GstEvent *event;gboolean result;...// construct a seek event to play the media from second 2 to 5, flush// the pipeline to decrease latency.event = gst_event_new_seek (1.0,GST_FORMAT_TIME,GST_SEEK_FLAG_FLUSH,GST_SEEK_TYPE_SET, 2 * GST_SECOND,GST_SEEK_TYPE_SET, 5 * GST_SECOND);...result = gst_element_send_event (video_sink, event);if (!result)g_warning ("seek failed");...

#include <string.h>
#include <stdio.h>
#include <gst/gst.h>typedef struct _CustomData
{GstElement *pipeline;GstElement *video_sink;GMainLoop *loop;gboolean playing;             /* Playing or Paused */gdouble rate;                 /* Current playback rate (can be negative) */
} CustomData;/* Send seek event to change rate */
static void
send_seek_event (CustomData * data)
{gint64 position;GstEvent *seek_event;/* Obtain the current position, needed for the seek event */if (!gst_element_query_position (data->pipeline, GST_FORMAT_TIME, &position)) {g_printerr ("Unable to retrieve current position.\n");return;}/* Create the seek event */if (data->rate > 0) {seek_event =gst_event_new_seek (data->rate, GST_FORMAT_TIME,GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE, GST_SEEK_TYPE_SET,position, GST_SEEK_TYPE_END, 0);} else {seek_event =gst_event_new_seek (data->rate, GST_FORMAT_TIME,GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE, GST_SEEK_TYPE_SET, 0,GST_SEEK_TYPE_SET, position);}if (data->video_sink == NULL) {/* If we have not done so, obtain the sink through which we will send the seek events */g_object_get (data->pipeline, "video-sink", &data->video_sink, NULL);}/* Send the event */gst_element_send_event (data->video_sink, seek_event);g_print ("Current rate: %g\n", data->rate);
}/* Process keyboard input */
static gboolean
handle_keyboard (GIOChannel * source, GIOCondition cond, CustomData * data)
{gchar *str = NULL;if (g_io_channel_read_line (source, &str, NULL, NULL,NULL) != G_IO_STATUS_NORMAL) {return TRUE;}switch (g_ascii_tolower (str[0])) {case 'p':data->playing = !data->playing;gst_element_set_state (data->pipeline,data->playing ? GST_STATE_PLAYING : GST_STATE_PAUSED);g_print ("Setting state to %s\n", data->playing ? "PLAYING" : "PAUSE");break;case 's':if (g_ascii_isupper (str[0])) {data->rate *= 2.0;} else {data->rate /= 2.0;}send_seek_event (data);break;case 'd':data->rate *= -1.0;send_seek_event (data);break;case 'n':if (data->video_sink == NULL) {/* If we have not done so, obtain the sink through which we will send the step events */g_object_get (data->pipeline, "video-sink", &data->video_sink, NULL);}gst_element_send_event (data->video_sink,gst_event_new_step (GST_FORMAT_BUFFERS, 1, ABS (data->rate), TRUE,FALSE));g_print ("Stepping one frame\n");break;case 'q':g_main_loop_quit (data->loop);break;default:break;}g_free (str);return TRUE;
}int
main (int argc, char *argv[])
{CustomData data;GstStateChangeReturn ret;GIOChannel *io_stdin;/* Initialize GStreamer */gst_init (&argc, &argv);/* Initialize our data structure */memset (&data, 0, sizeof (data));/* Print usage map */g_print ("USAGE: Choose one of the following options, then press enter:\n"" 'P' to toggle between PAUSE and PLAY\n"" 'S' to increase playback speed, 's' to decrease playback speed\n"" 'D' to toggle playback direction\n"" 'N' to move to next frame (in the current direction, better in PAUSE)\n"" 'Q' to quit\n");/* Build the pipeline */data.pipeline =gst_parse_launch("playbin uri=https://www.freedesktop.org/software/gstreamer-sdk/data/media/sintel_trailer-480p.webm",NULL);/* Add a keyboard watch so we get notified of keystrokes */
#ifdef G_OS_WIN32io_stdin = g_io_channel_win32_new_fd (fileno (stdin));
#elseio_stdin = g_io_channel_unix_new (fileno (stdin));
#endifg_io_add_watch (io_stdin, G_IO_IN, (GIOFunc) handle_keyboard, &data);/* Start playing */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);return -1;}data.playing = TRUE;data.rate = 1.0;/* Create a GLib Main Loop and set it to run */data.loop = g_main_loop_new (NULL, FALSE);g_main_loop_run (data.loop);/* Free resources */g_main_loop_unref (data.loop);g_io_channel_unref (io_stdin);gst_element_set_state (data.pipeline, GST_STATE_NULL);if (data.video_sink != NULL)gst_object_unref (data.video_sink);gst_object_unref (data.pipeline);return 0;
}

gcc basic-tutorial-7.c -o basic-tutorial-7 `pkg-config --cflags --libs gstreamer-1.0`

/* Process keyboard input */
static gboolean handle_keyboard (GIOChannel *source, GIOCondition cond, CustomData *data) {gchar *str = NULL;if (g_io_channel_read_line (source, &str, NULL, NULL, NULL) != G_IO_STATUS_NORMAL) {return TRUE;}switch (g_ascii_tolower (str[0])) {case 'p':data->playing = !data->playing;gst_element_set_state (data->pipeline, data->playing ? GST_STATE_PLAYING : GST_STATE_PAUSED);g_print ("Setting state to %s\n", data->playing ? "PLAYING" : "PAUSE");break;

case 's':if (g_ascii_isupper (str[0])) {data->rate *= 2.0;} else {data->rate /= 2.0;}send_seek_event (data);break;
case 'd':data->rate *= -1.0;send_seek_event (data);break;

/* Send seek event to change rate */
static void send_seek_event (CustomData *data) {gint64 position;GstEvent *seek_event;/* Obtain the current position, needed for the seek event */if (!gst_element_query_position (data->pipeline, GST_FORMAT_TIME, &position)) {g_printerr ("Unable to retrieve current position.\n");return;}

/* Create the seek event */
if (data->rate > 0) {seek_event = gst_event_new_seek (data->rate, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE,GST_SEEK_TYPE_SET, position, GST_SEEK_TYPE_END, 0);
} else {seek_event = gst_event_new_seek (data->rate, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE,GST_SEEK_TYPE_SET, 0, GST_SEEK_TYPE_SET, position);
}

if (data->video_sink == NULL) {/* If we have not done so, obtain the sink through which we will send the seek events */g_object_get (data->pipeline, "video-sink", &data->video_sink, NULL);
}
/* Send the event */
gst_element_send_event (data->video_sink, seek_event);

case 'n':if (data->video_sink == NULL) {/* If we have not done so, obtain the sink through which we will send the step events */g_object_get (data->pipeline, "video-sink", &data->video_sink, NULL);}gst_element_send_event (data->video_sink,gst_event_new_step (GST_FORMAT_BUFFERS, 1, ABS (data->rate), TRUE, FALSE));g_print ("Stepping one frame\n");break;