", (GCallback) error_callback, &data);
gst_object_unref(bus);
ret = gst_element_set_state(data.pipeline, GST_STATE_PLAYING);
if (ret == GST_STATE_CHANGE_FAILURE) {
g_printerr("Unable to set the pipeline to the playing state.\n");
gst_object_unref(data.pipeline);
exit(-1);
}
data.main_loop = g_main_loop_new(NULL, FALSE);
g_main_loop_run(data.main_loop);
return 0;
}
EDIT:
I seems fine all of a sudden. I don't understand. Is this suitable code? Can it be improved?
EDIT:
Setting a width and height on the videotestsrc in the sender seems to make it work. If I remove those, it breaks. Why?