1 /* GStreamer snapshot example
2 * Copyright (C) <2007> Wim Taymans <wim.taymans@gmail.com>
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
17 * Boston, MA 02110-1301, USA.
18 */
19
20 #include <gst/gst.h>
21 #include <gdk-pixbuf/gdk-pixbuf.h>
22
23 #include <stdlib.h>
24
25 #define CAPS "video/x-raw,format=RGB,width=160,pixel-aspect-ratio=1/1"
26
27 int
main(int argc,char * argv[])28 main (int argc, char *argv[])
29 {
30 GstElement *pipeline, *sink;
31 gint width, height;
32 GstSample *sample;
33 gchar *descr;
34 GError *error = NULL;
35 GdkPixbuf *pixbuf;
36 gint64 duration, position;
37 GstStateChangeReturn ret;
38 gboolean res;
39 GstMapInfo map;
40
41 gst_init (&argc, &argv);
42
43 if (argc != 2) {
44 g_print ("usage: %s <uri>\n Writes snapshot.png in the current directory\n",
45 argv[0]);
46 exit (-1);
47 }
48
49 /* create a new pipeline */
50 descr =
51 g_strdup_printf ("uridecodebin uri=%s ! videoconvert ! videoscale ! "
52 " appsink name=sink caps=\"" CAPS "\"", argv[1]);
53 pipeline = gst_parse_launch (descr, &error);
54
55 if (error != NULL) {
56 g_print ("could not construct pipeline: %s\n", error->message);
57 g_error_free (error);
58 exit (-1);
59 }
60
61 /* get sink */
62 sink = gst_bin_get_by_name (GST_BIN (pipeline), "sink");
63
64 /* set to PAUSED to make the first frame arrive in the sink */
65 ret = gst_element_set_state (pipeline, GST_STATE_PAUSED);
66 switch (ret) {
67 case GST_STATE_CHANGE_FAILURE:
68 g_print ("failed to play the file\n");
69 exit (-1);
70 case GST_STATE_CHANGE_NO_PREROLL:
71 /* for live sources, we need to set the pipeline to PLAYING before we can
72 * receive a buffer. We don't do that yet */
73 g_print ("live sources not supported yet\n");
74 exit (-1);
75 default:
76 break;
77 }
78 /* This can block for up to 5 seconds. If your machine is really overloaded,
79 * it might time out before the pipeline prerolled and we generate an error. A
80 * better way is to run a mainloop and catch errors there. */
81 ret = gst_element_get_state (pipeline, NULL, NULL, 5 * GST_SECOND);
82 if (ret == GST_STATE_CHANGE_FAILURE) {
83 g_print ("failed to play the file\n");
84 exit (-1);
85 }
86
87 /* get the duration */
88 gst_element_query_duration (pipeline, GST_FORMAT_TIME, &duration);
89
90 if (duration != -1)
91 /* we have a duration, seek to 5% */
92 position = duration * 5 / 100;
93 else
94 /* no duration, seek to 1 second, this could EOS */
95 position = 1 * GST_SECOND;
96
97 /* seek to the a position in the file. Most files have a black first frame so
98 * by seeking to somewhere else we have a bigger chance of getting something
99 * more interesting. An optimisation would be to detect black images and then
100 * seek a little more */
101 gst_element_seek_simple (pipeline, GST_FORMAT_TIME,
102 GST_SEEK_FLAG_KEY_UNIT | GST_SEEK_FLAG_FLUSH, position);
103
104 /* get the preroll buffer from appsink, this block untils appsink really
105 * prerolls */
106 g_signal_emit_by_name (sink, "pull-preroll", &sample, NULL);
107 gst_object_unref (sink);
108
109 /* if we have a buffer now, convert it to a pixbuf. It's possible that we
110 * don't have a buffer because we went EOS right away or had an error. */
111 if (sample) {
112 GstBuffer *buffer;
113 GstCaps *caps;
114 GstStructure *s;
115
116 /* get the snapshot buffer format now. We set the caps on the appsink so
117 * that it can only be an rgb buffer. The only thing we have not specified
118 * on the caps is the height, which is dependent on the pixel-aspect-ratio
119 * of the source material */
120 caps = gst_sample_get_caps (sample);
121 if (!caps) {
122 g_print ("could not get snapshot format\n");
123 exit (-1);
124 }
125 s = gst_caps_get_structure (caps, 0);
126
127 /* we need to get the final caps on the buffer to get the size */
128 res = gst_structure_get_int (s, "width", &width);
129 res |= gst_structure_get_int (s, "height", &height);
130 if (!res) {
131 g_print ("could not get snapshot dimension\n");
132 exit (-1);
133 }
134
135 /* create pixmap from buffer and save, gstreamer video buffers have a stride
136 * that is rounded up to the nearest multiple of 4 */
137 buffer = gst_sample_get_buffer (sample);
138 gst_buffer_map (buffer, &map, GST_MAP_READ);
139 pixbuf = gdk_pixbuf_new_from_data (map.data,
140 GDK_COLORSPACE_RGB, FALSE, 8, width, height,
141 GST_ROUND_UP_4 (width * 3), NULL, NULL);
142
143 /* save the pixbuf */
144 gdk_pixbuf_save (pixbuf, "snapshot.png", "png", &error, NULL);
145 gst_buffer_unmap (buffer, &map);
146 } else {
147 g_print ("could not make snapshot\n");
148 }
149
150 /* cleanup and exit */
151 gst_element_set_state (pipeline, GST_STATE_NULL);
152 gst_object_unref (pipeline);
153
154 exit (0);
155 }
156