blob: 6e081edc2987373401c07b155a805a8a346beeb3 [file] [log] [blame]
/*** block from ../../../docs/manual/advanced-dataaccess.xml ***/
#include <gst/gst.h>
#ifdef HAVE_GTK
#include <gtk/gtk.h>
#include <stdlib.h>
#define CAPS "video/x-raw,format=RGB,width=160,pixel-aspect-ratio=1/1"
main (int argc, char *argv[])
GstElement *pipeline, *sink;
gint width, height;
GstSample *sample;
gchar *descr;
GError *error = NULL;
gint64 duration, position;
GstStateChangeReturn ret;
gboolean res;
GstMapInfo map;
gst_init (&argc, &argv);
if (argc != 2) {
g_print ("usage: %s <uri>\n Writes snapshot.png in the current directory\n",
exit (-1);
/* create a new pipeline */
descr =
g_strdup_printf ("uridecodebin uri=%s ! videoconvert ! videoscale ! "
" appsink name=sink caps=\"" CAPS "\"", argv[1]);
pipeline = gst_parse_launch (descr, &error);
if (error != NULL) {
g_print ("could not construct pipeline: %s\n", error->message);
g_clear_error (&error);
exit (-1);
/* get sink */
sink = gst_bin_get_by_name (GST_BIN (pipeline), "sink");
/* set to PAUSED to make the first frame arrive in the sink */
ret = gst_element_set_state (pipeline, GST_STATE_PAUSED);
switch (ret) {
g_print ("failed to play the file\n");
exit (-1);
/* for live sources, we need to set the pipeline to PLAYING before we can
* receive a buffer. We don't do that yet */
g_print ("live sources not supported yet\n");
exit (-1);
/* This can block for up to 5 seconds. If your machine is really overloaded,
* it might time out before the pipeline prerolled and we generate an error. A
* better way is to run a mainloop and catch errors there. */
ret = gst_element_get_state (pipeline, NULL, NULL, 5 * GST_SECOND);
g_print ("failed to play the file\n");
exit (-1);
/* get the duration */
gst_element_query_duration (pipeline, GST_FORMAT_TIME, &duration);
if (duration != -1)
/* we have a duration, seek to 5% */
position = duration * 5 / 100;
/* no duration, seek to 1 second, this could EOS */
position = 1 * GST_SECOND;
/* seek to the a position in the file. Most files have a black first frame so
* by seeking to somewhere else we have a bigger chance of getting something
* more interesting. An optimisation would be to detect black images and then
* seek a little more */
gst_element_seek_simple (pipeline, GST_FORMAT_TIME,
/* get the preroll buffer from appsink, this block untils appsink really
* prerolls */
g_signal_emit_by_name (sink, "pull-preroll", &sample, NULL);
/* if we have a buffer now, convert it to a pixbuf. It's possible that we
* don't have a buffer because we went EOS right away or had an error. */
if (sample) {
GstBuffer *buffer;
GstCaps *caps;
GstStructure *s;
/* get the snapshot buffer format now. We set the caps on the appsink so
* that it can only be an rgb buffer. The only thing we have not specified
* on the caps is the height, which is dependant on the pixel-aspect-ratio
* of the source material */
caps = gst_sample_get_caps (sample);
if (!caps) {
g_print ("could not get snapshot format\n");
exit (-1);
s = gst_caps_get_structure (caps, 0);
/* we need to get the final caps on the buffer to get the size */
res = gst_structure_get_int (s, "width", &width);
res |= gst_structure_get_int (s, "height", &height);
if (!res) {
g_print ("could not get snapshot dimension\n");
exit (-1);
/* create pixmap from buffer and save, gstreamer video buffers have a stride
* that is rounded up to the nearest multiple of 4 */
buffer = gst_sample_get_buffer (sample);
/* Mapping a buffer can fail (non-readable) */
if (gst_buffer_map (buffer, &map, GST_MAP_READ)) {
#ifdef HAVE_GTK
pixbuf = gdk_pixbuf_new_from_data (,
GDK_COLORSPACE_RGB, FALSE, 8, width, height,
GST_ROUND_UP_4 (width * 3), NULL, NULL);
/* save the pixbuf */
gdk_pixbuf_save (pixbuf, "snapshot.png", "png", &error, NULL);
gst_buffer_unmap (buffer, &map);
gst_sample_unref (sample);
} else {
g_print ("could not make snapshot\n");
/* cleanup and exit */
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (pipeline);
exit (0);