example: add v4l2 example, demonstrating the use of gst controller

tests/examples/v4l2/.gitignore

@@ -1 +1,2 @@
+camctrl
 probe

tests/examples/v4l2/Makefile.am

@@ -1,4 +1,8 @@
-noinst_PROGRAMS = probe
+noinst_PROGRAMS = probe camctrl
+
+camctrl_SOURCES = camctrl.c
+camctrl_CFLAGS  = $(GST_BASE_CFLAGS) $(GST_CONTROLLER_CFLAGS) $(GST_CFLAGS)
+camctrl_LDADD = $(GST_BASE_LIBS) $(GST_CONTROLLER_LIBS) $(GST_LIBS)
 
 probe_SOURCES = probe.c
 probe_CFLAGS  = $(GST_PLUGINS_BASE_CFLAGS) $(GST_BASE_CFLAGS) $(GST_CFLAGS)

tests/examples/v4l2/camctrl.c

@@ -0,0 +1,195 @@
+/* demo for using gstcontroler with camera capture for e.g. bracketing
+ *
+ * gcc `pkg-config --cflags --libs gstreamer-0.10 gstreamer-controller-0.10` camctrl.c -o camctrl
+ *
+ * TODO:
+ * - handle stream status and switch capture thread to SCHED_RR/FIFO
+ * - the queue-size controls the controler offset
+ *   - right now we work with 1 queued picture and thus active settings for next
+ *     frame
+ * - we want some feedback about how precisely a program can be realized
+ *   - we might want to adjust the framerate to handle hardware limmits
+ * - we e.g. can't change resolution per frame right now
+ */
+
+#include <gst/gst.h>
+#include <gst/controller/gstcontroller.h>
+#include <gst/controller/gstinterpolationcontrolsource.h>
+
+static void
+event_loop (GstElement * bin)
+{
+  GstBus *bus;
+  GstMessage *message = NULL;
+
+  bus = gst_element_get_bus (GST_ELEMENT (bin));
+
+  while (TRUE) {
+    message = gst_bus_poll (bus, GST_MESSAGE_ANY, -1);
+
+    switch (message->type) {
+      case GST_MESSAGE_EOS:
+        gst_message_unref (message);
+        return;
+      case GST_MESSAGE_WARNING:
+      case GST_MESSAGE_ERROR:{
+        GError *gerror;
+        gchar *debug;
+
+        gst_message_parse_error (message, &gerror, &debug);
+        gst_object_default_error (GST_MESSAGE_SRC (message), gerror, debug);
+        gst_message_unref (message);
+        g_error_free (gerror);
+        g_free (debug);
+        return;
+      }
+      default:
+        gst_message_unref (message);
+        break;
+    }
+  }
+}
+
+static void
+set_program (GstController * ctrl, GstStructure * prog)
+{
+  const GstStructure *s;
+  GstInterpolationControlSource *cs;
+  GstClockTime ts, dur;
+  GValue val = { 0, };
+  gint v;
+  const GValue *frame;
+  GHashTable *css;
+  gint i, j;
+  const gchar *name;
+
+  css = g_hash_table_new (g_str_hash, g_str_equal);
+
+  g_value_init (&val, G_TYPE_INT);
+
+  ts = 0;
+  dur = gst_util_uint64_scale_int (GST_SECOND, 1, 15);
+
+  /* loop over each image in prog */
+  for (i = 0; i < gst_structure_n_fields (prog); i++) {
+    GST_DEBUG ("ctrl on %" GST_TIME_FORMAT, GST_TIME_ARGS (ts));
+
+    frame =
+        gst_structure_get_value (prog, gst_structure_nth_field_name (prog, i));
+    s = gst_value_get_structure (frame);
+    for (j = 0; j < gst_structure_n_fields (s); j++) {
+      name = gst_structure_nth_field_name (s, j);
+      cs = g_hash_table_lookup (css, name);
+      if (!cs) {
+        cs = gst_interpolation_control_source_new ();
+        gst_controller_set_control_source (ctrl, name, GST_CONTROL_SOURCE (cs));
+        gst_interpolation_control_source_set_interpolation_mode (cs,
+            GST_INTERPOLATE_NONE);
+        g_hash_table_insert (css, (gpointer) name, cs);
+        g_object_unref (cs);
+      }
+      gst_structure_get_int (s, name, &v);
+      g_value_set_int (&val, v);
+      gst_interpolation_control_source_set (cs, ts, &val);
+      GST_DEBUG ("  %s = %d", name, v);
+    }
+    ts += dur;
+  }
+
+  g_value_unset (&val);
+
+  g_hash_table_unref (css);
+}
+
+gint
+main (gint argc, gchar ** argv)
+{
+  GstElement *bin;
+  GstElement *src, *fmt, *enc, *sink;
+  GstCaps *caps;
+  GstController *ctrl;
+  GstStructure *prog;
+
+  /* init gstreamer */
+  gst_init (&argc, &argv);
+  gst_controller_init (&argc, &argv);
+
+  /* create a new bin to hold the elements */
+  bin = gst_pipeline_new ("camera");
+
+  /* create elements */
+  if (!(sink = gst_element_factory_make ("multifilesink", NULL))) {
+    GST_WARNING ("Can't create element \"multifilesink\"");
+    return -1;
+  }
+  g_object_set (sink, "location", "image%02d.jpg", NULL);
+
+  if (!(enc = gst_element_factory_make ("jpegenc", NULL))) {
+    GST_WARNING ("Can't create element \"jpegenc\"");
+    return -1;
+  }
+
+  if (!(fmt = gst_element_factory_make ("capsfilter", NULL))) {
+    GST_WARNING ("Can't create element \"capsfilter\"");
+    return -1;
+  }
+  caps =
+      gst_caps_from_string
+      ("video/x-raw-yuv, width=640, height=480, framerate=(fraction)15/1");
+  g_object_set (fmt, "caps", caps, NULL);
+
+  if (!(src = gst_element_factory_make ("v4l2src", NULL))) {
+    GST_WARNING ("Can't create element \"v4l2src\"");
+    return -1;
+  }
+  g_object_set (src, "queue-size", 1, NULL);
+
+  /* add objects to the main bin */
+  gst_bin_add_many (GST_BIN (bin), src, fmt, enc, sink, NULL);
+
+  /* link elements */
+  if (!gst_element_link_many (src, fmt, enc, sink, NULL)) {
+    GST_WARNING ("Can't link elements");
+    return -1;
+  }
+
+  /* get the controller */
+  if (!(ctrl = gst_controller_new (G_OBJECT (src), "brightness", "contrast",
+              "saturation", NULL))) {
+    GST_WARNING ("can't control source element");
+    return -1;
+  }
+
+  /* programm a pattern of events */
+#if 0
+  prog = gst_structure_from_string ("program"
+      ", image00=(structure)\"image\\,contrast\\=0\\;\""
+      ", image01=(structure)\"image\\,contrast\\=79\\;\""
+      ", image02=(structure)\"image\\,contrast\\=255\\;\""
+      ", image03=(structure)\"image\\,contrast\\=15\\;\";", NULL);
+#endif
+#if 1
+  prog = gst_structure_from_string ("program"
+      ", image00=(structure)\"image\\,brightness\\=255\\,contrast\\=0\\;\""
+      ", image01=(structure)\"image\\,brightness\\=127\\,contrast\\=79\\;\""
+      ", image02=(structure)\"image\\,brightness\\=64\\,contrast\\=255\\;\""
+      ", image03=(structure)\"image\\,brightness\\=0\\,contrast\\=15\\;\";",
+      NULL);
+#endif
+  set_program (ctrl, prog);
+  g_object_set (src, "num-buffers", gst_structure_n_fields (prog), NULL);
+
+  /* prepare playback */
+  gst_element_set_state (bin, GST_STATE_PAUSED);
+
+  /* play and wait */
+  gst_element_set_state (bin, GST_STATE_PLAYING);
+
+  /* mainloop and wait for eos */
+  event_loop (bin);
+
+  /* stop and cleanup */
+  gst_element_set_state (bin, GST_STATE_NULL);
+  gst_object_unref (GST_OBJECT (bin));
+  return 0;
+}