Add simple snapshot example program using appsink.

Original commit message from CVS:
* configure.ac:
* tests/examples/Makefile.am:
* tests/examples/snapshot/.cvsignore:
* tests/examples/snapshot/Makefile.am:
* tests/examples/snapshot/snapshot.c: (main):
Add simple snapshot example program using appsink.

ChangeLog

@@ -1,3 +1,12 @@
+2007-09-20  Wim Taymans  <wim.taymans@gmail.com>
+
+	* configure.ac:
+	* tests/examples/Makefile.am:
+	* tests/examples/snapshot/.cvsignore:
+	* tests/examples/snapshot/Makefile.am:
+	* tests/examples/snapshot/snapshot.c: (main):
+	Add simple snapshot example program using appsink.
+
 2007-09-20  Stefan Kost  <ensonic@users.sf.net>
 
 	* tests/check/generic/states.c:

configure.ac

@@ -699,6 +699,7 @@ tests/examples/Makefile
 tests/examples/dynamic/Makefile
 tests/examples/seek/Makefile
 tests/examples/volume/Makefile
+tests/examples/snapshot/Makefile
 tests/icles/Makefile
 docs/Makefile
 docs/design/Makefile

tests/examples/Makefile.am

@@ -1,9 +1,9 @@
 if HAVE_FT2
-FT2_SUBDIRS = seek
+FT2_SUBDIRS = seek snapshot
 else
 FT2_SUBDIRS =
 endif
 
 SUBDIRS = $(FT2_SUBDIRS) volume dynamic
 
-DIST_SUBDIRS = seek volume dynamic
+DIST_SUBDIRS = seek volume dynamic snapshot

tests/examples/snapshot/.gitignore

@@ -0,0 +1,2 @@
+snapshot
+snapshot.png

tests/examples/snapshot/Makefile.am

@@ -0,0 +1,10 @@
+if HAVE_GTK
+GTK_EXAMPLES=snapshot
+endif
+
+examples = $(GTK_EXAMPLES)
+
+noinst_PROGRAMS = $(examples)
+
+LIBS = $(GST_LIBS) $(GTK_LIBS)
+AM_CFLAGS = $(GST_CFLAGS) $(GTK_CFLAGS)

tests/examples/snapshot/snapshot.c

@@ -0,0 +1,144 @@
+/* GStreamer snapshot example
+ * Copyright (C) <2007> Wim Taymans <wim.taymans@gmail.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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include <gst/gst.h>
+#include <gtk/gtk.h>
+
+#define CAPS "video/x-raw-rgb,width=160,pixel-aspect-ratio=1/1,bpp=(int)24,depth=(int)24,endianness=(int)4321,red_mask=(int)0xff0000, green_mask=(int)0x00ff00, blue_mask=(int)0x0000ff"
+
+int
+main (int argc, char *argv[])
+{
+  GstElement *pipeline, *sink;
+  gint width, height;
+  GstBuffer *buffer;
+  gchar *descr;
+  GError *error = NULL;
+  GdkPixbuf *pixbuf;
+  gint64 duration, position;
+  GstFormat format;
+  GstStateChangeReturn ret;
+  gboolean res;
+
+  gst_init (&argc, &argv);
+
+  if (argc != 2) {
+    g_print ("usage: %s <uri>\n Writes snapshot.png in the current directory",
+        argv[0]);
+    exit (-1);
+  }
+
+  /* create a new pipeline */
+  descr =
+      g_strdup_printf ("uridecodebin uri=%s ! ffmpegcolorspace ! videoscale ! "
+      " appsink name=sink caps=\"" CAPS "\"", argv[1]);
+  pipeline = gst_parse_launch (descr, &error);
+  g_assert (error == NULL);
+
+  /* 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) {
+    case GST_STATE_CHANGE_FAILURE:
+      g_print ("failed to play the file\n");
+      exit (-1);
+    case GST_STATE_CHANGE_NO_PREROLL:
+      /* 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);
+    default:
+      break;
+  }
+  /* 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);
+  if (ret == GST_STATE_CHANGE_FAILURE) {
+    g_print ("failed to play the file\n");
+    exit (-1);
+  }
+
+  /* get the duration */
+  format = GST_FORMAT_TIME;
+  gst_element_query_duration (pipeline, &format, &duration);
+
+  if (duration != -1)
+    /* we have a duration, seek to 5% */
+    position = duration * 5 / 100;
+  else
+    /* 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, GST_SEEK_FLAG_FLUSH,
+      position);
+
+  /* get the preroll buffer from appsink, this block untils appsink really
+   * prerolls */
+  g_signal_emit_by_name (sink, "pull-preroll", &buffer, 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 (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_BUFFER_CAPS (buffer);
+    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 */
+    pixbuf = gdk_pixbuf_new_from_data (GST_BUFFER_DATA (buffer),
+        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);
+  } 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);
+}