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/* GStreamer
* Copyright (C) 2025 Seungha Yang <seungha@centricular.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/*
* Test application demonstrating the "resync" signal of GstClockSync.
*
* This example builds a simple pipeline using:
* videotestsrc ! timeoverlay ! clocksync ! autovideosink
*
* It simulates a temporary upstream stall by inserting blocking pad probe.
* After some delay, the probe is removed and the "resync" signal is emitted to
* request recalculation of the ts-offset on the next incoming buffer.
*
* This demonstrates how "resync" signal can be used to recover a correct
* ts-offset when buffer running-time progression becomes non-linear
* while keeping the element state unchanged.
*/
#include <gst/gst.h>
static GMainLoop *loop = NULL;
typedef struct
{
GstElement *clocksync;
GstPad *sinkpad;
gulong block_id;
} TestData;
static gboolean
bus_call (GstBus * bus, GstMessage * msg, gpointer data)
{
switch (GST_MESSAGE_TYPE (msg)) {
case GST_MESSAGE_EOS:{
g_print ("End-of-stream\n");
g_main_loop_quit (loop);
break;
}
case GST_MESSAGE_ERROR:{
gchar *debug;
GError *err;
gst_message_parse_error (msg, &err, &debug);
gst_printerrln ("Debugging info: %s", (debug) ? debug : "none");
g_free (debug);
g_print ("Error: %s\n", err->message);
g_clear_error (&err);
g_main_loop_quit (loop);
break;
}
default:
break;
}
return TRUE;
}
static gboolean
shutdown_cb (gpointer user_data)
{
g_main_loop_quit (loop);
return G_SOURCE_REMOVE;
}
static gboolean
after_blocking_timeout_cb (TestData * test_data)
{
gst_println ("Unblock and schedule resync");
/* Clocksync will calculate new ts-offset on the next buffer */
g_signal_emit_by_name (test_data->clocksync, "resync");
/* Unblock pad now */
gst_pad_remove_probe (test_data->sinkpad, test_data->block_id);
/* Shutdown pipeline after 10 seconds */
g_timeout_add_seconds (10, shutdown_cb, NULL);
return G_SOURCE_REMOVE;
}
static GstPadProbeReturn
clocksync_pad_blocked_cb (GstPad * pad, GstPadProbeInfo * info,
gpointer user_data)
{
return GST_PAD_PROBE_OK;
}
static gboolean
timeout_cb (TestData * test_data)
{
test_data->block_id = gst_pad_add_probe (test_data->sinkpad,
GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM,
clocksync_pad_blocked_cb, NULL, NULL);
gst_println
("Blocking pad probe added, waiting for 5 seconds for unblocking");
g_timeout_add_seconds (5, (GSourceFunc) after_blocking_timeout_cb, test_data);
return G_SOURCE_REMOVE;
}
gint
main (gint argc, gchar * argv[])
{
GstElement *pipeline;
GstBus *bus;
guint bus_watch_id;
GError *err = NULL;
TestData test_data;
gst_init (&argc, &argv);
loop = g_main_loop_new (NULL, FALSE);
pipeline =
gst_parse_launch
("videotestsrc ! timeoverlay ! clocksync name=c ! autovideosink sync=false",
&err);
if (!pipeline) {
gst_println ("Couldn't construct pipeline, %s", err->message);
g_clear_error (&err);
return 1;
}
test_data.clocksync = gst_bin_get_by_name (GST_BIN (pipeline), "c");
test_data.sinkpad = gst_element_get_static_pad (test_data.clocksync, "sink");
/* Enable automatic ts-offset calculation. "resync" signal will have an effect
* only if sync-to-first is enabled */
g_object_set (test_data.clocksync, "sync-to-first", TRUE, NULL);
/* Add 5 seconds timer to add blocking pad probe */
g_timeout_add_seconds (5, (GSourceFunc) timeout_cb, &test_data);
bus = gst_element_get_bus (pipeline);
bus_watch_id = gst_bus_add_watch (bus, bus_call, loop);
gst_object_unref (bus);
gst_element_set_state (pipeline, GST_STATE_PLAYING);
g_main_loop_run (loop);
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (test_data.sinkpad);
gst_object_unref (test_data.clocksync);
gst_object_unref (pipeline);
g_source_remove (bus_watch_id);
g_main_loop_unref (loop);
return 0;
}
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